JNTU
JNTU B.Tech II THERMAL ENGINEERING-I Previous Question Paper (May - 2019 - R15)
Note: This question paper contains two parts A and B. Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks and may have a, b, c as sub questions.
Part A
What is the purpose of lubrication to an engine?
Answer
The primary purpose of lubrication is to reduce friction between moving parts, minimize wear, act as a coolant by carrying away heat, and seal the gaps between piston rings and cylinder walls to prevent gas leakage.
What happens if the fuel is injected too early?
Answer
If fuel is injected too early, it leads to an excessively long ignition delay period. This causes a large accumulation of fuel in the combustion chamber, resulting in a rapid pressure rise upon ignition, which produces high peak pressures, increased thermal stress, and the characteristic 'diesel knock' or rough engine operation.
List out four antiknock additives.
Answer
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Why excess air is to be supplied to a CI engine?
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Define volumetric efficiency.
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Distinguish between blower and compressor.
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Define isentropic efficiency.
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What is the purpose of a roots blower?
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Define ton of refrigeration.
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List out are the applications of air refrigeration?
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Part B
Draw the valve timing diagram of a 4 stroke CI engine and explain.
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What are the merits and demerits of air cooled engines over water cooled engines?
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With a neat sketch explain the fuel injection system in a CI engine.
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What are the different types of lubrication systems?
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What are the effects of bad design combustion chambers?
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What is an aircell combustion chamber?
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What are the different stages of combustion in SI engines?
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List and explain various methods for finding frictional power of an engine.
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How do you measure mean effective pressure?
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Derive an expression for the optimums inter cooler pressure for two stage reciprocating air compressors with perfect inter cooling.
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What is the function of impeller and diffuser in a centrifugal compressor?
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Explain why nowadays axial flow compressors are largely used for aviation gas turbines.
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What is the benefit of using an after cooler with an air-compressor when air under pressure has to be stated over long period?
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Mention the important applications of compressed air.
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Explain the simple vapour compression system with the help of a P-V diagram.
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The inlet conditions to a Brayton cycle are 1 bar and 300 K. The cycle pressure ratio is 6.5. The temperature at the inlet to the turbine is 500 K. Calculate the performance parameters of the cycle.
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Explain with a neat sketch the working of an air refrigeration cycle.
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What is the effect of superheating and subcooling on COP?
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