Anatomy and SSSF Analysis of Ideal Turbo Jet Engine P M V Subbarao Professor Mechanical Engineering...
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Transcript of Anatomy and SSSF Analysis of Ideal Turbo Jet Engine P M V Subbarao Professor Mechanical Engineering...
Anatomy and SSSF Analysis of Ideal Turbo Jet Engine
P M V Subbarao
Professor
Mechanical Engineering Department
Features of A True Flying Machine Muscles ….
Inlet : Steady State Stead Flow
Conservation of mass mmm 21
CVCV WgzV
hmgzV
hmQ
2
2
1
2
22
First Law :
222111 VAVA
22
22
2
21
1
Vh
Vh
No heat transfer and no work transfer : A Pure Passive compressor : No Change in potential energy.
Assume gas as an ideal and calorically perfect.
22
22
2
21
1
VTc
VTc pp
p
pp
p c
VTc
c
VTc
22
22
2
21
1
eTemperaturDynamicc
V
p
2
2
Kinetic energy that can produce enthalpy and hence temperature rise and vice versa.
More fundamentally,
• Temperature (Static Temperature) is a measure of microscopic kinetic energy.
• Dynamic Temperature is a measure of macroscopic kinetic energy.
• Define:
• Total Temperature = Static Temperature + Dynamic Temperature
0102
22
2
21
1 22TcTc
c
VTc
c
VTc pp
pp
pp
• A fluid at rest (zero macroscopic kinetic energy) can convert its internal energy or enthalpy into kinetic energy, provided:
• It is above absolute zero pressure and temperature.
• A moving fluid (finite macroscopic kinetic energy) can convert its kinetic energy into internal energy or enthalpy.
• Maximum possible conversion corresponds to fluid coming to rest.
p
pp
p c
VTc
c
VTc
22
22
2
21
1 222111 VAVAwith
Measure of An Action Measure of Hardware
Measure of benefits at zero running cost Measure of capital cost
An Inlet of A Jet engine is a passive compressor, i.e. zero running cost
Measure of Compression
p
pp
p c
VTc
c
VTc
22
22
2
21
1
An ideal intake device is an isentropic compressor with zero power input.
1
1
2
1
2
T
T
p
p
At design condition: 1
22
T
T
p
p
Maximum Possible Compression
0102
22
2
21
1 22TcTc
c
VTc
c
VTc pp
pp
pp
An inlet device with zero exit velocity will produce maximum compression.
1
1
02
1
02
T
T
p
p
At design condition:
10202
T
T
p
p 10101
T
T
p
p 100
T
T
p
p
Control Volumes Can never Afford to Generate Maximum Compression
Total Pressure and Total Temperature are just reference measures…..
Compressor : Steady State Stead Flow Process
CVCV WgzV
hmgzV
hmQ
3
2
2
2
22
First Law :
Conservation of mass mmm 32 333222 VAVA
No heat transfer, change in potential energies is negligible
3
2
2
2
22
Vh
VhmW compressor
CVWV
hmV
hm
3
2
2
2
22
3
2
2
2
22
VTc
VTcmW ppcompressor
0302 TTcmW pcompressor
0302 hhmW compressor
A compressor of A Jet engine is an active device, i.e. there exist capital and running cost.
If so, why is this?
Do I get more befit than the expenditure?
Does it also compensate extra capital cost too?
Measure of Extra Life Generation
compressorpp WTcmTcm
0203
Isentropic active compression
1
02
03
02
03
T
T
p
p
1
2
02
2
02
T
T
p
p 1
3
03
3
03
T
T
p
p 1
2
3
2
3
T
T
p
p
Anatomy of A Jet Engine: Combustion Chamber
3 4 3 -- 4s : increasingT: increasingp : constant???
Vac
Vjet
3 – 4 : Isobaric Heat addition
CVQ
No work transfer and change in potential energies is negligible
CVCV WgzV
hmgzV
hmQ
3
2
4
2
2
3 22
3
2
4
2
2
3 22
Vhm
VhmQCV
3 – 4 : Ideal Combustor
No work transfer and change in potential energies is negligible & adiabatic combustion
fmfmmmm airfairgas 11
CV
gas
gas
air
airfuelCV WgzV
hmgzV
hmHVmQ
22
22
gas
gas
air
airfuel
Vhm
VhmHVm
22
22
03 041fuel p pm HV mc T m f c T
How much fuel should be added to get High fuel economy?
How to get a compact jet engine ?
0403 )1( TcfTcHVf pp
pc
HVfTTf
0304)1(
Turbine : SSSF Process :
No heat transfer. Change in potential energies is negligible
4
5
T
04 051turbineW m f h h
2 2
4 5
1 12 2
CVCVV V
Q m f h gz m f h gz W
CVWV
hfmV
hfm
5
2
4
2
21
21
04 051turbine pW m f c T T
Turbine is to produce just enough power.
turbine compressorW W
04 05 02 031p pm c f T T m c T T
02 03
05 04 1
T TT T
f
The vigor of Jet: 051pmc f T
Anatomy of An Ideal Jet Engine
1 2 3 4 5 6
1 -- 2s = constantT0 = constantP0 = constant
2 -- 3s = constantT0 = increasingP0 = increasing
3 -- 4s = increasingT0 = increasingP0 = constant
4 -- 5s = constantT0 = decreasingP0 = decreasing
5 -- 6s = constantT0 = constantP0 = constant