Thermal & Fluid Power Enngineering - Dec 2015
Mechanical Engineering (Semester 6)
TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks.
Solve any five:
1 (a) Give difference between ram jet and pulse jet.(4 marks)
1 (b) Explain the functions of draft mode tube with neat diagram.(4 marks)
1 (c) What are the limitations of Pelton wheel turbine?(4 marks)
1 (d) Define the following terms for a turbine:
i) Stage efficiency
ii) Blade efficiency.(4 marks) 1 (e) Differentiate between high pressure and low pressure boilers.(4 marks) 1 (f) Make a list of any five boiler mountings and write down their functions.(4 marks) 2 (a) Derive the expression for the force exerted by a jet of water of velocity V and area A on a plate when:
i) Plate in vertical
ii) Plate is inclined at θ.(8 marks) 2 (b) The following data was recorded during a test performed on a boiler, economizer and a superheater.
Steam generated = 5000 kg/hr at 14 bar pressure: Mass of coal brunt = 660 kg/hr; Calorific value of coal = 29500 kJ/kg: Temperature of feed water at entry and exit of economizer = 30°C and 130°C respectively; Temperature of steam leaving the superheater = 320°C; Dryness fractions of steam leaving the boiler = 0.95; Cp (superheated steam)= 2.3 kJ/kg K; Cp(water) = 4.18 kJ/kg K. Calculate
i) Factor of evaporation
ii) Overall efficiency of the plant.
iii) The percentage of available heat utilized in the boiler, economizer and superheater. Hence determine percentage of heat lost.(12 marks) 3 (a) With neat sketch explain the working of closed cycle gas turbine plant and discuss the advantages of closed cycle over open cycle gas turbine plant.(8 marks) 3 (b) The following particulars refers to a single row impulse turbine:
Mean diameter of blade ring = 2.5 m; speed = 3000 RPM; nozzle angle = 20°; ratio of blade velocity to steam velocity = 0.4; blade friction factor = 0.8; blade angle at exit = 3° less than that at inlet; steam flow = 36,000 kg/hr.
Draw velocity diagram for moving blade and estimate (a) power developed; (b) blade efficiency; and (c) steam consumption in kg/kW hr.(8 marks) 3 (c) With neat sketch explain the principle of operation of Turbofan engine.(4 marks) 4 (a) Derive the expression for Maximum discharge through steam nozzle.(6 marks) 4 (b) A gas turbine unit receives air at 100 kPa and 300 K and compresses it adiabatically to 620 kPa with efficiency of the compressor 88%. The fuel has heating value of 44180 kJ/kg and the fuel/air ratio is 0.017kg fuel/kg air. The turbine internal efficiency is 90%. Calculate the compressor work, turbine work and thermal efficiency.(10 marks) 4 (c) Draw general layout of a reaction turbine plant and explain various heads on turbine.(4 marks) 5 (a) Explain the working of any types of high pressure boiler with the help of neat sketch.(8 marks) 5 (b) A single jet Pelton turbine operates a 10,000 kW generator. The generator efficiency is 92%, turbine efficiency is 86%, turbine head is 350m, coefficient of nozzle velocity is 0.98, speed ratio is 0.46 and jet ratio is approximately 12. Find the size of jet, mean diameter of runner, synchronous speed, specific speed of turbine and bucket dimensions.(12 marks) 6 (a) Explain turbojet engine with neat diagram. What are the advantages and disadvantages of turbojet engine?(10 marks) 6 (b) The nozzle of an impulse turbine are supplied with superheated steam at 10 bar. 250°C. The steam leaves the nozzles at a pressure of 1.0 bar. The steam consumption for the turbine is 16 kg/kW hr when it develops 225 kW. If the throat diameter is 0.8 cm determine the number of nozzle required and exit diameter of the nozzle, assuming that the 10% of the total heat drop is lost in overcoming the friction in the divergent portion only. Neglect the velocity of approach.(10 marks)