U.S. patent application number 12/250452 was filed with the patent office on 2009-04-30 for adjustable cooling system for airplane electronics.
Invention is credited to Steven E. Bivens, Jeffrey E. Montminy.
Application Number | 20090107657 12/250452 |
Document ID | / |
Family ID | 40581331 |
Filed Date | 2009-04-30 |
United States Patent
Application |
20090107657 |
Kind Code |
A1 |
Montminy; Jeffrey E. ; et
al. |
April 30, 2009 |
ADJUSTABLE COOLING SYSTEM FOR AIRPLANE ELECTRONICS
Abstract
Airplane ground service equipment includes an air conditioning
system for an airplane and also a fluid cooling system for airplane
electronics which detachably connects to a first port and a second
port on the airplane. The fluid cooling system includes a first
connector, a second connector, and a fluid conduit therebetween,
the first and second connectors being adapted to be connected to
the first and second ports, respectively, such that the connection
of the ports to the connectors completes a fluid circuit. A fluid
pump directs fluid through the fluid conduit, and a heat exchanger
in the fluid conduit removes heat from the fluid circuit and
transfers it into the air conditioning system of the ground support
equipment. A temperature regulation mechanism stabilizes the
temperature of the fluid in the fluid conduit to compensate for
changes in the amount of heat that is drawn from the airplane
electronics.
Inventors: |
Montminy; Jeffrey E.;
(Riverview, FL) ; Bivens; Steven E.; (Saint
Petersburg, FL) |
Correspondence
Address: |
PERRY HOFFMAN AND ASSOCIATES, P.C.
P.O. BOX 1649
DEERFIELD
IL
60015
US
|
Family ID: |
40581331 |
Appl. No.: |
12/250452 |
Filed: |
October 13, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60984002 |
Oct 31, 2007 |
|
|
|
61036727 |
Mar 14, 2008 |
|
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Current U.S.
Class: |
165/104.31 ;
165/104.19 |
Current CPC
Class: |
F25B 2400/06 20130101;
B64F 1/364 20130101 |
Class at
Publication: |
165/104.31 ;
165/104.19 |
International
Class: |
F28D 15/00 20060101
F28D015/00 |
Claims
1. A fluid cooling system for airplane electronics which detachably
connects to a first port and a second port on an airplane, the
cooling system comprising: a first connector, a second connector,
and a fluid conduit therebetween, the first and second connectors
being adapted to be connected to the first and second ports,
respectively, and wherein such connection of the ports to the
connectors completes a fluid circuit; a fluid pump that directs
fluid through the fluid conduit; a first bypass that redirects
fluid past the first and second connectors and the airplane to
stabilize the pressure applied across the first and second
connectors. a heat exchanger that removes heat from the fluid in
the fluid conduit; and a temperature regulation mechanism that
stabilizes the temperature of the fluid in the fluid conduit to
compensate for changes in the amount of heat drawn from the
airplane electronics.
2. A fluid cooling system in accordance with claim 1 further
comprising a pressure sensor arranged to sense the pressure of
fluid across the connectors and generating a pressure indication
signal; and a pressure comparator that compares the pressure
indication signal to a setpoint pressure chosen in accordance with
the requirements of the type and class of the airplane and that
generates a pressure comparison signal which is fed to the first
bypass to control its redirection activities.
3. A fluid cooling system in accordance with claim 2 further
comprising a plurality of fluid setpoint pressures in a memory each
corresponding to the needs and requirements of different types or
classes of airplanes, a display on which the different types or
classes of airplanes are identified for manual selection by a human
operator, and a control system that responds to manual selection of
a particular type or class of airplane by retrieving the setpoint
pressure corresponding to that airplane from the memory and
conveying that setpoint pressure to the pressure comparator.
4. A fluid cooling system in accordance with claim 1 wherein the
temperature regulation mechanism comprises a second bypass
connected in parallel with the heat exchanger and controlled by the
temperature regulator mechanism to bypass the heat exchanger as
needed to regulate the temperature of the fluid.
5. A fluid cooling system in accordance with claim 4 further
comprising a pressure sensor arranged to sense the pressure of
fluid applied across the connectors and generating a pressure
indication signal; and a pressure comparator that compares the
pressure indication signal to a setpoint pressure chosen in
accordance with the requirements of the type or class of airplane
and that generates a pressure comparison signal which is fed to the
first bypass to control its redirection activities.
6. A fluid cooling system in accordance with claim 5 further
comprising a plurality of setpoint pressures in a memory each
corresponding to the needs and requirements of a different type or
class of airplane, a display on which the different types and
classes of airplanes are identified for manual selection by a human
operator, and a control system responsive to manual selection of a
particular type or class of airplane for retrieving the setpoint
pressure corresponding to that type or class of airplane from the
memory and conveying it to the pressure comparator.
7. A ground support equipment cart having an air conditioning
system for an airplane and also having a fluid cooling system for
airplane electronics which cooling system detachably connects to a
first port and a second port on an airplane, the fluid cooling
system comprising: a first connector, a second connector, and a
fluid conduit therebetween, the first and second connectors being
adapted to be connected to the first and second ports,
respectively, and wherein such connection of the ports to the
connectors completes a fluid circuit; a fluid pump that directs
fluid through the fluid conduit; a heat exchanger in the fluid
conduit that removes heat from the fluid circuit and transfers it
into the air conditioning system of the ground support equipment
cart; and a temperature regulation mechanism that stabilizes the
temperature of the fluid in the fluid conduit to compensate for
changes in the amount of heat drawn from the airplane
electronics.
8. A ground support equipment cart in accordance with claim 7
further comprising: a first bypass that redirects fluid past the
first and second connectors and the airplane to stabilize the
pressure applied across said first and second connectors.
9. Aground support equipment cart in accordance with claim 8
further comprising a pressure sensor arranged to sense the pressure
of fluid across the connectors and generating a pressure indication
signal; and a pressure comparator that compares the pressure
indication signal to a setpoint pressure chosen in accordance with
the requirements of the type and class of airplane and that
generates a pressure comparison signal which is fed to the first
bypass to control its redirection activities.
10. A ground support equipment cart in accordance with claim 9
further comprising a plurality of fluid setpoint pressures and air
conditioning setpoint pressures in a memory each corresponding to
the needs and requirements of different types and classes of
airplanes, a display on which the different types and classes of
airplanes are identified for manual selection by a human operator,
and a control system that responds to manual selection of a
particular type or class of airplane by retrieving the fluid and
air conditioning setpoint pressures corresponding to that type and
class of airplane from the memory and conveying the fluid setpoint
pressure to the pressure comparator and the air conditioning
setpoint to the air conditioning system.
11. A ground support equipment cart in accordance with claim 8
wherein the temperature regulation mechanism comprises a second
bypass connected in parallel with the heat exchanger and controlled
by the temperature regulator mechanism to bypass the heat exchanger
as needed to regulate the temperature of the fluid.
12. A ground support equipment cart in accordance with claim 11
further comprising a pressure sensor arranged to sense the pressure
of fluid applied across the connectors and generating a pressure
indication signal; and a pressure comparator that compares the
pressure indication signal to a setpoint pressure chosen in
accordance with the requirements of the type or class of airplane
and that generates a pressure comparison signal which is fed to the
first bypass to control its redirection activities.
13. A ground support equipment cart in accordance with claim 12
further comprising a plurality of fluid setpoint pressures and air
conditioning setpoint pressures in a memory each corresponding to
the needs and requirements of different types or classes of
airplanes, a display on which the different types and classes of
airplanes are identified for manual selection by a human operator,
and a control system responsive to manual selection of a particular
type or class of airplane by retrieving the fluid and air
conditioning setpoint pressures corresponding to the type or class
of airplane from the memory and conveying fluid setpoint pressure
to the pressure comparator and the air conditioning setpoint to the
air conditioning system.
14. A ground support equipment cart having a dual, pre-cool and
post-cool air conditioning system for an airplane and also having a
fluid cooling system for airplane electronics which cooling system
detachably connects to a first port and a second port on an
airplane, the fluid cooling system comprising: a first connector, a
second connector, and a fluid conduit therebetween, the first and
second connectors being adapted to be connected to the first and
second ports, respectively, and wherein such connection of the
ports to the connectors completes a fluid circuit; a fluid pump
that directs fluid through the fluid conduit; a heat exchanger in
the fluid conduit that removes heat from the fluid circuit and
transfers it into the pre-cool portion of the dual air conditioning
system of the ground support equipment cart; and a temperature
regulation mechanism that stabilizes the temperature of the fluid
in the fluid conduit to compensate for changes in the amount of
heat drawn from the airplane electronics, the temperature
regulation mechanism also adjusting the parameters of the pre-cool
and post-cool portions of the air conditioning system to compensate
for the added cooling load of the fluid cooling system.
15. A ground support equipment cart in accordance with claim 14
further comprising: a first bypass that redirects fluid past the
first and second connectors and the airplane to stabilize the
pressure across said first and second connectors.
16. A ground support equipment cart in accordance with claim 15
further comprising a pressure sensor arranged to sense the pressure
of fluid across the connectors and generating a pressure indication
signal; and a pressure comparator that compares the pressure
indication signal to a setpoint pressure chosen in accordance with
the requirements of the type and class of the airplane and that
generates a pressure comparison signal which is fed to the first
bypass to control its redirection activities.
17. A ground support equipment cart in accordance with claim 16
further comprising a plurality of fluid setpoint pressures and air
conditioning setpoint pressures in a memory each corresponding to
the needs and requirements of different types or classes of
airplanes, a display on which the different types of airplane are
identified for manual selection by a human operator, and a control
system that responds to manual selection of a particular type or
class of airplane by retrieving the fluid and air conditioning
setpoint pressures corresponding to the type or class of airplane
from the memory and conveying the fluid setpoint pressure to the
pressure comparator and the air conditioning setpoint to the air
conditioning system, adjusting the air conditioning setpoints to
reflect whether the fluid cooling system is or is not in
operation.
18. A ground support equipment cart in accordance with claim 16
wherein the temperature regulation mechanism comprises a second
bypass connected in parallel with the heat exchanger and controlled
by the temperature regulator mechanism to bypass the heat exchanger
as needed to regulate the temperature of the fluid.
19. A ground support equipment cart in accordance with claim 18
further comprising a pressure sensor arranged to sense the pressure
of fluid applied across the connectors and generating a pressure
indication signal; and a pressure comparator that compares the
pressure indication signal to a setpoint pressure chosen in
accordance with the requirements of the type or class of airplane
and that generates a pressure comparison signal which is fed to the
first bypass to control its redirection activities.
20. A ground support equipment cart in accordance with claim 19
further comprising a plurality of setpoint pressures and air
conditioning setpoint pressures in a memory each corresponding to
the needs and requirements of different types or classes of
airplanes, a display on which the different types and classes of
airplanes are identified for manual selection by a human operator,
and a control system responsive to manual selection of a particular
type or class of airplane by retrieving the fluid and air
conditioning setpoint pressures corresponding to that type or class
of airplane from the memory and conveying the fluid setpoint it to
the pressure to the pressure comparator and the air conditioning
setpoint to the air conditioning system.
Description
[0001] This application is a non provisional of provisional
application Ser. No. 60/984,002 filed Oct. 31, 2007 (Atty. Docket
No. 21585-P1) and provisional application Ser. No. 61/036,727 filed
Mar. 14, 2008 (Atty. Docket No. 50-003 ITW 21585-P2).
