U.S. patent application number 13/673036 was filed with the patent office on 2014-05-15 for systems and methods for directing cooling flow into the surge plenum of an exhaust eductor cooling system.
This patent application is currently assigned to HONEYWELL INTERNATIONAL INC.. The applicant listed for this patent is HONEYWELL INTERNATIONAL INC.. Invention is credited to Bruce Dan Bouldin, Yogendra Yogi Sheoran, Eric Shepard, Larry Smalley.
Application Number | 20140130510 13/673036 |
Document ID | / |
Family ID | 49328385 |
Filed Date | 2014-05-15 |
United States Patent
Application |
20140130510 |
Kind Code |
A1 |
Bouldin; Bruce Dan ; et
al. |
May 15, 2014 |
SYSTEMS AND METHODS FOR DIRECTING COOLING FLOW INTO THE SURGE
PLENUM OF AN EXHAUST EDUCTOR COOLING SYSTEM
Abstract
A method and apparatus is provided for cooling the external
surface of an aircraft APU eductor assembly. A processor is
configured to open a surge valve by a predetermined amount when the
surge valve is closed and the temperature of the exhaust gas
exceeds a predetermined temperature in order to cool the surge
plenum surfaces.
Inventors: |
Bouldin; Bruce Dan;
(Phoenix, AZ) ; Shepard; Eric; (Phoenix, AZ)
; Smalley; Larry; (Phoenix, AZ) ; Sheoran;
Yogendra Yogi; (Scottsdale, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HONEYWELL INTERNATIONAL INC.; |
|
|
US |
|
|
Assignee: |
HONEYWELL INTERNATIONAL
INC.
Morristown
NJ
|
Family ID: |
49328385 |
Appl. No.: |
13/673036 |
Filed: |
November 9, 2012 |
Current U.S.
Class: |
60/782 ;
60/785 |
Current CPC
Class: |
F01D 25/12 20130101;
B64D 33/08 20130101; B64D 41/00 20130101; F02C 3/32 20130101; F05D
2220/50 20130101; F02C 7/14 20130101; Y02T 50/675 20130101; Y02T
50/60 20130101 |
Class at
Publication: |
60/782 ;
60/785 |
International
Class: |
F01D 25/12 20060101
F01D025/12 |
Claims
1. A method for cooling the external surface of an aircraft APU
inductor assembly surge plenum, comprising diverting customer
airflow to the surge plenum when there is otherwise no surge
flow.
2. The method of claim 1 wherein the step of diverting comprises
opening a surge valve by a predetermined amount.
3. The method of claim 2 wherein the step of opening comprises
opening the surge valve at least ten percent.
4. The method of claim 3 wherein the step of opening comprises
opening the surge valve no more than fifteen percent.
5. The method of claim 2 wherein the step of opening comprises
opening the surge valve if the temperature of APU exhaust is at
least 1,000.degree. F.
6. The method of claim 2 further comprising opening the surge valve
if an APU inlet door is open no more than thirty degrees.
7. The method of claim 2 further comprising determining if the
aircraft is on the ground.
8. The method of claim 2 further comprising first determining if
the surge valve is closed.
9. The method of claim 2 wherein the step of opening comprises
opening the surge valve between ten and fifteen percent.
10. An eductor system for use in conjunction with an aircraft APU,
the system comprising: a surge plenum; a surge duct coupled to the
surge plenum for providing excess airflow not required by the
aircraft to the surge plenum; and a processor coupled to the surge
duct and configured to divert airflow to the surge plenum when
there is otherwise no excess customer airflow, the diverted air for
cooling the surge plenum.
11. The system of claim 10 further comprising a surge valve coupled
to the surge duct, and wherein the processor is configured to open
the surge valve between ten and fifteen percent to divert air to
the surge plenum.
12. The system of claim 11 further comprising an exhaust gas
temperature sensor and wherein the processor is configured to open
the surge valve when the APU exhaust gas exceeds a predetermined
temperature.
