Design of IC engine components

1. Prepared by:
Bhosale K.C.
Assistant Professor,
Department of Mechanical Engineering,
Sanjivani College of Engineering, Kopargaon
Savitribai Phule Pune University, Pune
Design of I.C. Engine Components

2. I.C. Engine Components
•Cylinder & Cylinder liner
•Piston & Piston Rings

3. I.C. Engine Components

4. Materials
•Made of Gray C.I. with homogeneous and
closed structure.
•Centrifugally cast
•For heavy duty cylinder-Ni C.I. & Ni-Cr C.I.
•Cast steel & Al. Alloys

5. Bore & Length Of Cylinder
• Bore means I.D. of Cylinder
• Where,
• IP=Indicated power or power produced inside cylinder, W
• BP=Brake power or power developed at crankshaft, W
• m= mechanical efficiency ( in fraction)
• if not specified assume 0.8
I.P = B.P. / ηm

6. Bore & Length Of Cylinder
•Where,
•Pm= Indicated mean effective pressure (N/mm2)
•l = Length of Stroke (m)
•A= Cross Sectional Area of Cylinder (mm2),
•N= Engine speed (rpm)
•D= Dia. Of cylinder ( mm),
•n= No. of working strokes / min.
•For 2 Stroke engine n=N
•For 4 Stroke engine n=N/2
IP= PM LAN/60, Watts

7. •( if not specified assume 1.5)
•Length of cylinder is more than the length of
stroke. There is clearance on both the sides of
the stroke. Total clearance is taken as 15% of
the stroke.
Bore & Length Of Cylinder
l/D ratio is assumed from 1.25 to 2.
L= length of the cylinder = 1.15 l

8. Thickness of the cylinder Wall
• The engine cylinder is treated as Thin cylinder.
• t= Thickness of cylinder wall (mm)
• Pmax=Maximum gas pressure inside the cylinder (N/mm2)
• D= I.D. of Cylinder (mm)
• c=Permissible circumferential stress (N/mm2)
• C= Reboring allowance (mm)
𝑡 =
𝑝 𝑚𝑎𝑥 × 𝐷
2 × 𝜎𝑐
+ 𝐶

9. Thickness of the cylinder Wall
• Max. Pressure is assumed 10 times mean effective
pressure Pmax=10(pm)
• Permissible c= 35 to 100 N/mm2) where, 𝜎𝑐 = 𝜎𝑡 =
𝑆 𝑢𝑡
𝑓𝑠
• Reboring allowance is taken from table
D 75 100 150 200 250 300 400 450 500
C 1.5 2.4 4.0 6.3 8.0 9.5 12.
5
12.
5
12.
5

10. Empirical Relations
• Thickness varies from 5-10 mm , Thickness=t=0.045D+1.6 mm
•Thickness of dry liner = 0.03D to 0.035 D
•Thickness of water jacket wall = (1/3 )t to (3/4) t
•Thickness of water jacket wall =0.032D+ 1.6 ( mm)
•Water space = 9 mm for 75 mm to 75 for 750 mm of D
•Water space = 0.08 D + 6.5 mm
•Thickness of cylinder flange= 1.2 t to 1.4 t
•Radial distance between O.D. of flange & PCD of studs=
(d+6) to 1.5 d
•d= nominal dia. Of bolt or stud

11. Cylinder Head
•In preliminary design, cylinder head is assumed
as flat circular head
•Where,
•th=thickness of cylinder head (mm),
•K=0.162
•Permissible c=35 to 50 N/mm2)
𝑡ℎ = 𝐷
𝐾 × 𝑝 𝑚𝑎𝑥
𝜎𝑐

12. Design of studs for cylinder head
•Studs are used to connect cylinder,
cylinder head & gasket for leak proof
joint.
•Initially studs are tightened by spanner
to induce preload, and
•In working condition they are subjected
to tensile stresses due to internal gas
pressure acting on cylinder head.