CROSS-REFERENCE TO RELATED APPLICATIONS
[0002] The present patent application is one of a set of commonly
owned applications filed on the same day as the present
application, sharing some inventors in common, and relating to
airplane ground support equipment and carts. The other applications
in this set, listed here, are hereby incorporated by reference into
the present application: "A Multi-Voltage Power Supply for a
Universal Airplane Ground Support Equipment Cart," James W. Mann,
III and David Wayne Leadingham (Ser. No. ______, Atty. Doc. No.
50-002 ITW 21608U); "A Frame and Panel System for Constructing
Modules to be Installed on an Airplane Ground Support Equipment
Cart," Jeffrey E. Montminy, Brian A. Teeters, and Kyta Insixiengmay
(Ser. No. ______, Atty. Doc. No. 50-004 ITW 21588U); "A System of
Fasteners for Attaching Panels onto Modules that are to be
Installed on an Airplane Ground Support Equipment Cart," Jeffrey E.
Montminy, Brian A. Teeters, and Kyta Insixiengmay (Ser. No. ______,
Atty. Doc. No. 50-005 ITW 21587U); "Airplane Ground Support
Equipment Cart Having Extractable Modules and a Generator Module
that is Separable from Power and Air Conditioning Modules," James
W. Mann, III and Jeffrey E. Montminy (Ser. No. ______, Atty. Doc.
No. 50-006 ITW 21586U); "An Adjustable Air Conditioning Control
System for a Universal Airplane Ground Support Equipment Cart,"
James W. Mann, III, Jeffrey E. Montminy, Benjamin E. Newell, and Ty
A. Newell (Ser. No. ______, Atty. Doc. No. 50-007 ITW 21606U); "A
Compact, Modularized Air Conditioning System that can be Mounted
Upon an Airplane Ground Support Equipment Cart," Jeffrey E.
Montminy, Kyta Insixiengmay, James W. Mann. III, Benjamin E.
Newell, and Ty A. Newell (Ser. No. ______, Atty. Doc. No. 50-008
ITW 21583U); and "Maintenance and Control System for Ground Support
Equipment," James W. Mann, III, Jeffrey E. Montminy, Steven E.
Bivens, and David Wayne Leadingham (Ser. No. ______, Atty. Doc. No.
50-009 ITW 21605U).
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention relates generally to the field of
cooling using fluid coolants, and more particularly to airplane
ground support equipment that, in addition to providing air and
electrical conditioning services to airplanes, is also able to
provide airplanes requiring liquid coolants with polyalphaolefin
(PAO) or other similar liquid coolants at controlled temperatures
and pressures to cool airplane electronics.
[0005] 2. Description of the Related Art
[0006] When an airplane is on the ground with its engines shut
down, the airplane is typically unable to provide power for its
electrical systems and chilled air for its air conditioning
systems; and some airplanes are also unable to provide liquid
coolant for some critical electronic (or "avionic") components. It
is customary to connect such a grounded airplane to an airplane
ground support equipment system. Such a system may have its
components mounted upon a mobile equipment cart that is called an
airplane ground support equipment cart and that may be parked,
placed, or mounted conveniently close to an airplane requiring
ground support. Such a cart typically contains an air conditioner
that can provide conditioned and cooled air to an airplane plus an
electrical power converter that can transform power drawn from the
local power grid into power of the proper voltage (AC or DC) and
frequency required by the airplane. Such an airplane ground support
equipment cart may also contain a diesel engine connected to an
electrical generator that enables the cart to provide both air
conditioning and also electrical power for an airplane without any
connection to the local power grid. And if an airplane requires a
source of cooled liquid for its electronics, some carts may also
include a source of liquid coolant.
[0007] In the past, particularly with regard to military airplanes,
such ground support equipment carts have been custom designed to
meet the specialized needs of a single particular type or class of
airplane. Hence, a cart designed to support the specific
requirements and needs of a first type or class of airplane cannot
be used to support the differing specific requirements and needs of
other types or classes of airplanes. Different airplanes typically
may require different pressures and volumes of cooled air,
different amounts of electrical power, different electrical voltage
levels, and different electrical frequencies (or direct current).
And different airplanes typically may require differing pressures
and volumes of cooled liquid for use in cooling onboard
electronics. Accordingly, every airport must be supplied with as
many different types of ground support equipment carts as there are
different types or classes of airplanes that may land and take off
at each airport or military base. Problems arise when more
airplanes of a particular type arrive at a specific location than
there are ground support equipment carts suitably designed to
service the needs of that particular type or class of airplane.
[0008] To be more specific, some airplanes require their ground
support equipment to provide considerably more airflow at higher
pressures than do other airplanes having smaller interiors. Some
airplanes require their electrical power to be adjusted to 115
volts of alternating current (A.C.) which alternates, or flows back
and forth, 400 times each second (115 volts, 400 Hz A.C.). Other
airplanes require 270 volts direct current (270 volts, D.C.) that
does not flow back and forth. Yet other airplanes require a source
of 28 volts of direct current (28 volts, D.C.). And airplanes also
differ in the amount of electrical power that they draw.
[0009] Some airplanes, particularly jet fighters, need an
additional source of cooling from their ground support equipment in
the form of a liquid coolant that is applied to the so-called
avionics systems, including electronics and radar systems. This
liquid is typically a polyalphaolefin, or PAO, heat transport fluid
or liquid coolant. This fluid is propelled by a pump through one or
more heat exchangers within the airplane that cool the liquid using
cool air that is present whenever the airplane's turbo fan
propulsion engine is in operation. The cooled liquid is then passed
through the avionics.
[0010] When such an airplane's engine is not in operation, the PAO
fluid must be cooled in some other manner to prevent the avionics
from overheating. One way to accomplish this is to include in the
airplane ground support equipment a PAO pump and a mechanism for
cooling the PAO heat transport fluid. A pair of hoses can connect
the airplane's PAO fluid system to the ground support equipment,
and a circular flow between the airplane and the ground support
equipment is established whereby the PAO fluid flows out of the
avionics in the airplane to the ground support equipment where the
pump propels the fluid through some form of heat exchange mechanism
to cool the fluid, which then flows back into the airplane and into
the avionics. Since the temperature and pressure and fluid flow
volume requirements for PAO cooling may vary from one type or class
of airplane to the next, a PAO cooling system designed to meet the
specialized PAO cooling needs of one airplane will not necessarily
meet the somewhat different needs of another type or class of
airplane.
[0011] As an example of an airplane cart arrangement that provides
air and electrical conditioning for an airplane, PCT patent
application No. PCT/US2006/043312 (Intl. Pub. No. WO 2007/061622 A1
published on May 31, 2007) discloses an airplane ground support
cart that has a modular design of its electrical conditioning
components. This cart provides air conditioning and electrical
power conversion as well as optional electrical power generation
services to airplanes. FIG. 5 reveals that the cart disclosed in
this patent application may receive interchangeable, modular power
conversion modules. Thus, a module 72, which generates 3-phase 115
volt 400 Hz A.C. power, may be removed and replaced with a module
78, which generates 270 volt D.C. power. FIG. 6 illustrates that
this cart may also accept a module 92, which generates 28 volt D.C.
electrical power.
[0012] FIG. 2 of the above PCT patent application illustrates a
typical arrangement of the mechanical components of a dual air
conditioning system within an airplane ground support equipment
cart 14. The air conditioner's mechanical components are spread all
across the entire length of the cart 14. Two sets of condenser
coils 34 are positioned at one end of the cart 14; and the
thickness of the coils 34 and their housing, together with the
thickness of the associated cooling fans, occupies roughly
one-fifth of the cart's overall length. A filter and upstream
evaporation coil 30 and a downstream evaporation coil 40 and outlet
connection 42 (to which can be attached a duct leading to an
airplane) are positioned at the other extreme end of the cart 14,
occupying somewhat less than one-fifth of the cart's overall
length. A blower fan 32, a discharge plenum 38, and two compressors
36 are shown positioned in the central portions of the cart 14.
These mechanical components of the air conditioning system are not
confined within a rectangular module within a portion of the volume
of the cart 14--these components are spread all across the cart 14
and thus cannot be conveniently removed from the cart for servicing
or for use away from the cart 14. Other cart components, such as a
diesel engine 54 and generator 56 (shown in FIG. 4 of the PCT
application) and an electrical power converter unit 72 (shown in
FIG. 5 of the PCT application) are squeezed in among the air
conditioning components wherever there is room. This intermixing of
non-air-conditioning components with the air-conditioning
components greatly complicates servicing of all the components,
since they are all crowded into the same cramped space. A service
man working on the air conditioner compressors or blowers may find
the diesel engine 54 and generator 56 are in the way of these
components, for example.
[0013] The air conditioning systems of such a conventional ground
support equipment system is also designed to provide a particular
volume of cooled air at a particular temperature and pressure to a
particular type or class of airplane. If such a system has its cool
air ducted into some other type or class of airplane, too much or
too little air will flow from the air conditioner system, and this
will throw off the balance of the air conditioning system, causing
the air to be cooled too little or too much and possibly causing
icing of the internal evaporator arrays or damage to the airplane.
And the temperature and pressure provided may not be proper for
some other type or class of airplane. Likewise, the electrical
systems may not be able to supply the needs of differing types or
classes of airplanes, and the PAO liquid cooling system may not be
properly balanced when used to cool the avionics of differing types
or classes of airplanes.
SUMMARY OF THE INVENTION
[0014] An embodiment of the invention relates to ground support
equipment including an air conditioning system for an airplane and
also including a fluid cooling system for airplane electronics
which detachably connects to a first port and a second port on the
airplane. The fluid cooling system includes a first connector, a
second connector, and a fluid conduit there between, the first and
second connectors being adapted to be connected to the first and
second ports, respectively, such that the connection of the ports
to the connectors completes a fluid circuit. A fluid pump directs
fluid through the fluid conduit, and a heat exchanger in the fluid
conduit removes heat from the fluid circuit and transfers it into
the air conditioning system of the ground support equipment. A
temperature regulation mechanism stabilizes the temperature of the
fluid in the fluid conduit to compensate for changes in the amount
of heat that is drawn from the airplane electronics.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is an isometric view of an embodiment of a universal
airplane ground support equipment cart having a modular design.
[0016] FIG. 2 is an isometric view of the cart shown in FIG. 1 with
the diesel engine and generator module portion that forms the back
portion of the cart shown separated from the rest of the cart.
[0017] FIG. 3 is an isometric view of an electrical conversion
module of the cart shown in FIG. 1 to illustrate how it may be slid
out of and away from the side of the cart for maintenance purposes
or to be replaced with a different module.
[0018] FIG. 4 is a perspective view of a two-stage air conditioning
module that is mounted on the front portion of the cart shown in
FIG. 1, the air conditioning module shown with both of its
microchannel condenser coil supporting doors shown swung open to
reveal its internal structural details.
[0019] FIG. 5 is a schematic diagram illustrating the flow path of
air as it flows through the two-stage air conditioning module shown
in FIG. 4.
[0020] FIG. 6 is a schematic diagram illustrating the refrigerant
circulation paths within the first, or "pre-cool," air conditioning
unit within the two-stage air conditioning module shown in FIG. 4,
and also showing a heat exchanger which transfers heat from a
separate PAO cooling system (not shown) to the refrigerant within
this first air conditioning unit.
[0021] FIG. 7 is a schematic diagram illustrating the refrigerant
circulation paths within the second, or "post-cool," air
conditioning unit within the two-stage air conditioning module
shown in FIG. 4.
[0022] FIG. 8 is a schematic diagram of a PAO cooling system within
the air conditioning module shown in FIG. 4 which transfers heat
from an airplane to the first, or "pre-cool," air conditioning unit
within the two-stage air conditioning module shown in FIG. 4.
