JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II THERMAL ENGINEERING I Previous Question Paper (September/October - 2023 - R13)
Note: 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
(25 Marks)
What are the events recorded in port timing diagram of a diesel engine?
Answer
The port timing diagram of a two-stroke diesel engine records the following key events: Exhaust port opening (EPO), Transfer port opening (TPO), Transfer port closing (TPC), and Exhaust port closing (EPC). These events are measured in degrees of crank angle relative to the Top Dead Center (TDC) and Bottom Dead Center (BDC) positions.
What do you mean by combustion stoichiometry?
Answer
Combustion stoichiometry refers to the theoretical calculation of the minimum amount of oxygen or air required for the complete combustion of a fuel. It is based on the principle of conservation of mass, where the number of atoms of each element in the reactants must equal the number of atoms of the same element in the products.
In this process, the fuel is assumed to react completely with oxygen such that no fuel remains unburnt and no oxygen is left over, resulting in products consisting only of carbon dioxide, water vapor, and nitrogen (if air is used). The stoichiometric air-fuel ratio is the specific ratio where the chemical reaction is perfectly balanced, leaving zero excess oxygen in the exhaust gases.
What are the phases of combustion in SI engines?
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What do you mean by anti knock additive? Give some examples.
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What are the components of heat balance sheet?
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What are the differences between reciprocating and rotary type compressors?
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What is the working principle of roots blower?
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Define degree of reaction and work done factor.
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What is the effect of superheating on COP?
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What are the refrigerant and absorbent combinations used in VARS?
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PART - B
(50 Marks)
What are the reasons for variation of events in ideal valve timing diagram to actual valve timing diagram?
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Write a note on fuel injection system in SI engines.
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The carburetor is not required in compression ignition engine. Why? Justify the statement. How it is meeting the requirement?
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Draw the cross section of a single cylinder spark ignition engine and discuss the important components.
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Explain the phenomenon of knock in CI engines and compare it with SI engine knock.
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Explain different stages of combustion in CI engine, with the help of p-Ɵ diagrams both theoretical and actual.
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Explain the method of conducting retardation test in internal combustion engine and compare this method with Willaan’s line method.
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Determine the size of the cylinder for a double acting air compressor of 37 kW in which air is drawn in at 1.01325 bar and 150C and compressed according to the law pv
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A full load test was conducted on a 2 stroke engine and the following results were obtained: Speed = 500 rpm, Brake load = 500N, imep = 3 bar, Oil consumption = 5kg/h, Jacket water temperature rise = 350C, Jacket water flow rate = 7 kg/min, A/F ratio by mass = 30, Exhaust gas temperature = 3500 C, Room temperature = 250 C, Atmospheric pressure = 1 bar, Cylinder diameter = 22 cm, Stroke = 28 cm, Brake diameter = 1.6 m, CV of fuels = 42000 kJ/kg, Proportion of H2 by mass in fuel = 15%, Specific heat of exhaust gas = 1.0 kJ/kgK, Specific heat of dry stream = 2.0kJ/kgK. Calculate: a) Indicated thermal efficiency b) Specific fuel consumption c) Volumetric efficiency based on atmospheric conditions. Draw up a heat balance sheet for test.
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Draw the schematic diagram of vane compressor and explain its working.
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Explain the phenomena of surging and its effects in the centrifugal compressor.
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What is the function of impeller and diffuser in a centrifugal compressor?
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What are different losses occurring in the centrifugal compressor due to different blade shapes? Explain.
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Explain the working of simple vapour compression system with the help of a p-h diagram.
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Explain with a neat sketch the working of an air refrigeration cycle.
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A Freon-12 refrigerator producing a cooling effect of 20 kJ/s operates on a simple vapour compression cycle with pressure limits of 1.509 bar and 9.607 bar. The vapour leaves the evaporator dry saturated and there is no under cooling. Determine the power required by the machine.
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