STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH &
DEVELOPMENT
This invention was made with government support under F33615-03-
D-2352-GOVT awarded by U.S. Air Force. The government has certain rights in the
invention.
BACKGROUND
The field of the disclosure relates generally to turbine engines and,
more particularly, to methods and systems for dynamic on-line power management of
an engine. In at least some known aircraft engines, the power management system is
configured offline. In an offline configuration, individual optimization of control
reference schedules for the controlled outputs (e.g., total thrust, fan speed), the openloop
schedules for inputs (e.g., some variable geometry), and constraint limits (e.g.
fuel-air ratio, rotor speed rate of change, etc.) are determined. The reference
schedules are then utilized by the engine during operation and are not updated again
until the next offline configuration.
Given the increased complexity and multivariable interaction
between the inputs and outputs of current engines, offline configuration of the power
management system unnecessarily limits the overall performance capability of the
engine despite the advanced engine control techniques used. The design of optimum
power management becomes even more challenging given that some engines,
especially aircraft engines, will most frequently be operating under transient
conditions due to the close integration between the flight and engine controls wherein
the flight controls will be continuously modulating certain critical engine control
variables.
BRIEF DESCRIPTION
In one embodiment, a method for online power management of a
turbine engine is provided. The method includes operating an engine control system
on a first bandwidth, filtering at least one data input from the engine control system to
a second bandwidth, and receiving, by a power management system operating on the
second bandwidth, the at least one filtered data input. The method also includes
predicting an engine operating condition using the at least one filtered data input,
determining an optimal engine control based on the prediction, solving a constrained
optimization for a desired optimization objective, and outputting the optimal engine
control to the engine control system.
In another embodiment, a power management system is provided.
The power management system includes a baseline power management component
configured to receive at least one data input and a model predictive control. The
model predictive control is configured to predict an engine operating condition using
the at least one data input, determine an optimal engine control based on the
prediction, solve a constrained optimization for a desired optimization objective, and
output the optimal engine control.
In another embodiment, a gas turbine engine for use in an aircraft is
provided. The gas turbine engine includes at least one sensor configured to sense an
engine parameter and to generate a sensor input representing the engine parameter, a
control system configured to control at least one of said gas turbine engine and the
aircraft, and a power management system for dynamically managing the operation of
an engine. The power management system includes a baseline power management
component configured to receive at least one data input and a model predictive
control. The model predictive control is configured to predict an engine operating
condition using the at least one data input, determine an optimal engine control based
on the prediction, solve a constrained optimization for a desired optimization
objective, and output the optimal engine control.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of an exemplary variable cycle gas turbine
engine.
FIG. 2 is a schematic illustration of an exemplary power management
system that may be used with the gas turbine engine shown in FIG. 1.
FIG. 3 is a schematic illustration of an exemplary implementation of
the power management system shown in FIG. 2, employing a modification to an
existing baseline power management scheme.
FIG. 4 is an exemplary flow chart for use with the power
management system shown in FIG. 2.
DETAILED DESCRIPTION
The embodiments described herein provide a model within a control
system, such as a Full Authority Digital Engine Control (FADEC) andlor an on-board
computer. The model is used to manage power in a control system during operation
using measured parameters. The embodiments described herein can be implemented
within a system and are flexible enough to satisfy stringent control specifications for
different operating modes of the system. For example, the embodiments described
herein may be implemented in an aircraft having a wing-borne mode and jet-borne
mode, wherein the embodiments described herein are adaptable to the requirements
for operating in jet-borne, or hover, mode.
The following detailed description illustrates embodiments by way of
example and not by way of limitation. As used herein, an element or step recited in
the singular and proceeded with the word "a" or "an" should be understood as not
excluding plural elements or steps, unless such exclusion is explicitly recited.
Furthermore, references to "one embodiment" of the present disclosure are not
intended to be interpreted as excluding the existence of additional embodiments that
also incorporate the recited features.