[0023] FIG. 9 presents an exploded, perspective view of four plate
fin evaporator arrays assembled into a square array, mounted within
a rectangular frame, and attached to a funnel-shaped duct that
conveys cooled air to the external piping which leads to an
airplane.
[0024] FIG. 10 presents a perspective view of the assembly of plate
fin evaporator arrays shown in FIG. 9 mounted between two
funnel-shaped ducts that spread the air to be cooled uniformly
across the surface of the plate fin evaporator arrays.
[0025] FIG. 11 presents a perspective view of a microchannel
condenser unit of the type used in pairs and mounted upon the two
doors of the two-stage air conditioning module shown in FIG. 4.
[0026] FIG. 12 presents a partly sectional view, taken along the
lines A-A in FIG. 10, of a microchannel condenser unit illustrating
interior details of the air channels.
[0027] FIG. 13 is a block diagram illustrating the signal-carrying
bus and the way in which it interconnects the power generating
module, two power converter modules, and the two-stage air
conditioning module with a control module that includes a display
screen with eight pushbuttons and a universal control and
diagnostics processor.
[0028] FIG. 14 is a combined flow diagram and state diagram
illustrating the normal start-up and run procedures of the overall
system and also illustrating the warning, alarm, and shut down
states.
[0029] FIG. 15 is a simplified schematic diagram (combining
elements taken from FIGS. 5, 6, 7, and 8) illustrating the air flow
and the refrigerant circulation paths in the pre-cool and post-cool
air conditioning units and also in the PAO cooling system, and
identifying in particular the eight feedback control loops and
controllers that control the operation of these systems and also
the temperatures and pressures and set-points that provide input
signals to these controllers.
[0030] FIG. 16 is a state diagram illustrating the operation of the
compressors within the two air conditioning units.
[0031] FIG. 17 is a flow diagram illustrating how the operation of
the blower fan which blows air through the two air conditioner
units and into the airplane is automatically controlled through the
use of a variable frequency drive for the motor that drives the
blower fan.
[0032] FIG. 18 is a schematic diagram showing the connection of the
two compressors, the two-speed condenser cooling fan, and the
blower fan's variable frequency drive to a three-phase source of
380 to 500 volt, 50 to 60 Hz electrical power and also showing
control signals for the compressors, cooling fan, and blower
fan.
[0033] FIG. 19 illustrates and names all of the significant system
state signals (temperatures, pressures, etc.) that enter the air
conditioning and PAO processor, and it also illustrates all of the
significant on/off and 0-to-10 volt output control signals which
that processor generates to control all of the air conditioning
processes, thereby allowing the air conditioner system to respond
flexibly and properly to widely varying load conditions that can be
caused by different types and classes of airplanes.
[0034] FIG. 20 presents a block diagram of all the menus and
submenus that may be displayed on the face of the control module's
display screen, together with the navigation paths between these
menus and submenus.
[0035] FIG. 21 presents a view of the main menu.
[0036] FIG. 22 presents a view of a help menu that appears when the
"Help" item is selected on the main menu shown in FIG. 21.
[0037] FIG. 23 presents a view of a menu that appears when the
airplane "T-50 Golden Eagle" is selected on the main menu shown in
FIG. 21.
[0038] FIG. 24 presents a view of a help menu that appears when the
"Help" item is selected on the "T-50 Golden Eagle" menu shown in
FIG. 23.
[0039] FIG. 25 presents a view of a maintenance menu that appears
when the "Maintenance" item is selected on the main menu shown in
FIG. 21.
[0040] FIG. 26 presents a view of a scrollable data logging menu
and viewing window that appears when the "Data Log Screen" item is
selected on the maintenance menu shown in FIG. 25.
[0041] FIG. 27 illustrates a view of a pre-cool air conditioning
unit's status values that appears when the "A/C Maintenance" item
is selected on the maintenance menu shown in FIG. 25.
[0042] FIG. 28 illustrates a view of one of two actuator status and
relay status screens that appear when the "Relay Status Screen"
item is selected on the maintenance menu shown in FIG. 25--the
values displayed correspond to the more important output control
signals generated by the air conditioning and PAO processor shown
in FIG. 19.
[0043] FIG. 29 presents an exploded isometric view of the control
module's display screen, illustrating that the screen is covered by
metal screening that serves as a radio frequency wave blocking
screen.
DETAILED DESCRIPTION OF THE INVENTION
[0044] The detailed description which follows is broken into two
sections. Section A presents an introduction to the environment of
the present invention, which relates to the design of a PAO liquid
cooling system that is incorporated and integrated into the air
conditioning system of a modularized universal airplane ground
support equipment cart (FIGS. 1-3). Section B presents a detailed
description of the PAO liquid cooling system in the context of the
complete ground support air conditioning system, including that
system's internal mechanical details (FIGS. 1-4, 9-12, and 29), air
flow details (FIG. 5), refrigerant and PAO coolant flow path
details (FIGS. 6-8), electronic control system details (FIGS.
13-19), and display system and human interaction details (FIGS.
20-28). While the focus of the present invention is the PAO liquid
cooling system and the related control systems (disclosed primarily
in FIGS. 6, 8, and 15), the PAO system is so closely integrated
into the overall air conditioning system that the two systems are
described below as a single, integrated system.
A. Modular and Universal Airplane Ground Support Equipment Cart
[0045] Airplane ground support equipment carts are wheeled, towable
carts or fixed mounted (permanently or temporarily) devices that
provide air conditioning, avionics equipment liquid cooling, and
electrical power conversion and generation services to airplanes
whose engines are shut down. These carts preferably should be
conveyed by military and other airplanes to airports and military
bases all over the world, so it would be convenient and an
advantage to have this equipment be no larger than a standard
military equipment conveyance palette. However, many such carts
today do not fit one standard palette, and this reduces the numbers
of ground support equipment that is available in the field.
Traditionally, such ground support equipment carts are
custom-designed--they provide such services to only one type or
class of airplane. Hence, different carts must be provided for each
different type of airplane. Also traditionally, the air
conditioning components mounted on such carts are so bulky that
they occupy the entire area of the cart, making it necessary to
sandwich electrical power conversion and other components wherever
there is room and thereby making it extremely awkward to service or
replace such cart-mounted components.
[0046] The present invention is embodied in a universal airplane
ground support equipment cart--universal in the sense that it is
designed to service the varied needs of a variety of types and
classes of airplanes, rather than just one type or class. This
ground support equipment cart is also modular--its components are
rectangular modules that may be easily separated or removed from
the cart for service or exchange. The modules may also be used
independently of the cart, and modules not needed for a particular
type of airplane may be readily removed and used elsewhere,
standing by themselves, in a highly flexible manner. Such a cart 10
and several of its modules--an electrical power generation module
14, an electrical power conversion module 20, and a dual air
conditioning module 400 (which also provides PAO liquid
cooling)--are illustrated in simplified form in FIGS. 1-3. (Much
more detailed drawings of these components are included in this
application and also in the related applications cited above).
[0047] In use, the cart 10 is mounted near or drawn up to an
airplane (not shown) by a suitable tractor or truck (not shown). An
operator connects an air conditioning plenum or air duct 26 from
the dual air conditioning module 400 to a cooled air input port
(not shown) on the airplane. And if the airplane has avionics or
other electronic components that require a supply of liquid
coolant, then the operator also connects a pair of PAO liquid
coolant conduits 28 from the air conditioning module 400 to a pair
of PAO ports on the airplane. The operator then uses a suitable
electrical power cable (not shown) to connect an electrical power
output port or receptacle (not shown in FIGS. 1-3) on the
electrical power conversion module 20 to a matching port or cable
on the airplane. To supply the varying needs of different types of
airplanes, there may be as many as two electrical power conversion
modules 20 the cart 10, a first module 20 having both a 115 volt,
400 Hz AC power output port and also a separate 270 volt DC power
output port, and a second module 1308 (FIG. 13) having a 28 volt DC
power output port (one or the other of these modules 20 or 1308 may
be removed from the cart 10).
[0048] Next, with reference to FIG. 13, the operator depresses a
"Start" pushbutton 1316 on the front panel of a control module 22
having a display screen 24 that then displays a main menu such as
that shown in FIG. 21. If the airplane is a T-50 Golden Eagle, the
operator depresses one of four pushbuttons 1304 that is adjacent
the label "T-50 Golden Eagle" on this menu (FIG. 21), and then the
operator depresses one of four pushbuttons 1302 that is adjacent
the label "Start" on a "T-50" menu that then appears (FIG. 23). In
response, all of the modules automatically reconfigure themselves
as needed to service this specific type of airplane with air
conditioning of the proper pressure and volume of air, with
electrical power of the proper type, voltage, and frequency, and
with liquid coolant (if needed). If the operator selects the wrong
type of airplane, pressure and air flow measurements can detect
this and shut down the system, illuminating a colored status light
1314 to signal an error and displaying an appropriate error message
on the control panel 24 to the operator. The system is halted when
the operator depresses a "Stop" pushbutton 1318 on the front of the
control 22 or a pushbutton 1302 or 1304 that is adjacent the label
"Stop" on one of the display screen 24 menus.
[0049] A universal airplane ground support equipment cart is
designed to provide flexible support for the needs of many
different types and classes of airplanes having widely varying air
conditioning and liquid cooling and electrical power support needs.
The present invention can provide different pressures and volumes
of cooled air and cooled liquid to different airplanes, and it can
provide different types and quantities of electrical power to
different airplanes. It also provides a simplified, integrated
control panel where airplane service personnel can simply select
the type of airplane that is to be serviced and have the various
appliances on the cart automatically configured to optimize the
support for that particular type of airplane.
[0050] A modular airplane ground support equipment cart is one
where the different support systems provided by the cart are each
confined to rugged, compact, optionally EMI shielded, rectangular
modules that may be easily removed, serviced, replaced, and used
stand-alone separate from the cart and its other modular
components.
[0051] In the cart 10, for example, a two-stage air conditioning
module 400 contains all of the air conditioning components of the
cart 10, including a liquid PAO cooling system. An electrical power
converter module 20 contains the power conversion components of the
cart 10, including a 270 volt D.C. supply and a 115 volt 400 Hz
A.C. supply; and the module 20 may be replaced or supplemented with
another module 1308 (FIG. 13) that includes a 28 volt D.C. supply,
providing up to three different types of electrical power
conversion in accordance with the specialized needs of different
types and classes of airplanes.
[0052] A power supply module 14 contains a diesel engine and a
generator for producing 60 cycle, three-phase, 460 volt electrical
power when the cart cannot be conveniently hooked up to a 360 to
500 volt, 50 or 60 cycle A.C., three phase supply provided by the
local power grid. The power supply module 14 is confined to one end
of the cart 10 and may be detached from the cart 10, as is
illustrated in FIG. 2.
[0053] Any or all of these modules 14, 20, 400, and 1308 may
optionally be equipped with an internal transformer (not shown)
that transforms the incoming high voltage electrical power down to
120 volts or 240 volts at 50- or 60-Hz and feeds this low voltage
to standard, weather protected outlets (not shown) which can be
used to provide power to hand tools and to portable lighting
equipment and the like, with ground fault protection also provided
to these appliances.
[0054] As is illustrated in FIG. 13, a control module 22 is mounted
on the cart 10 above the power converter module 20. The control
module 22 has on its front panel a pair of start and stop
pushbuttons 1316 and 1318, colored status lights 1314, and a
display screen 24 having sets of four pushbuttons 1302 and 1304
positioned adjacent the display screen 24's left and right sides.