13. The system according to claim 12 wherein the predetermined
temperature is 1,000.degree. F.
14. The system of claim 13 further comprising an APU inlet door and
wherein the processor is configured to open the surge valve when
the inlet door is open no more than thirty degrees.
15. The system of claim 14 further comprising an altitude sensor
coupled to the processor and wherein the processor opens the surge
valve when the aircraft is on the ground.
16. The system according to claim 10 wherein the surge valve is
opened between then and fifteen percent.
17. A method for cooling the external surface of an aircraft APU
eductor assembly surge plenum, comprising diverting customer
airflow to the surge plenum by opening a surge valve between ten
and fifteen degrees when the APU exhaust gas temperature exceeds
1,000.degree. F.
18. The method of claim 17 wherein the step of diverting comprises
first determining if the aircraft is on the ground.
19. The method of claim 17 wherein the step of diverting comprises
first determining if the surge valve is closed.
20. The method of claim 17 wherein the step of diverting comprises
first determining if the APU inlet door is open no more than thirty
degrees.
Description
TECHNICAL FIELD
[0001] Embodiments described herein relate to an exhaust eductor
system, and more particularly, to a system and method for cooling
the surge plenum of an eductor exhaust system.
BACKGROUND
[0002] Many modern aircraft are equipped with an auxiliary power
unit ("APU") that generates and provides electrical and pneumatic
power to various parts of the aircraft for tasks such as
environmental cooling, lighting, powering electronic systems, and
main engine starting. Typically, such APUs are located in the aft
section of the aircraft such as the tail cone and are isolated by a
firewall. During operation, an APU produces exhaust gas that is
directed through a nozzle and out of the aircraft through an
exhaust opening. The nozzle may communicate with an eductor system
that utilizes the APU exhaust gas to draw and direct other gases
through the aircraft.
[0003] To achieve this, eductor systems have been developed that
include a first plenum (i.e. the oil cooler plenum) that draws gas
across an oil cooler, and a second plenum (i.e. the surge plenum)
that directs surge flow to an exhaust duct (i.e. air not required
by the aircraft to satisfy its pneumatic requirements, commonly
referred to as surge bleed flow or customer airflow. The cooling
plenum collects the air as it exits the oil cooler and allows the
airflow to pass into the exhaust stream. The surge plenum collects
the surge airflow before it passes into the exhaust airflow.
[0004] As previously stated, surge airflow occurs when the APU
system produces more customer airflow than is required by the
aircraft. In this case, a customer bleed valve will close to
restrict the amount of airflow provided to the aircraft. To prevent
the APU compressor from surging, a second valve (i.e. the surge
valve) will open. This open surge valve directs the excess air flow
(i.e. the surge flow) into the surge plenum and then into the
exhaust.
[0005] During normal APU operation, the surge valve is frequently
closed providing no airflow into the surge plenum. When this
occurs, the surge plenum becomes a dead-headed cavity permitting
hot exhaust gases to flow into it. The accumulation of hot exhaust
gases in the surge plenum heats the exterior skin of the surge
plenum to unacceptable levels. These high temperatures on the
exterior skin of the eductor can potentially damage tail cone
skins.
[0006] Furthermore, the aft facing outlet of the dead-headed surge
plenum cavity is exposed to the mixed eductor flow; i.e. the
turbine exhaust at perhaps 1000.degree. F. and the cooling air from
the cooling plenum at approximately 200.degree. F. Thus, the mixed
eductor flow, which may be about 500.degree. F., enters the surge
plenum, circulating in and out of the surge plenum, and heating the
surge plenum to approximately 500.degree. F., exceeding the strict
temperature limits (i.e. 450.degree. F.) that is imposed on the
outer surfaces of the APU including the surge plenum.
