UNIT 5

QUESTIONS

1. Why are liners used in IC engine Cylinders?
2. What are the conditions on which materials are choose for IC engine.
3. With a neat sketch explain wet liners and dry liners.
4. What are the functions of piston in an IC engine?
5. What is the function of connecting rod
6. What is a crankshaft and explain the two types of crankshaft with sketch.
7. The cylinder of a four-stroke diesel engine has the followingspecifications:

Brake power = 3 kW Speed = 800 rpm

Indicated mean effective pressure = 0.3 MPa Mechanical efficiency = 80%

Determine the bore and length of the cylinder liner.

[D = 118 mm (116.75); L= 204 mm (203.55)]

8.      The cylinder of a four-stroke diesel engine has the followingspecifications:

Cylinder bore = 150 mm Maximum gas pressure = 3 MPa

Allowable tensile stress = 50 N/mm2

Determine the thickness of cylinder wall. Also, calculate the apparent and net circumferential and longitudinal stresses in cylinder wall.

[t = 10 mm (8.5);  sc = 22.5N/mm2;s1=10.55N/mm2;(sc)net=19.86N/mm2;(s1)net = 4.93N/mm2]

9.      The following data is given for a four-stroke diesel engine:

Cylinder bore = 100 mm

Length of stroke = 125 mm

Speed = 2000 rpm

Brake mean effective pressure = 0.65 MPa

Maximum gas pressure = 5 MPa

Fuel consumption = 0.25 kg per BP per h

Higher calorific value of fuel = 42 000 kJ/kg

Assume that 5% of the total heat developed in the cylinder is transmitted by the piston. The piston is made of grey cast iron and the permissible tensile stress is 37.5 N/mm2 (k =46.6 W/m/°C). The temperature difference between the center and edge of the piston  head is 220°C.

(i)   Calculate the thickness of the piston head by strength consideration.

(ii)   Calculate the thickness of the piston head by thermal consideration.

(iii)   Which criterion decides the thickness of the piston head?

(iv)   State whether the ribs are required.

(v)   If so, calculate the number and thickness of piston ribs.

(vi)   State whether a cup is required in the top of piston head.

(vii)   If so, calculate the radius of the cup.

[(i) 15.81 mm (ii) 12.05 mm (iii) strength (th= 16 mm) (iv) yes (v) 4 ribs of 7 mmthickness (vi) yes (vii) 70 mm]

10. The following data is given for the cap and bolts of the big end of the connecting rod: Engine speed = 1500 rpm

Length of connecting rod = 320 mm

Length of stroke = 140 mm

Mass of reciprocating parts = 1.75 kg

Length of crank pin = 54 mm

Diameter of crank pin = 38 mm

Permissible tensile stress for bolts= 120 N/mm2

Permissible bending stress for cap= 120 N/mm

Calculate the nominal diameter of bolts and thickness of cap for the big end.

[d = 6 mm (dc = 4.42 mm), tc = 6 (5.49) mm]