When turned on, the display screen 24 presents a main menu display,
shown in FIG. 21, which permits airplane maintenance personnel to
select the type of plane that is to be serviced by depressing one
of the adjacent pushbuttons 1302 and 1304. A maintenance menu
display, shown in FIG. 25, permits service personnel to view and
(in some cases) to alter the state of the air conditioning and PAO
module 400, the electrical power converter modules 20 and 1308, and
the power supply module 14. As is illustrated schematically in FIG.
13, all of the modules 14, 20, 22, 400, and 1308 are automatically
networked together by a network 1312 when they are installed upon
the cart 10. In addition, each of the modules 14, 20, 22, 400, and
1308 is equipped with a network jack (not shown) that can be
connected to an external portable computer (not shown) which can
then serve as the control module and display for all of the
modules, with mouse clicks on the menus shown in FIGS. 20 to 28
replacing depressions of the pushbuttons 1302 and 1304.
[0055] The cart 10 is optionally mounted upon two wheel and axle
truck assemblies 18 and 19. In the space on the cart 10 between the
power generation module 14 and the two-stage air conditioning
module 400, one or both of the electrical power converter modules
20 and 1308 may be slid into place and attached to the cart 10, as
is illustrated in FIGS. 2 and 3. (If both are installed, they may
be on opposite sides of the cart, as shown, or they may be
installed one above the other.)
[0056] If the power generation module 14 is not required for a
particular airplane support task, the module 14 and the wheel and
axle truck assembly 19 beneath the module 14 may be completely
detached from the rest of the cart 10, as is illustrated in FIG. 2,
and removed to be used entirely separately elsewhere, wherever a
portable source of 60 Hz, 460 volt, three-phase power is required.
As illustrated in FIGS. 2 and 3, the electrical power converter
modules 20 and 1308 may be slid out on tracks and locked in
position to give service personnel convenient access for the
servicing of these modules 20 and 1308 and their internal
electrical and electronic components. They may also be removed for
repair or for use elsewhere as stand-alone power converters, or
they may be replaced with different power converter modules that
generate different voltages and frequencies as needed for servicing
different airplanes.
B. Two-Stage Air Conditioning and PAO Liquid Cooling System
[0057] The two-stage air conditioning system and PAO liquid cooling
system that is described below has many valuable attributes. Among
others: It can achieve a 30-second air conditioner startup, rather
than the many minutes that are required to start up conventional
airplane ground support equipment air conditioners, due to the
close control that is exerted over all aspects of the system and
inherently low refrigeration system charge by minimizing internal
volume of the refrigeration system (see FIG. 15 and the
accompanying descriptive material presented below). Since the
digital control algorithms may be varied dynamically by the
processor 1900 to suit unusual conditions, the air conditioner can
still operate even if many sensors and controllers are inoperative
based upon memory of past operations which can be relied upon to
predict conditions in place of actual sensor readings to give
control guidance. And as will be explained, an operator indicates
on a menu (FIG. 18) which type or class of airplane is to be
serviced. If, when the air conditioner is started up initially at a
lower blower speed than the final blower speed, the pressure and
air flow measurements captured by the temperature, pressure, and
power consumption measurement sensors do not correspond to that
choice of type or class of airplane, the air conditioner can shut
down and give the operator an appropriate warning message that the
wrong type of airplane has most likely been selected. Other
examples of the system's attributes are set forth below. An
improved user interface is presented in an appendix to this
application, where start and stop buttons and colored lamps are
added to the display to improve its usability and the menus are
adjusted accordingly.
[0058] Referring now to FIGS. 4 through 12, the internal mechanical
and fluid flow path details of the two-stage air conditioning
module 400 are shown. The module 400 contains two air conditioning
stages--a pre-cool air conditioner 520 (shown in FIGS. 5 and 6) and
a post-cool air conditioner 522 (shown in FIGS. 5 and 7). The flow
of air along a path 500 through the two air conditioners 520 and
522 stages are described in FIG. 5. The flow of coolant through the
two air conditioners 520 and 522 stages are illustrated in FIG. 6
(pre-cool air conditioner 520) and in FIG. 7 (post-cool air
conditioner 522). The pre-cool air conditioner 520 has associated
with it a PAO liquid cooling system 700. FIG. 8 illustrates the
flow of avionics liquid coolant through this PAO liquid cooling
system 700 and between the system 700 and avionics 825 within an
airplane 823. The mechanical details of each of the air
conditioner's plate fin evaporator arrays are illustrated in FIGS.
9 and 10, and the mechanical details of each of the air
conditioner's micro-channel condenser coils are illustrated in
FIGS. 11 and 12.
[0059] FIG. 4 presents a perspective view of the two-stage air
conditioning module 400 as seen from its rear side 402, with the
air duct 26 that conveys air conditioned air to the airplane (not
shown) shown extending to the right (in FIGS. 1 and 2, the air duct
26 extends to the left). The side 402 is accordingly the side of
the module 400 that is not adjacent the electrical power converter
modules 20 and 1308 and the control module 22 when these modules
400, 20, 22, and 1308 are all mounted on the cart 10, as shown in
FIG. 1. Accordingly, the module 400's rear side 402 is always
accessible for servicing the module 400 and is not blocked by the
presence of the other modules.
[0060] A hinged, louvered door 404 is shown swung open from the
rear side 402 (FIG. 4) of the module 400, and this door gives
service personnel unfettered access to all the air conditioning and
PAO components within the module 400 for service and maintenance
procedures, but would not be left open during operation. A second
hinged, louvered door 408 is shown swung upwards from the top side
of the module 400. This door 408 gives service personnel access to
the PAO system 700 components which are mounted near the top of the
module 400.
[0061] The two louvered doors 404 and 408 each support a pair of
thin, microchannel air conditioner condenser coils 406 and 410 the
details of which coils are shown in FIGS. 11 and 12 (discussed
below). Each pair of two condenser coils 406 and 410 is associated
with a respective one of the two air conditioners 520 and 522
stages mounted within the air conditioning module 400. A two-speed
condenser fan 414 blows air out of a fan portal 418 in one side 416
of the air conditioning module 400--the side that is not connected
by the air duct 26 to the airplane. When both the doors 404 and 408
are closed, the condenser fan 414 sucks air through both of the
pairs of microchannel condenser coils 406 and 410, cooling the
refrigerant within the two condenser coils 406 and 410. The fan 414
blows the air heated by passage through the two condenser coils 406
and 410 out the fan portal 418 on the side 416 of the cart 10 away
from where service personnel viewing the display screen 24 or
connecting up the air duct 26 or the PAO liquid coolant conduits 28
would normally stand. With reference to FIGS. 15 and 18, the fan
414 has low speed 415 and high speed 417 fan control signals which
are generated by a controller 1518 which is implemented as an
algorithm within the air conditioning and PAO processor 1900. The
controller responds to the ambient temperature and to various
temperature and pressure signals shown in FIGS. 5, 6, and 7 by
varying the fan 414 from off to low speed to high speed as needed
to aid the processor in maintaining the proper operation of the two
air conditioners 520 and 522. This is another way for the system to
adjust rated capacity, a way that is especially useful when the
system is running at low capacities--that is, at low ambient
conditions.
[0062] FIG. 5 presents a schematic diagram of the air pathway 500
taken by air which is cooled, dehumidified, and compressed as it
passes through the two-stage air conditioning module 400. Outside
air shown at 501 is sucked through the pre-cool air conditioner 520
by a blower 508 which then propels the air through the post-cool
air conditioner 522 and through the air duct 26 from which it
emerges as a stream of cooled, dehumidified, pressurized air that
flows directly into the airplane (not shown).
[0063] The pre-cool air conditioner 520 includes as components a
first evaporator array 504 (FIGS. 4 and 5) and a pair of the
microchannel condenser coils 406 (FIG. 4) plus other components all
of which are shown together in FIG. 6 (described below). The
post-cool air conditioner 522 includes as components a second
evaporator array 514 (FIGS. 4 and 5) and a second pair of the
microchannel condensers 410 (FIG. 4) plus other components all of
which are shown in FIG. 7 (described below). The two air
conditioners 520 and 522 are essentially identical except that the
pre-cool air conditioner 520 includes a PAO heat exchanger 602
(FIGS. 6 and 8) that absorbs heat from the PAO liquid coolant
circuit 700 shown in FIG. 8.
[0064] Referring now to FIGS. 4 and 5, air 501 that is to be
dehumidified and cooled flows along the air pathway 500 first
through an air filter 502 and next through the pre-cool air
conditioner's 520 plate fin evaporator array 504, where the air is
partially cooled and dehumidified. The air next flows through a
narrowing plenum 505 (FIG. 4) and then onwards to the blower 508,
which propels the air forward at increased pressure. The air next
passes through an outlet cone 510 (FIG. 4) designed to convert
velocity pressure coming from the blower 508 into static pressure
(static regain) before making a turn through an elbow 512 (FIG. 4).
The air then flows into an expansion chamber or air funnel 513
(FIG. 10) which contains a baffle plate that spreads out the air so
that the air passes uniformly through all parts of the post-cool
air conditioner 522's plate fin evaporator array 514. The further
cooled and dehumidified air then flows through a narrowing plenum
516 (FIGS. 4, 9, and 10) and through a circular coupling 518 (FIGS.
4, 9, and 10) out the air duct 26 (FIGS. 1, 4, and 5) and onwards
to the interior of the airplane (not shown).
[0065] The blower 508 is driven by a variable-speed electric motor
506 the speed of which motor is controlled by the frequency of the
motor 506's incoming electric power. A voltage-to-frequency
converter 525 accepts a serialized digital control signal 1706
which specifies the motor 506's frequency and which is supplied by
an air conditioner and PAO processor 1900 (a real-time process
control computer system--see FIG. 19). The converter 525 responds
to that signal 1706 by varying the frequency of the input power to
the motor 506 up and down in accord with the frequency called for
by the control signal 1706 based upon a control algorithm that
monitors the output pressure (measured by the pressure sensor 526).
The processor 1900 receives a 0-to-10 volt pressure measurement
signal from a pressure sensor 526 that measures the pressure within
the ring 518 and air duct 26 that supplies cooled air to the
airplane (not shown). With reference to FIGS. 5 and 15, the
processor 1900 compares the pressure read by the pressure sensor
526 to a set-point desired pressure, which may vary from one type
and class of plane to the next, and then adjusts the control signal
1706 so as to adjust the blower 508's speed to a setting that
maintains the pressure within the air duct 26 at or close to the
proper pressure that is required to cool the particular type or
class of airplane.
[0066] In FIG. 15, a controller 1514 is shown symbolically
comparing a setpoint pressure Psp to the air duct pressure measured
by the pressure sensor 526 and then generating the signal 1706
which controls the blower 508 speed. The controller 1514 is
actually implemented digitally within the processor 1900. The
controller 1514 would typically have a proportional component to
minimize the pressure error and an integral component to drive that
pressure error towards zero over time. The airplane selection
process, described below in conjunction with the selection menu
shown in FIG. 21, can alter the pressure setpoint Psp value as well
as other temperature setpoint Tsp values (described below) to
customize the air conditioner and PAO controllers shown in FIG. 15
to the specific needs and requirements of differing types and
classes of airplanes. When one of the pushbuttons 1304 adjacent the
display screen 24 (FIG. 13) is depressed, for example, to program
the modules on the cart 10 to service the T-50 Golden Eagle (see
FIG. 21), the optimal temperature Tsp and pressure Psp setpoints
for that airplane are selected by the air conditioning and PAO
processor 1900 and are placed into a memory of setpoints 1317 (FIG.