[0007] In accordance with the forgoing, it would be desirable to
provide a system and method for directing a cooling flow into the
surge plenum to reduce the temperature of the surge plenum surfaces
when there is otherwise no surge flow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a cross-sectional view of an aircraft auxiliary a
power unit (APU) including an eductor system disposed therein;
[0009] FIG. 2 is a cross-sectional view of an exemplary eductor oil
cooler and surge flow plenum assembly that may be incorporated into
the tail cone depicted in FIG. 1;
[0010] FIG. 3 is a cross-sectional view of the exemplary eductor
oil cooler and surge flow plenum illustrating the recirculation of
exhaust gas in the surge plenum when there is no surge flow;
[0011] FIG. 4 is a flow-chart illustrating an exemplary embodiment
of a process for determining when airflow should be diverted to the
surge plenum;
[0012] FIG. 5 is a block diagram of a system for carrying on the
process described in FIG. 4;
[0013] FIG. 6 is an isometric view of an APU exhaust nozzle;
and
[0014] FIG. 7 is a graph illustrating the improvement in surge
plenum skin temperature when the techniques described herein are
employed.
BRIEF SUMMARY
[0015] This summary is provided to introduce a selection of
concepts in a simplified form that are further described below in
the detailed description. This summary is not intended to identify
key features or essential features of the claimed subject matter,
nor is it intended to be used as an aid for determining the scope
of the claimed subject matter.
[0016] In accordance with the foregoing, there is provided a method
for cooling the external surface of an aircraft APU inductor
assembly surge plenum comprising diverting customer airflow to the
surge plenum when there is otherwise no surge flow.
[0017] There is also provided an eductor system for use in
conjunction with an aircraft APU. The system comprises a surge
plenum and a surge duct for providing excess air not required by
the aircraft to the surge plenum. A processor is coupled to the
surge duct and the surge plenum and is configured to divert air
intended for the aircraft to the surge plenum when there is no
excess air, the diverted air for cooling the surge plenum.
[0018] Also, provided is a method for cooling the external surface
of an aircraft APU eductor assembly surge plenum when there is
otherwise no surge flow, comprising diverting customer air to the
surge plenum by opening a surge valve between ten and fifteen
percent when the APU exhaust gas temperature exceeds 1,000.degree.
F.
DETAILED DESCRIPTION
[0019] The following detailed description is merely illustrative in
nature and is not intended to limit the embodiments of the subject
matter or the application and uses of such embodiments. As used
herein, the word "exemplary" means "serving as an example,
instance, or illustration." Any implementation described herein as
exemplary is not necessarily to be construed as preferred or
advantageous over other implementations. Furthermore, there is no
intention to be bound by any expressed or implied theory presented
in the preceding technical field, background, brief summary or the
following detailed description.
[0020] Techniques and technologies may be described herein in terms
of functional and/or logical block components and with reference to
symbolic representations of operations, processing tasks, and
functions that may be performed by various computing components or
devices. Such operations, tasks, and functions are sometimes
referred to as being computer-executed, computerized,
software-implemented, or computer-implemented. It should be
appreciated that the various block components shown in the figures
may be realized by any number of hardware, software, and/or
firmware components configured to perform the specified functions.
For example, an embodiment of a system or a component may employ
various integrated circuit components, e.g., memory elements,
digital signal processing elements, logic elements, look-up tables,
or the like, which may carry out a variety of functions under the
control of one or more microprocessors or other control
devices.
[0021] Turning now to the description, FIG. 1 illustrates a housing
100 within which a power unit 102, an eductor 104, an oil cooler
105, and an air plenum 107 are disposed. The housing 100, which may
be an aircraft tail cone or helicopter housing, is generally
conical and has a sidewall 108, an inlet door 111, inlet 110, an
inlet duct 112, and an exhaust opening 114 formed therein. The
power unit 102, which may be an auxiliary power unit ("APU"), used
to drive a number of non-illustrated devices, including, for
example, a gearbox, a generator, etc., is mounted within the
housing 100 and receives air from inlet duct 112. The power unit
102 communicates with the eductor 104 and may include an engine
compressor, an engine, and a turbine, as is well known. It will be
appreciated that the power unit 102 and eductor 104 may indirectly
or directly communicate with each other. In any case, exhaust gas
from the power unit 102 flows through the eductor 104 and nozzle
109 and exits the aircraft via the exhaust opening 114. Also shown
in FIG. 1 is a load compressor and scroll 116 which supplies air to
bleed duct 115 and surge duct 117. Cooperating with bleed duct 115
is a bleed valve 118 and surge valve 119.
