RAFAEL Ltd. A NORMALIZED CONTROL SYSTEM for a TURBOJET ENGINE 1
A NORMALIZED CONTROL
SYSTEM FOR A TURBOJET
ENGINE
Ori Yekutiel, Yinon AmirRAFAEL Ltd- P.O.B 2250 (39)
Haifa 31021, Israel
6th Symposium on Jet Engines and Gas TurbinesNovember 2006
RAFAEL Ltd. A NORMALIZED CONTROL SYSTEM for a TURBOJET ENGINE 2
APPROACH:
–Normalization of fuel flow and RPM
correction for altitude, mach, DISA, and
linearization
–Normalize Measurements
–Design single controller (for all flight
conditions)
– "de-normalize” output (normalized fuel
flow) and apply to engine
RAFAEL Ltd. A NORMALIZED CONTROL SYSTEM for a TURBOJET ENGINE 3
FEATURES:
Engine normalization
simplifies control system design for all control design approaches
Only a simple PI example
included in presentation
RAFAEL Ltd. A NORMALIZED CONTROL SYSTEM for a TURBOJET ENGINE 4
A PREVIOUS CONTROLLER(1/5)
GAIN SCHEDULING (Mach,Altitude,
RPM)
Requires Tables – extensive testing
for modeling and verification
Limited use of knowledge of the
physical engine behavior
RAFAEL Ltd. A NORMALIZED CONTROL SYSTEM for a TURBOJET ENGINE 5
A PREVIOUS CONTROLLER(2/5)
RAFAEL Ltd. A NORMALIZED CONTROL SYSTEM for a TURBOJET ENGINE 6
A PREVIOUS CONTROLLER(3/5)
COMMAND
LIMITER
RPM comACCELERATION
LIMITER
CONTROLLER
( P I )
LIMITER
ELECTRONIC
INTERFACE
UNIT
AMPLIFIER
&
PUMPENGINE
RPM XDUCER
P2, T2, T5
XDUCERS
CUTOFF
MIN/MAX RPM BW, ACCEL
error
Wf com
[Volt]
RPM,...
satlo, sathi
RPM
Wf com
[g/s]
RPM
T5
+
-
PUMP RPM
XDUCER
Mach, Altitude
Other Telemetry Data
(Temperatures, Pressures, ...)
RAFAEL Ltd. A NORMALIZED CONTROL SYSTEM for a TURBOJET ENGINE 7
A PREVIOUS CONTROLLER(4/5)
PI RPM2Wfcom Wfcom2RPM
ENGINE
DYNAMICS
(GAIN=1)
RPM
Measurement
RPMcom
RPMmeas
CTRLLR ENGINE
LIMIT
RAFAEL Ltd. A NORMALIZED CONTROL SYSTEM for a TURBOJET ENGINE 8
A PREVIOUS CONTROLLER(5/5)
RPMcom
RPMmeas
LIMIT
s eng1 +
1
s
KI1 + 1 OL
KI
eng
1
RAFAEL Ltd. A NORMALIZED CONTROL SYSTEM for a TURBOJET ENGINE 9
THE NORMALIZED CONTROLLER
T0 = 288.15
TISA = T0 - 0.0065 * Alt
Tamb = TISA + DISA
Beta = 1+ ( Mach ^ 2 ) / 5
Ttot = Tamb * Beta
Delta = ( ( TISA / T0 )^5.256 ) * Beta^3.5
= Ptot/P0
Theta = Ttot / T0
RPM* = RPM / Sqrt ( Theta )
Wf* = Wf / ( Delta * Sqrt ( Theta ) )
RAFAEL Ltd. A NORMALIZED CONTROL SYSTEM for a TURBOJET ENGINE 10
THE CONCEPT:
RPM * RPM
RPMcom * e Wf ' Wf * Wf
Wf ' (RPM *)
Engine with normalized controller
Tau
ENGINEC TJ
C TJ
Wf MachCorrection
inverseC TJ
Dynamics
RPMNormalization
Wf-TagLIMITER
C TJRPM MachCorrection
C TJC TJ Wfde-normalization
RPM MachCorrection
C TJ
RPMNormalization
RPMcom *LIMITER
PI
6 M, H, DISA
5 M, H, DISA 4M
3M 2M, H, DISA
1RPMcom
red: physical normalization (valid for all engines);cyan: Engine-dependent blocks (note: only 2 different
types) yell: PI parameters, per individual controller requirement
(BW, Disturbance Rejection, …).
