school of aerospace engineering mite school of aerospace engineering mite active and passive control...
TRANSCRIPT
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
OverviewOverview
Future Work
Research Team
Problem Statement
Objectives
List Of Accomplishments
Significant Findings
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
Research TeamResearch TeamPI’s: Dr. J.V.R. Prasad
Dr. Y. NeumeierPost Doctoral Fellows:
Dr. N. MarkopoulosDr. M. Lal (Took up a position
in ME School)Graduate Students:
Mr. A. Krichene, AE, Ph.D. studentDr. C. Rivera, AE (graduated)Dr. T-Y. Ziang, AE (graduated)Mr. R. Swaminathan, AE (graduated)Mr. S. Bae, AE (graduated)Mr. A. Meehan, ME (graduated)
School of Aerospace Engineering
MITE
Problem Statement Problem Statement
Rotating stall and surge limit the operation of modern day turbine engine compressors due to associated severe loss of performance, component failure, etc.
Current practice is to limit operation with roughly 20% stall margin and limitations on fuel flow authorityduring acceleration and decelerations, representingloss of opportunity
Active and/or passive control strategies can result in reduced stall margin that will correspond to reducedweight and fuel savings
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
ObjectivesObjectives
Improved understanding of compressor stall and surge phenomena through modeling, simulation and experimentation
Investigation of Passive and active control mechanisms for reducing compressor stall and surge
Development of hybrid control methods by combining control-theoretic and decision-theoretic techniques
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
List of AccomplishmentsList of Accomplishments
Using theoretical extensions to Moore-Greitzer model to include finite duct effects, analytically showed that the inlet shape affects the stall inception point in axial compressors. This finding has animportant bearing on the design of appropriate inlets for passive control of rotating stall. (Presented a paper at the 1999 JPC)
Further experimental evaluations of passive control schemes forsuppression of rotating stall. (Presented a paper at the 1999 IEEEConference on Control Applications)
Combined the backstepping control method from the literature with the adaptive neural net/fuzzy logic scheme for improving robustness of the controller and evaluated the scheme in simulations. (Presented papers at the 1999 JPC and 1999 AIAA GNC)
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
Implemented the observer scheme for on-line identification of stall precursor waves and experimentally evaluated a novel active control scheme based on stall precursors for active surge control in the centrifugal compressor experimental facility at Georgia Tech.
List of Current Year Accomplishments (Continued)List of Current Year Accomplishments (Continued)
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
List of AccomplishmentsList of Accomplishments
Using theoretical extensions to Moore-Greitzer model to include finite duct effects, analytically showed that the inlet shape affects the stall inception point in axial compressors. This finding has animportant bearing on the design of appropriate inlets for passive control of rotating stall. (Presented a paper at the 1999 JPC)
Experimental evaluations of passive control schemes forsuppression of rotating stall. (Presented a paper at the 1999 IEEEConference on Control Applications)
Combined the backstepping control method from the literature with the adaptive neural net/fuzzy logic scheme for improving robustness of the controller and evaluated the scheme in simulations. (Presented papers at the 1999 JPC and 1999 AIAA GNC)
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
MODELING OF COMPRESSOR ROTATING STALL
AND SURGE - RECENT PROGRESS
by
N. Markopoulos
MODELING OF COMPRESSOR ROTATING STALL
AND SURGE - RECENT PROGRESS
by
N. Markopoulos
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
PREVIOUS WORK…
Complete stability analysis of the Moore-Greitzer model under stall amplitude feedback
REASONS FOR THE MODELING WORK…
Moore-Greitzer model highly approximate - does not predict correct r.s. frequency, does not include effects of finite compressor length
Moore has suggested in a patent that a separator would eliminate rotating stall – we showed experimentally that this is not true