13).
[0067] FIG. 17, which is described below, describes other aspects
of the blower 508 control algorithm in somewhat greater detail.
[0068] Differential pressure sensors 528, 530, 532, and 534 enable
the processor 1900 to monitor the pressure drop across various air
conditioning system components. These pressure readings are
collected by the processor 1900 and saved in a data log 1319 (FIG.
13) and are used later on for maintenance purposes. For example, an
excessive pressure drop across the air filter 502 measured by the
differential pressure sensor 528 signals that it soon will be time
to clean or replace the air filter 502. Excessive pressure drop
across the evaporator arrays 504 or 514 measured by the
differential pressure sensors 530 and 534 can signal icing of an
evaporator array that is running too cold or a clogged evaporator
array that requires cleaning. The pressure drop across the blower
508, when compared to the signal 1706 frequency value and also the
electrical power applied to the blower 508 (as measured by voltage
sensor 1720 and current sensor 1722 both shown in FIG. 18) can
indicate the condition of the blower and its motor and whether
servicing is needed. This information is saved in the processor
1900's data log 1319 (FIG. 13).
[0069] Pressure sensor 536 (see FIG. 5) monitors the outside air
pressure, which is recorded by the processor 1900 in the data log
1319. Pressure sensor 543 (FIG. 5) monitors the output air pressure
generated by the blower 508 which is also the air pressure within
the air plenums, a pressure that can also be recorded by the
processor 1900 in the data log 1319. RTD (resistor temperature
device) temperature sensors 538, 540, 542, and 544 monitor the air
temperature before and after the air passes through the two
evaporator arrays 504 and 514. These temperature measurements are
fed into the processor 1900 which records them in the data log 1319
and can use them for predictive maintenance. As an option, some or
all of these temperatures and pressures may be used to adjust the
amount of cooling that is generated by each of the two air
conditioners, as is illustrated in FIG. 15.
[0070] FIGS. 6 and 7 present detailed schematic diagrams of the
pre-cool air conditioner 520 and the post-cool air conditioner 522.
In one embodiment of the invention, the refrigerant tubing used in
the construction of these air conditioners 520 and 522 is ACR
copper tubing, with brazed joints and with many sweated fittings
used to achieve a curved path of refrigerant flow. In another
embodiment, aluminum tubing is used instead of copper tubing. A
tube bender is then used in lieu of many sweated joints, and this
reduces the number of parts used on each system, a great cost
reducer. A great feature of aluminum is that it makes the system
very lightweight and cost less when compared to copper, as aluminum
weighs about 70% less than copper and cost approximately one-third
as much. In addition, the use of flared fittings would also allow
assembly to take place with pre-made lengths and tube
configurations where the assembly technician would just need to
turn a wrench instead of waiting for a skilled worker certified in
copper brazing. This would also make field repairs much quicker
than ever before.
[0071] FIG. 6 presents a schematic diagram of the pre-cool air
conditioner 520. With reference to FIG. 6, a compressor 601
compresses the refrigerant and sends it along a path 604 to one of
the pair of condenser coils 406, where the refrigerant is cooled by
air flowing through the air conditioning module 400 under the
impetus of the condenser fan 414, as was described above, where the
refrigerant cools and becomes liquefied. The air conditioning and
PAO processor 1900 (FIG. 19) sends out a first on/off pre-cool
shutoff signal to a solenoid valve 603 and an on/off pre-cool
compressor on signal 1702 which can turn the pre-cool compressor
601 on and off (see FIGS. 18 and 19) and which can shut down the
pre-cool air conditioner 520 by shutting off the compressor 601 and
isolating the compressor 601 from refrigerant migration by closing
the solenoid valve 603. The shutdown algorithm will then close all
the refrigeration valves 620, 638, and 632 (FIG. 6) to further
prevent refrigerant migration back to the compressor 601.
[0072] The cooled and liquefied refrigerant next flows past a
charging valve 608, a filter dryer 606, and a sight glass 610 over
a path 612 to a brazed plate heat exchanger 614 (FIGS. 4 and 6)
that is mounted at the very bottom of the air conditioning module
400, as is shown at 614 in FIG. 4. The brazed plate heat exchanger
614 has a multi-purpose in its design: it serves as a liquid
refrigerant accumulator that collects any excess liquid refrigerant
and any excess oil that may be in the suction line between the
compressor 601 and the evaporator array 504 to prevent damage to
the compressor 601 (which is designed to pump vapor). The brazed
plate heat exchanger 614 also serves as a liquid suction line
sub-cooler that sub cools the liquid refrigerant by allowing the
expanded gasses flowing along the path 628 and 630 and entering the
compressor 601 to absorb heat from the liquid refrigerant in the
lines 612 and 618 and in the brazed plate heat exchanger 614. The
liquid line side of the brazed plate heat exchanger 614 acts as a
refrigerant receiver, accumulating excess refrigerant charge on the
condenser side of the system. The brazed plate heat exchanger 614
increases the capacity and efficiency of the cooling system at high
load conditions. Finally, the brazed plate heat exchanger is used
to control the suction line superheat, allowing the evaporators to
be fully flooded. Flooding the evaporators allows high cooling
capacity from the evaporators as well as increasing the evaporator
capacity while maintaining higher refrigerant temperature which
helps avoid evaporator frosting.
[0073] The path 618 conducts the cooled but still liquefied
refrigerant to an electronically controlled expansion valve 620
that is controlled by a 0-to-10 volt signal generated by the
processor 1900. The liquid refrigerant flows through the expansion
valve 620 into the low pressure, cool side of the refrigerant
circuit, where the liquid begins to vaporize and absorb heat from
its surroundings. This boiling liquid passes first through the PAO
heat exchanger 602, where it cools the liquid PAO fluid flowing
into a line 622 and out a line 624 which lines lead to the PAO
fluid circuit (shown at 700 in FIG. 8). The boiling refrigerant
flows onward over the path 626 to the plate fin evaporator array
504 essentially identical to the evaporator array 514 shown in FIG.
9, where the refrigerant cools the air that is sucked into the
module 400 at 501 (FIG. 5) from the outside air, through the air
filter 502 and the plate fin evaporator array 504 and into the
blower 508. The gaseous refrigerant leaves the plate fin evaporator
array 504 and flows along the path 628 back through the brazed
plate heat exchanger 614 and over the path 630 back to the
compressor 601 where it is once again compressed and fed into the
pair of condenser coils 406 to be compressed, thus completing the
passage of refrigerant through this vapor compression cycle.
[0074] Combined temperature and pressure transducers monitor the
condition of the refrigerant throughout this circuit. An RTD
(resistor temperature device) temperature and pressure transducer
607 monitors the temperature and pressure of the liquid refrigerant
as it leaves the condenser coils 406 and enters the brazed plate
heat exchanger 614. A second RTD temperature and pressure
transducer 616 monitors the temperature and pressure of the liquid
refrigerant as it leaves the brazed plate heat exchanger 614 over
the path 618 and flows through the expansion valve 620. Another
temperature and pressure transducer 634 monitors the temperature
and pressure of the gaseous, cooled refrigerant flowing out of the
plate fin evaporator array 504. A pair of temperature and pressure
transducers 609 and 611 monitors the temperature and pressure of
the gaseous refrigerant entering the compressor 601 and also
leaving the compressor 601. The refrigerant temperature and
pressure readings generated by all of these transducers 607, 616,
634, 609, and 611 and also the pre-cool condenser air output
temperature measured by the RTD air temperature transducer 540 are
fed into the air conditioning and PAO processor 1900 (see FIG. 19)
where these temperatures and pressures may be stored in the data
log 1319 (FIG. 13).
[0075] The refrigerant temperatures measured by the RTD temperature
transducers 609, 616 and 634 and the air temperature measured by
the pre-cool air conditioner output RTD temperature transducer 540
are also used for air conditioner control purposes, as is
illustrated in FIG. 15.
[0076] The pre-cool air conditioner output temperature measured by
the RTD temperature transducer 540 is compared to a setpoint
temperature, typically 10 degrees Celsius or thereabouts, by means
of a controller 1506 which is implemented as a digital process
control algorithm within the air conditioner and PAO processor
1900. As the desired output temperature is adjusted by the user,
this setpoint temperature can be altered. This controller 1506 is
given both proportional and integral outputs which are summed and
used (as a 0-to-10 volt signal) to control an electronic exhaust
gas bypass valve 638 (EGBV--FIGS. 6 and 15) which, to the degree it
is open, permits compressed, hot gas to bypass the condenser coils
406 and the expansion valve 620 and to flow directly from the
compressor 601 into the evaporator array 501, thereby raising the
temperature and boiling excess liquid refrigerant within the
evaporator array 504. The processor 1900 continuously adjusts this
EGB valve 638 to maintain the air temperature at the pre-cool air
conditioner's plate fin evaporator array 504 outlet at or just
above freezing so that the evaporator array 504 is not permitted to
ice up.
[0077] The refrigerant temperature (measured by the RTD transducer
616) at the outlet of the electronic expansion valve (EEV) 608,
which is the inlet into the PAO heat exchanger 602 and plate fin
evaporator array 504, is fed into another controller 1502 (FIG.
15), which is also implemented as a digital process control
algorithm within the air conditioner and PAO processor 1900. This
controller 1502 is also given both proportional and integral
outputs which are summed and used (as a 0-to-10 volt signal) to
control an electronic evaporator array pressure regulator valve EPR
632 (FIGS. 6 and 15) which valve controls how much cooled,
expanded, gaseous refrigerant is permitted to enter the compressor
601. In this manner, the temperature at the input to the evaporator
array 504 and the PAO liquid heat exchanger 602 are controlled and
maintained at a setpoint value Tsp, which value is fed into the
controller 1502 (FIG. 15). This setpoint is typically kept at 1
degree Celsius. As the desired unit output temperature is adjusted
by the user, this setpoint may be altered. The air conditioning and
PAO processor 1900 maintains this setpoint value, as well as other
similar temperature and pressure setpoint values, in a memory for
setpoints 1317 (FIG. 13) where these values may sometimes be
altered when different types and classes of airplanes are being
serviced.
[0078] The refrigerant temperature (measured by the RTD transducer
616) at the outlet of the electronic expansion valve (EEV) 608,
which is the inlet into the PAO heat exchanger 602 and plate fin
evaporator array 504, is compared to the refrigerant temperature
(transducer 634) at the outlet of the plate fin evaporator array
504 by another controller 1504, which is also implemented as a
digital process control algorithm within the air conditioner and
PAO processor 1900. This controller 1504 may initially be given
both proportional and integral outputs which are summed and used
(as a 0-to-10 volt signal) to control the electronic expansion
valve EEV 608 (FIGS. 6 and 15) which valve controls to what extent
the entire evaporator array 504 is thoroughly wetted and
participating in the cooling process. Experiments have shown,
however, that the controller 1504 may have to be programmed in a
nonlinear manner, with the control parameters worked out
empirically by experiment and varying from a simple proportional
and integral controller to some degree. The EEV 608 is adjusted to
maximize the effective cooling area of the evaporator array, as is
indicated by a maximum temperature drop across the plate fin
evaporator array 504. The air conditioning and PAO processor 1900
may maintain different control algorithms for the controller 1504
as well as the other controllers 1502 and 1506 in the memory of
setpoints 1315 (FIG. 13) so that different control algorithms and
strategies may be selected and implemented for different types and
classes of airplanes which are being serviced.
