U.S. patent application number 13/086309 was filed with the patent office on 2011-08-04 for emergency power engine restart system.
This patent application is currently assigned to HONEYWELL INTERNATIONAL INC.. Invention is credited to STEVEN R. ECCLES, MIKE S. KOERNER, FILIP A. REINIS.
Application Number | 20110185745 13/086309 |
Document ID | / |
Family ID | 40220375 |
Filed Date | 2011-08-04 |
United States Patent
Application |
20110185745 |
Kind Code |
A1 |
ECCLES; STEVEN R. ; et
al. |
August 4, 2011 |
EMERGENCY POWER ENGINE RESTART SYSTEM
Abstract
An engine starting apparatus and method may allow for two
methods of engine start where only one engine gearbox accessory pad
exists off the aircraft engine. A gearbox lubricating apparatus may
also be provided to lubricate the gearbox at altitude without added
complexity. Two engine starting inputs (for example, one input for
ground start and one input for in-flight engine start) are provided
while avoiding complex gearbox designs. Clutches may also be used
to prevent the starter gearbox from continuous operation (rotation)
after the engine has started. Apparatus and methods are also
provided for improving the air-fuel combustion of the hot-gas
turbine start input (for in-flight engine start) to minimize the
build-up of solid carbon (soot) in and around the combustor and
turbine nozzle flow passages.
Inventors: |
ECCLES; STEVEN R.;
(TORRANCE, CA) ; KOERNER; MIKE S.; (RANCHO PALOS
VERDES, CA) ; REINIS; FILIP A.; (LONG BEACH,
CA) |
Assignee: |
HONEYWELL INTERNATIONAL
INC.
MORRISTOWN
NJ
|
Family ID: |
40220375 |
Appl. No.: |
13/086309 |
Filed: |
April 13, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11772675 |
Jul 2, 2007 |
7937949 |
|
|
13086309 |
|
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Current U.S.
Class: |
60/778 |
Current CPC
Class: |
F05D 2260/84 20130101;
F02C 7/268 20130101 |
Class at
Publication: |
60/778 |
International
Class: |
F02C 7/26 20060101
F02C007/26 |
Claims
1. A method for in-flight engine start using an engine start
system, the method comprising: burning fuel and air in a combustor
to drive a turbine; turning a starter gear via the rotation of the
turbine, wherein the starter gear is mounted on an accessory pad of
the engine; disconnecting a ground-based engine starter with an
over-running clutch; and driving an engine shaft through the
rotation of the starter gear to affect engine start or restart.
2. The method according to claim 1, further comprising driving a
pitot pump lubrication system from rotation of the turbine to
lubricate the starter gear of the engine start system.
3. The method according to claim 1, wherein the step of burning the
fuel and air in the combustion chamber includes burning the fuel
incompletely.
4. The method according to claim 3, wherein the step of burning the
fuel incompletely is accomplished by at least one of the following
techniques: the combustor has a characteristic length of less than
about 486 inches; the air to fuel ratio is below about 3.5:1; and
the fuel has a Sauter Mean Diameter of about 20 microns or
greater.
5. A method of starting an engine comprising: enabling a gearbox to
be selectively connectable to turn an engine shaft; enabling a hot
gas turbine to be selectively connectable to drive the gearbox to
turn the engine shaft; and enabling an air turbine to be
selectively connectable to turn the engine shaft.
6. The method according to claim 5, wherein the hot gas turbine has
a combustor with a characteristic length of less than about 486
inches.
7. The method according to claim 6, wherein an air to fuel ratio is
below about 3.5:1.
8. The method according to claim 5, further comprising producing
fuel droplets with a Sauter Mean Diameter of about 20 microns or
greater.
9. The method according to claim 5, further comprising:
disconnecting the air turbine when torque is applied to the engine
shaft by either the engine or by the gearbox.
10. The method according to claim 5, further comprising:
disconnecting the gearbox when torque is applied to the engine
shaft by the engine.
11. The method according to claim 5, further comprising:
disconnecting the gearbox when the air turbine is operating.
