U.S. patent application number 15/332045 was filed with the patent office on 2017-02-09 for free gas turbine with constant temperature-corrected gas generator speed.
The applicant listed for this patent is Pratt & Whitney Canada Corp.. Invention is credited to Francois BELLEVILLE, Keith MORGAN.
Application Number | 20170037785 15/332045 |
Document ID | / |
Family ID | 44318306 |
Filed Date | 2017-02-09 |
United States Patent
Application |
20170037785 |
Kind Code |
A1 |
MORGAN; Keith ; et
al. |
February 9, 2017 |
FREE GAS TURBINE WITH CONSTANT TEMPERATURE-CORRECTED GAS GENERATOR
SPEED
Abstract
A method of controlling a speed of a gas turbine engine, the gas
turbine engine including a high pressure spool and a low pressure
spool rotating independently from one another, including
determining a temperature-corrected rotational speed of the high
pressure spool based on an actual rotational speed of the high
pressure spool and on an air temperature measured outside of the
gas turbine engine; controlling the rotation of the high pressure
spool to maintain the temperature-corrected rotational speed of the
high pressure spool at least substantially constant throughout a
range of a power demand on the gas turbine engine; and controlling
a rotational speed of the low pressure spool independently of the
rotation of the high pressure spool.
Inventors: |
MORGAN; Keith; (Westmount,
CA) ; BELLEVILLE; Francois; (Varennes, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Pratt & Whitney Canada Corp. |
Longueuil |
|
CA |
|
|
Family ID: |
44318306 |
Appl. No.: |
15/332045 |
Filed: |
October 24, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12696341 |
Jan 29, 2010 |
9512784 |
|
|
15332045 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02C 9/26 20130101; F02C
9/20 20130101; F02C 9/00 20130101; F05D 2270/023 20130101; F02C
3/10 20130101 |
International
Class: |
F02C 9/20 20060101
F02C009/20; F02C 9/26 20060101 F02C009/26 |
Claims
1. A method of controlling a speed of a gas turbine engine, the gas
turbine engine including a high pressure spool and a low pressure
spool rotating independently from one another, the method
comprising: determining a temperature-corrected rotational speed of
the high pressure spool based on an actual rotational speed of the
high pressure spool and on an air temperature measured outside of
the gas turbine engine; controlling the rotation of the high
pressure spool to maintain the temperature-corrected rotational
speed of the high pressure spool at least substantially constant
throughout a range of a power demand on the gas turbine engine; and
controlling a rotational speed of the low pressure spool
independently of the rotation of the high pressure spool.
2. The method as defined in claim 1, wherein the
temperature-corrected rotational speed of the high pressure spool
is calculated as Ng/ {square root over (.theta.)}, where Ng is the
actual rotational speed of the high pressure spool and .theta. is
the air temperature measured outside of the gas turbine engine.
3. The method as defined in claim 1, wherein the
temperature-corrected rotational speed of the high pressure spool
is maintained at least substantially constant by modulating an
angle of variable inlet guide vanes throughout the power demand
variation, the variable inlet guide vanes being located upstream of
a compressor having at least one rotor rotating with the high
pressure spool.
4. The method as defined in claim 1, further comprising maintaining
the rotational speed of the low pressure spool at least
substantially constant.
5. The method as defined in claim 4, wherein the rotational speed
of the low pressure spool is maintained at least substantially
constant by modulating a fuel flow of the gas turbine engine
throughout the range of the power demand.
6. The method as defined in claim 1, wherein the
temperature-corrected rotational speed of the high pressure spool
is maintained at least substantially constant while the power
demand varies from 0 to a maximum power available from the gas
turbine engine.
7. A method of controlling a speed of a gas turbine engine
throughout a range of a power demand thereon, the gas turbine
engine including a gas generator spool and a power turbine spool
rotating independently from one another, the method comprising:
determining a temperature-corrected rotational speed of the gas
generator spool based on an actual rotational speed of the gas
generator spool and on an air temperature measured outside of the
gas turbine engine; controlling the rotation of the gas generator
spool to maintain the temperature-corrected rotational speed of the
gas generator spool within 5% of a nominal desired value throughout
the range of the power demand, wherein the nominal desired value is
constant throughout the range of the power demand; and controlling
a rotational speed of the power turbine spool independently of the
rotation of the gas generator spool.