[0079] FIG. 7 presents a schematic diagram of the post-cool air
conditioner 522. With reference to FIG. 7, a compressor 702
compresses the refrigerant and sends it along a path 704 to one of
the pair of condenser coils 410, where the refrigerant is cooled by
air flowing through the air conditioning module 400 under the
impetus of the condenser fan 414, as was described above, where the
refrigerant cools and becomes liquefied. The air conditioning and
PAO processor 1900 (FIG. 19) sends out a first on/off post-cool
shutoff signal to a solenoid valve 703 and an on/off post-cool
compressor on signal 1704 which can turn the post-cool compressor
702 on and off (see FIGS. 18 and 19) and which can shut down the
post-cool air conditioner 522 by shutting off the compressor 702
and isolating the compressor 702 from refrigerant migration by
closing the solenoid valve 703. The shutdown algorithm will then
close all the refrigeration valves 720, 738, and 732 (FIG. 7) to
further prevent refrigerant migration back to the compressor
702.
[0080] The cooled and liquefied refrigerant next flows past a
charging valve 708, a filter dryer 706, and a sight glass 710 over
a path 712 to a brazed plate heat exchanger 714 (FIGS. 4 and 7)
that is mounted at the very bottom of the air conditioning module
400, as is shown at 714 in FIG. 4. The brazed plate heat exchanger
714 has a multi-purpose design: it serves as a liquid refrigerant
accumulator that collects any excess liquid refrigerant and any
excess oil that may be in the suction line between the compressor
702 and the evaporator array 514, preventing damage to the
compressor 702 (which is designed to pump vapor). The brazed plate
heat exchanger 714 also serves as a liquid suction line sub-cooler
that sub cools the liquid refrigerant by allowing the expanded
gasses flowing along the path 728 and 730 and entering the
compressor 702 to absorb heat from the liquid refrigerant in the
line 712 and 718 and in the brazed plate heat exchanger 714. The
liquid line side of the brazed plate heat exchanger 714 acts as a
refrigerant receiver, accumulating excess refrigerant charge on the
condenser side of the system. The brazed plate heat exchanger 714
increases the capacity and efficiency of the cooling system at high
load conditions. Finally, the brazed plate heat exchanger is used
to control the suction line superheat, allowing the evaporators to
be fully flooded. Flooding the evaporators allows high cooling
capacity from the evaporators as well as increasing the evaporator
capacity while maintaining higher refrigerant temperature which
helps avoid evaporator frosting.
[0081] The path 718 conducts the cooled but still liquefied
refrigerant to an electronically controlled expansion valve 720
that is controlled by a 0-to-10 volt signal generated by the
processor 1900. The liquid refrigerant flows through the expansion
valve 720 into the low pressure, cool side of the refrigerant
circuit, where the liquid begins to vaporize and absorb heat from
its surroundings. This boiling liquid flows to the plate fin
evaporator array 514, shown in FIGS. 9 and 10, where the
refrigerant cools the air that is blown out through the air duct 26
to the airplane (not shown). The gaseous refrigerant leaves the
plate fin evaporator array 514 and flows along the path 728 back
through the brazed plate heat exchanger 714 and over the path 730
back to the compressor 702 where it is once again compressed and
fed into the pair of condensers 410 to be cooled and liquefied,
thus completing the passage all the way through this circular
refrigerant circuit.
[0082] Combined temperature and pressure transducers monitor the
condition of the refrigerant throughout this circuit. An RTD
temperature and pressure transducer 707 monitors the temperature
and pressure of the liquid refrigerant as it leaves the pair of
condensers 410 and enters the brazed plate heat exchanger 714. A
second RTD temperature and pressure transducer 716 monitors the
temperature and pressure of the liquid refrigerant as it leaves the
brazed plate heat exchanger 714 over the path 718 and flows through
the electronic expansion valve 720. Another temperature and
pressure transducer 734 monitors the temperature and pressure of
the gaseous, cooled refrigerant flowing out of the plate fin
evaporator array 514. A pair of temperature and pressure
transducers 709 and 711 monitors the temperature and pressure of
the gaseous refrigerant entering the compressor 702 and also
leaving the compressor 702. The refrigerant temperature and
pressure readings generated by all of these transducers 707, 716,
734, 709, and 711 and also the post-cool condenser air output
temperature measured by the RTD air temperature transducer 544 are
fed into the air conditioning and PAO processor 1900 (see FIG. 19)
where these temperatures and pressures may be stored in the data
log 1319 (FIG. 13).
[0083] The refrigerant temperatures measured by the RTD temperature
transducers 709, 716 and 734 and the air temperature measured by
the pre-cool air conditioner RTD output temperature transducer 544
are also used for air conditioner control purposes, as is
illustrated in FIG. 15.
[0084] The pre-cool air conditioner output temperature measured by
the RTD temperature transducer 544 is compared to a setpoint
temperature, typically 10 degrees Celsius or thereabouts, by means
of a controller 1512 which is implemented as a digital process
control algorithm within the air conditioner and PAO processor
1900. As the desired output temperature is adjusted by the user,
this setpoint temperature can be altered. This controller 1512 is
given both proportional and integral outputs which are summed and
used (as a 0-to-10 volt signal) to control an electronic exhaust
gas bypass valve 738 (EGBV--FIGS. 7 and 15) which, to the degree it
is open, permits compressed, hot gas to bypass the pair of
condenser coils 410 and the expansion valve 720 and to flow
directly from the compressor 702 into the evaporator array 514,
thereby raising the temperature and boiling excess refrigerant
liquid within the evaporator array 514. The processor 1900
continuously adjusts this EGB valve 738 to maintain the air
temperature at the pre-cool air conditioner's plate fin evaporator
array 514 outlet at or just above freezing so that the evaporator
array 514 is not permitted to ice up.
[0085] The refrigerant temperature (measured by RTD transducer 716)
at the outlet of the electronic expansion valve (EEV) 708, which is
the inlet into the plate fin evaporator array 514, is fed into
another controller 1508 (FIG. 15), which is also implemented as a
digital process control algorithm within the air conditioner and
PAO processor 1900. This controller 1508 is also given both
proportional and integral outputs which are summed and used (as a
0-to-10 volt signal) to control an electronic evaporator array
pressure regulator valve EPR 732 (FIGS. 7 and 15) which valve
controls how much cooled, expanded, gaseous refrigerant is
permitted to enter the compressor 702. In this manner, the
temperature at the input to the evaporator array 514 is controlled
and maintained at a setpoint value Tsp, which value is fed into the
controller 1508 (FIG. 15). This setpoint is typically kept at 1
degree Celsius. As the desired unit output temperature is adjusted
by the user, the setpoint may be altered. The air conditioning and
PAO processor 1900 maintains this setpoint value, as well as other
similar temperature and pressure setpoint values, in a memory for
setpoints 1317 (FIG. 13) where these values may sometimes be
altered when different types and classes of airplanes are being
serviced.
[0086] The refrigerant temperature (measured by RTD transducer 716)
at the outlet of the electronic expansion valve (EEV) 708, which is
the inlet into the plate fin evaporator array 514, is compared to
the refrigerant temperature (transducer 734) at the outlet of the
plate fin evaporator array 514 by another controller 1510, which is
also implemented as a digital process control algorithm within the
air conditioner and PAO processor 1900. This controller 1510 may
initially be given both proportional and integral outputs which are
summed and used (as a 0-to-10 volt signal) to control the
electronic expansion valve EEV 708 (FIGS. 7 and 15) which valve
controls to what extent the entire evaporator array 514 is
thoroughly wetted and participating in the cooling process.
Experiments have shown, however, that the controller 1510 may have
to be programmed in a nonlinear manner, with the control parameters
worked out empirically by experiment and varying from a simple
proportional and integral controller to some degree. The EEV 708 is
adjusted to maximize the effective cooling area of the evaporator
array, as is indicated by a maximum temperature drop across the
plate fin evaporator array 514. The air conditioning and PAO
processor 1900 may maintain different control algorithms for the
controller 1510 as well as the other controllers 1512 and 1508 in
the memory of setpoints 1315 (FIG. 13) so that different control
algorithms and strategies may be selected and implemented for
different types and classes of airplanes which are being
serviced.
[0087] The compressors 601 and 702 are part number
ZR300-KCE-TWD-250 of Copeland, Sidney, Ohio. The suction line
subcoolers or brazed plate heat exchangers 614 and 714 are part
number AA6259 of SWEP International, Landskrona, Sweden. Pressure
transducers are part number MX5018 provided by Gems Sensors &
Controls, Plainville, Conn. The pairs of 60'' by 34'' preassembled
microchannel condenser coils 406 and 410 are part number 26944 D13
custom assembled by Trilectron Industries, Palmetto, Fla.
[0088] Clearly, the proper operation of the air conditioner
components just described is dependent upon the proper operation of
many air and refrigerant temperature and pressure measurements. If
any of the measurement instruments fail, the air conditioners 520
and 522, under the control of the air conditioning processor 1900,
tries to continue operating, with warning messages, substituting
for actual temperature and pressure measurements historical
temperature and pressure measurements recorded on earlier days when
the ambient weather conditions and the type or class of airplane
were the same. In this manner, the air conditioning system
continues to operate even when some of its sensors and controllers
are inoperative.
[0089] A major advantage of the air conditioning system just
described is its ability to enter a fully operative state,
providing full pressure of air cooled to the proper temperature,
within 20 seconds or so of when it is first started up, rather than
several minutes later as in conventional air conditioning airplane
ground support equipment.
[0090] As explained above, the PAO liquid coolant system 700
derives its cooling from the heat exchanger 602 which is part of
the pre-cool air conditioner 520. The PAO system 700 does not
derive its cooling from the post-cool air conditioner 522.
Accordingly, when the PAO system is in operation, it reduces the
cooling capacity of the pre-cool air conditioner 520. The post-cool
air conditioner 522 may be adjusted upwards in the amount of
cooling which it provides to the air flowing through the air duct
26 to the airplane so that the turning on and off of the PAO system
700 does not necessarily alter the temperature and pressure of the
cooled and dehumidified air provided to the airplane by the air
duct 26.
[0091] The PAO cooling system 700 is illustrated schematically in
FIG. 8. Most of the elements of the PAO cooling system are
positioned within the air conditioning module 400 near the top of
that module, adjacent to the pair of PAO liquid coolant conduits 28
shown in FIGS. 1 and 2 that convey the PAO liquid to and from the
airplane to shorten the length of the PAO liquid coolant conduits
28 as much as possible. A PAO liquid reservoir 803 is positioned
lower down within the module 400 to serve as a reservoir for
reserve amounts of the PAO liquid coolant.
[0092] With reference to FIG. 8, a PAO fluid pump 805 pumps PAO
fluid through a first check valve 807 and through a second check
valve 809 to the heat exchanger 602, which is part of the pre-cool
air conditioner 520, as was explained above. The cooled PAO fluid
then flows onwards over a path 811 through filters 813 and over a
path 817 to a supply solenoid valve 819 that is turned on and off
by the processor 1900 (FIG. 19). When the valve 819 is open, the
PAO fluid flows over a path 820 out of the air conditioning module
400 and over a conduit 822 into an airplane 823 where it flows
through and cools electronics and avionics components 825.
[0093] The PAO fluid then flows over a second conduit 824 back from
the airplane 823 to the air conditioning module 400 and over a path
826 that leads to the PAO liquid reservoir 803 where it collects,
waiting to be drawn back out by the pump 828 and sent back to the
heat exchanger 602 again. That completes the PAO liquid coolant
circuit.
[0094] The PAO liquid coolant collects in the liquid reservoir 803.