12. The method according to claim 5, wherein: the gearbox includes
a starter gear, an idler gear, a compound gear, a turbine pinion
gear and a pitot pump gear; a hot gas turbine drives the turbine
pinion gear; the turbine pinion gear drives the compound gear; the
compound gear has two separate spur gears, a first spur gear which
receives rotational torque from the turbine pinion gear, and a
second spur gear which drives both the pitot pump gear and the
idler gear; and the idler gear turns the starter gear, which, in
turn, drives the engine shaft.
13. The method according to claim 12, wherein the starter gear, the
idler gear, the compound gear, the turbine pinion gear and the
pitot pump gear are spur gears.
14. A method of starting an engine comprising: selectively
connecting an air turbine starter to turn an engine shaft;
attaching a gearbox to an accessory pad of the engine, the gearbox
being connected to turn the engine shaft only if the air turbine
starter is disconnected from the engine shaft; enabling a hot gas
turbine to drive the gearbox to turn the engine shaft.
15. The method according to claim 14, further comprising: turning
oil by a gear in the gearbox to generate a circular velocity of the
oil.
16. The method according to claim 15, further comprising:
delivering the oil to locations in the gearbox requiring
lubrication.
17. The method according to claim 14, further comprising:
disconnecting a ground-based engine starting system when torque is
applied to the engine shaft by either the engine or by the
gearbox.
18. The method according to claim 14, further comprising:
disconnecting the gearbox when torque is applied to the engine
shaft by the engine.
19. The method according to claim 14, further comprising:
disconnecting the gearbox when a ground-based engine starting
system is operating.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a divisional of and claims the benefit
of U.S. patent application Ser. No. 11/772,675, filed Jul. 2, 2007,
which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention generally relates to engine restart
systems and methods and, more specifically, to an emergency power
engine restart system and method having separate hot and cold gas
turbine wheels and an interconnecting gearbox.
[0003] In an aircraft gas turbine engine, an electric starter motor
may be used to apply torque to the engine's shaft in order to start
the engine. Alternatively, gas turbine engines may be started on
the ground by providing a stream of pressurized air from a ground
cart to an air turbine starter which can apply torque to the
engine's shaft in order to start the engine. As the shaft starts to
rotate, air is inducted into the compressor, compressed and then
discharged into the combustor. Concurrently, the engine's fuel
control system feeds fuel into the combustor in accordance with a
pre-programmed fuel schedule in order to precisely maintain the
proper fuel/air ratio in the combustor, thereby achieving a
light-off condition. After light-off, the starter torque is
augmented by torque from the engine's turbine. Before reaching
idling speed of the engine, the starter is shut off. This operation
constitutes a starting cycle of a gas turbine engine.
[0004] Typically, propulsion engines on aircraft will have an
accessory gearbox either mounted to the engine or mounted to the
airframe. Either way, this gearbox is connected to the shaft of the
turbine engine. Typically, there are several "pads" located on this
gearbox where several accessory components can attach and be driven
by the gear and shafts within the gearbox. The accessories can be
pumps, generators, and the like. For example, U.S. Pat. No.
4,372,517 discloses engine accessory pads for mounting a gearbox
onto the shaft of a turbine engine.
[0005] Engine starters may also be connected to the main engine
shaft via accessory gearboxes. U.S. Pat. No. 3,951,008 describes a
gearbox used to start a turbine engine. The gearbox may include two
inputs and one overrunning clutch. The two inputs are used in
sequence to perform the starting process. One starter input is used
to drive from zero rpm up to a particular speed, through the
clutch. Then, the second starter input acts to slip the overrunning
clutch and bring the turbine up to full starting speed. Both inputs
are required to bring the engine up to starting speed.
[0006] U.S. Pat. No. 5,201,798 describes an assembly which combines
the function of both an auxiliary power unit (APU) and an emergency
power unit (EPU) into one unit. The unit also includes the primary
APU turbine engine. The gearbox utilized in the '798 patent has
several output shaft pads to drive pumps and an electrical
generator. The '798 patent describes the use of an air turbine
starter mounted onto the gearbox via a clutch to permit
disengagement once the engine is started. There is also a hot-gas
impulse turbine attached to the gearbox via another clutch, which
allows for EPU restarts during flight. The '798 system is a single
integrated system which may require complex disassembly and
maintenance procedures for system servicing.