To our knowledge, there is no model that takes into account at a fundamental level of compressibility effects is available in the open literature - Mach numbers between 0.4 – 0.6
No control oriented models available for centrifugal compressors
Bottom line: Develop a basic physical understanding of the phenomena that we are trying to control
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
Inlet
B
Plenum TOutlet
Schematic of a CompressorSchematic of a Compressor
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
Our model:
Moore-Greitzer model:
When Q = 0 the two models become qualitatively the same
Moore-Greitzer model is obtained as a limiting case from our model as the inlet and outlet duct lengths go to infinity
For our model stall inception occurs slightly before or beyond the peak – depending on the sign of Q, representing the effect of the inlet
AQLUdsinsinAUT
AQT R2
2
0
22
TLUdsinsinAUA
QQT R
22
0
22
mLR2R
LU;dsinsinAU
mLR2
1A R
2
0
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
COMPARISON WITH THE MOORE-GREITZER MODEL…COMPARISON WITH THE MOORE-GREITZER MODEL…
Stall inception point
M-G: Ours:
Stable operation
M-G: Ours:
Unstable operation
M-G: Ours:
Conclude: It is very desirable to have Q > 0 for delaying loss of stability
P q p n s g m
h
f d e k l
a c
b r
o U
0U
0U
0U
T
QLUU R
T
QLUU R
T
QLUU R
)lsinhklcoshk(
kkQ;0vkuk
i22
ui22
v
vuvu
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
Quantitative account of instability dynamics for axial compressors - extends well-known Moore-Greitzer model
Chief difference effect of finite inlet and outlet duct lengths
What happens at entrance to inlet slightly hastens or delays settling of instabilities before or beyond peak of compressor map
Predicted r. s. frequency higher than Moore-Greitzer and function of compressor inlet length
Needed: a more fundamental account of effect of inlet in terms of inlet design parameters - future work
Brings up practical questions for the design of inlets and control of instabilities - transition to industry
MAIN RESULTS ON MODELING SO FAR…MAIN RESULTS ON MODELING SO FAR…
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
Axial velocity in real compressors varies between 150 to 200 m/sec corresponding to Mach numbers between 0.4 and 0.6
Inclusion of compressibility effects into our model
Governing equation is Classical wave eq. rather than Laplace’s eq.
Implies two qualitatively different types of disturbances (bound and scattering)
CURRENT WORK – AXIAL COMPRESSORS…CURRENT WORK – AXIAL COMPRESSORS…
Disturbance analysis for purely radial flow
Disturbance theory and modeling for centrifugal compressors
CURRENT WORK – CENTRIFUGAL COMPRESSORS…CURRENT WORK – CENTRIFUGAL COMPRESSORS…
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
List AccomplishmentsList Accomplishments
Using theoretical extensions to Moore-Greitzer model to include finite duct effects, analytically showed that the inlet shape affects the stall inception point in axial compressors. This finding has animportant bearing on the design of appropriate inlets for passive control of rotating stall. (Presented a paper at the 1999 JPC)
Further experimental evaluations of passive control schemes forsuppression of rotating stall. (Presented a paper at the 1999 IEEEConference on Control Applications)
Combined the backstepping control method from the literature with the adaptive neural net/fuzzy logic scheme for improving robustness of the controller and evaluated the scheme in simulations. (Presented papers at the 1999 JPC and 1999 AIAA GNC)
School of Aerospace Engineering
MITE
Schematic of Experimental Set-up(Flow Separators and Flow Recirculation)
Schematic of Experimental Set-up(Flow Separators and Flow Recirculation)
Controller
Pressure Measurements
Servomotor and bleed
Computer
Bleed/recirculation loop
Main Throttle
School of Aerospace Engineering
MITE
Flow Separators in the InletFlow Separators in the Inlet
•Moore predicted that one separator in the inlet should eliminate the rotating stall altogether (Patent No. 5,297,930 by Moore F, K. “Rotating Stall Suppression” )
School of Aerospace Engineering
MITE
Time [sec]
No separator One separator
Transducers' angular
locations
Pressure Oscillations with and without an Inlet Separator
Pressure Oscillations with and without an Inlet Separator
• The separator seems to have no apparent effect upon the traveling waves
School of Aerospace Engineering
MITE
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
0.018
0.02
35.0 40.0 45.0 50.0 55.0 60.0
Main Throttle Openning (%)
Rot
atin
g St
all A
mpl
itud
e (%
of
Pam
b) No Separator
8 Separators
8 Separators with active ambient bleed
No Separator with active ambient bleed
Effect of Eight Flow Separators on Rotating Stall Amplitude
Effect of Eight Flow Separators on Rotating Stall Amplitude
School of Aerospace Engineering
MITE
0
0.005
0.01
0.015
0.02
0.025
0.03
0 0.1 0.2 0.3 0.4 0.5
Normalized Mass Flow
Rot
atin
g St
all A
mpl
itud
e(%
of
Pam
b)
50% Bleed to ambient 50% Bleed to inlet
100% Bleed to ambient 100% Bleed to inlet
Effect of Flow Recirculation on Rotating StallEffect of Flow Recirculation on Rotating Stall
School of Aerospace Engineering
MITE
0
0.005
0.01
0.015
0.02
0.025
0.03
0 0.05 0.1 0.15 0.2 0.25 0.3
Normalized Mass Flow
Rot
atin
g S
tall
Am
plitu
de(%
of
Pam
b)
100% Bleed to inlet 50% Bleed to inlet (Feedback) 50% Bleed to inlet
Effect of Flow Recirculation with Active Control on Rotating Stall
Effect of Flow Recirculation with Active Control on Rotating Stall
School of Aerospace Engineering
MITE
0.1
0.15
0.2
0.25
0.3
0.35
0.0 20.0 40.0 60.0 80.0 100.0
Main Throttle Opening (%)
Nor
mal
ized
Tot
al P
ress
ure
Bleed(0%) Bleed(50%) Bleed(100%)
Compressor Pressure Rise versus Main Throttle Opening for Different Ambient Bleed Openings
Compressor Pressure Rise versus Main Throttle Opening for Different Ambient Bleed Openings
School of Aerospace Engineering
MITE
0.1
0.15
0.2
0.25
0.3
0.35
0 0.1 0.2 0.3 0.4 0.5 0.6
Normalized Mass Flow
Nor
mal
ized
Tot
al P
ress
ure
Bleed 0% Bleed 50% Bleed 100%
Compressor Pressure Rise versus Normalized Flow Rate for Different Ambient Bleed Openings
Compressor Pressure Rise versus Normalized Flow Rate for Different Ambient Bleed Openings
School of Aerospace Engineering
MITE
0.1
0.15
0.2
0.25
0.3
0.35
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35
Normalized Mass Flow
Nor
mal
ized
Tot
al P
ress
ure
Bleed 0% Bleed 50% Bleed 100%
Compressor Pressure Rise versus Normalized Flow Rate for Different Recirculation Bleed Openings
Compressor Pressure Rise versus Normalized Flow Rate for Different Recirculation Bleed Openings
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
xc
System Linear controller
Model inversion
Adaptive neural net/fuzzy logic
Model based controller
+
-+
+
x
Adaptive Neuro-fuzzy Controller
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
Adaptive Neuro-fuzzy Controllers
Hybrid control methodology which combines modelinversion with neural nets and fuzzy logic
Parameterization of uncertainty using neural nets andfuzzy logic and adaptation of parameters based onLyapunov stability theory
Rule base adaptation and linear controller gainadaptation to accommodate actuator limits
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
Model based controller
Hybrid controller with fixed linear controller gain
Hybrid controller with variable linear controller gain
Non-dimensional time
Rot
atin
g st
all a
mpl
itud
eResponse to Initial Disturbance with Model
UncertaintyController is based on fifth order compressor mapSimulation is based on third order compressor map
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
Related Work
T700 Engine Fuel Control Using Adaptive Neural networks
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
PI
Network
Neural
FgP ZPPPTNNe ,,,,,,,,0.1 4541341
adu
u
ou u
PREFN
ECU
),:(Feedforward2
TQrr
GovernorRateCompensationand Dynamics
T700Engine
HMU(NonlinearStateFeedback)-
Np
T700 Engine Fuel Controller
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
0 2 4 6 8 10 1290
95
100
105
Time (sec)
pow
er
turb
ine s
peed (
perc
ent)
Inversion ControlSet point
Performance of the T700 Engine Fuel Controller
PowerTurbineSpeed(%)
Time (sec)
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
0 2 4 6 8 10 1290
95
100
105
pow
er
turb
ine s
peed (
perc
ent)
Time (sec)
neural network inversion control
Performance of the T700 Engine Fuel Controller to a Periodic Load Disturbance with and without adaptive neural networks
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
Implemented the observer scheme for on-line identification of stall precursor waves and experimentally evaluated a novel active control scheme based on stall precursors for active surge control in the centrifugal compressor experimental facility at Georgia Tech.