A liquid level sensor 824 signals to the air conditioning and PAO
processor 1900 (FIG. 19) when the liquid level is too low. When the
PAO system is cabled up to an airplane, there is typically air in
the conduits 822 and 824 and possibly in the electronics and
avionics as well. When the PAO system is first turned on, the
solenoid valve 819 is opened and then the PAO pressure is slowly
raised up to the proper operating pressure. Any air present in the
system collects above the liquid in the reservoir 803, and a vacuum
pump 833, actuated by the air conditioning and PAO processor 1900
(FIG. 19), pumps this air out of the liquid reservoir 803. This
prevents overheating of the electronics and avionics 825 caused by
air displacing the PAO liquid coolant in the circulating
system.
[0095] A 3-way proportional flow regulator valve 828 (FIGS. 8 and
15) controls and continuously adjusts a liquid coolant bypass path
829-830 that bypasses the heat exchanger 602 with some of the PAO
liquid to reduce the cooling effect. The regulator 828 receives
temperature signals directly from a temperature and pressure sensor
transducer 832. Alternatively, the processor 1900 can implement a
digital controller which can compare the temperature measured by
the transducer 832 to an adjustable setpoint temperature and then
adjusts the regulator valve 828 accordingly.
[0096] A bypass path 834 is controlled by an electronically
controlled proportional flow restriction valve 821 having a
pressure setpoint that can be set and varied by the air
conditioning and PAO processor 1900. As is illustrated in FIG. 15,
a controller 1516 compares the PAO system output pressure, as
measured by the temperature and pressure sensing transducer 832, to
a setpoint pressure Psp (stored in the memory for setpoints 1317
(FIG. 13) and then amplifies the pressure difference using
proportional and integral control functions to generate control
signals which are summed and then fed as a control signal to the
electronically controlled proportional flow restriction valve 821.
The controller 1516 can be implemented as a control algorithm
within the air conditioning and PAO processor 1900. The pressure
setpoint Psp may be varied in accordance with the specific needs of
different types and classes of airplanes being serviced in response
to airplane selection using the main menu shown in FIG. 21. It is
also possible to have the restriction valve 821 respond directly to
pressure indicating signals from the transducer 832 without the use
of the processor 1900 and the controller 1516, and this is the
arrangement actually shown in FIG. 8 (for this reason, FIG. 19 does
not presently show an output signal from the processor 1900 leading
to the valve 821).
[0097] To protect the PAO system 700 from transients, a bypass
valve 835 can be actuated by excessive pressure sensed by the
transducer 832 and opened to bypass the heat exchanger 602, pump
805, and reservoir 803. The controller 1516, implemented within the
processor 1900, opens the bypass valve 835.
[0098] A PAO hydraulic manifold assembly, part number AGA15700-0-C,
which includes the components 819, 821, and 835, can be obtained
from the Rexroth Bosch Group. The PAO pump 833, Model 4600-20,
comes from McNally Industries, Grantsburg, Wis. The PAO heat
exchanger 602 is part number AA 6283 of Swep International,
Landskrona, Sweden. The PAO pump pressure relief system is part
number a971207 zc 04a2 is supplied by Sun Hydraulics, Sarasota,
Fla.
[0099] To increase the efficiency and also to decrease the size of
the evaporator arrays 504 and 514, in one embodiment these
evaporator arrays are each constructed from four automotive plate
fin evaporator arrays 802, 804, 806, and 808 (FIGS. 9 and 10)
assembled into a roughly square frame 810 and held in place by a
cover plate 812. The assembled frame 810 and plate fin evaporator
arrays 802-808 shown in FIG. 8 is used to construct each of the two
evaporator arrays 504 and 514. The evaporator array 514 is shown in
FIGS. 9 and 10 attached to an incoming expansion chamber or air
funnel 513 (FIG. 9) which accepts air flowing out of the blower 508
and spreads this air out in a uniform manner over the surface of
the four plate fin evaporator arrays 802-808 to maximize the
cooling efficiency of this unit. Air flows out of the evaporator
array 514 into a second funnel 516 which ducts the air to an
outgoing cooled air port 518 to which is attached the air duct 26
(FIGS. 1, 2, 4, and 5) that conveys the cooled air to the airplane.
The evaporator array 504 (not shown in FIGS. 8 and 9--shown in
FIGS. 4 and 5) receives outside air 501 that flows through the air
filter 502 directly into the evaporator array 504. Air flows out of
the evaporator array 504 through a funnel 505 (FIG. 4) directly
into the blower 508. The plate and fin design of the evaporator
arrays 504 and 514 allows them to be inexpensive, compact, and
highly efficient.
[0100] To decrease the size and increase the efficiency of the
condenser coils 406 and 410, each condenser is constructed from a
pair of overlaid and interconnected microchannel condenser coils.
With reference to FIG. 4, these pairs of condenser coils 406 and
410 are long and wide enough to be mounted on the panels or door
assemblies 404 and 408. The door 404 may be swung open to give
convenient access to the other mechanical air conditioning
components within the module 400, as is shown. The pairs of
condenser coils 406 and 410 are quite thin, so they do not take up
much room within the air conditioning module 400, unlike prior tube
and fin arrangements which were much more bulky.
[0101] With reference to FIGS. 11 and 12, the microchannel
condenser coils (used in pairs to construct the condenser coils 406
and 408) are each constructed as a pair of parallel, spaced-apart
refrigerant pipes 1002 and 1004 having narrowed or tapered end
sections 1006 and 1008 for convenient attachment to copper or
flexible tubing. Hollow, rectangular ducts 1010 are mounted between
and perpendicular to the pipes 1002 and 1004, with the ends of the
ducts 1010 passing through slots cut partway through the sides of
the pipes 1002 and 1004, as is best shown in FIG. 12. The
rectangular ducts 1010 are further partitioned internally by
partitions 1012 into very small, rectangular channels that provide
paths through which the refrigerant may pass between the two pipes
1002 and 1004 flowing through the ducts 1010. The spaces between
the rectangular ducts 1010 are then filled in with folded, thin
aluminum fins folded accordion style to maximize heat transfer
between the air flowing through the microchannel condenser coil and
the refrigerant flowing from the pipe 1002 to the pipe 1004. These
aluminum fins, as well as the arrangement of pairs of condenser
coils, force the air to travel a zigzag course, and this further
adds to the efficiency of the design.
[0102] Further details concerning the general design of such
microchannel condenser coils may be found in U.S. Pat. No.
6,988,538 which issued to Justin P. Merkys, et al. on Jan. 24,
2006.
[0103] Referring now to FIG. 13, all of the modules 14, 20, 22,
400, and 1308 are shown to be networked together by a network 1312,
which in one embodiment is realized using a CAN bus, developed by
CIA (CAN In Automation), Erlangen, Germany. Clearly, other bus
protocols can also be used, including Ethernet and TCP/IP to
network these components together. The CAN bus is one designed
particularly for use in a hostile, automotive, outdoors
environment. The control module 22 communicates with the can bus
network 1312 using a cart network bus driver 1310, and all the
other module-based processors do likewise (not shown in FIG.
13).
[0104] The control module 22 is shown to have a display screen 24
that has an array of four pushbuttons 1302 to its left and a second
array of four pushbuttons 1304 to its right, aligned with menu
selections on displayed images (see menus and submenus, FIGS.
21-28). The menus are stored within a universal control and
diagnostic processor 1306 which manages the display screen 24 and
also manages some diagnostics tasks and the like. The processor
1306 inquires over the bus network 1312 as to which modules are
present, and it tailors the displayed information accordingly.
Menus and diagnostics are not displayed for any module that is not
present and operating.
[0105] A hierarchical arrangement of one possible set of menus and
other displays is shown in FIG. 20. When the system is first turned
on, a main screen or menu (shown in detail in FIG. 21) is
displayed. This main menu permits the operator of the cart 10 to
simply select which of several airplanes the ground support
equipment cart is to service. If the operator depresses the
pushbutton adjacent the "T-50 Golden Eagle" item, a secondary menu
shown in FIG. 23 is displayed. When the operator depresses the
pushbutton adjacent the "Start" item, the air conditioners, one of
the power sources, and the PAO liquid cooling system are all
started up. The processor 1306 conveys to the processors within
other modules, and in particular the air conditioner and PAO
processor 1900, the identity of the plane that is to be serviced
(the T-50), and this allows, for example, the air conditioner and
PAO processor to adjust the setpoints 1317 that control the
operation of the two air conditioners and the PAO system in
accordance with the specialized needs of the T-50 class of
airplanes. FIG. 15 illustrates many of the temperature Tsp and
pressure Psp setpoints whose settings may be adjusted in this
manner to adapt the equipment on the cart 10 to the needs of
particular types and classes of airplanes.
[0106] The operator may return to the main menu (FIG. 21) and
depress the pushbutton adjacent "Maintenance," and then a
maintenance menu is displayed (FIG. 25). From this maintenance
menu, one may navigate to a Data Log display (FIG. 26) where one
may scroll through a log of temperatures, pressures, and other data
gathered over time. This data log information 1319 (FIG. 13) is
also available for further processing by the universal control and
diagnostics processor 1306 which can generate reports predicting
such things as when certain components will require service or are
likely to fail. For example, a gradual increase in the differential
pressure across the air filter 502 measured by the differential
pressure sensor 528 would enable one to predict when the filter 502
will have to be cleaned or replaced. Other similar maintenance and
repair prediction reports can be generated in this manner by the
diagnostic processor 1306. The data log 1319 is maintained by
processors (such as the processor 1900) within each module, so that
this information stays with each module if the modules are moved
about and separated.
[0107] Other more focused maintenance reports may be displayed. For
example a pre-cool air conditioner status report (FIG. 27)
indicates the current status of the air conditioner 520, indicating
such useful things as how much refrigerant is currently bypassing
the pair of condenser coils 406 by flowing through the bypass valve
638 to reduce the temperature of the evaporator array 504, as was
explained above. The current settings of the expansion valve 620
and of other valves and the speed of the condenser fan 414 are also
indicated, along with the on/off state of the two compressors 601
and 702.
[0108] Help menus are also provided, as is shown in the
illustrative menus shown in FIGS. 22 and 24.
[0109] FIG. 29 presents some mechanical details of the display
screen 24. The display screen 24 is a black-and-white,
electroluminescent display that is fully operable over extreme
ranges of temperature. The display screen 24 is sandwiched together
with a metal screen 2902 and with a protective plastic cover plate
2904 all of which are mounted to the side of the control module 22
facing an operator standing before the cart 10. The screen 2902
provides radio frequency shielding to the display, preventing
signals from leaking either into the control module 22 or out of
the control module 22. This rugged, simple arrangement of an
all-weather display and eight rugged pushbuttons 1302 and 1304
provides an all-weather display that combines many displays and
controls which, in prior designs for ground support equipment
carts, were scattered all over the cart, with separate gauges and
controls for each appliance, and with no uniformity of control.
[0110] Referring now to FIG. 14, the state machine of a master
process 1400 for the air conditioner and PAO processor 1900 is
shown. When power is applied to the module 400, the processor 1900
initiates a boot sequence 1402 that prepares the processor 1900 for
operation. The boot sequence 1402 enables the processor 1900 to
determine whether it is configured as a "stand-alone" or
"cart-mounted" module. If the module 400 is cart mounted, it waits
(at step 1406) for the start command to come in from the CAN data
bus after actuation of a START menu command on an airplane-specific
menu such as that shown in FIG. 23. Otherwise, the processor 1900
seeks discrete signals from its own more primitive user interface
(possibly a portable computer plugged into the module 400 using an
Ethernet, CAN, or USB portal.
