Thermal Engineering-I B.Tech Question Paper : vardhaman.org
College : Vardhaman College Of Engineering
Degree : B.Tech
Department : Mechanical Engineering
Semester : IV
Subject : Thermal Engineering-I
Document type : Question Paper
Website : vardhaman.org
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Thermal Engineering-I Question Paper :
Four Year B. Tech IV Semester Regular/Supplementary Examinations May – 2014
(Mechanical Engineering)
All Questions Carry Equal Marks
All parts of the question must be answered in one place only
Related : Vardhaman College Of Engineering Control Systems B.Tech Question Paper : www.pdfquestion.in/6340.html
Unit – I :
1. a) What is the difference between air standard cycle and fuel air cycle analysis? Explain the significance of the fuel air cycle. 7M
b) Compare the actual and theoretical p-v diagrams of a 4-S diesel engine. 8M
2. a) Describe with a suitable sketch the two stroke cycle spark ignition engine. How its indicator diagram differs from that of a four stroke engine 10M
b) Discuss the differences between theoretical and actual valve timing diagrams of a diesel engine 5M
Unit – II :
3. a) Briefly explain the stages of combustion in S.I. engines elaborating the flame front propagation. 10M
b) What is meant by abnormal combustion? Explain the phenomenon of knock in S.I. engines. 5M
4. a) Bring out clearly the process of combustion in C.I. engines and also explain the various stages of combustion. 8M
b) Explain the phenomenon of knock in C.I. engines and compare it with S.I. engine knock. 7M
Unit – III :
5. a) Define air-fuel ratio and briefly state its effect on power output, fuel consumption and combustion pressure.7M
b) The following readings are taken on a single cylinder ,4-stroke gas engine 30cm in diameter and 40cm in stroke. RPM=200, No. of explosions= 80 per minute, Brake diameter= 150cm, Net load on the brake= 1200N, Net mean effective pressure= 6bar, Gas used= 11.5cu.m/hr, Pressure of the gas= 15cm of water above atmospheric pressure, Barometric reading= 755mm of Hg. Ambient temperature =200C, C.V of the gas used= 21000KJ/m3 at N.T.P. Find out(i) the mechanical efficiency and (ii) the brake thermal efficiency. 8M
6. a) What are the methods available for improving the performance of an engine? 6M
b) A test on single cylinder 4-stroke oil engine having bore 180mm and stroke 360mm gave the following results. Speed-290rpm, brake torque- 392N-m, indicated mean effective pressure 7.2 bar, oil consumption 3.5kg/hr, cooling water flow 270kg/hr, cooling water temperature rise 360C air-fuel ratio by weight 25. Exhaust gas temperature 4150C, barometric pressure 1.013bar, room temperature 210C .The fuel has calorific value of 45,200KJ/kg and contains 15% of hydrogen by weight. Calculate (a) the indicated thermal efficiency (b) the volumetric efficiency based on atmospheric conditions. Take R=0.287KJ/kgK, Cp for dry exhaust gases =1.0035KJ/kgK, and Cps for superheated steam= 2.093KJ/kgK.
Unit – IV :
7. a) A single stage reciprocating compressor takes 1m3 of air per minute at 1.013 bar and 150C and delivers it at 7 bar. Assuming that the law of compression is pV1.35 = constant, and the clearance is negligible, calculate the indicated power. 8M
b) Explain the principle of working of a reciprocating compressor 7M
8. An air compressor having stroke length of 88cm and clearance volume of 2% of the swept volume delivers air at a pressure of 8.2 bar. In order to study the effect of clearance on free air delivery and work expended, the compressor was overhauled and a distance piece of 0.55cm was fitted between the cylinder head and the cylinder. The compressor was thencommissioned under the changed clearance. Calculate: Percentage change in the volume of free air delivered, Percentage change in power expended Before and after overhauling the piston had a suction pressure 1.025 bar and the index of compression and expansion was 1.3 15M
Unit – V :
9. The following data refers to a centrifugal compressor Total pressure ratio = 3.6:1, Diameter of inlet eye of compressor impeller = 35cm, Axial velocity at inlet = 140m/s, Mass flow = 12kg/s, Velocity in delivery duct = 120m/s, The tip speed of the impeller = 460m/s, Speed of the impeller = 16000 rpm. Total head isentropic efficiency = 80%, Pressure coefficient = 0.73, Ambient conditions = 1.013 bar and 150C.
Calculate
i. The static pressure and temp at inlet and outlet of the compressor
ii. The static pressure ratio
iii. Work of compressor per kg of air
iv. The theoretical power required. 15M
10. a) Draw a neat velocity diagram of a axial flow compressor and derive an equation for degree of reaction
12M
b) List the applications of axial flow compressors 3M