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Reg. No. : .................................... Name : .........................................
Third Semester B.Tech. Degree Examination, November 2009 (2008 Scheme) Branch : Industrial Engineering 08.306 : THERMAL ENGINEERING Time : 3 Hours
Max. Marks : 100
Instructions : 1) Use of Mollier chart and steam tables permitted. 2) Answer all questions from Part A and any one question from each of the Module in Part – B. PART – A 1. Write notes on Mollier Chart. 2. List the advantages of Benson Boiler. 3. Explain what do you mean by stage efficiency of a steam turbine. 4. Sketch and explain a jet condenser. 5. Sketch and explain a binary vapour cycle. 6. What are the desirable properties of fuels for boilers ? 7. Sketch two combustion chambers for a CI engine. 8. Derive an expression for the work done in a single stage reciprocating air compressor. 9. Explain the working of a Roots blower. 10. With the help of a block diagram, explain an open cycle gas turbine. (10×4= 40 Marks) P.T.O.
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PART – B Module – I 11. a) Find the enthalpy, internal energy and entropy of 1 kg of steam at a pressure of 10 bar and temperature of 250° C.
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b) Dry saturated steam at a pressure of 10 bar is discharged through a convergent divergent nozzle. The mass flow rate is 0.56 kg/s. The back pressure is 0.2 bar. Determine the throat pressure. If 10% of the overall isentropic enthalpy drop reheats, by friction, the steam in the divergent portion of the nozzle, calculate the throat area and the exit area of the nozzle. 12 OR 12. a) Describe the pressure-velocity compounding of steam turbines.
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b) Steam issues from the nozzles of an impulse turbine with a velocity of 750 m/s. The nozzle is inclined at 20°. The mean blade velocity is 350 m/s. The mass flow rate is 1000 kg/hr. Friction factor is 0.8. Determine. i) Blade angles (assume symmetrical blades) ii) Power developed iii) Blade efficiency and iv) Stage efficiency. 12 Module – II 13. a) Sketch the common performance characteristics of an IC engine and discuss their significance.
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b) The analysis of a sample of coal is given below. Carbon = 82%; Hydrogen = 6%; Oxygen = 4%, Moisture = 2% and rest ash. Determine the theoretical minimum air required for complete combustion of 1 kg of coal. If the actual air supplied in 18 kg per kg of coal, the hydrogen is completely burned and 80% carbon is burned to CO2, the remainder to CO, determine the volumetric analysis of the dry products of combustion. 12 OR 14. a) Discuss the combustion phenomena in IC engines. b) Explain in detail, the heat balance test of IC engines.
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Module – III 15. a) Explain why intercooling is desirable in reciprocating air compressors.
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b) A gas turbine plant works between the fixed adiabatic temperature limits of 350°K and 900°K. The pressure limits are 1 bar and 5 bar. The isentropic efficiency of the blower is 0.8 and that of the turbine is 0.85. Determine the actual thermal efficiency of the plant and the power developed for a fuel consumption of 2.5 kg/s. Take calorific value of the fuel as 40,000 kJ/kg. 12 OR 16. a) Compare and contrast between reciprocating compressors and centrifugal blowers.
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b) Derive an expression for the efficiency of a two-stage air compressor with inter cooling. Assume no clearance.
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