Question 7

A non–afterburning turbojet with a single–spool axial compressor has the following reference data

(a) Perform the parametric cycle analysis to obtain single-point output. (Note: It is advisable to write down all relevant temperature and pressure ratios as you calculate them, as you will likely have to use them again subsequently.)

(i) Compute the compressor total temperature ratio.
(ii) Determine the compressor efficiency.
(iii) Calculate the fuel-air ratio
(iv) Evaluate the turbine pressure ratio.
v) Determine the exhaust nozzle exit Mach number M9.
(vi) Compute the exhaust velocity ratio 𝑉9 𝑎0
(vii) Analyse the engine specific thrust.
(viii) Determine the thrust specific fuel consumption.

(b) Discuss the typical input and output parameters in the parametric analysis of a turbojet engine. Hence, explain the difference between parametric cycle analysis and engine performance analysis (or off–design analysis).

(c) Perform an off–design analysis on the reference engine, with its burner exit temperature reduced to 1350K as it flies at Mach 0.78 in the same ambient conditions:
(i) Compute the combustor enthalpy ratio.
(ii) Analyse the off–design compressor pressure ratio. State your assumptions for this analysis to be valid.
(iii) Determine the new fuel–air ratio.