[0007] As can be seen, there is a need for a simple engine restart
system which may be attached to the primary engine accessory
gearbox via a single drive shaft pad. Moreover, there is
a.sub..need for an engine restart apparatus and method providing
dual turbine inputs for ground starting and in-flight engine
restart capability.
SUMMARY OF THE INVENTION
[0008] In one aspect of the present invention, a starting apparatus
for an engine comprises a ground-based engine starting system
connected to turn an engine shaft; and a gearbox connected to an
accessory pad of the engine, the gearbox connected to turn the
engine shaft.
[0009] In another aspect of the present invention, a starting
apparatus for an engine comprises an air turbine starter connected
to turn an engine shaft; a gearbox connected to an accessory pad of
the engine, the gearbox connected to turn the engine shaft; a hot
gas turbine driving the gearbox, the hot gas turbine including a
combustor for burning fuel and air to give a hot gas exhaust to
drive the hot gas turbine; and a pitot pump lubrication system
comprising an oil trough containing oil, the oil being turned by a
gear in the gearbox to generate a circular velocity of the oil, and
an open-ended tube receiving the oil and delivering the oil to
locations in the gearbox requiring lubrication.
[0010] In a further aspect of the present invention, a method for
in-flight engine start using an engine start system comprises
burning fuel and air in a combustor to drive a turbine; turning a
starter gear via the rotation of the turbine, wherein the starter
gear is mounted on an accessory pad of the engine; disconnecting a
ground-based engine starter with an over-running clutch; and
driving an engine shaft through the rotation of the starter gear to
affect engine start or restart.
[0011] These and other features, aspects and advantages of the
present invention will become better understood with reference to
the following drawings, description and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a cross-sectional view of an emergency power
engine restart system according to the present invention;
[0013] FIG. 2 is a partially cut-away end view of the emergency
power engine restart system of FIG. 1;
[0014] FIG. 3 is an end view of the emergency power engine restart
system of FIG. 1;
[0015] FIG. 4 is a close-up view showing one clutch configuration
for the emergency power engine restart system according to the
present invention;
[0016] FIG. 5 is a close-up view showing another clutch
configuration for the emergency power engine restart system
according to the present invention; and
[0017] FIG. 6 is a flow chart describing a method for emergency
power engine restart according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The following detailed description is of the best currently
contemplated modes of carrying out the invention. The description
is not to be taken in a limiting sense, but is made merely for the
purpose of illustrating the general principles of the invention,
since the scope of the invention is best defined by the appended
claims.
[0019] Broadly, the present invention provides an engine starting
apparatus and method having two methods of engine start where only
one engine gearbox accessory pad exists off the aircraft engine.
The present invention may provide a gearbox lubricating apparatus
and method that may lubricate the starter gearbox at altitude
without added complexity. The present invention may provide two
starting inputs (for example, one input for ground start and one
input for in-flight engine start) while avoiding complex engine
accessory gearbox designs. The present invention may also provide
an apparatus and method for preventing the starter gearbox from
continuous operation (rotation) after the engine has started.
Finally, the present invention may provide apparatus and methods
for improving the air-fuel combustion of the hot-gas turbine start
input (for in-flight engine start, as described in more detail
below) to minimize the build-up of solid carbon (soot) in and
around the combustor and turbine nozzle flow passages.
[0020] Unlike conventional engine start systems which may provide
for only one engine starting input, the present invention may
provide for an accessory pad mounted gearbox with dual turbine
inputs for engine starting. Also unlike conventional engine start
systems, which may be integrated to the engine, the engine start
system of the present invention may provide an engine starting
system that attaches to the primary engine accessory gearbox via a
single drive shaft pad. The engine start system of the present
invention may be useful for engine start both on the ground and
in-flight. The engine start system of the present invention may be
useful for starting gas turbine engines, such as those found on
commercial and military aircraft.