[0022] Surge airflow occurs when the aircraft requires less
customer airflow than the APU is producing. When this happens,
bleed valve 118 closes; however, to prevent load compressor 116
from surging, surge valve 119 will open producing a surge flow into
the surge plenum 122 (FIGS. 2 and 3), which is subsequently drawn
into the exhaust flow and exits at exhaust opening 114. However,
surge valve 119 is frequently closed providing no air to the surge
plenum, permitting hot exhaust gasses to accumulate in the surge
plenum, which in turn heats the exterior skin of the surge plenum
to unacceptable levels as previously described.
[0023] Referring now to FIG. 2, an oil cooler plenum 120 includes a
fluid inlet 134 and a fluid outlet 136. The fluid inlet 134
communicates with an oil cooler duct 138 in cooperation with which
an oil cooler 105 is disposed. Preferably, the oil cooler plenum
120 surrounds an entire circumference of nozzle 114 to maximize
contact between high velocity APU exhaust gas that flows through
the nozzle 114 and the gas that is pulled through the oil cooler
plenum 120 to thereby increase pumping of gas through the fluid
inlet 134. To further increase pumping of gas through the fluid
inlet 134, the fluid outlet 136 is aligned with an end 144 of the
nozzle 114. Thus, gas flowing through the fluid outlet 136 will be
entrained by the high velocity APU exhaust gas and both will flow
together through the exhaust duct 113 (shown in FIG. 1).
[0024] It will be appreciated that the volume of space needed to
accommodate the cooled gas decreases as distance from the fluid
inlet 134 increases, and that the gas in the oil cooler plenum 120
preferably flows around the circumference of nozzle 114 at a
substantially constant flow velocity. In this regard, wall 126 may
slope toward the longitudinal axis 116 forward to aft and is
disposed nonconcentric ally therewith. As a result, the oil cooler
plenum 120 includes a plurality of variously sized radial
cross-sectional areas at different axial locations along the
longitudinal axis 116 and a plurality of variously sized axial
cross-sectional areas at different angular locations relative to
the longitudinal axis 116. The cross-sectional areas, which,
preferably gradually decrease in size when the distance from the
fluid inlet 134 increases, may be disposed asymmetrically about the
longitudinal axis 116.
[0025] The surge flow plenum 122 is partially defined by walls 126
and 132 and includes a fluid inlet 154 and a fluid outlet 156. The
fluid inlet 154 communicates with a surge bleed entry duct 158 that
is coupled to or integrally formed as part of the outer wall 132.
The fluid outlet 156 is preferably axially aligned with and
coterminous with the oil cooler plenum fluid outlet 136.
[0026] Similar to the oil cooler plenum 120, the surge flow plenum
122 preferably includes a plurality of variously sized axial
cross-sectional areas at different angular locations relative to
the longitudinal axis 116. Most preferably, the areas of the axial
cross-sections gradually decrease as the distance away from the
surge flow fluid inlet section increases without overlapping the
oil cooler plenum 120. In other embodiments, the oil cooler plenum
120 may surround the first circumferential section of the nozzle
109 (FIG. 1) and the surge flow plenum 122 may surround the second
circumferential section and a portion of the first circumferential
section.