13. Numerical 1
•A four stroke diesel engine has the following
specifications :
•Brake power = 3.75 kW ;
•Speed = 1000 r.p.m. ;
•Indicated mean effective pressure = 0.35 N / mm 2 ;
•Mechanical efficiency = 80 %.
•Determine :
•1. bore and length of the cylinder ;
•2. thickness of the cylinder head ; and
•3. size of studs for the cylinder head.

14. Given:
•B.P. = 3.75kW = 3750 W ;
•N = 1000 r.p.m. or
•n = N / 2 = 500 ;
•pm = 0.35 N/mm2;
•ηm = 80% = 0.8

15. Bore and length of cylinder
•Let D = Bore of the cylinder in mm,
•A = Cross-sectional area of the cylinder
•l =Length of the stroke in m.
•= 1.5 D mm = 1.5 D / 1000 m ....(Assume)
•We know that the indicated power,
= (π/4)× D2 mm2
I.P = B.P. / ηm = 3750 / 0.8 = 4687.5 W

16. Bore and length of cylinder
•=
0.35
60
×
1.5𝐷
1000
×
𝜋𝐷2
4
× 500
•l=1.5 D=168 mm
IP=
𝑝 𝑚×𝑙×𝐴×𝑛
60
D=112 mm
The length of stoke is 168 mm

17. Bore and length of cylinder
•Taking a clearance on both sides of the
cylinder equal to 15% of the stroke,
therefore
length of the cylinder,
L = 1.15 l = 1.15 × 168 = 193.2 say 195 mm
Ans.

18. Numerical 2
The cylinder of 4 stroke diesel engine has the
following specifications:
Cylinder bore=150mm;
Maximum gas pressure=3.5 Mpa;
Cylinder material =Grey cast iron FG200
(Sut=200 Mpa)
Factor of safety =5;
Poisson’s ratio =0.25;
Determine the thickness of the cylinder wall.

19. Given
•Pmax = 3.5 Mpa;
•D=150mm;
•Sut=200 N/mm2
•Fs=5;
•µ=0.25

20. Thickness of wall cylinder
•The permissible tensile stress
•C for 150 mm is 4 mm
•The thickness of cylinder wall is
•𝑡 =
3.5×150
2×40
+ 4
𝜎𝑐 = 𝜎𝑡 =
200
5
=40 N/mm2
𝑡 =
𝑝 𝑚𝑎𝑥 × 𝐷
2 × 𝜎𝑐
+ 𝐶
t= 10.56 or 12 mm

21. Numerical 3
•The bore of a cylinder of a 4 stroke diesel engine is
150mm. The maximum gas pressure inside the
cylinder is limited to 3.5 Mpa. The cylinder head is
made of grey cast iron FG200 (Sut =200 N/mm2) and
factor of safety is 5. Determine the thickness of the
cylinder head.
•Studs are used to fix the cylinder head to the cylinder
and obtain leakproof joint. They are made of steel
FeE250(Syt 250 N/mm2) and factor of safety is 5.
calculate:
•1) number of studs
•2) nominal diameter of studs
•3)pitch of studs

22. Given
•Pmax=3.5 N/mm2;
•D=150mm;
•For cylinder head
•Sut= 200 N/mm2, fs=5
•For studs
•Syt= 200 N/mm2 ; fs=5

23. Thickness of cylinder head
• 𝜎𝑐 = 𝜎𝑡 =
200
5
=40 N/mm2
•
•K=0.162;
𝑡ℎ = 𝐷
𝐾 × 𝑝 𝑚𝑎𝑥
𝜎𝑐
Th=17.86=18 mm

24. Numerical 4
•The cylinder of a 4 stroke diesel engine has the following specifications:
•Brake power = 7.5kW,
•Speed = 1400 rpm,
•Indicated mean effective pressure =0.35 Mpa,
•Maximum gas pressure = 3.5 Mpa,
•Mechanical efficiency,
The cylinder liner and head are made of grey cast iron FG260 (Sut = 260
N/mm2, Poisson’s ratio = 0.25).The studs are made of plain carbon steel 40C8
(Sut = 380 N/mm2)The factor of safety for all parts is6.
1) Bore and length of cylinder liner
2) Thickness of the cylinder liner
3) Thickness of cylinder head
4) Size, number and pitch of studs