[0021] Referring to FIG. 1, there is shown a cross-sectional view
of an emergency power engine restart system 10 according to the
present invention. The engine restart system 10 may include a
ground-based engine starting system, such as a conventional air
turbine starter 12. Air turbine starter 12 may be any typical air
turbine starter used to turn a shaft 14 to start an engine (not
shown). As shown in more detail in FIG. 4, the air turbine starter
12 may include an air turbine starter clutch 16 to prevent the
engine from driving the air turbine starter 12 after the engine is
started. The air turbine starter clutch 16 may be, for example, an
over-running clutch. The over-running clutch 16 may allow a drive
shaft 20, in this case, the shaft driven by the air turbine starter
12 to turn a driven shaft 22 (in this case, ultimately tied to the
engine's shaft via the engine restart system output spline shaft
14). The over-running clutch 16, however, may disconnect the drive
shaft 20 and the driven shaft 22 if a torque is applied to the
driven shaft 22, such as when, for example, the engine is
started.
[0022] The engine restart system 10 may include an accessory pad
mounted gearbox 18. The gearbox 18 may be mounted onto an accessory
pad (not shown) of the engine in any conventional manner, for
example, in a manner similar to that of how typical accessories,
such as pumps, generators, starters and the like may be Mounted.
The gearbox 18 may be driven by a hot gas turbine 24, as described
in more detail below, to drive the engine's shaft via the engine
restart system output spline shaft 14 to affect engine start. In
one embodiment of the invention, the air turbine starter 12 may be
used to start the engine on the ground and the hot gas turbine 24
may be used for in-flight engine restart.
[0023] The engine restart system 10 may include an accessory pad
clutch 26. The accessory pad clutch 26 may be an over-running
clutch, similar to the air turbine starter clutch 16. The accessory
pad clutch 26 may prevent the engine from driving the gearbox 18
after the engine has been started or restarted.
[0024] Referring now to FIGS. 2 and 3, along with FIG. 1, the
gearbox 18 may include a plurality of gears, typically spur gears,
such as a starter gear 28, an idler gear 30, a compound gear 32, a
turbine pinion gear 34 and a pitot pump gear 36. The hot gas
turbine 24 may drive the turbine pinion gear 34. The turbine pinion
gear may be designed, via, for example, spur gears, to drive the
compound gear 32. The compound gear may have two separate spur
gears, a first spur gear 32a which may be used to receive the
rotational torque from the turbine pinion gear 34 and a second spur
gear 32b which may be used to drive both the pitot pump gear 36 and
the idler gear 30. Finally, the idler gear 30 may be used to turn
the starter gear 28, which, in turn, drives the engine's shaft via
the engine restart system output spline shaft 14 to start or
restart the engine.
[0025] The pitot pump gear 36 may be used to drive a pitot pump
lubrication system. The pitot pump lubrication system, as it
typically known in the art may include an open-ended tube 40
located in an oil trough 38. One of the gears, in this case, the
pitot pump gear 36, may put the oil inside the oil trough 38 into
circular motion. The open ended tube 40 may be installed into the
circular flow of oil in the oil trough 38 to harness the kinetic
energy of this circular flow. This kinetic energy is used to
deliver the oil, through the open ended tube 40, to locations where
lubrication may be needed. Pitot pump lubrication systems may be
useful, especially in the engine restart system 10 of the present
invention, because they may be reliable, relatively inexpensive
(compared to other conventional lubrication systems) and relatively
insensitive to variations in altitude, attitude and oil
quantity.
[0026] The hot gas turbine 24 may include an air inlet 42 and a
fuel delivery channel 44 for delivering air and fuel in, to a
combustor 46. Hot combustion gases may be used to drive a turbine
wheel 48, which, in turn, drives the hot gas turbine pinion gear
34. The hot gas turbine 24 may use a fuel rich jet-fuel and air
combustor 46 which only partially reacts the propellants to avoid
the formation of solid carbon (soot). A more complete reaction may
clog the combustor and turbine nozzle flow passages (not
shown).
