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Parametric Study of Turbofan Performance
P M V Subbarao Professor Mechanical Engineering Department Identification of Sensitive Design & Operationa Variables ……
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Performance of An Ideal Turbofan
Inlet
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Performance Analysis of Turbofan
Performance Parameters: Specific Thrust & TSFC Operational Parameters : Flight Mach number & Ambient conditions. Design Variables : Fan Pressure Ratio, Bypass Ratio, Compressor Pressure Ratio, Combustion Chamber Temperature Ratio. Fan Effects : Fan Pressure Ratio Bypass Ratio. Fan Stream Thrust Vs Total Thrust.
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Influence of Fan: Pressure Ratio: Mac = 0.75
r0,p,comp=15.0 a=4.0 T0max=1200K
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Combined Effect of Fan & Compressor Pressure Ratios
T0max=1200K Mac =0.75
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Combined Effect of Fan & Compressor Pressure Ratios
T0max=1200K Mac =0.75 TSFC
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Optimum Fan Pressure Ratio for Fuel Economy
=3 a =4 =6 =5 r0,p,comp=24 T0max=1800K Mac =0.9 7 12 8 10 TSFC Fan Pressure Ratio
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Optimum Fan Pressure Ratio for Compactness
=3 =4 =5 6 Specific Thrust kN.s/kg 7 8 10 r0,p,comp=24 T0max=1800K Mac =0.9 12 Fan Pressure Ratio
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Optimum Fan Pressure Ratio for Propulsion Efficiency
r0p,comp=24 T0max=1800K Mac =0.9 a Fan Pressure Ratio
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Combined Effect of Fan & Compressor Pressure Ratios
T0max=1200K Mac =0.75 Fan Pressure Ratio r0p,fan=4.0 r0p,fan=3.5 r0p,fan=4.5 r0p,fan=3.0 r0p,fan=2.0 Specific Thrust kN.s/kg r0p,fan=1.5 Compressor Pressure Ratio
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Combined Effect of Fan & Compressor Pressure Ratios
T0max=1200K Mac =0.75 Fan Pressure Ratio TSFC Compressor Pressure Ratio
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Fan Effects on Fuel Economy: r0,p,fan=2.5 & Mac=0.75
=5 =4 =3 =2 =1.5 =1.0 a =0.5 TSFC =8 =12 Compressor Pressure Ratio
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Optimization Analysis of Turbofan
Operational Parameters : Flight Mach number & Ambient conditions. Design Variables : Fan Pressure Ratio, Bypass Ratio, Compressor Pressure Ratio, Combustion Chamber Temperature Ratio. Maximization of specific thrust is not an important issue. Fuel economy is the main focus for optimization.
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Neglect the value of f in denominator, as the value of f is <<1
Thrust Specific Fuel Consumption TSFC Neglect the value of f in denominator, as the value of f is <<1
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Simplified Model for TSFC
For maximum fuel economy, maximize the denominator.
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Simplified Objective Function
Core Effects : Bypass Ratio, Compressor Pressure Ratio & Combustion Chamber Temperature Ratio. Fan Effects : Fan Pressure Ratio & Bypass Ratio.
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Selection of Optimum Bypass Ratio
As fan handles the entire air intake, Vcoldjet is independent of bypass ratio
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Modified Objective Function
Rewrite OF for best as:
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Relative change in Turbine TR to BPR
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The final Objective function for best
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