Internal Combustion Engines - December 2016

MU Mechanical Engineering (Semester 5)

Total marks: --
Total time: -- INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

Solve any one question from Q.1 &Q.2

Solve any four questionQ.1(a,b,c,d,e)

1(b) What will be the effect on the efficiency of an Otto cycle having compression ratio of 8, if C_v increases by 1.6% C_v, specific heat? 6 marks

1(c) What is the difference between physical delay and chemical delay? State the factors on which delay period depends. 6 marks

1(d) Compute the bmep in bar, mean piston speed in m/3 and torque in Nm for a two stroke, four cylinder C.I. Engine having following specifications bore dia. 150 mm, brake power 265kW at 2400 rpm, L/d ratio of 0.90. Also identify whether this engine is square, over square or under square engine. 6 marks

1(e) List out and define various engine efficiencies with their tentative values for the modern engines. 6 marks

2 Discuss the provision made for airport & ports with reference of 12 th five year plan. 6 marks

2(a) During an engine trial on six cylinder four stroke diesel engine, cylinder bore 180 mm, the stroke 200 mm, the following observations were recorded: speed 1500 rpm, BP=245 Kw, mep=8 bar, fuel consumption : 70 kg/hr, heating valve of fuel 44 MJ/kg, Hydrogen content of the fuel 12%, air consumption 28 kg/min, mass of cooling water 85kg/min, cooling water temperature rise 42°C, cooling oil circulated through the engine= 50kg/min, temperature rise of cooling oil= 24°C, specific heat of cooling oil 2.1 kJ/KgK, room temperature 30 °C, exhaust gas temperature 400 °C, Cp of the dry exthaust gas 1.045 kJ/kgK, partial pressure of the steam in a exhaust gases 0.035 bar. Estimate the meachanical efficiency and Draw of the heat balance sheet. 6 marks

2(b) What are the sources of HC formation inpetrol engine? Explain the different factors which affect the HC formation. 6 marks

Solve any one question fromQ.3 and Q.4(a,b)

3(a) Why C.I engines exhibit more favorable fuel consumption at part load and idling, comapared to the carbureted S.I engines? 6 marks

3(b) Describe the phenomenon of knocking In S.I. engines with the help of P-Θ and P-V plots. 6 marks

3(c) Willan's line test is conducted on a constant speed diesel engine operating at 1500 rpm and developing 50 kW power output at full load. Willan's line may be considered as a straight line up to 60% load, with the slope of the line being 8° (eight degrees). The fuel consumptions for this engine is 2.46 kg/h at 10% load. Calorific Value (C.V) of fuel used is 42 MJ/kg. Calculate i) Frictional power ii) Fuel consumption in kg/h at 60% load. Iii) Brake thermal efficiency at 60% load. iv) Mechanical efficiency at 40% load. v) Brake torque at 40% load. 6 marks

4(a) Define the following:
i) Turnout
ii) Tongue rail
iii) Stock rail
iv) Switch 6 marks

Wriet short note Any two 4(a) (i, ii, iii)

4(a)(ii) Wankel Engine 6 marks

4(a)(iii) Dissociation 6 marks

4(b) A 4-stroke cycle C.I. engine develops 11 KW per cyclinder while running at 1800 r.p.m. and using fuel oil of 32° API. Fuel injection occupies 32°C of crank travel and takes place through a fuel injection orifice 0.47 mm diameter with a flow coefficient of 0.9. Fuel is injected at a pressure of 118.2 bar in to combustion chamber where the presssure is 31.38 bar. Estimate the quantity of fuel injected in kg/Kwh. Specific gravity of fuel oil is given by: 141.5/(13.5+° API) 6 marks

4(b) What is creep? What are its effects? 6 marks

Solve any one question from Q.5 & Q.6

Wriet short note Any two 5(a) (i, ii, iii)

5(a)(ii) Alternative Fuels fo I.C. Engine. 6 marks

5(a)(iii) Electronic Fuel-Injection systems 6 marks

5(b) Determine the size of fuel orifice to give A:F =12 :1. The diameter of venturi throat is 3.5 cm and the vacuum at the venturi is 6.9 cm of Hg. The pressure and temperature of atmospheric air are 1.013 bar and 25°C. The nozzle lip= 5 mm. Take Cd_a=0.9, Cd_f=0.7, density of fuel 760 Kg/m³. Consider the compressibility of air. 6 marks

6 What is slip form shuttering? State the distinct advantages of this method over the conventional method. 6 marks

6(a) The average indicated power in a C.I. engine is 15 kw/m ^{of free air inducted per minute. It is a four stroke engine having swept volume 3.4 liter. The speed of the engine is 3300 rpm and has a volumetric efficiency 80% referred to free air conditions of 1.013 bar and 22°C. It is proposed to provide with a blower, driven mechanically from the engine. The blower has a pressure ratio 1.8 and adiabatic efficiency 75%. It can be assumed that at the end of suction, in the supercharged condition, the cylinder contain a volume of air equal to the swept volume at the pressure and temperature of delivery from the blower. Calculate the net increase in break power. Take Mechanical efficiency of engine and blower as 80%.} 6 marks

6(b) Explain briefly various methods of control Emission. 6 marks

Solve any one question from Q.7(a, b, c) & Q.8 (a, b, c)

7(b) Write short note on: Earth Prressure Balance Method. 6 marks

7(c) State the general sequence of operation for driving tunnels through hard rock. 6 marks

8(a) Explain in detail NATM construction technique. 6 marks

8(b) Discuss in detail classification of tunnels based on shape. 6 marks

8(c) Write short Note on: Pilot Tunnel. 6 marks

Solve any one question fromQ.9(a,b,c) and Q.10(a,b,c)

9(b) Define Harbour. Explain in brief classification of harbour based upon utility. 6 marks

9(c) Define breakwater. What is the necessity of it. 6 marks

10(a) Discuss indetail various methods of construction of breakwater. 6 marks

10(b) Write short note on: Marin Railway. 6 marks

10(c) Differentiate between natural and artificial harbor. 6 marks

Solve any one question fromQ.11(a,b,c) and Q.12(a,b)

11(b) What are the factros affecting for the selection of machinery for any earth work. 6 marks

11(c) Write short note on : Preventative maintenance of equipment. 6 marks

12(a) What are the factors to be considered for calculation of output estimation of equipment. 6 marks

12(b) Write short note on:
i) Economic life of equipment
ii) Bakhoe
iii) Dumpers 6 marks