List of Accomplishments (Continued)List of Accomplishments (Continued)
School of Aerospace Engineering
MITE
Centrifugal Compressor SetupCentrifugal Compressor Setup
Control Law
Frequency/Amplitude Observer
Fuel Valve
Control Computer
Throttle Valve
servomotor
servomotor
Throttle and FuelValve Commands
Data AcquisitionComputer
Pressure Measurements
PressureTransducer
Pressures
Self entrainingcombustor
Inlet pressure readout
Control Variables
School of Aerospace Engineering
MITE
Controller EssentialsController Essentials
• Utilizes real time observer that identifies the frequency and amplitude of the most dominant modes of oscillations in the inlet pressure signal
• Sets on-off alarm signal when precursors waves are identified with strong enough amplitude
• Varies the fuel flow rate or other actuators according to the alarm signal
School of Aerospace Engineering
MITE
• Rejecting rather than suppressing stall
• Provides global stability
• Does not require high bandwidth actuator
• Can work with existing fuel injection systems
• Requires very little information about compressor characteristics
Controller Essentials (Cont.)Controller Essentials (Cont.)
School of Aerospace Engineering
MITE
Real-Time Mode ObservationReal-Time Mode ObservationLow Back Pressure, 15 KRPM
School of Aerospace Engineering
MITE
Real-Time Mode ObservationReal-Time Mode ObservationHigh Back Pressure Nearing Surge, 15 KRPM
School of Aerospace Engineering
MITE
Real-Time Mode ObservationReal-Time Mode ObservationUncontrolled Surge, 15 KRPM
School of Aerospace Engineering
MITE
Real-Time Mode ObservationReal-Time Mode ObservationUncontrolled Surge, 15 KRPM
School of Aerospace Engineering
MITE
Real-Time Mode ObservationReal-Time Mode ObservationUncontrolled Surge, 30 KRPM
School of Aerospace Engineering
MITE
Real-Time Mode ObservationReal-Time Mode ObservationUncontrolled Surge, 30 KRPM
School of Aerospace Engineering
MITE
Real-Time Mode ObservationReal-Time Mode ObservationUncontrolled Surge, 30 KRPM
School of Aerospace Engineering
MITE
Real-Time Mode ObservationReal-Time Mode ObservationUncontrolled Surge, 30 KRPM
School of Aerospace Engineering
MITE
Control Using Throttle ActuationControl Using Throttle Actuation
School of Aerospace Engineering
MITE
Control Using Throttle Actuation (Cont.)Control Using Throttle Actuation (Cont.)
School of Aerospace Engineering
MITE
Control Using Fuel Valve ActuationControl Using Fuel Valve Actuation
School of Aerospace Engineering
MITE
Control Using Fuel Valve Actuation (Cont.)Control Using Fuel Valve Actuation (Cont.)
School of Aerospace Engineering
MITE
School of Aerospace Engineering
MITE
Future WorkFuture Work
Further theoretical, simulation (using Dr. Sankar’s CFD models) and experimental evaluations of control actuation schemes (e.g., bleed valve, fuel flowmodulations, etc.) using the centrifugal compressorfacility.
Experimental evaluation of novel controllers.
Further analysis of the effect of inlet parameters on rotating stall in axial compressors.