[0111] After the boot sequence 1402, the processor 1900 enables a
data logging sub-machine 1404. The data logging sub-machine 1404
receives present sensor signals from the module 400 and records
them in the data log 1319. This data log is used by the processors
1900 and 1306 for predictive failure and for enhanced diagnostic
functioning, as has been explained.
[0112] After the processor 1900 enables the data logging
sub-machine 1404, it enters an idle state at 1406. In the idle
state 1406, the processor 1900 waits for an "On" command to arrive,
as from the "Start" command on the airplane-specific menu shown in
FIG. 23. This "On" command may come from the CAR data bus or the
user interface of the module 400. After the processor 1900 receives
the "On" command, it exits the idle state 1406 and enters the check
power state at 1408.
[0113] In the check power state 1408, the processor 1900 performs a
self test. Stored default parameters or menu-selected operating
parameters are given to the processor 1900 at power up. These
operating parameters set the setpoint 1317 temperatures and
pressures that the processor 1900 desires to achieve (see the
values Tsp and Psp shown in FIG. 15). These operating parameters
are adjusted to those appropriate to the output temperatures and
pressures (and electrical power) required by any given airplane
that may need to be connected to the air conditioning and PAO
module 400. After the check power state is done, the processor 1900
stages the compressors 601 and 702 and the blower 508 on to assure
that the air conditioner output temperature (measured by the
transducer 544) is not permitted to exceed an undesired level.
Additionally, the processor 1900 stages all of the remaining big
loads on to prevent undue transient loading of the electrical
source of power. Thus, the PAO system 700 is gradually brought up
to pressure and down in temperature, and the vacuum pump 833 clears
the PAO system of air before it comes fully on line.
[0114] While in the check power state 1408, the processor 1900 also
auto-detects the input power type (using transducers 1708 to 1718
shown in FIG. 18) and varies the two air conditioners' 520 and 522
and the PAO system's 700 settings accordingly, degrading the
maximum obtainable performance to reflect less power availability
or the need to provide PAO cooling in addition to air cooling. For
example, if the processor 1900 detects a lower input voltage than a
desired input voltage on the transducers 1710, 1712, and 1716, the
processor 1900 may adjust the setpoints 1317 to provide less
cooling to the airplane to compensate for this. This automatic
response to changing power conditions allows the user seamless use
of the unit regardless of the city or country in which the unit is
being operated.
[0115] If the processor 1900 senses no power or abnormal power for
ten seconds, it disables any machines presently running, attempts
to isolate the power fault, and then enters a system fault
triggering alarm state 1422. Such a system fault is announced with
an audible and visible alarm. So long as any power is available to
it, the processors 1900 and 1306 continue operate, allowing
isolation of the fault and continued use of the remainder of the
modules. Capacitors that momentarily store charge provide brief
continued running time for the processors 1900 and 1306 following a
power failure. In an alternative arrangement, back-up batteries
could be provided within each module to provide the module
processors with continued power to operate and to perform
diagnostics when power is not available for some reason.
[0116] If adequate power is available, the processor 1900 enters
the enable sub-state machines state 1410 where it starts up various
real-time background processes. From the state 1410, the processor
1900 proceeds to the run state 1412. In the run state 1412, the
processor 1900 commences normal operation. Under normal operation,
the processor 1900 achieves the desired output parameters (the
given setpoint temperatures and pressures) as efficiently as
possible by staging the condenser fan 414 to slow and fast settings
and by adjusting the air conditioning and PAO parameters to produce
the desired output. The selected parameters or setpoints are
utilized as is shown in FIG. 15, where the controllers 1502, 1504,
1506, 1508, 1510, 1512, 1514, and 1516 are all implemented as
process control digital algorithms executing as control chains
instituted within the air conditioning and PAO processor 1900 such
that each controller implements a control chain within the
processor 1900 that becomes part of one of the feedback control
loops shown in FIG. 15 within the two air conditioners 520 and 522
and the PAO system 700. Data log processing continues during this
normal operation of the processor 1900.
[0117] Maintenance and diagnostics are also carried out by the two
processors 1900 and 1306. The data log 1319 is collected for use in
predictive failure and enhanced diagnostics. In the event of a
minor component failure or imminent major component failure, the
processor 1306 enters a fail safe state 1418. If, based on the data
collected, there is a danger of continued operation, the processor
1306 announces a fatal system fault and enters the alarm state 1422
and immediately shuts down the unit at 1420. If the data log 1319
indicates that the unit is operating outside of its normal
operating range, the processor 1306 announces a system fault and
enters the alarm state 1422 but does not necessarily shut down the
entire module 400. If the data log 1319 indicates that a problem
may occur in the near future, the processor 1306 may simply
announce a systems warning and enter the fail safe state 1418. The
fail safe state 1418 does not sound an alarm, but it shows an
indication on the display 22 as to the nature of the warning. The
alarm 1422, fail safe 1418, and shutdown 1422 states may be entered
from all other states 1416 in the master process 1300 of the
processor 1900.
[0118] The controller continues normal operation in the run state
1412 until it receives an "Off" or "Stop" command, typically from
one of the menus shown in FIGS. 21, 23, and 25. After receiving the
"Off command," the processor 1900 enters the disable sub-state
machines state 1414. While in this state 1414, the processor 1900
winds down the operation of all of the system components and stores
any data log 1319. The processor 1900 then returns to the idle
state 1406 and awaits another "On" or "Start" command.
[0119] Referring now to FIG. 16, a processor 1900 implemented state
machine 1501 for one of the compressors 601 or 702 is shown. The
compressor state machine 1501 begins in an idle state 1503. Once
the processor 1900 enables the compressor state machine 1501 and
there is no current fault, the compressor state machine 1501 enters
the wait state 1505. While in the wait state 1505, the compressor
state machine 1501 runs a short cycle timer to produce a delay.
Once the short cycle timer reaches zero, the compressor state
machine 1501 moves from the wait state 1505 to the starting state
1507 and starts the compressor 601 or 702. While in the starting
state 1507, the compressor state machine 1501 pauses for thirty
seconds before advancing to the running state 1509.
[0120] The compressor state machine 1501 remains in the running
state 1509, and the compressor 601 or 702 continues to operate,
until the processor 1900 signals for the compressor to be disabled.
Once the compressor disable command is received, the compressor
state machine 1501 moves from the running state 1509 to the shut
down state 1511. The compressor state machine 1501 may be signaled
that the compressor has been disabled during any normal state 1513
in case of a system fault. Upon receipt of such a signal, the
compressor state machine 1501 enters the shut down state 1511.
Finally, from the shut down state 1511, the compressor state
machine 1501 reenters the idle state 1503.
[0121] Referring now to FIG. 17, the blower 508 state machine 1600
is shown. The goal of the blower state machine 1600 is to achieve
the desired flow rate of air and pressure to meet the operating
parameters of any given airplane by controlling the variable speed
impeller located within the duct of the two air conditioners. The
blower 508 begins in an idle state at 1602. Once the processor 1900
enables the blower state machine 1600 and provides a pressure
operating setpoint, the blower state machine enters a first of two
troubleshooting states 1604. In this state, the impeller is set to
low speed to troubleshoot any initial problems, such as a blockage
or failure of the blower 508 to operate. The blower state machine
1600 then enters a second troubleshooting state 1606 in which
checks of pressure and power to the blower 508 are run to see if an
air duct 26 is connected between the cart 10 and an airplane or if,
in some other respect, there is bad pressure. If no air duct 26 is
connected, or if the air duct 26 is connected to the wrong type or
class of airplane, or if sensors on the blower system otherwise
sense bad pressure readings for ten seconds, the blower state
machine 1600 will enter the alarm state 1622, giving forth an
appropriate warning to the operator.
[0122] If an air duct 26 is connected and there is otherwise good
pressure, the blower state machine 1600 will enter the adjust
blower motor frequency state 1610. Here the motor 506 A.C. power
frequency is set. The blower state machine 1600 then enters a state
1608 where it checks the pressure change across the blower 508. If
no air duct 26 is connected, or if the air duct 26 is connected to
the wrong type or class of airplane, or if sensors on the blower
system otherwise sense bad pressure for ten seconds, once again the
blower state machine 1600 enters the alarm state 1622, giving forth
an appropriate warning to the operator. If an air duct 26 is
connected and if there is good pressure, and if a type or class of
airplane has been selected using the menu shown in FIG. 21, then
the pressure change across the blower 508, measured by the
differential pressure sensor 532 (FIG. 5), and the power consumed
by the blower voltage-to-frequency converter 525, measured by
multiplying the voltage 1720 by the current 1722 (FIG. 18), are
compared to normal logged values found in the data log 1319 for the
type or class of airplane that was selected on the menu shown in
FIG. 21. If the pressure and power consumed do not correspond to
that type of airplane, then the operator is given an alarm 1622 and
the idle state 1602 is entered while the problem is checked
out.
[0123] The blower state machine 1600 next checks the blower map
1612. The blower map contains data that helps guide and shape the
control algorithm within the processor 1900 that sets the blower
motor frequency. This data sets the operational limits of the
blower system and also includes information assessing the health of
the blower system.
[0124] If the status data of the blower 508 is contained within the
blower map, the blower state machine 1600 enters a state 1614 where
the blower 508 is permitted to run at a given frequency while the
deviation of the cart 10 output pressure (as measured by the
pressure transducer 526) is checked. If the deviation or error
exceeds a threshold value (step 1650), then the blower frequency is
once again adjusted at step 1615 to minimize the error.
[0125] If, at step 1612, data for the blower is not found within
the blower map, the blower state machine 1600 enters the alarm
state 1422 and shuts down the air conditioners.
[0126] FIG. 18 presents a partly block and partly schematic diagram
of the signal and electrical power connections to the compressors
601 and 702, the two speed condenser fan 414, and the blower 508,
its motor 506, and its voltage-to-frequency converter 525. The
locations of voltage and current sensors are shown, all of which
feed signals into the air conditioning and PAO processor 1900 shown
in FIG. 19. Signals generated by the processor 1900 (shown in FIG.
19) and fed into the components 601, 702, 414, and 525 are also
shown in FIG. 18 to complete the disclosure of all significant
signals connecting the processor 1900 to the various air
conditioning processes.
[0127] FIG. 19 presents the air conditioning and PAO processor
1900. FIG. 19 reveals and lists and categorizes all of the signals
that flow from various types of sensors associated with the air
conditioning processes and the PAO process into the processor 1900.
It also reveals and lists and categorizes all of the control
signals generated by the processor 1900 that flow back to and that
control the components of the air conditioning processes and the
PAO process. In FIG. 19, all the signals are identified by name and
by the same reference number that is assigned to the transducer
that is the source of an incoming signal or to the device that is
the target of an outgoing signal. "PRE-C" is a signal relating to
the pre-cool air conditioner 520 shown primarily in FIG. 6.
"POST-C" is a signal relating to the post-cool air conditioner 522
shown in FIG. 7. "PAO" is a signal relating to the PAO liquid
coolant processor shown in FIG. 8. Many of the signals shown in
FIG. 19 which relate to the actual control of processes are also
shown in the process control diagram presented in FIG. 12. Other
signals originate in or go to FIG. 18. The use of these signals has
already been explained above.
[0128] While an embodiment of the invention has been disclosed,
those skilled in the art will recognize that numerous modifications
and changes may be made without departing from the true spirit and
scope of the claims as defined by the claims annexed to and forming
a part of this specification.
* * * * *