JNTU
JNTU B.Tech III THERMAL ENGINEERING Previous Question Paper (May - 2018 - 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.
Main
What is Pre- Ignition? How can it be detected?
Answer
Pre-ignition is the premature ignition of the air-fuel mixture in the combustion chamber before the spark occurs, caused by a hot spot such as an overheated spark plug or carbon deposit. It can be detected by the presence of a distinct pinging or knocking sound that persists even when the ignition is switched off, or by observing a sudden rise in cylinder head temperature.
What are the causes of Knocking in C.I Engines?
Answer
Knocking in C.I. engines is primarily caused by a long ignition delay period. Factors contributing to this include: 1) Low cetane number of the fuel, 2) Low compression ratio or low intake air temperature and pressure, and 3) High engine speed or excessive fuel injection advance, which allows an accumulation of fuel that detonates rapidly upon auto-ignition.
Define Break Power of an Engine?
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What do you know about Heat Balance sheet of a Steam engine cylinder?
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What is a slip factor and pressure co-efficient in Compressors?
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What are the main differences between Jet Propulsion and Rocket Propulsion?
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Write a short note on ‘Pulverized fuel firing’.
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What do you mean by a super saturated flow?
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Discuss the advantages of a steam turbine over the steam Engines.
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State and explain in brief the ‘Dalton’s law of Partial Pressures.
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A four cylinder engine running at 1200 RPM, delivers 20 KW. The average Torque when one cylinder was cut is 110Nm. Find the Indicated Thermal efficiency if the calorific value of fuel is 43 MJ/Kg and the Engine use 360 grams of gasoline per kWh?
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Explain the phenomenon of Knocking in SI Engine.
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What are the important basic components of an IC Engine and explain them in brief?
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Explain the valve and port diagrams of an IC Engine with a neat sketch.
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What is the function of Boiler mounting? Can a boiler work without mountings?
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Explain the construction and working of any high pressure Boiler with a neat sketch.
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Explain the various Accessories of Boilers with a neat sketch.
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What are basic differences between Fire tube and water tube Boilers?
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Describe the operations of Rankine cycle and derive the expression for its efficiency?
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A 35 kW (IP) system engines consumes 284 kg/hr at 15 bar and 2500 C. If condenser pressure is 0.14 bar, determine (i) Final condition of steam (ii) Rankine efficiency (iii) relative efficiency?
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State the methods of increasing the thermal efficiency of a Rankine cycle.
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Explain briefly the following methods of governing: (i) Throttle governing (ii) Cut- off governing?
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Classify the Surface Condensers and explain with neat sketch any two of them?
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The volume of a condenser which contains 0.144 kg of air with steam is 4.05 m3. Temperature in the condenser is 400C and there is some water in the condenser. Determine the pressure in the condenser. R for air = 287 J/kgK.
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Define the term Steam Nozzle? Explain various types of Nozzles.
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Air is expanded reversibly and adiabatically in a Nozzle from 13bar and 1500C to a pressure of 6 bar. The Inlet velocity of the Nozzle is very small and the process occurs under steady state flow conditions. Calculate the Exit velocity of the Nozzle.
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What is the difference between an Impulse turbine and a Reaction turbine?
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The speed of a single stage Impulse turbine is 3000rpm and the mean blade diameter is 1m, the Nozzle of the turbine is inclined at 200 to the plane of the wheel and the moving blade inlet and exit angles are 300 and 350. Assuming a friction factor (blade velocity coefficient) of 0.8, determine: i) The power developed for a steam consumption rate of 9000 kg/hr ii) The blade or diagram efficiency iii) The axial thrust. Assume that the steam enters the blade without stock.
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Explain with the help of a neat sketch a single stage Impulse turbine also explain pressure and velocity variation along the axial direction.
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