Part-A: 1. Define the second law of thermodynamics. 2. Mention the function of reheat in the modified cycle. 3. State the reason for increase in compressor exit temperature in a practical cycle. 4. Mention the purpose of intercooler in modified Brayton cycle. 5. Define surging. 6. Draw the velocity triangle for axial flow compressor. 7. Mention the function of liners in combustion chamber. 8. Mention how the aviation fuel differs from other fuels. 9. Draw the velocity diagram of turbine blade. 10. State the various types of blade cooling.
Part-B: 11. A gas turbine operates on a pressure ratio of 4. The inlet air temperature to the compressor is 280 K and the air entering the turbine is at a temperature of 777 C. Assume that the cycle operates under ideal condition. Determine compressor exit temperature in Kelvin Take k = 1.4, Cp = 1.005 kJ/kg K. 12. Mention the influence of pressure thrust on the overall thrust of an aircraft. 13. State the importance of pre-whirl in the inlet of the compressor. 14. With the help of neat sketches, explain the variation of pressure and velocity in an axial compressor. 15. State the mechanism of the catalyst influencing the reaction rate. 16. Mention the purpose of stator, rotor, shroud and case of an axial flow turbine.
Part-C: 17. a. A gas turbine operates on a pressure ratio of 4. The inlet air temperature to the compressor is 270 K and the air entering the turbine is at a temperature of 677 ̊C. If the volume rate of air entering the compressor is 280 m3/s. Calculate the net power output of the cycle in MW. Also compute its efficiency. Assume that the cycle operates under ideal condition.
18. a. In a gas turbine plant air enters the compressor at 1.1 bar and 277 K. It is compressed to 5.5 bar with an isentropic efficiency of 82%. The maximum temperature at the inlet to the turbine is 1000 C. The isentropic efficiency of the turbine is 85%. The calorific value of the fuel used is 43.1 MJ/kg. Calculate the following
1.Compressor work in KJ/kg 2. Heat supplied in KJ//kg 3. Turbine work in KJ/kg 4. Net-work in KJ/kg 5.Thermal efficiency 6. Air/Fuel ratio 7. Specific fuel consumption in kg Take Cpa = 1.005 kJ/kg K, ϒa = 1.4, Cpg = 1.147 kJ/kg K,ϒg = 1.33
19. a. Determine the impeller diameters and the width at the impeller exit and the power required to drive the compressor, from the following given data
Speed N = 12,500 rev/min Mass flow rate = 15 kg /s Pressure ration = 4:1 Isentropic efficiency = 75 % Slip factor =0.9 Flow coefficient at the impeller exit = 0.3 Hub diameter of the eye = 15 cm Axial velocity of air at the entry to and exit from the impeller = 150 m/s Stagnation temperature at the inlet = 295 K Stagnation pressure at inlet = 1 bar Assume equal pressure ratio in the impeller and diffuser.
20. a. Air at a temperature of 273 K enters a ten stage axial flow compressor at the rate of 7 kg/s. The pressure ratio is 6.5 and the isentropic efficiency is 92%, the compression process being adiabatic. The compressor has symmetrical blades. The axial velocity of 110 m/s is uniform across the stage and the mean blade speed of each stage is 190 m/s. Determine the direction of the air at the entry to the exit from the rotor and the stator blades and also the power given to the air. Assume Cp = 1.005 kJ/kg K and ϒ= 1.4.
21. a. Discuss the behavior of turboprop engine for fuel flow rate as function of true air speed with the help of a neat sketch. b. Mention the advantage and disadvantage of a turboprop engine.
22. a. List the requirement of a good atomizer. b. With the help of a neat sketch explain the breakup mechanism for a swirl injector.
23. a. Briefly explain the working of afterburner with neat sketch.
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