[0027] The incomplete or "non-equilibrium" reaction may leave the
carbon in the combustion products bonded to oxygen as carbon
monoxide or carbon dioxide gas or bonded to hydrogen in relatively
low-molecular-weight hydrocarbon molecules such as methane
(CH.sub.4), ethane (C.sub.2H.sub.6), propane (C.sub.3H.sub.8),
butane (C.sub.4H.sub.10), pentane (C.sub.5H.sub.12), hexane
(C.sub.6F.sub.14), heptane (C.sub.7H.sub.16) and octane
(C.sub.8H.sub.18). In essence, the hydrocarbon molecules that make
up the fuel are broken down into smaller hydrocarbon molecules
rather than being more completely oxidized into products which
include free carbon. The incomplete reaction may be achieved by
some combination of a) restricting the residence time of the
reactants in the combustion chamber; b) restricting the combustion
chamber temperature; and c) maximizing the size of the droplets of
fuel injected into the chamber.
[0028] Restricting the residence time of the reactants in the
combustor may be achieved by restricting the characteristic length
(also referred to as "L-star" and written as "L*") of the
combustion chamber. Characteristic length is the volume of the
chamber divided by its exit area. A combustion chamber
characteristic length of less than about 485 inches may provide
relatively clean and soot-free reaction products.
[0029] Restricting the combustion chamber temperature may limit the
rate of the oxidation reaction. This can be achieved by limiting
the air-to-fuel (A/F) ratio of the reactants. A/F ratios below
about 3.5:1 (about 1800.degree. F. combustion chamber temperature)
have been found to result in relatively clean and soot-free
reaction products.
[0030] Maximizing the size of the fuel droplets may also decrease
the rate of reaction in that the larger droplets have a lower
surface area to volume ratio, and thus vaporize more slowly. Fuel
sprays with a Sauter Mean Diameter (SMD) of 20 microns or more may
burn relatively clean and soot-free.
[0031] Referring now to FIG. 4, along with FIG. 1, there is shown a
close-up view of one clutch configuration for the emergency power
engine restart system 10 according to the present invention. In
this configuration, which is similar to that shown in FIG. 1, the
air turbine starter clutch 16 may disconnect the air starter
turbine 12 when the engine is operating or when the hot gas turbine
24 is operating to restart the engine. In other words, if a torque
is applied to the driven shaft 22, the air turbine starter clutch
16 may prevent the drive gear 20 from turning. Similarly, the
accessory pad clutch 26 may prevent the started engine from driving
the gearbox 18 but may allow the gearbox 18 to turn the engine's
shaft 14 to affect start or restart of the engine. In this
embodiment, the air starter turbine 12 may drive the gearbox
18.
[0032] Referring to FIG. 5, along with FIG. 1, there is shown a
close-up view of another clutch configuration for the emergency
power engine restart system 10 according to the present invention.
In this embodiment, a secondary clutch 50 may be used to prevent
the air turbine starter 12 from back-driving the gearbox 18 (and,
in turn, the hot gas turbine 24) but allows the air turbine starter
12 to turn the engine's shaft 14 to affect engine start. In this
embodiment, the accessory pad clutch 26 and the air starter turbine
clutch 16 may also be employed as described above with reference to
FIGS. 1 and 4.
[0033] Referring to FIG. 6, there is shown a flow chart describing
a method for in-flight engine start using an engine start system 10
according to the present invention. The method 100 may include a
first step 102 of burning fuel and air in a combustor to drive a
turbine. A second step 104 may include turning a starter gear via
the rotation of the turbine, wherein the starter gear is mounted on
an accessory pad of the engine. A third step 106 may include
disconnecting a ground-based engine starter (such as air turbine
starter 12) with an over-running clutch. A fourth step 108 may
include driving an engine's shaft through the rotation of the
starter gear to affect engine start or restart. An optional step
110 may include driving a pitot pump lubrication system from the
turbine's rotation in order to lubricate the gears of the engine
start system 10. The first step 102 may be carried out, in one
embodiment of the present invention, by techniques described above
to affect the incomplete burning of the fuel, thereby minimizing
carbon deposits in the hot gas turbine.
[0034] It should be understood, of course, that the foregoing
relates to exemplary embodiments of the invention and that
modifications may be made without departing from the spirit and
scope of the invention as set forth in the following claims.
* * * * *