8. The method as defined in claim 7, wherein the
temperature-corrected rotational speed is calculated as Ng/ {square
root over (.theta.)}, where Ng is the actual rotational speed of
the gas generator spool and .theta. is the air temperature measured
outside of the gas turbine engine.
9. The method as defined in claim 7, wherein the rotational speed
of the gas generator spool is controlled by modulating an angle of
variable inlet guide vanes located upstream of a compressor having
at least one rotor rotating with the gas generator spool.
10. The method as defined in claim 7, further comprising
controlling the rotational speed of the power turbine spool to
remain at least substantially constant throughout the range of the
power demand.
11. The method as defined in claim 10, wherein the rotational speed
of the power turbine spool is controlled by modulating a fuel flow
of the gas turbine engine.
12. A gas turbine engine comprising: a low pressure spool
supporting at least one rotor of a low pressure turbine; a high
pressure spool supporting at least one rotor of a high pressure
turbine located upstream of the low pressure turbine rotor and at
least one rotor of a high pressure compressor located upstream of
the high pressure turbine, the low and high pressure spools being
rotatable independently from one another; and at least one
controller configured to control a rotation of the low pressure
spool throughout a range of a power demand on the gas turbine
engine, determine a temperature-corrected rotational speed of the
high pressure spool based on an actual rotational speed of the high
pressure spool and on an air temperature measured outside of the
gas turbine engine, control a rotation of the high pressure spool
to maintain the temperature-corrected rotational speed at an at
least substantially constant value throughout the range of the
power demand on the gas turbine engine, and control a rotation of
the low pressure spool independently from the rotation of the high
pressure spool.
13. The gas turbine engine as defined in claim 12, wherein the at
least one controller is configured to determine the
temperature-corrected rotational speed of the high pressure spool
as Ng/ {square root over (.theta.)}, where Ng is the actual
rotational speed of the high pressure spool and .theta. is the air
temperature measured outside of the gas turbine engine.
14. The gas turbine engine as defined in claim 12, wherein the at
least one controller is configured to control the low pressure
spool to rotate at an at least substantially constant speed
throughout the range of a power demand on the gas turbine
engine.
15. The gas turbine engine as defined in claim 14, wherein the at
least one controller is configured to control the rotational speed
of the low pressure spool by modulating a fuel flow of the gas
turbine engine throughout the range of the power demand.
16. The gas turbine engine as defined in claim 12, wherein the at
least one controller is configured to control the rotational speed
of the high pressure spool by modulating an angle of variable inlet
guide vanes located upstream of the high pressure compressor
throughout the range of the power demand.
17. The gas turbine engine as defined in claim 12, wherein the
range of the power demand throughout which the at least one
controller is configured to control the rotation of the high
pressure spool to maintain the temperature-corrected rotational
speed at the at least substantially constant value extends from
zero to a maximum available power from the gas turbine engine.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. application Ser.
No. 12/696,341 filed Jan. 29, 2010, the entire contents of which
are incorporated by reference herein.
TECHNICAL FIELD
[0002] The application relates generally to power and rotational
speed control of a gas turbine engine and, more particularly, to
the control of the rotational speed of the main shafts or spools in
a free gas turbine engine
BACKGROUND OF THE ART
[0003] In a conventional free gas turbine engine, the rotational
speed Ng of the high pressure or gas generator spool usually varies
in a fixed relationship with the engine power or thrust, as can be
seen in FIG. 3. Inlet guide vanes are typically controlled to a
predetermined position as a function of the Ng rotational speed.
For gas turbine engine applications where the rotational speed Np
of the low pressure or power turbine spool is maintained constant
(e.g. turbo shafts), a controller usually maintains the Np
rotational speed constant through a modulation of the fuel flow and
as such reacts to any changes in Np rotational speed due to a
change in the load applied to the power turbine. For gas turbine
engine application where the rotational speed Np of the low
pressure or power turbine spool is changing with thrust demand
(e.g. turbofans), the Np rotational speed is controlled at the
commanded reference speed through a modulation of fuel flow.
[0004] However, improvements are desirable.
SUMMARY
[0005] In one aspect, there is provided a method of controlling a
speed of a gas turbine engine throughout a power demand variation
thereon, the gas turbine engine including a high pressure spool and
a low pressure spool rotating independently from one another, the
method comprising maintaining a temperature-corrected value of a
rotational speed of the high pressure spool at least substantially
constant, the temperature-corrected value being determined based on
the rotational speed of the high pressure spool and an air
temperature measured outside of the gas turbine engine.
