School of Aerospace Engineering MITE RECENT PROGRESS IN COMPRESSOR STALL AND SURGE CONTROL L. N....
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Transcript of School of Aerospace Engineering MITE RECENT PROGRESS IN COMPRESSOR STALL AND SURGE CONTROL L. N....
School of Aerospace Engineering
MITE
RECENT PROGRESS IN RECENT PROGRESS IN COMPRESSOR COMPRESSOR
STALL AND SURGE CONTROLSTALL AND SURGE CONTROL
L. N. Sankar, J. V. R. Prasad, Y. Neumeier, W. M. HaddadN. Markopoulos, A. Stein, S. Niazi, A. Leonessa
School of Aerospace EngineeringGeorgia Institute of Technology
Supported by the U.S. Army Research Office Under the Multidisciplinary University Research Initiative (MURI) on Intelligent Turbine Engines
School of Aerospace Engineering
MITE
Background
• Modern turbine engines are highly developed, complex systems.
• There is a continuing trend towards fewer stages, and high pressure ratios per compression stage.
• Compressor instabilities (rotating stall and surge) develop, that must be controlled at high pressure ratios, especially at low mass flow rates.
School of Aerospace Engineering
MITE
Compressor Performance Map
Cho
ke L
imi t
Sur
ge L
imit
Volumetric Flow Rate
Tot
al P
ress
ure
Ris
e
Desired Extension of Operating Range
Lines of Constant Efficiency
Lines of Constant Rotational Speed
School of Aerospace Engineering
MITE
SurgePressure Rise
Flow Rate
PeakPerformance
Mild Surge Deep Surge
An “axisymmetric” phenomenon that causes periodic variations in mass flow rate and pressure rise. Deep surge can create a reversed flow in the entire compression system.
Pressure Rise
Flow Rate
MeanOperating Point
Limit CycleOscillations
School of Aerospace Engineering
MITE
ROTATING STALL
Loca
l Sep
arat
ion
Loca
l Sep
arat
ion
1
Rotating Stall is a local separation patternthat rotates at a fraction of the spool RPM
School of Aerospace Engineering
MITE
Different Strategies for Compressor Control
Controller UnitBleed Air
PressureSensors
AirInjection
Bleed Valves
Movable Plenum Walls
Guide Vanes
Steady Blowing
School of Aerospace Engineering
MITE
Prior Work• An excellent survey by Bram de Jager summarizes
worldwide activities on rotating stall and surge control.
• A number of researchers in U. S. are exploring compressor stall and surge control, using theoretical, computational, and experimental techniques.
– MIT, Purdue, Penn State, Cal Tech, Wright Labs, and all major U. S. Industries
• This presentation will focus on Georgia Tech Activities.
School of Aerospace Engineering
MITE
Georgia Tech Center for IntelligentTurbine Engines
– Start Date: November 1, 1995
– Research Team: Eleven faculty members with expertise in controls, compressors, combustion,
propulsion, fluid mechanics, diagnostics, MEMS and neural net.
– Facilities: Combustion, compressor, micro- electronics and fluid mechanics laboratories
– Research Areas: Control of combustor processes, Nonlinear control theory, Control of compressor stall and surge,
MEMS
School of Aerospace Engineering
MITE
MITE Program Objectives Develop general
• Control approaches
• Sensors/actuators
• Computational approaches
that will permit engine manufacturers to improve the design process,performance, operability and safety of future gas turbines.
Demonstrate developed technologies on small-scale experiments
Transfer developed technologies to industry and government
School of Aerospace Engineering
MITE
MITE Research TeamName School Research Area
Dr. Mark Allen ECE MEMS
Dr. Martin Brooke ECE Hardware Neural Networks
Dr. Ari Glezer ME Flow control/actuators
Dr. Wassim Haddad AE Nonlinear control theory
Dr. Jeff Jagoda AE Combustion and spray diagnostics
Dr. Suresh Menon AE LES of reacting flows
Dr. Y. Neumeier AE Control of combustor and compressor processes
Dr. J.V. R. Prasad AE Control of compressor instabilities
Dr. L.N. Sankar AE CFD of compressor flow
Dr. Jerry Seitzman AE Combustion mixing control and sensors
Dr. Ben Zinn AE/ME Control of instabilities and combustion processes
Supporting Staff: Research engineers, post doctoral fellows, graduate students, machineand electronic shops personnel, computer group, library and administrative supportpersonnel.
