JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III THERMAL ENGINEERING Previous Question Paper (November/December - 2017 - R15)
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.
Part A
What is the use of air standard cycle analysis?
Answer
Air standard cycle analysis is used to provide a simplified theoretical model of internal combustion engine operation. It allows for the calculation of the maximum possible thermal efficiency and performance limits of an engine by assuming air behaves as an ideal gas and the combustion process is replaced by heat addition.
How SI engine fuels are rated?
Answer
SI engine fuels are rated using the Octane Number. This scale measures the anti-knock quality of the fuel by comparing it to a reference mixture of iso-octane (assigned a value of 100) and n-heptane (assigned a value of 0). A higher octane number indicates greater resistance to auto-ignition or engine knocking.
List three principal factors that influence engine performance.
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Write a short note on P-θ Diagrams in Engine testing.
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Classify different types of compressors.
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Explain the advantages and disadvantages of reheating in gas turbines.
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Define the term 'steam nozzle' and explain various types of nozzles.
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List the primary requirements of steam generators.
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Classify different types of turbines.
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What is mean by compounding in turbine?
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Part B
Compare Otto, diesel and dual cycles for same maximum pressure and heat input condition.
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What is meant by ignition lag in SI engines and explain the factors affecting the ignition lag.
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A six cylinder, single acting internal combustion engine has the piston speed of 540 m/min, piston diameter 12 cm and stroke length 18 cm. While developing 60 kW BP, it gave mechanical efficiency equal to 80%. Mean effective pressure acting on the piston face is 4.063 bars. The specific fuel consumption per BP hour is 0.3 kg. If the calorific value of the fuel used is 42000 kJ/kg, determine (a) whether it is a two stroke or four stroke engine (b) thermal efficiency of the engine based on brake power.
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In a test with a four cylinder four stroke petrol engine, the following results are obtained for a particular setting and speed. BP with all cylinders working = 24.0 kW, BP with No.1 cylinder cut off = 16.2 kW BP with No.2 cylinder cut off = 16.7 kW, BP with No.3 cylinder cut off = 16.8 kW BP with No.4 cylinder cut off = 17.3 kW. Estimate the IP of the engine and its mechanical efficiency.
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An axial flow compressor with compression ratio of 5, draws air at 20°C and delivers it at 50°C. Assuming 50% degree of reaction, find the velocity of flow if the blade velocity is 100m/s. Also find the number of stages if work factor=0.85, α=10°, β=40° and Cp=1.005 kJ/kg K.
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State the merits of gas turbines over IC Engine and steam turbines. Discuss also the demerits over gas turbine.
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Give the construction and working of the Babcock Wilcox water tube boiler.
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Derive the conditions for discharge and its maximum value of a nozzle.
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Derive the expression for condition for maximum efficiency of an impulse turbine.
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A surface condenser is designed to handle 10000 kg of steam per hour. The steam enters at 0.08bar abs. and 0.9 dryness and the condensate leave at the corresponding saturation temperature. The pressure is constant throughout the condenser. Estimate the cooling water flow rate per hour if the cooling water temperature rise is limited to 10°C.
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