Turbojet engine thrust O TONG UN The rate of flow of fuel entering the engine is very small compared with the rate of flow of air.If the contribution of fuel to the nozzle gross thrust is ignored,the net thrust is: FN =mair (Ve-v) The velocity of the jet(ve)must exceed the true airspeed of the aircraft (v)if there is to be a net forward thrust on the aircraft.The velocity (ve) can be calculated thermodynamically based on adiabatic expansion. MT333 Materials Applications Practice Prof.XiaoQi Chen A17 Turbofan High-pressure High-pressure Fan compressor turbine High-pressure O TONG UN shaft Low-pressure shaft Low-pressure Combustion Low-pressure Nozzle compressor chamber turbine Turbofan's Bypass ratio(BPR):the ratio between the amount of air(kg)which bypasses the core of the engine and that passes through the core. Low bypass:2:1 or less. High bypass:4:1 to 8:1,Rolls-Royce Trent XWB approaching 10:1 MT333 Materials Applications Practice Prof.XiaoQi Chen A.18MT333 Materials Applications A.17 & Practice Prof. XiaoQi Chen Turbojet engine thrust The rate of flow of fuel entering the engine is very small compared with the rate of flow of air. If the contribution of fuel to the nozzle gross thrust is ignored, the net thrust is: The velocity of the jet (ve) must exceed the true airspeed of the aircraft (v) if there is to be a net forward thrust on the aircraft. The velocity (ve) can be calculated thermodynamically based on adiabatic expansion. F m (v v) e N  air   MT333 Materials Applications A.18 & Practice Prof. XiaoQi Chen Turbofan • Turbofan’s Bypass ratio (BPR): the ratio between the amount of air (kg) which bypasses the core of the engine and that passes through the core. • Low bypass: 2:1 or less. • High bypass: 4:1 to 8:1, Rolls-Royce Trent XWB approaching 10:1