School of Aerospace Engineering
MITE
Research Activities Control of combustor mixing processes (e.g., fuel-air, combustor
pattern factor) via synthetic jets
Control of axial and centrifugal compressor stall by passive andactive (e.g., flow throttling, fuel flow rate control) means
Wireless MEMS pressure sensor for high temperature applications
Neural net control of combustion processes
Nonlinear control framework for engine compression systems
CFD of compression systems
LES of two-phase reacting flows
“Smart” fuel injection systems
School of Aerospace Engineering
MITE
Compressor Control- Modeling Efforts
• Two and three-dimensional compressible flow solvers for modeling compressor stall and surge control
• Multi-mode models for rotating stall and surgein axial flow compressors
• Centrifugal compressor model for surge control involving pressure, mass flow rate, and impeller RPM dynamics
• Model extensions for compressor stall control via fuel modulations
School of Aerospace Engineering
MITE
Compressor Control- Theory
• Reduced order models based on CFD for modelingcompression system transients
• Optimal nonlinear control framework to address disturbance rejection, control saturation and robustness
• Adaptive control framework for elimination of rotating stall and surge
• Nonlinear stabilization framework for interactionbetween higher order system modes
• Combined model and fuzzy rule based methodologyto address actuator rate and amplitude limits
• Corrections to rotating stall control theories.
School of Aerospace Engineering
MITE
A Simplified Compressor Model with Heat Addition
pN
oddnn
nAnrn
ncK
ddA
1!
)()(
1
pN
evennn
nAnsn
ncK
dd
0!
)()(
2
outTΔΨ
TK5KΦ4K7KdτGd
~~
)ct1(toutT1ΔΨ9KG1
8KdτoutTd
~
~
~
Q6KoutT
~TK5K4K3K
d)(d ΔΨ
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MITE
Experimental Studies
• Experimental Demonstrations– Rotating stall control through
• Throttling
• Recirculation of air from plenum to inlet
• Combustion process modulations
• Passive means
• New facility development– A centrifugal compressor facility for the study of
flow dynamics, and for the development of active and passive control methods
School of Aerospace Engineering
MITE
Sample Results
• Experimental Studies
• Control Theory
• CFD Modeling
School of Aerospace Engineering
MITE
Schematic of the Axial Compressor Facility (Bleed Control)
Controller
Rotatingstallamplitude
Servo motor and throttle
Computer Main Throttle
Bleed/recirculation loop
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MITE
Schematic of the Axial Compressor Facility (Fuel Control)
Fuel Supply
Main Throttle
Controller
Rotatingstallamplitude
Needle Valve
Servo motor
Computer
Fuel modulation loop
Diffusion flame simulates heat release in a real engine combustorOperating point around 300 0F
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MITE
Fuzzy Logic Control of Rotating Stall
• Fuzzy Rules were developed using numerical simulations.
• The numerical simulations utilized the Moore-Greitzer Model, a system of ODEs.
• Control variable was the amount of opening of a bleed valve placed in the plenum chamber.
• Following simulations, these rules were implemented in hardware, at our axial compressor facility.
