UNIT II INTERNAL COMBUSTION ENGINES

UNIT II INTERNAL COMBUSTION ENGINES

Two marks questions

1.       What is scavenging?

2.       What are the effective characteristics of effective cooling system?

3.       The bore and stroke of a water cooled vertical single cylinder 4S diesel engine are 80mm and 110mm respectively and the torque is 23.5Nm. Find the mep of the engine.

4.       [Ans. Power = 2PiNT/60 =  mep Lank/60 => mpe = 534kPa.]

5.       Compare advantages and disadvantages of ic engines with external combustion engines

6.       Why cooling is necessary in ic engines

7.       State limitations of battery ignition system.

8.       State applications of 2S and 4S engines.

9.       Draw the valve timing diagram for CI engine.

10.   During peak power operation why petrol engine required rich mixtures?

11.   What do you mean by mist lubrications?

12.   Draw port timing diagram of petrol engine

13.   What is splash lubrication?

14.   What are the requirements of fuel injection system of a diesel engine?

Part B

1. In a laboratory experiment the following observations were noted during the test of 4Stroke SI engine. Area of indicator diagram = 510mm2; length of indicator diagram = 55 mm; spring index = 1.25 bar/mm; diameter of the piston =  20mm; length of the stroke = 180mm; engine rpm = 480 rpm; effective brake load = 25 kg; effective brake radius = 0.45m;  Find i) indicated mep ii) indicated power iii) brake power iv) mechanical efficiency.

[Ans;  i) Indicated mep = Pm=AS/L = 1159kN/m2;              ii)IP=Pm*l*a*n*k = 9.43kW;       iii) brake power BP = 2PiNWR = 5.54kW;            iv) mech effcy. = 58%;]

2. Discuss the construction and working principle of a four stroke engine with sketch

3. Explain the construction and working of battery coil ignition system with neat sketch

4. Explain the construction and working of fuel injector with a neat sketch and explain port timing diagram of 2S diesel engine

5. The following observations were taken during attest on a single cyinder 4S cycle engine having a bore of 300mm and stroke of 450mm.  Ambient temp= 22C; fuel consumption = 11kg/hr; CV of fuel = 42,000kJ/kg; N = 300rpm; mep = 6bar; net brake load W = 1KN; quantity of jacket cooling water = 590 kg/hr; cooling water entry temp = 22C; cooling water leaving temp = 70C; quantity of air measured = 225 kg/hr; Temp of gas =405C; rope diameter = 2cm;

Find ip; bp; mech efficiency; and draw a heat balance sheet on hour basis.

[Ans. IP= 47.7kW; mech effcy = 66.5%; Qs = 8.2kw; Qw = 1.7; Qg = 3.91; Qua = .75]

6. Compare SI and CI engine with respect to a) basic cycle b) fuel used c) introduction of fuel d) ignition e) compression ratio f) speed g) efficiency h) weight.

7. Explain the difference between 2S and 4S ic engine.

8. In a constant speed CI engine operating on 4S and fitted with band brake the following observations were taken.

Brake wheel diameter = 60cm; band thickness = 5mm; speed = 450 rpm; loan on band = 210N; spring balance reading = 30 N; area of indicator diagram = 4.15 cm2;  length of indicator diagram = 6.25 cm; spring no 11 is = 11 bar / cm; bore = 10cm; stroke = 15cm; SFC = 0.3 kg/kw-hr; heating value of fuel = 41800 kJ/kg; Find the brake power, indicated power, mechanical efficiency, indicated thermal efficiency and brake thermal efficiency.