[0027] During operation, the power unit 102 directs high velocity
exhaust gas out of nozzle 109. When gas is needed to cool the oil
cooler 140, the gas enters the oil cooler 140, travels through
fluid inlet 134, and flows through the oil cooler duct 138 into the
oil cooler plenum 120. When the gas exits the oil cooler fluid
outlet 136, it is pulled through the exhaust duct 113 by the high
velocity exhaust gas. The pull of the exhaust gas causes additional
gas to be pumped into the oil cooler plenum 120. Occasionally,
surge flow gas may be dumped into the surge bleed entry duct 158
and into the surge flow plenum 122 as previously described.
[0028] As stated earlier, when there is no surge flow, the surge
plenum becomes a dead-headed cavity with its aft outlet exposed to
the mixed eductor flow which is about 500.degree. F. This flow
enters the surge plenum 122 and may continuously recirculate in and
out of the surge plenum 122 heating the surge plenum surface to an
unacceptable level. This situation is illustrated in FIG. 3. With
no surge flow in to surge plenum 122, heated mixed eductor flow 160
recirculates in and out of surge plenum 122 as is indicated by
arrows 162 and 164.
[0029] Embodiments described herein contemplate the diversion and
use of a portion of the customer airflow being generated by the APU
to purge the hot air recirculating in the surge plenum as described
in connection with FIG. 3. It has been discovered that the use of a
small portion of the customer airflow for this purpose does not
significantly impact the customer. Thus, the external wall of the
eductor plenum may be cooled by opening the surge valve a
predetermined amount to divert customer airflow into the surge
plenum.
[0030] FIG. 4 is a flow chart of an exemplary embodiment for
determining when customer air should be diverted to the surge
plenum. It has been determined that there are four conditions
precedent to taking corrective action; i.e. diverting customer
airflow into the surge plenum. First, it should be determined that
the APU exhaust gas temperature (EGT) has reached a predetermined
temperature (e.g. greater than 1,000.degree. F.) (STEP 700). This
may be accomplished my means of a processor that monitors the EGT
by means of temperature probes positioned in the exhaust gas flow
stream. Of course this threshold temperature may vary depending on
the eductor plenum material, plenum size and shape, proximity of
the tail cone to the hot eductor surfaces, etc. In addition, the
APU inlet door 111 should be less than a predetermined angle such
as thirty degrees. Once again, this may vary depending on
circumstances such as customer power requirements (STEP 702). It
should be understood that the problem of excessive surge plenum
skin temperature occurs mostly when the aircraft is on the ground
but consuming customer air; e.g. during passenger boarding.
Therefore, it is determined whether or not the aircraft is on the
ground (STEP 704). This may be accomplished, for example, providing
the processor with the output of a weight-on-wheels (WOW) sensor.
Finally, it should be determined if the surge valve is currently
closed (STEP 706). Finally, the processor knows and controls the
position of the surge valve. It should be understood that while the
determinations made in STEPS 700, 702, 404 and 706 are shown as
occurring sequentially, they may occur in any order, and in a
preferred embodiment will occur substantially simultaneously.
[0031] If any of the questions asked in STEPS 700, 702, 404 and 706
are answered in the negative, the system determines if the surge
valve is closed (STEP 708). If not, the surge valve is closed (STEP
710), and the process returns to START. If all conditions precedent
are met, the surge valve is opened (STEP 712) by, for example,
10-15% providing air to the surge plenum to cool its outer
skin.
[0032] FIG. 5 is a block diagram of a system for carrying out the
process of FIG. 4. As can be seen, a processor 720 receives (1) the
exhaust gas temperature (EGT) from probes in the exhaust stream
722; (2) an indication that the aircraft is on the ground from WOW
sensor 724; the degree to which APU inlet door 726 is open
(monitored by processor 720); and an indication of whether or not
the surge valve is open or closed from 728 (monitored and
controlled by processor 720). As indicated above, processor 720
receives an indication of whether or not the surge valve is open or
closed and will open the surge valve if the conditions precedent
described earlier are met.
