Q 8. A low pressure turbine within a turbofan jet engine consists of five repeating stages....

 

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Q 8. A low pressure turbine within a turbofan jet engine consists of five repeating stages. The turbine inlet stagnation temperature is 1200 K and the inlet stagnation pressure is 213 kPa. It operates with a mass flow of 15 kgs 1 and generates 6.64 MW of mechanical power. The stator in each turbine stage turns the flow from 15° at stator inlet to 70° at stator outlet. The turbine mean radius is 0.46 m and the rotational shaft speed is 5600 rpm. (a) Calculate the turbine stage loading coefficient and flow coefficient. Hence, show that the reaction is 0.5 and sketch the velocity triangles for one complete stage. (b) Calculate the annulus area at inlet to the turbine. Use this to estimate the blade height and the hub- to-tip radius ratio for the stator in the first turbine stage. Take y=1.333, R=287.2 J/kgK, and cp=1150 J/kgK for the gas flowing through both designs of turbine. (Ans: a). 1:217, 0:403. b). 0:226 m?) Q 8. A low pressure turbine within a turbofan jet engine consists of five repeating stages. The turbine inlet stagnation temperature is 1200 K and the inlet stagnation pressure is 213 kPa. It operates with a mass flow of 15 kgs 1 and generates 6.64 MW of mechanical power. The stator in each turbine stage turns the flow from 15° at stator inlet to 70° at stator outlet. The turbine mean radius is 0.46 m and the rotational shaft speed is 5600 rpm. (a) Calculate the turbine stage loading coefficient and flow coefficient. Hence, show that the reaction is 0.5 and sketch the velocity triangles for one complete stage. (b) Calculate the annulus area at inlet to the turbine. Use this to estimate the blade height and the hub- to-tip radius ratio for the stator in the first turbine stage. Take y=1.333, R=287.2 J/kgK, and cp=1150 J/kgK for the gas flowing through both designs of turbine. (Ans: a). 1:217, 0:403. b). 0:226 m?)