FIG. 1 is a schematic illustration of an exemplary variable-cycle gas
turbine engine 10 having a longitudinal centerline 12. Gas turbine engine 10 is shown
as being used with an aircraft 14. However, it should be understood that gas turbine
engine 10 can be used in any suitable commercial, industrial, and/or residential
system and/or application. Gas turbine engine 10 includes an annular inlet 16 that
receives ambient air 18 that is channeled downstream to a fan assembly 20. Engine
10 also includes a core gas turbine engine 22 that includes a high pressure compressor
(HPC) 24, a combustor 26, a high-pressure turbine (HPT) 28, a low pressure turbine
(LPT) 30 and an augmentor 32 that are coupled in an axial-flow relationship with inlet
16. HPT 28 powers HPC 24 via a first shaft 34. LPT 30 powers fan assembly 20 via
a second shaft 36. Engine 10 also includes an outer casing 38 that is spaced from an
inner casing 40. Inner casing 40 includes a forward section 42 that defines a bypass
duct 44. In the exemplary embodiment, augmentor 32 includes a difhser liner 46.
In the exemplary embodiment, gas turbine engine 10 also includes a
valve assembly 48 coupled within bypass duct 44. Valve assembly 48 separates
bypass duct 44 into a radially inner bypass duct 50 and a radially outer bypass duct
52. More specifically, in the exemplary embodiment, inner bypass duct 50 and outer
bypass duct 52 are aligned substantially concentrically. Accordingly, and in the
exemplary embodiment, fan bypass flow 54 entering bypass duct 44 is divided into an
inner bypass flow 56 and an outer bypass flow 58 by valve assembly 48. Moreover,
in the exemplary embodiment, valve assembly 48 regulates a volume of inner bypass
flow 56 channeled through inner bypass duct 50 and a volume of outer bypass flow 58
that is channeled through outer bypass duct 52.
In the exemplary embodiment, a separation liner 60 contacts an aft
portion 62 of valve assembly 48 and is coupled to diffuser liner 46 to facilitate
channeling inner bypass flow 56 through inner bypass duct 50. Furthermore,
separation liner 60 also facilitates channeling outer bypass flow 58 through outer
bypass duct 52. A seal 64 extends between valve portion 62 and separation liner 60 to
facilitate reducing leakage of outer bypass flow 58 into inner bypass duct 50.
During operation, air entering engine assembly 10 through inlet 16 is
compressed by fan assembly 20. The flow of compressed air exiting fan assembly 20
is split into a first airflow portion 66 that is channeled into core turbine engine 22 and
a second airflow portion, or bypass air 68, which is channeled through bypass duct 44.
First airflow portion 66 is compressed by HPC 24 and is channeled to combustor 26.
Airflow discharged from combustor 26 rotates turbines 28 and 30 prior to being
discharged from engine 10 through an exhaust 70. Further, bypass air 68 channeled
by valve assembly 48 is discharged from engine 10 through exhaust 70.
In the exemplary embodiment, gas turbine engine 10 is a military
turbine engine, such as an FllO engine, that is available from General Electric
Company, Cincinnati, Ohio. Alternatively, gas turbine engine 10 is a commercial
turbine engine, such as a CFM56 gas turbine engine and/or a CF34-10 gas turbine
engine, and/or a marinelindustrial engine, such as an LM6000 engine, all of which are
also available from the General Electric Company. Furthermore, it should be
appreciated that in other embodiments, gas turbine engine 10 may be any gas turbine
engine containing similar components, such as an F136 engine available from the
General Electric Company.
FIG. 2 is a schematic illustration of an exemplary power management
system 100 that may be used with gas turbine engine 10. In the exemplary
embodiment, power management system 100 includes a power management
component 102 that is in communication with a closed-loop engine control system
104. Control system 104 includes engine 10, a plurality of sensors 106, a plurality of
actuators 108, and an engine control 1 10.
Sensors 106 monitor engine and/or aircraft operation and input realtime
actual sensor data or sensor input 112 during engine operation to a power
management model, such as a component 102. Exemplary sensors 106 include, but
are not limited to, a fan inlet temperature sensor 72, a compressor inlet total pressure
sensor 74, a fan discharge static pressure sensor 76, a compressor discharge static
pressure sensor 78, an exhaust duct static pressure sensor 80, an exhaust liner static
pressure sensor 82, a flame detector 84, an exhaust gas temperature sensor 86, a
compressor discharge temperature sensor 88, a compressor inlet temperature sensor
90, a fan speed sensor 92, and a core speed sensor 94. In the exemplary embodiment,
sensors 102 monitor engine rotor speeds, engine temperatures, engine pressures, fluid
flows, andor torques.
