Answer Happy

Question 3 An aircraft turbojet engine, without bypass, burns hydrogen (lower heating value 120 MJ/kg). The pressure ratio is 30, compressor small-stage (or polytropic) efficiency is 85%, and turbine small-stage efficiency is 88%. Intake air is at -20°C and 60 kPa, intake speed is 220 m s', and turbine inlet total temperature is 1450 K. Throughout this question, use the cold-air-standard model. ms (a) Draw a schematic diagram of the engine, and T-s and p-v diagrams. Label the states sequentially with the intake as state 1. [4] [12] (b ) b Calculate the total temperature and pressure at the turbine exit. [2] (c) Hence, determine if the exhaust is choked. [4] (d) Determine the mass air-fuel ratio. (e) Determine the stoichiometric air-fuel ratio for hydrogen from first principles, and the equivalence ratio for this engine. [3]