[0033] FIG. 5 is a simplified block representation, and for the
sake of clarity and brevity, does not depict the vast number of
systems and subsystems that would appear onboard a practical
implementation of an aircraft. Instead, FIG. 1 merely depicts some
of the notable functional elements and components that support the
various features, functions, and operations described herein. In
this regard, the aircraft may include, without limitation: a
multiple processor architecture; one or more primary thrust
engines; an engine-based taxi system; a fuel supply; wheel
assemblies; an auxiliary power unit (APU); an electric taxi system;
and a brake system. These elements, components, and systems may be
coupled together as needed to support their cooperative
functionality.
[0034] Each processor architecture 720 may be implemented or
realized with at least one general purpose processor, a content
addressable memory, a digital signal processor, an application
specific integrated circuit, a field programmable gate array, any
suitable programmable logic device, discrete gate or transistor
logic, discrete hardware components, or any combination designed to
perform the functions described herein. A processor device may be
realized as a microprocessor, a controller, a microcontroller, or a
state machine. Moreover, a processor device may be implemented as a
combination of computing devices, e.g., a combination of a digital
signal processor and a microprocessor, a plurality of
microprocessors, one or more microprocessors in conjunction with a
digital signal processor core, or any other such configuration. As
described in more detail below, the processor architecture 720 is
configured to support various processes, operations, and display
functions.
[0035] In practice, processor 720 may be realized as an onboard
component of an aircraft (e.g., a flight deck control system, a
flight management system, or the like), or it may be realized in a
portable computing device that is carried onboard the aircraft. For
example, the processor 720 could be realized as the central
processing unit (CPU) of a laptop computer, a tablet computer, or a
handheld device.
[0036] Processor 720 may include or cooperate with an appropriate
amount of memory (not shown), which can be realized as RAM memory,
flash memory, EPROM memory, EEPROM memory, registers, a hard disk,
a removable disk, a CD-ROM, or any other form of storage medium
known in the art. In this regard, the memory can be coupled to
processor 720 such that the processor can read information from,
and write information to, the memory. In the alternative, the
memory may be integral to the processor architecture. In practice,
a functional or logical module/component of the system described
here might be realized using program code that is maintained in the
memory. Moreover, the memory can be used to store data utilized to
support the operation of the system.
[0037] FIG. 6 is an isometric view of the nozzle portion 109
through which the exhaust gasses flow, and FIG. 7 illustrates the
temperature characteristics at locations 730 (close to oil cooler
140) and 732 (at top center of the eductor system approximately
thirty degrees counterclockwise from 730) as a function of the
position of the surge valve. During time period T.sub.1, the surge
valve is closed, and the temperature is approximately
276-283.degree. C. During time period T.sub.2, the surge valve is
only slightly opened (less than ten percent) as shown in FIG. 7.
While there is a slight initial drop in temperature (25-30.degree.
C.), the temperature rapidly increases to substantially its
original value. However, during time period T.sub.3, the surge
valve is opened to between ten and fifteen percent, and the
temperature drop is significant; i.e. approximately 70.degree. C.
or approximately twenty-five percent. Above ten percent, the
temperature again rises.
[0038] Thus, there has been provided a system and method for
directing a cooling flow into the surge plenum to reduce the
temperature of the surge plenum surfaces when there is otherwise no
surge flow by diverting aircraft customer air to the surge plenum
without significantly impacting aircraft operation.
[0039] While at least one exemplary embodiment has been presented
in the foregoing detailed description, it should be appreciated
that a vast number of variations exist. It should also be
appreciated that the exemplary embodiment or embodiments described
herein are not intended to limit the scope, applicability, or
configuration of the claimed subject matter in any way. Rather, the
foregoing detailed description will provide those skilled in the
art with a convenient road map for implementing the described
embodiment or embodiments. It should be understood that various
changes can be made in the function and arrangement of elements
without departing from the scope defined by the claims, which
includes known equivalents and foreseeable equivalents at the time
of filing this patent application.
* * * * *