In the exemplary embodiment, actuator position data 118 is input to
component 102. Actuator position data 118 includes, but is not limited to, a fuel flow
actuator, variable area actuators, variable stator actuators, and/or bleed valve
positions. In the exemplary embodiment, ambient flight condition data 120 is input to
component 102. Ambient flight condition data 120 includes, but is not limited to,
ambient temperature, ambient pressure, aircraft mach number, andor engine power
setting parameters, such as fan speed or engine pressure ratio. In an alternative
embodiment, any suitable data is input to power management system 100. In one
embodiment, a low pass filter 1 14 is placed between sensors 106 and component 102
and between actuators 108 and component 102 such that only low pass frequencies in
sensor data 1 12 and actuator position data 1 18 are received by component 102.
In the exemplary embodiment, control system 110 is implemented in
a FADEC. Alternatively, control system 110 can be implemented in an on-board
computer andor any other system that is suitable for controlling engine 10 and/or
aircraft 14. More specifically, in the exemplary embodiment, control system 1 10
controls operations of engine 10, such as fuel injection, positioning of nozzle, variable
bypass, andor lift fan areas, inner and outer blocker doors in systems with multiple
bypass streams, variable stators, andor valve positions. Further, in the exemplary
embodiment, references 122 and constraints 124 are used by control system 110 to
control at least one engine operation. Control system 110 also receives sensor inputs
112 to control at least one operation of engine 10.
In operation, component 102 receives data 1 12, 1 18, and 120,
predicts engine performance based on received data 112, 118, and 120, and optimizes
engine controls in response to the engine performance predictions. In the exemplary
embodiment, component 102 outputs references 122 and constraints 124 to control
system 110 and control inputs 126 directly to the actuators 108 within aircraft 14
based on the engine performance prediction.
In the exemplary embodiment, all components within control system
104 run on an inner loop bandwidth also known as a fast inner loop. In the exemplary
embodiment, inner loop bandwidth provides near real-time updates of the dynamics of
engine 10, control 1 10, sensors 106, and actuators 108. Component 102 and ambient
flight condition data 120 run on an outer loop bandwidth that is also known as a slow
outer loop. In the exemplary embodiment, received data 112 and 118 are an
approximation of the dynamics found in the inner loop bandwidth. An approximation
of the inner loop bandwidth is achieved by filtering the sensor information from the
inner loop through low pass filter 114. Low pass filter 114 receives sensor data 112
and actuator position data 108 near instantaneously and averages out the fast variation
of the data. In the exemplary embodiment, filter 114 provides an approximation of
data 1 12 and 1 18 to component 102 of 1 second. Alternatively, filter 114 can provide
any time approximation of data 112 and 118 that facilitate managing power of an
engine as described herein including, but not limited to, 2 seconds and any multiple of
seconds.
FIG. 3 is a schematic illustration of an exemplary implementation
200 of the power management system 100 shown in FIG. 2. In the exemplary
embodiment, the implementation 200 illustrates the details of the component 102 of
FIG. 2. Implementation 200 includes a baseline power management component 202
and a model predictive control (MPC) 204. In the exemplary embodiment, baseline
component 202 receives sensor data 112, actuator position data 118, and ambient
flight condition data 120. Baseline power management component 202 includes
tables preloaded into the component that provide references and constraint limits that
are preconfigured during an offline configuration. Received data 104 and 1 18 are
compared against the preloaded tables to output a preferred control 210 that will be
received by engine control 110. In the exemplary embodiment, MPC 204 reviews
preferred control 2 10 and produces optimal modifications 2 12 to preferred control
2 1 0. Optimal modifications 2 12 can include references 2 14, open-loop inputs 2 1 6,
and constraint limits 2 1 8.
