JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III THERMAL ENGINEERING Previous Question Paper (July/August - 2023 - R16)
i) Question paper consists of Part A, Part B. ii) Part A is compulsory, which carries 25 marks. In Part A, answer all questions. iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
How are heat engines classified?
Answer
Heat engines are primarily classified into two categories based on the location of the combustion process:
- External Combustion Engines (ECE): Engines where the fuel burns outside the main cylinder, such as steam engines and steam turbines, where heat is transferred to a working fluid.
- Internal Combustion Engines (ICE): Engines where the fuel burns inside the cylinder, such as petrol (spark ignition) and diesel (compression ignition) engines, where the products of combustion act as the working fluid.
What is the function of a carburettor?
Answer
The primary function of a carburettor in a spark-ignition engine is to prepare a combustible mixture of air and fuel by atomizing the fuel and mixing it with the incoming air in the correct proportions. It ensures that the engine receives the appropriate air-fuel ratio required for different operating conditions, such as starting, idling, cruising, and acceleration.
Define Indicated power.
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What is brake horse power?
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How are gas turbines classified?
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What is meant by stage compression?
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State the uses of steam produced by the boilers.
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What are the functions of a steam nozzle?
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Define a steam condenser and state its objects.
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What do you mean by compounding of steam turbines?
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Part B
With a neat sketch, explain the working principle of a simple carburetor.
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Explain the phenomenon of diesel knock.
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List various assumptions made in air - standard cycle analysis.
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Briefly explain the stages of combustion in CI engines.
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Briefly discuss the various efficiency terms associated with an engine.
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Define mean effective pressure and distinguish between mean effective pressure and indicated mean effective pressure.
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A four-cylinder engine running at 1200 rpm gave 18.6 kW brake power. The average torque when one cylinder was cut out was 105 N-m. Determine the indicated thermal efficiency if the calorific value of the fuel is 42000 kJ/kg and engine uses 0.34 kg of petrol per break power hour.
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What do you mean by multi-stage compression? State its advantages.
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Differentiate between fan, blower and compressor.
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Describe with neat sketches the working of a simple constant pressure open cycle gas turbine.
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Enumerate the various uses of gas turbine.
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Enumerate the factors which should be considered while selecting a boiler.
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List the advantages of high pressure boilers.
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Steam is expanded in a set of nozzles from 10 bar and 200°C to 5 bar. What type of nozzle is it? Neglecting the initial velocity, find minimum area of the nozzle required to allow a flow of 3 kg/s under the given conditions. Assume that expansion of steam to be isentropic.
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In a De-Laval turbine steam issues from the nozzle with a velocity of 1200 m/s. The nozzle angle is 20°, the mean blade velocity is 400 m/s, and the inlet and outlet angles of blades are equal. The mass of steam flowing through the turbine per hour is 1000 kg. Calculate: a) Blade angles. b) Relative velocity of steam entering the blades. c) Tangential force on the blades. d) Power developed. e) Blade efficiency. Take blade velocity co-efficient as 0.8.
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Explain the difference between an impulse turbine and a reaction turbine.
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Explain the reasons for inefficiency in surface condensers.
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