School of Aerospace Engineering
MITE
Fuzzy Logic Controller
Compression System
Defuzzifier Inference Engine Fuzzifier
Measured/ComputedPressure Fluctuationsat compressor casing
Throttle OpeningOutput
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MITE
Fuzzy Logic Control of Rotating Stall
0
100000
200000
300000
400000
500000
600000
700000
800000
0 10 20 30 40 50 60 70 80 90 100
Main Throttle(%)
Ro
tati
ng
Sta
ll A
mp
litu
de Closed-Loop Fuzzy Logic
Control 50% Bleed
bleed
bleed
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MITE
Rotating Stall Control by Flow Separators
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
. Sta
ll A
mpl
itude
(%
of
Pam
b)
No Separator
8 Separators
8 Separators with active feedback control
No Separator with active feedback control
School of Aerospace Engineering
MITE
CFD ModelingCFD Modeling
Perspective View of the NASA Low Speed Centrifugal Compressor
• Detailed study and simulation of NASA Low Speed Centrifugal Compressor
• Simulation and Validation of Air Bleeding & Blowing/Injection as a Means to Control and Stabilize Compressors Near Surge Line
• Useful Operating Range of Compressor was Extended to 60% Below Design Conditions
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MITE
Simulation Setup
• 20 Full Blades with 55° Backsweep
• Inlet Diameter 0.87 m
• Exit Diameter 1.52 m
• Tip Clearance 2.54 mm (1.8% of Blade Height )
• Design Conditions:
– Mass Flow Rate 30 kg/sec
– Rotational Speed 1862 RPM
– Total Pressure Ratio 1.14
– Adiabatic Efficiency 0.992
NASA Low Speed Centrifugal CompressorNASA Low Speed Centrifugal Compressor
School of Aerospace Engineering
MITE
Uncontrolled Operation
1.05
1.07
1.09
1.11
1.13
1.15
1.17
1.19
1.21
1.23
1.25
15 20 25 30 35 40 45
Corrected Mass Flow (kg/s)
Tot
al P
ress
ure
Rat
io
Experiment
CFD
Stall, Unstable
Design Point
Stable OperationC
Uncontrolled, Stall OperationLarge, Unbounded Fluctuations
-2
-1
0
1
2
-25 -15 -5 5
% of Mass Flow Rate Fluctuations
% o
f Tot
al P
ress
ure
Fluc
tuat
ions C
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MITE
Off-Design Results (Uncontrolled)
Unstable Condition Blades Stall After 3 Cycles (t*)
At Beginning
After 1 Cycle
After 3 Cycles (t*)
Velocity Vectorsat Midpassage
GrowingReversed Flow
LE
TE
School of Aerospace Engineering
MITE
Compressor Control Setup
0.04RInlet
Impeller
Casing
°
RInlet
Rotation Axis
Injection Angle, =5ºYaw Angle, =0º5% or 10%Injected Mass Flow Rate
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MITE
Controlled Operation
Controlled Operation with 10% Air Injection (Fluctuations are Decreased to 2~3%Extension of Useful Operating Range (60% Below Design)
-2
-1
0
1
2
-25 -5
% of Mass Flow Rate Fluctuations
% o
f Tot
al p
ress
ure
Fluc
tuat
ions
D
1.05
1.07
1.09
1.11
1.13
1.15
1.17
1.19
1.21
1.23
1.25
5 15 25 35 45
Corrected Mass Flow (kg/s)
Tot
al P
ress
ure
Rat
io
Experiment
CFD
10% Injection
5% Injection
Stall, Unstable
Design PointControlledAir Injection
D
.m=17.5 kg/sec )
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MITE
Air Injection
0
25
50
75
100
-0.3 -0.1 0.1 0.3 0.5Normalized Axial Velocity, Vn/Ut
Per
cent
Im
mer
sion
No Injection (t*)
5% Injection
10% Injection
Controlled, Stable Operation
Injected Air (10%)
Injection SuppressesStalled Reverse FlowRegions Near LE
School of Aerospace Engineering
MITE
DLR Centrifugal Compressor
0
0.5
1
1.5
2
2.5
3
0 0.2 0.4 0.6 0.8 1
Meridional Chord, S/Smax
Loc
al S
tatic
Pre
ssu
re,
p/pt
o Experiment (time mean)
CFD
Control simulationsare currently inprogress
School of Aerospace Engineering
MITE
NASA ROTOR-67Axial Compressor
0.6
0.8
1
1.2
1.4
1.6
-125 -50 25 100 175 250
% Chord
M
CFD
EXP.l
Relative Mach No. at 30% Pitch
Results for Rotating Stall Simulation considering six flow passages are in progress
51.4 cm
School of Aerospace Engineering
MITE
Concluding Remarks
• A concerted effort involving control theory, simulations and experimental studies is underway at Georgia Tech to understand and control compressor instabilities.
• Encouraging results have been obtained in all these areas.
• A combined CFD-Feedback Control simulation is currently in progress.