The optimization occurs by the following manner:
where 0 is the optimization objective for MPC 204, which computes the optimized
variables A, 212 and denotes their rate of change. Y represents the controlled
outputs and YrefJlt are filtered references for controlled outputs from baseline power
management component 202. In the exemplary embodiment, references are filtered to
achieve a desired bandwidth that matches the outer loop bandwidth. YP' is an
optimization output and L"~' is a linear weight for the optimization output. Q is a
diagonal matrix with weights on tracking error for each control output and R is a
diagonal matrix with weights on rate of change of MPC action.
In the exemplary embodiment, the use of equations (1) and (2) ensure
offset-less tracking of critical controlled outputs to original design values. Equation
(3) achieves max feasible improvement in desired performance objective, e.g.
enhanced thrust performance (FGT), or a reduction in turbine temperature, or reduced
specific fuel consumption (SFC) subject to limiting constraints. In one embodiment, a
quadratic cost is used in this manner with a specified target provided for the
optimization output.
In an alternative embodiment, a frequency weighted function is used
to determine the optimal modifications 212. In such an embodiment, the following is
used:
Similar to (I), (2), and (3), 0 is the optimization objective for MPC 204, which
computes the optimized variables AWc 212 and A, denotes their rate of change.
Variable Y represents the controlled outputs and Ywk are filtered references for
controlled outputs from baseline power management component 202. In the
exemplary embodiment, references are filtered to achieve a desired bandwidth that
matches the outer loop bandwidth. Variable YOP' is an optimization output and Lop' is a
linear weight for the optimization output. Parameter Q is a diagonal matrix with
weights on tracking error for each control output, and R is a diagonal matrix with
weights on rate of change of MPC 204 action. In such an Fy(Z)'F6(Z)'Fp(Z)
embodiment, are frequency-weighting functions meant to operate on the discrete time
functions. The solution to the problem in equation (4-6) is recast as an un-weighted
Linear Quadratic control problem on the linear system with:
The constraints on the unfiltered variables, constraint outputs Yk, and MPC 204
changes A,,,, are translated into equivalent constraints on the filtered variables
-
and kpc.
The use of (4), (9, and (6) enables systems 100 and 200 to operate
without low pass filter 114. The frequency-weighting functions enable dynamic
online power management at the desired lower bandwidth without interfering with the
high-bandwidth performance of the closed-loop control system 104.
FIG. 4 is an exemplary flow chart 300 for use with power
management system 100 shown in FIG. 2. In the exemplary embodiment, data is
received 302 by component 102. In one embodiment, received 302 data includes at
least one of sensor data, actuator position data, and ambient flight condition data.
Alternatively, system 100 can receive any data that facilitates managing power as
described herein. In the exemplary embodiment, a baseline engine power
management is determined 304 from the received data. The baseline engine power
management is determined 304 using baseline power management component 202,
which includes predefined look-up tables. A determination is then made whether to
use dynamic online power management. If the dynamic online power management is
not used, determined 304 baseline engine power management is output 308. In one
embodiment, engine power management includes references and constraints and is
output 308 to engine controller 110. In an alternative embodiment, engine power
management includes open loop input schedules and is output 308 to actuators 108
(see note about correcting signal 126 in Figure 2). Alternatively, engine power
management can include any combination of references, constraints, and open loop
input schedules that can be output to any component within an engine that facilitates
managing power as described herein.
If dynamic online power management is used, a closed-loop engine
model prediction is performed 310 by MPC 204, using determined 304 baseline
engine power management and received 302 data. In the exemplary embodiment, the
closed-loop engine model predicts an operating condition of engine 10 using
determined 304 baseline engine power management and received 302 data for a
predetermined time in the future. In one embodiment, MPC 204 performs the model
prediction 310 for 5 seconds in the future. Alternatively, MPC 204 can perform
model prediction 310 for any future time increment, including, but not limited to, 1
second, 10 seconds, 30 seconds, and 60 seconds.