[0006] In another aspect, there is provided a method of controlling
a speed of a gas turbine engine throughout a variation of output
power thereof, the gas turbine engine including a gas generator
spool and a power turbine spool rotating independently from one
another, the method comprising controlling a rotational speed of
the gas generator spool according to a fixed relationship with
respect to an outside air temperature throughout the variation of
output power.
[0007] In another aspect, there is provided a gas turbine engine
comprising a low pressure spool supporting at least one rotor of a
low pressure turbine, a high pressure spool supporting at least one
rotor of a high pressure turbine located upstream of the low
pressure turbine rotor and at least one rotor of a high pressure
compressor located upstream of the high pressure turbine, the low
and high pressure spools being rotatable independently from one
another, and at least one controller controlling a rotation of the
low pressure spool throughout a range of a power demand on the gas
turbine engine and controlling the high pressure spool to rotate at
a rotational speed having an at least substantially constant
temperature-corrected value throughout the range of the power
demand on the gas turbine engine, the temperature-corrected value
being determined based on the rotational speed of the high pressure
spool and an air temperature measured outside of the gas turbine
engine.
[0008] In another aspect, there is provided a method of controlling
a speed of a gas turbine engine, the gas turbine engine including a
high pressure spool and a low pressure spool rotating independently
from one another, the method comprising: determining a
temperature-corrected rotational speed of the high pressure spool
based on an actual rotational speed of the high pressure spool and
on an air temperature measured outside of the gas turbine engine;
controlling the rotation of the high pressure spool to maintain the
temperature-corrected rotational speed of the high pressure spool
at least substantially constant throughout a range of a power
demand on the gas turbine engine; and controlling a rotational
speed of the low pressure spool independently of the rotation of
the high pressure spool.
[0009] In another aspect, there is provided a method of controlling
a speed of a gas turbine engine throughout a range of a power
demand thereon, the gas turbine engine including a gas generator
spool and a power turbine spool rotating independently from one
another, the method comprising: determining a temperature-corrected
rotational speed of the gas generator spool based on an actual
rotational speed of the gas generator spool and on an air
temperature measured outside of the gas turbine engine; controlling
the rotation of the gas generator spool to maintain the
temperature-corrected rotational speed of the gas generator spool
within 5% of a nominal desired value throughout the range of the
power demand, wherein the nominal desired value is constant
throughout the range of the power demand; and controlling a
rotational speed of the power turbine spool independently of the
rotation of the gas generator spool.
[0010] In another aspect, there is provided a gas turbine engine
comprising: a low pressure spool supporting at least one rotor of a
low pressure turbine; a high pressure spool supporting at least one
rotor of a high pressure turbine located upstream of the low
pressure turbine rotor and at least one rotor of a high pressure
compressor located upstream of the high pressure turbine, the low
and high pressure spools being rotatable independently from one
another; and at least one controller configured to control a
rotation of the low pressure spool throughout a range of a power
demand on the gas turbine engine, determine a temperature-corrected
rotational speed of the high pressure spool based on an actual
rotational speed of the high pressure spool and on an air
temperature measured outside of the gas turbine engine, control a
rotation of the high pressure spool to maintain the
temperature-corrected rotational speed at an at least substantially
constant value throughout the range of the power demand on the gas
turbine engine, and control a rotation of the low pressure spool
independently from the rotation of the high pressure spool.
DESCRIPTION OF THE DRAWINGS
[0011] Reference is now made to the accompanying figures in
which:
[0012] FIG. 1 is a schematic cross-sectional view of a gas turbine
engine;
[0013] FIG. 2 is a schematic diagram of a control system used to
control the rotational speed of spools of a gas turbine engine such
as shown in FIG. 1;
[0014] FIG. 3 illustrates a relationship between power demand and
rotational speed for a high pressure spool of a gas turbine engine
of the prior art;
[0015] FIG. 4 illustrates a relationship between power demand and
rotational speed for a high pressure spool of a gas turbine engine
controlled through a control system such as shown in FIG. 2;
and
[0016] FIG. 5 is a schematic cross-sectional view of another type
of gas turbine engine.
