Parametric Study of Turbofan Engine Performance P M V Subbarao Professor Mechanical Engineering Department Its Time to think about fuel Economy……
Thrust Specific Fuel Consumption TSFC
Effect of Fan Bypass Ratio r 0,p,fan =2.5 r 0,p,comp =15 T 0max =1200K M ac =0.75
TSFC Combined Effect of Fan & Compressor Pressure Ratios T 0max =1200K M ac =0.75
Combined Effect of Fan & Compressor Pressure Ratios T 0max =1200K M ac =0.75
Combined Effect of Fan & Compressor Pressure Ratios TSFC Compressor Pressure Ratio Fan Pressure Ratio
Combined Effect of Fan & Compressor Pressure Ratios Specific Thrust kN.s/kg Compressor Pressure Ratio Fan Pressure Ratio r 0p,fan =1.5 r 0p,fan =2.0 r 0p,fan =4.0 r 0p,fan =3.5 r 0p,fan =4.5 r 0p,fan =3.0
Optimum Fan Pressure Ratio for Fuel Economy Fan Pressure Ratio TSFC r 0,p,comp =24 T 0max =1800K M ac =0.9
Optimum Fan Pressure Ratio for Compactness Specific Thrust kN.s/kg Fan Pressure Ratio r 0,p,comp =24 T 0max =1800K M ac =0.9
Optimum Fan Pressure Ratio for Propulsion Efficiency Fan Pressure Ratio r 0,p,comp =24 T 0max =1800K M ac =0.9
Fan Effects on Thrust Ratio Fan Pressure Ratio r 0,p,comp =24 T 0max =1800K M ac =0.9
Thrust Ratio : r 0,p,fan =2.5 & M ac =0.75 Compressor Pressure Ratio
Turbofan with After Burner
Effect of After Burner : Compactness Turbojet w AB Turbojet w/o AB Turbofan w AB Turbojfan w/o AB For same level of life & Energy
Effect of After Burner : Fuel Economy TSFC Turbofan w/o AB Turbojet w/o AB Turbojet w AB Turbofan w AB
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.
Thrust Specific Fuel Consumption TSFC
For small fuel/air ratios: Assume that the value of f is constant:
For maximum fuel economy, maximize the denominator. Defined D as Fan Effects : Fan Pressure Ratio & Bypass Ratio. Core Effects : Bypass Ratio, Compressor Pressure Ratio & Combustion Chamber Temperature Ratio.
Optimal Selection of Bypass Ratio As fan handles the entire air intake, V coldjet is independent of bypass ratio
Rewrite as:
Condition for optimum bypass ratio at minimum TSFC. Solve above equation for optimum bypass ratio to give minimum specific fuel consumption. Further use of opt to calculate velocities of cold and hot jets will gives ? ????
Maximum Fuel Economy : Effect of Compressor Pressure Ratio opt r 0,p,comp T 04 =1700K r 0,p,fan =2.0 M ac =0.9
Maximum Fuel Economy : Effect of Fan Pressure Ratio opt r 0,p,fan T 04 =1700K r 0,p,comp =24.0 M ac =0.9
Maximum Fuel Economy : Effect of Flight Mach Number opt ac T 04 =1700K r 0,p,comp =24.0 r 0,p,fan =3.0 r 0,p,fan =2.0
Optimal Selection of Fan Pressure Ratio
Maximum Fuel Economy : Effect of Bypass Ratio r fan,opt r 0,p,comp =24.0 M ac =0.9
Maximum Fuel Economy : Effect of Compressor Pressure Ratio r fan,opt r comp T 04 =1700K =4.0 M ac =0.9
r fan,opt TSFC Contours of Constant TSFC
Contours of Constant Specific Thrust r fan,opt
Mixed Flow Turbofan Engine h 7 6c 8