Using the performed 3 10 model prediction, an optimal engine power
management is determined 312. In one embodiment, the optimal engine power
management is determined 3 12 using an objective function. The objective functions
used in determining 3 12 an optimal engine power management include, but are not
limited to, a maximum thrust performance (FGT) or total thrust, a minimum turbine
temperature, or a minimum specific fuel consumption (SFC). In one embodiment,
system 100 can switch between different objectives online as desired by the user. The
switching between different objectives allows dynamic power management using
MPC as opposed to conventional off-line baseline power management that is
manually designed offline and cannot be changed online. In the exemplary
embodiment, the determined 312 optimal engine power management is obtained
through optimization of the above-mentioned objective functions subject to
constraints that include, but are not limited to, engine safety and operability output
limits, magnitude limits, and rate limits on MPC 204 modifications.
In the exemplary embodiment, determined 3 12 optimal engine power
management is output 314. In one embodiment, optimal engine power management
includes references and constraints that are output 3 14 to engine controller 110. In an
alternative embodiment, optimal engine power management includes open loop input
schedules that are output 314 to actuators 108. Alternatively, optimal engine power
management can include any combination of references, constraints, and open loop
input schedules and optimal engine power management can be output to any
component within an engine that facilitates managing power as described herein.
The above-described embodiments provide a dynamic online power
management system for an engine. More specifically, the dynamic online power
management systems described herein may be implemented in an aircrafi to optimize
an operating parameter, such as thrust, for controlling the gas turbine engine. Further,
the power management systems described herein provide a bandwidth separation
design. As such, it is possible to achieve low bandwidth power management that does
not interfere with the fast bandwidth engine controls in an aircraft engine or similar
dynamic physical system performance optimization space.
Exemplary embodiments of methods and systems for managing
power of an engine are described above in detail. The methods and systems are not
limited to the specific embodiments described herein, but rather, components of
systems andfor steps of the methods may be used independently and separately from
other components and/or steps described herein. For example, the methods may also
be used in combination with other power management systems and methods, and are
not limited to practice with only the gas turbine engine systems and methods as
described herein. Rather, the exemplary embodiment can be implemented and used in
connection with many other power management applications.
Although specific features of various embodiments of the disclosure
may be shown in some drawings and not in others, this is for convenience only. In
accordance with the principles of the disclosure, any feature of a drawing may be
referenced and/or claimed in combination with any feature of any other drawing.
This written description uses examples for disclosure, including the
best mode, and also to enable any person skilled in the art to practice the disclosure,
including making and using any devices or systems and performing any incorporated
methods. The patentable scope of the disclosure is defined by the claims, and may
include other examples that occur to those skilled in the art. Such other examples are
intended to be within the scope of the claims if they have structural elements that do
not differ from the literal language of the claims, or if they include equivalent
structural elements with insubstantial differences from the literal languages of the
claims.
PARTS LIST
Engine ..................................................................................................1..0. .
Longitudinal centerline ............................................................................. 12
Aircraft ......................................................................................................1 4
Inlet ........................................................................................................... 16
Ambient air ............................................................................................... 18
Fan assembly ...........................................................................................2..0
Turbine engine ..........................................................................................2 2
HPC ...........................................................................................................2 4
Combustor ................................................................................................. 26
HPT ................... .. .............................................................................. 28
LPT .....................................................................................................3..0.. ..
Augmentor ..........................................................................................3.2.. ...
First shaft .................................................................................................3. 4
Second shaft .............................................................................................. 36
Outer casing ..............................................................................................3 8
Inner casing ...............................................................................................4 0
Forward section ...................................................................................4..2.. ..
Bypass duct ............................................................................................... 44
Diffuser liner ......................................................................................4..6.. ...
Valve assembly .........................................................................................4 8
Inner bypass duct ................................................................................... -50
Outer bypass duct ...................................................................................... 52
Fan bypass flow ........................................................................................ 54
Inner bypass flow ...................................................................................... 56
Outer bypass flow ..................................................................................5.8..
Separation liner ....................................................................................... 60
Valve portion ............................................................................................ 62
A seal .......................................................................................................6. 4
First airflow portion .................................................................................. 66
Bypass air .................................................................................................. 68
Exhaust ...................................................................................................... 70
Fan inlet temperature sensor .................................................................... -72
Total pressure sensor ................................................................................7.4
Discharge static pressure sensor ............................................................ 76
Discharge static pressure sensor ............................................................... 78
Duct static pressure sensor ........................................................................ 80
Liner static pressure sensor ....................................................................... 82
Flame detector ........................................................................................... 84
Exhaust gas temperature sensor ................................................................8 6
Compressor discharge temperature sensor ................................................ 88
Compressor inlet temperature sensor ........................................................ 90
Fan speed sensor .................................................................................9.2.. ...