25. Given
BP= 7.5 kW =7500 W,
N= 1400 rpm,
Pm=0.35 N/mm2;
Pmax=3.5 N/mm2;
fs=6,
ηm = 80% = 0.8
 = 0.25
For cylinder head
Sut= 260 N/mm2,
For studs
Syt= 380 N/mm2 ;

26. Bore and length of cylinder
•Let D = Bore of the cylinder in mm,
•A = Cross-sectional area of the cylinder
•l =Length of the stroke in m.
•= 1.5 D mm = 1.5 D / 1000 m ....(Assume)
•We know that the indicated power,
= (π/4)× D2 mm2
I.P = B.P. / ηm = 7500 / 0.8 = 9375 W

27. Bore and length of cylinder
•=
0.35
60
×
1.5𝐷
1000
×
𝜋𝐷2
4
× 700
•l=1.5 D=187.5 mm
IP=
𝑝 𝑚×𝑙×𝐴×𝑛
60
D=125 mm
The length of stoke is 187.5 mm

28. Bore and length of cylinder
•Taking a clearance on both sides of the
cylinder equal to 15% of the stroke,
therefore
length of the cylinder,
L = 1.15 l = 1.15 × 187.5 = 216 mm Ans.

29. Thickness of cylinder liner
• The permissible tensile stress is given by
• 𝜎𝑡 =
260
6
=43.33 N/mm2
• The reboring allowance is calculated from table below
• By linear interpolation, the C value for 125 mm is 3.2 mm.
• The thickness of cylinder wall is
• 𝑡 =
3.5×125
2×43.33
+ 3.2
• t= 8.25 or 10 mm
D 75 100 150 200 250 300 400 450
C 1.5 2.4 4.0 6.3 8.0 9.5 12.5 12.5
𝑡 =
𝑝 𝑚𝑎𝑥 × 𝐷
2 × 𝜎𝑐
+ 𝐶

30. • Apparent stresses
• 1) circumferential stress = 21.88 N/mm2
• ( 𝑐 < 43.33 N/mm2
• 2) Longitudinal stress
• Do= D+2t=145 mm
• 𝑙= 10.13 N/mm2
Thickness of cylinder liner
 𝑐 =
𝑝 𝑚𝑎𝑥 × 𝐷
2 × 𝑡
𝑙 =
𝑝 𝑚𝑎𝑥 × 𝐷2
(𝐷0
2 − 𝐷2)

31. • Net stresses
• 1) circumferential stress =  𝑐 - 𝑙 = 19.35 N/mm2
• 2) ) circumferential stress = 𝑙 -  𝑐 = 4.66 N/mm2
Thickness of cylinder liner

32. Thickness of cylinder head
• 𝜎𝑐 = 𝜎𝑡 =
260
6
=43.33 N/mm2
•
•K=0.162;
𝑡ℎ = 𝐷
𝐾 × 𝑝 𝑚𝑎𝑥
𝜎𝑐
Th=14.3=15 mm

33. Number of studs
• Limits
• Minimum number of studs= 0.01D+4 = 5.25
• Maximum number of studs= 0.02D+4 = 6.5
• The number of studs should be within 5.25 to 6.5.
• It is assumed that there are 6 number of studs

34. Nominal diameter of studs
• The permissible stress is given by
• 𝜎𝑡 =
380
6
=63.33 N/mm2
• 1)Force acting on cylinder head =
• (π/4)× D2 P max= 42951.46 N
• 2)Resisting force offered by all studs = (π/4)× dc2 z  𝜎𝑡
• Equating equation 1 and 2,
• d=15 mm
dc=12 mm

35. Pitch of studs
• Pitch circle diameter of studs (Dp)= D+3d= 170 mm
• Pitch of studs = (π× Dp )/6= 89.01 mm
• Limits
• