Parametric Cycle Analysis of Ideal Turbo Jet Engine

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Parametric Cycle Analysis of Ideal Turbo Jet
Engine

• P M V Subbarao
• Professor
• Mechanical Engineering Department
• Lecture - 8

Selection of Optimal Design Cruising Conditions.
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Effect of Flight Mach Number on Compactness
t0,cc4.5
Specific Thrust kN.s/kg
Mac
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Effect of Flight Mach Number on Fuel Air Ratio
t0,cc4.5
1
2
3
5
10
20
30
Mac
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Effect of Flight Mach Number on Fuel Economy
t0,cc4.5
TSFC kg/ kN.hr
Mac
5
Effect of Flight Mach Number on Fuel Air Ratio
t0,cc4.5
1
2
3
5
10
20
30
Mac
6
Effect of Flight Mach Number on Propulsion
Efficiency
t0,cc4.5
Mac
7
Effect of Flight Mach Number on Thermal Efficiency
t0,cc4.5
Mac
8
Effect of Flight Mach Number on Overall
Efficiency
t0,cc4.5
hO
r0p
Mac
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Effect of Pressure Ratio on Compactness
t0,cc4.5
Specific Thrust kN.s/kg
rp
10
Effect of Pressure Ratio on Fuel Economy
t0,cc4.5
Mac
TSFC kg/ kN.hr
rp
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Effect of Pressure Ratio on Fuel Air Ratio
t0,cc4.5
rp
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Effect of Pressure Ratio on Propulsive Efficiency
t0,cc4.5
rp
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Effect of Pressure Ratio on Thermal Efficiency
t0,cc4.5
rp
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Effect of Pressure Ratio on Overall Efficiency
t0,cc4.5
rp
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Effect of Pressure Ratio on Compactness
t0,cc4.5
Specific Thrust kN.s/kg
rp
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Turbo Jet with Afterburner
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Elevation of Temperature of the Jet
After Burner More Energy at Same Life
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Minimum Jet Temperature
Jet Total Temperature
Jet Static Temperature
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Characterization of AB Jet
Maximum obtainable Mach number of Jet
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Performance of Jet
Propulsive Power or Thrust Power
Specific Thrust S
Thrust Specific Fuel Consumption TSFC
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AB No AB
rp 10
TSFC
Specific Thrust
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Ideal Afterburning Turbojet Engine Performance
Specific Thrust Vs Compressor Pressure Ratio
2.5
Specific Thrust kN.s/kg
3.0
rp
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Ideal Turbojet Engine Performance Specific
Thrust Vs Compressor Pressure Ratio
Maircraft
Specific Thrust kN.s/kg
Compressor Pressure Ratio rp
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Ideal Afterburning Turbojet Engine Performance
TSFC Vs Compressor Pressure Ratio
TSFC kg/ kN.hr
rp
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Effect of Pressure Ratio on Fuel Economy
Constant TIT
TSFC kg/ kN.hr
Mac
rp
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Ideal Afterburning Turbojet Engine Performance
TSFC Vs Compressor Pressure Ratio
rp
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Ideal Afterburning Turbojet Engine Performance
Efficiencies Vs Compressor Pressure Ratio
rp
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Summary of Turbojet Performance

• A high compressor pressure ratio is desirable for
  subsonic flight for good specific thrust and low
  fuel consumption.
• A special care must be used in selecting the
  compressor pressure ratio for the supersonic
  flight Mach number.
• Rapid drop in specific thrust with pressure ratio
  at supersonic conditions.
• There exist a pressure ratio for each Mach number
  of a supersonic flight, that gives maximum
  specific thrust.
• The fuel air ratio decreases with increasing Mach
  number and compressor pressure ratio.
• Propulsive efficiency increases with increasing
  Mach number.
• Rapid fall in specific thrust under supersonic
  conditions is a serious concern.

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Optimization of Turbojet Performance

• P M V Subbarao
• Professor
• Mechanical Engineering Department

Better Deal for Compactness Fuel Economy
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Optimum Compressor Pressure Ratio

• At supersonic flight conditions, a maximum value
  of Specific thrust is Exhibited at certain
  compressor pressure ratio.
• The value of pressure ratio to maximize the
  specific thrust at a given flight Mach number
  should be found by differentiation of specific
  thrust equation.

For Maximum Specific Thrust
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Optimum Compressor Pressure Ratio Vs Mach Number
W AB
r0p,opt
W/o AB
Mac
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Optimal Turbojet Engine Performance
With After Burner
Specific Thrust kN.s/kg
TSFC kg/ kN.hr
Without After Burner
Mac
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Energy Flow in Jet Engine
Energy input
Long distance travel demands high flight
velocity. High flight velocity leads to drop in
compactness and fuel economy. A Single Jet is
blackmailing the jet engine !!!