DETAILED DESCRIPTION
[0017] FIG. 1 illustrates a turbo shaft gas turbine engine 10 of a
type preferably provided for use in subsonic flight, generally
comprising in serial flow communication a compressor section 14 for
pressurizing the air, a combustor 16 in which the compressed air is
mixed with fuel and ignited for generating an annular stream of hot
combustion gases, and a turbine section 18 for extracting energy
from the combustion gases.
[0018] The engine 10 includes a low pressure/power turbine shaft or
spool 20 supporting the rotor(s) 22 of the low pressure portion of
the turbine section 18. The low pressure spool 20 also rotates,
through a reduction gearbox 70, a propeller shaft 12 supporting a
propeller (not shown).
[0019] The engine 10 also includes a high pressure/gas generator
shaft or spool 24 supporting the rotor(s) 26 of a high pressure
portion of the compressor section 14 and the rotor(s) 28 of a high
pressure portion of the turbine section 18. The low pressure and
high pressure spools 20, 24 are concentric and rotate independently
from one another.
[0020] The engine 10 also includes variable inlet guide vanes 30
positioned upstream of the high pressure portion of the compressor
section 14.
[0021] Referring to FIG. 2, the engine 10 includes a control system
40 including at least one controller 42 which controls the
rotational speed of the low and high pressure spools 20, 24. The
controller 42 thus receives relevant data from engine sensors 58,
including the rotational speed Np of the low pressure spool 20, the
rotational speed Ng of the high pressure spool 24, and the
temperature .theta. outside of the engine 10. In the embodiment
shown, a single controller 42 controls both spools 20, 24, although
alternately different controllers can be provided.
[0022] The controller 42 controls the rotational speed of the low
pressure spool 20 by sending a command signal to a fuel control
unit 44, which controls the flow of fuel through a manifold 54
delivering the fuel to the combustor. The controller 42 receives a
feedback signal from the fuel control unit 44 indicative of the
fuel flow through the manifold 54.
[0023] In a particular embodiment, the fuel control unit 44
includes a servo pressure regulator which provides fuel to a
metering valve controller at a regulated pressure determined by the
controller 42. The controller 42 controls the position of a
metering valve through the metering valve controller. The metering
valve may include, for example, a piston moved by fuel pressure on
each side, with the fuel pressure being provided by the metering
valve controller as requested by the controller 42. The position of
the metering valve determines the fuel flow provided to the fuel
manifold(s) 54 of the gas turbine engine 10.
[0024] The controller 42 controls the rotational speed of the high
pressure spool 24 by sending a command signal to an inlet guide
vane actuator 56, which controls the orientation of the inlet guide
vanes 30. The controller 42 receives a feedback signal from the
inlet guide vane actuator 56 indicative of the orientation of the
inlet guide vanes 30.
[0025] In a particular embodiment, the vane actuator 56 includes a
piston moved by fuel pressure on each side, with the fuel pressure
being provided by a vane controller as requested by the controller
42. The vane actuator 56 moves the variable inlet guide vanes 30,
for example through rings (not shown) transferring the linear
movement of the actuator 56 into a rotational movement for the
vanes 30. An example of a connection between the actuator and the
guide vanes is shown in U.S. Pat. No. 4,890,977 issued Jan. 2,
1990, which is incorporated herein by reference. It is to be
understood that any adequate type of connection between the guide
vanes 30 and the actuator 56 can alternately be used.
[0026] Thus, the controller 42 controls the rotational speed Np of
the low pressure spool 20 through a modulation of the fuel flow, by
acting on the fuel control unit 44. The controller also controls
the rotational speed Ng of the high pressure spool 24 through a
modulation of the angle of the variable inlet guide vanes 30, by
acting on the vane actuator 56. The controller 42 thus controls the
rotational speed of the two spools 20, 24 independently from one
another.
[0027] It is understood that any other adequate type of control
system can be provided, depending on the type of metering valve and
guide vane actuator provided. For example, one or both of the
metering valve and guide vane actuator may be electrically actuable
instead of fuel-pressure operated, and the controller may thus
controls them directly through an electrical signal.
[0028] The controller 42 controls the rotational speed Np of the
low pressure spool 20 such that it remains at least substantially
constant throughout a range of a power demand on the gas turbine
engine 10, and preferably throughout the complete range of power
demand, i.e. from 0 to a maximum power available. In the present
application, "substantially constant" includes a variation within a
range of approximately 5% of the nominal value.
