Apr 6, 1993 - efficiencies of the engine and the compressor pressure ratio of the engine. A b .... generator feeding a free power turbine, rather than a.
31
Coolant optimization of a gas turbine engine A Brown, PhD, DSc, CEng, FIMechE, F ASME School of Mechanical, Materials and Civil Engineering, Cranfield Institute of Technology, Royal Military College of Science, Shrivenham, Swindon
B A Jubran, BSc, PhD Mechanical Engineering Department, University of Jordan '·
••
-•
B W Martin, BSc, MSc, PhD, DSc(Eng), CEng, FIMechE University of Wales, Cardiff
'.,
-. •
•
This paper describes an analysis used to study the performance of the gas turbine engine with particular emphasis on the optimum amount of coolant required for maximum overall efficiency of the engine. The effect of pre-bled air, as well as that drawn from the exit of the compressor, is also studied. The optimum amount of coolant for the engine is found to depend on the effectiveness of the heat extraction parameter A, component efficiencies of the engine and the compressor pressure ratio of the engine.
NOTATION
A
surface area or heat extraction factor as defined by equation (25) function of fluid properties, gas mass flow and blade dimensions in equation (23) function of fluid properties, gas mass flow and blade dimensions in equation (23) specific heat of fluid fuel-air ratio heat-transfer coefficient mass fl.owrate number of blades number of rows of blades being cooled absolute pressure compressor pressure ratio specific gas constant specific work output absolute temperature
b c
c f
h •
m
N
Nr p r R
swo
.
•"'
'.'
•
Subscripts
T y €1
• !
€2
er 11 11comp 17turb
11generator turb 11power t~rb 11oo
isentropic index mass fraction of coolant to gas generator turbine mass fraction of coolant to free power turbine mass fraction of pre-bled coolant to free power turbine error criterion component isentropic·efficiency compressor efficiency isentropic efficiency of both turbines gas generator turbine efficiency power turbine efficiency overall engine efficiency based on heat rejected overall engine efficiency based on work output calorific value of fuel
The MS was received on 2 September 1992 and was accepted for publication on 6 April 1993. A02392
© !MechE 1993
1
2 2p 3 4
air entering the compressor or air bled to cool generator turbine air leaving the compressor pre-bled air leaving the compressor gas generator turbine inlet mainstream gas immediately before mixing with bled air mainstream gas immediately after mixing with bled air bled air at turbine blade roots bled air at blade tips after cooling all components · gas generator turbine exit and free power turbine inlet free power turbine exit based on average temperature blade mean condition coolant condition gas condition maximum value condition in power turbine corresponding to that in compressor turbine uncooled condition
E
·--
Q.
0
0.07
''lcomp =
0. 85
0.06
'1turb =
0.88
0.05
IU
w
0 .04 0.03 0.02 0.01 0 1400
1500
1600
1700
1800
r3 K
Fig. 10 Variation of optimum coolant with generator turbine inlet temperature for A = 0.25 and 0.5 Part A: Journal of Power and Energy
© IMechE 1993
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41
COOLANT OPTIMIZATION OF A GAS TURBINE ENGINE 0.42------------------------------------------------~
- - - Pre-bled - - - Coolant bled from the exit of the compressor
-- --- ----- -- --- -
0.40
0.38 t'lcomp = '1turb
0.36
= 0.88
L . . . . - - . - - - - r - - r - --
0
•
0.80
0.02
--
0.04
0.06
-r--
---r--- . - -.------,------r---ol
0.08
0. 10
0.12
0.14
0.16
0.18
0.20
L-€
(a) A = 0.25 •
0.42 r---- - - - ------- - - - - - -- - - - - -- ---, - --Pre-bled •
-
-
-
-
- Coolant bled from the exit of the compressor
-- -...__......_
- - _ --
0.40
--
0.38 0.80 = 0.88
t'lcomp = t'lturb
0.36 .___ - . - - ---,.-- . - - - - - r - - - - - , - - . , . - - - - r - - r - - - . - - - - " 0 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 (b) A = 0.5
Fig. 11 The effects of coolant pre-bleeding on ratio of 16 and '7comp = 80 per cent
- . __""-
0.40t'lcomp t'lturb
0.38
'
•
- """- -
= 0.90 = 0.88
I
0
0.02
•
•
0.04
0.06
0.08
--- ----- ---
0.10
0.12
0.14
0.16
0.18 0.20
0. 16
0.18
L€
(a) A = 0.25
•
for compressor pressure
Pre-bled - - - Coolant bled from the exit of the compressor
0.44 -
0.42 _.....
'7w
~
Pre-bled
0.44
-
-
-
Coolant bled from the exit of the compressor
-'-..
0.42
0.40
t'lcomp = t'lturb
0.02 (b) A = 0.5
0.90
= 0.88
0.04
0.06
0.08
0.10
0.12
0.14
0.20
L€
Fig. 12 The effects of coolant pre-bleeding on '1w for compressor pressure ratio of 16 and '1comp = 90 per cent ©!MechE 1993
Proc Instn Mech Engrs Vol 207
42
A BROWN, B A JUBRAN AND B W MARTIN
Pre-bled
0.44r--~-----...._._
- - - Coolant bled from the exit of the compressor
..._
~--
- ..._ - - -...
0.42-
--... -...
\.
0.40 -
~
0.95 = 0.88
'1comp = '1turb
- - --
0. 38 '------r---,-----,..---,-, - ---r---,,-- -.. . - --.,.--.,--__J 0 0.02 0.04 0.06 0.08 0.10 0. 12 0.14 0.16 0.18 0.20
LE (a) A = 0.25
• •'•
Pre-bled -- -
Coolant bled from the exit of the compressor
1.
0.42-
0.400.95 '1rurb - 0.88 0. 38 1-------.- --r---..--------.-----r---..------r---.-----..---.....J 0 0.02 0.04 0.06 0.08 0. 10 0.12 0.14 0.16 0.18 0.20 '1comp -
I
I
I
I
I
I
I
I
I
LE (b) A = 0.5
Fig. 13 The effects of coolant pre-bleeding on 1Jw for compressor pressure ratio of 16 and 1Jcomp = 95 per cent •