Core speed sensor ................................. . ............................................9..4.
Power management system .................................................................... 100
Power management component .............................................................. 102
Control system ........................................................................................ 104
Sensors .................................................................................................... 106
Actuators .................................................................................................. 108
Engine controller .....................................................................................1 10
Sensor data .........................................................................................1..1. 2
Low pass filter ...................................................................................1..1..4..
Actuator position data .......................................................................1..1..8..
Ambient flight condition data ............................................................... 120
References ............................................................................................... 122
Constraints .............................................................................................. 124
Control inputs .......................................................................................... 126
Implementation ....................................................................................2..0.0.
Baseline power management component .............................................2..0. 2
Model predictive control (MPC) ............................................................. 204
Preferred control ..................................................................................... 210
Optimal modifications ............................................................................ 212
References ............................................................................................... 214
Open-loop inputs ..................................................................................... 216
Constraint limits ................... .. ........................................................2..1..8.
Exemplary flow chart .............................................................................. 300
Received data .......................................................................................... 302
Power management is determined .......................................................... 304
Power management is output .................................................................. 308
Performs model prediction ...................................................................... 310
Power management is determined .......................................................3..1. 2
Power management is output .................................................................. 314

WE CLAIM:
1. A power management system (100) for online power management
of an engine (10), said power management system comprising:
a baseline power management component (102) configured to receive
at least one data input (112) from an engine control system (104) operating on a first
bandwidth, wherein said baseline power management component is configured to
operate on a second bandwidth; and
a model predictive control (204) configured to:
predict an engine operating condition over a desired future
^ ^ horizon using the at least one data input and a closed-loop model of the
engine;
determine an optimal engine power management based on the
prediction;
solve a constrained optimization for a desired optimization
objective; and
output the optimal engine power management.
2. The power management system in accordance with Claim 1,
wherein said baseline power management component is further configured to
determine a baseline engine power management using the at least one data input.
^ ^ 3. The power management system in accordance with Claim 1,
wherein the at least one data input comprises at least one of a sensor input, an actuator
position input, and an ambient condition input.
4. The power management system in accordance with Claim 1,
wherein said model predictive control is further configured to predict an engine
operating condition over a future horizon using the determined baseline engine power
management and a closed-loop engine model.
17
5. A power management system in accordance with Claim 1, wherein
the optimal engine power management ftirther comprises at least one of references,
open-loop inputs, and constraint limits.
6. The power management system in accordance with Claim 1,
wherein said baseline power management component is further configured to receive
at least one data input filtered by a low pass filter.
7. A gas turbine engine (10) for use in an aircraft; (14), said gas turbine
engine comprising:
at least one sensor (106) configured to sense an engine parameter and
to generate a sensor input (112) representing the engine parameter;
a control system (104) configured to control at least one of said gas
turbine engine; and
a power management system (100) for online power management of an
engine, said power management system comprising:
a baseline power management component (202) configured to
receive at least one data input; and
a model predictive control (204) configured to:
predict an engine operating condition over a fiiture
horizon using the at least one data input and a closed-loop engine
model;
determine an optimal engine control based on the
prediction;
solve a constrained optimization for a desired
optimization objective; and
output the optimal engine power management.
18
8. The gas turbine engine in accordance with Claim 7, wherein said
control system is configured to control one of said gas turbine engine using the
optimal engine power management.
9. The gas turbine engine in accordance with Claim 7, wherein said at
least one sensor is at least one of a temperature sensor, a pressure sensor, a speed
sensor, a torque sensor, a flow sensor, an ambient condition sensor, and an actuator
position sensor.
10. The gas turbine engine in accordance with Claim 7, wherein said
at least one sensor and said control system operate in a closed-loop engine control
system configured to operate on a first bandwidth.