# EAS201: In an ideal unmixed-exhaust turbofan engine where the exhaust exit pressures of both the core engine: Aerospace Propulsion Assignment, SUSS

Question 4

Question 4a
In an ideal unmixedโexhaust turbofan engine where the exhaust exit pressures of both the core engine and bypass duct are equal to ambient pressure, the thrust produced by the core engine ๐น๐ถ, and the fan ๐น๐น are:

Where
๐ฬ ๐ถ = mass flowrate of air through core engine

๐ฬ ๐น = mass flowrate of air through bypass duct

๐ฬ๐ = fuel mass flowrate

๐0 = forward velocity

๐9 = core engine exhaust nozzle exit velocity

๐19 = bypass duct nozzle exit velocity

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Question 4a(i)
For a turbofan engine, explain the term specific thrust. If its bypass ratio ๐ผ = ๐ฬ ๐น/๐ฬ ๐ถ, show that the specific thrust can be expressed as:

Question 4a(ii)
Define the term thrust specific fuel consumption of a turbofan engine, and hence show that it can be expressed in terms of its specific thrust as in the following:

Question 4b
At forward speed of 750 km/h, a turbofan engine with bypass ratio of 5 has a fuel-air ratio of 0.03. At the exhaust nozzles of both the bypass duct and core engine, the gases are fully expanded. The bypass exhaust exits at 450 m/s while the core engine exhaust exits at 500 m/s. Analyse the engine specific thrust.