[0029] The controller 42 controls the rotational speed Ng of the
high pressure spool 24 according to a fixed relationship with
respect to the outside air temperature .theta. and throughout the
variation of power demand on the gas turbine engine 10.
[0030] Referring to FIG. 4, in a particular embodiment, the
controller 42 maintains a temperature-corrected rotational speed
Ng' of the high pressure spool 24 at least substantially constant
throughout the range of the power demand on the gas turbine engine
10, and preferably throughout the complete range of the power
demand on the engine, i.e. from 0 to a maximum power available. The
controller 42 determines the temperature-corrected rotational speed
Ng' based on the actual rotational speed Ng of the high pressure
spool 24 and on the outside air temperature .theta. as indicated by
the appropriate sensor 58.
[0031] In a particular embodiment, the temperature-corrected
rotational speed Ng' is defined as Ng/ {square root over
(.theta.)}.
[0032] In use, when the power demand increases on the power
turbine, the rotational speed Np of the low pressure spool 20
starts to decrease. In response, the controller 42 commands the
fuel flow to increase through the fuel control unit 44 such as to
bring the rotational speed Np of the low pressure spool 20 back to
the desired constant value. However, as the fuel flow increases,
the rotational speed Ng of the high pressure spool 24 and its
temperature-corrected value Ng' start to increase. In response, the
controller 42 commands the inlet guide vanes 30 to open through the
inlet guide vane actuator 56 such as to reduce the rotational speed
Ng of the high pressure spool 24 and bring its the
temperature-corrected value Ng' back to the desired constant value
while maintaining power.
[0033] FIG. 5 illustrates another embodiment of a gas turbine
engine 110. The turbofan engine 110 comprises in serial flow
communication a fan 112 through which ambient air is propelled, a
compressor section 114 for pressurizing the air, a combustor 116 in
which the compressed air is mixed with fuel and ignited for
generating an annular stream of hot combustion gases, and a turbine
section 118 for extracting energy from the combustion gases.
[0034] The engine 110 includes a low pressure/power turbine shaft
or spool 120 supporting the fan 112 and the rotor(s) 122 of the low
pressure portion of the turbine section 118. The engine 110 also
includes a high pressure/gas generator shaft or spool 124
supporting the rotor(s) 126 of a high pressure portion of the
compressor section 114 and the rotor(s) 128 of a high pressure
portion of the turbine section 118. The low pressure and high
pressure spools 120, 124 are concentric and rotate independently
from one another.
[0035] The engine 110 also includes variable inlet guide vanes 130
positioned upstream of the high pressure portion of the compressor
section 114.
[0036] The engine 110 further includes a control system 140 which
controls the rotational speed of the high and low pressure spools
120, 124. The control system 140 may be similar to the control
system 40 of the previous embodiment, or may be any other adequate
system for controlling the rotational speed of the high and low
pressure spools 120, 124 as required.
[0037] As above, the control system 140 controls a rotational speed
Ng of the high pressure spool 124 according to a fixed relationship
with respect to the outside air temperature throughout the
variation of output power. In a particular embodiment, the
rotational speed Ng of the high pressure spool 124 is controlled
such that a corrected value of the rotational speed Ng' of the high
pressure spool 124, determined based on the outside air temperature
.theta., remains at least substantially constant throughout the
variation of output power.
[0038] As above, in a particular embodiment, the corrected value of
the rotational speed Ng' of the high pressure spool 124 is
calculated as Ng/ {square root over (.theta.)}.
[0039] However in this embodiment, the rotational speed Np of the
low pressure spool 120 varies with the variation of output
power.
[0040] The above described control of the rotational speed of the
high pressure spool 120, 124 may provide improvements in engine
operability and result in rapid augmentation and reduction of
delivered power, which may improve response times over a
conventional two spool free turbine engine.
[0041] The above description is meant to be exemplary only, and one
skilled in the art will recognize that changes may be made to the
embodiments described without departing from the scope of the
invention disclosed. For example, the described control method is
not limited to the specific gas turbine engines shown and can be
used in any type of free gas turbine engine including various
configurations of APUs, turbofans, turboprops and turboshafts.
Still other modifications which fall within the scope of the
present invention will be apparent to those skilled in the art, in
light of a review of this disclosure, and such modifications are
intended to fall within the appended claims.
* * * * *