RAFAEL Ltd. A NORMALIZED CONTROL SYSTEM for a TURBOJET ENGINE 11
FEATURES (1/2):
Gain is practically constant and unity
over RPM, altitude, mach and DISA
A single gain P and Fuel Flow limits
can be designed.
Other Controller designs (not PI) also
simplified (no, or less, envelope
dependence)
RAFAEL Ltd. A NORMALIZED CONTROL SYSTEM for a TURBOJET ENGINE 12
FEATURES (2/2):
Integral Gain I is dependent on engine dynamics.
A mach-Altitude-RPM table may be used (as in
the Present Solution)
Alternately a model of Corrected Tau can be
explored.
– Otto, E.W. and Taylor, B.L, "Dynamics of a Turbojet Engine Considered
as a Quasi-Static System," NACA TR 1011, 1951.
RAFAEL Ltd. A NORMALIZED CONTROL SYSTEM for a TURBOJET ENGINE 13
FUEL LIMITER:
OBJECTIVES:
Avoid surge, stall, over-temperature,
blowout
DESIGN:
In normalized controller !!
IMPLEMENTATION (PI case):
Include anti-windup
RAFAEL Ltd. A NORMALIZED CONTROL SYSTEM for a TURBOJET ENGINE 14
SIMULATION RESULTS (1/2):
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
80
100
RP
M [
%]
RPM C.L. Step response: Full envelope
RPM COM
RPM-Meas
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90
50100
No
rm W
f [%
]
Sat-High
Sat-Low
Wf-Tag
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-100
0100
Normalized timeNo
rm.
en
ve
lop
e
Mach [%]
Alt [%]
DeltaISA: -100 -> 100 [%]
0.6 0.62 0.64 0.66 0.68 0.7 0.72 0.7472
99
RP
M [
%]
RPM C.L. Step response: Full envelope
RPM COM
RPM-Meas
0.6 0.62 0.64 0.66 0.68 0.7 0.72 0.74
55.5106.
No
rm W
f [%
]
Sat-High
Sat-Low
Wf-Tag
0.6 0.62 0.64 0.66 0.68 0.7 0.72 0.74-100
0
100
Normalized timeNo
rm.
en
ve
lop
e
Mach [%]
Alt [%]
DeltaISA: -100 -> 100 [%]
RAFAEL Ltd. A NORMALIZED CONTROL SYSTEM for a TURBOJET ENGINE 15
SIMULATION RESULTS (2/2):
20 30 40 50 60 70 80 90 10030
40
50
60
70
80
90
100
Corrected Air Mass Flow [%]
Pre
ss
ure
Rati
o:
P0
3/P
02
[%
]
COMPRESSOR MAP.M=0 [%] ; H=0[%]; DISA=0[K];
Corrected RPM [%]
38 47
55
64
73
82
91
100
Surge Line
Steady-State Line
SM = 5% Line
response
0 0.2 0.4 0.6 0.8 140
60
80
100
RP
M [
%]
RPM C.L. Step response: M=0 [%] ; H=0[%]; DISA=0[K];
RPM COM
RPM-Meas
0 0.2 0.4 0.6 0.8 10
0.5
1
No
rm W
f [%
]
Normalized time
Sat-High
Sat-Low
Wf-Tag
(Increased gain !!)
RAFAEL Ltd. A NORMALIZED CONTROL SYSTEM for a TURBOJET ENGINE 16
BENEFITS of the APPROACH:
good physical basis for design
simple controller - single design
simple limiter - single design
easier testability - fewer envelope points
simpler transportability of the controller to
other engines
RAFAEL Ltd. A NORMALIZED CONTROL SYSTEM for a TURBOJET ENGINE 17
THANK YOU