(a) Classify the internal combustion engines with respect to the
(i) working cycle;
() method of mixture preparation;
() method of ignition;
(iv) combustion chamber design;
(v) method of cooling,
(vi) method of load control;
(vi) type of fuels used.
Click here to join us on Social Media for getting instant update on every notice(b) Describe with a neat sketch the working principle of a crankcase scavenged two-stroke engine. Explain why four stroke engines are preferred over two-stroke engines in spite of the fact that two-stroke engines have higher power per unit displaced volume relative to four-stroke engine.
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3. (a) Compare the Otto, diesel and diesel -cycle for the
(i) same compression ratio and heat input;
(ii) same maximum pressure and heat input.
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(b) An air-standard dual cycle has pressure and temperature at the beginning of compression as 1 bar and 35 °C, respectively. The compression ratio is 11, the pressure ratio during heat addition 1-6 and cut-off ratio 17. Calculate the
(i) percentage clearance;
(i) pressure and temperature at the
salient points of the cycle;
(ii) heat added;
(iv) heat rejected;
(u) net work done;
(vi) thermal efficiency;
(vii) mean effective pressure.
Assume 0.5 kg of air is flowing in the cycle and, C, and C, of air to be 1-005 and 0-717 kJ/Kg-K, respectively.
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4. (a) Draw a typical heat release diagram for direct injection CI engine. Briefly explain the different phases encoun tered in this diagram.
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(b) With the help of neat sketch, explain the type of fuel nozzles used in diesel fuel injection system.
5. (a) What are the functions of lubrication in an IC engine? State the essential properties of lubricating oil used in IC engine.
(b) A four-cylinder, four-stroke gasoline engine working at 3000 r.p.m. develops a brake power of 21 kW. A Morse test was conducted on this engine and the brake powers obtained when each cylinder was made inoperative by short circuiting the spark plug are 15 kW, 14.2 kW, 14.7 kW and 14-4 kW, respectively. The Morse test was conducted at constant speed. Find the indicated power, mechanical efficiency and bmep when all the cylinders are firing. The bore and stroke of the engine are 8 cm and 9 cm, respectively.
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6. (a) In a gas turbine plant, air is compressed
from state (P. T) to a pressure rp and heated to a temperature T3. The air is then expanded into two stages with reheat to T3 between the turbines. If xp is the intermediate pressure between the two turbines, show that, for the given values of P. T, T3 and r, the specific work output is maximum, when x= √r.
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(b) In a compound gas turbine, the air from the compressor passes through a heat exchanger heated by the exhaust gasesActivate Windo from the low-pressure turbine, and then
into the high-pressure combustion
chamber. The high-pressure turbine drives the compressor only. The exhaust gases from the high-pressure turbine combustion chamber the low to pressure turbine which is coupled to an external load. The following data refer to this installation:
pass through the low-pressure
Pressure ratio of the compressor - 4.1 Isentropic efficiency of compressor
-0-86
Isentropic efficiency of high
pressure turbine-0-84
Isentropic efficiency of low
pressure turbine-0-80
Mechanical efficiency of drive
to compressor - 0-92 Turbine inlet temperature for
high-pressure turbine 660 °C Turbine inlet temperature for
low-pressure turbine 625 °C
Atmospheric temperature 288 K
Atmospheric pressure 1 bar
In the heat exchanger, 75% of the available heat is transferred to the air.
Assuming that the specific heats Cp and C, of both air and gas to be 1.005 and 0.717 kJ/kg-K, respectively, calculate (i) the pressure of the gases entering the low-pressure turbine and (ii) the overall efficiency.
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7.
(a) With the aid of a schematic diagram, explain the working principle of pulse jet engine and also draw the ideal and actual p-V diagram of pulse jet cycle.
(b)
What are the requirements of ignition system in spark ignition engine? Discuss the limitations of conventional ignition systems.
8. (a)
What are the effects of engine under cooling and overcooling on the performance of an IC engine? With the help of a neat sketch, explain the principle and working of evaporative cooling system.
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(b) Sketch and explain the valve-timing diagram of four-stroke internal combustion engine. Describe how the valve timings will differ between Activate Wind low-speed and high-speed engines.
9. Write short notes on any four of the
following:
(a) Three-way catalytic converter
(b) SAE ratings of lube oil
(c) Octane rating of fuel determination
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and
its
(d) Turbocharging and supercharging of an
IC engine
(e) Working principle of jet propulsion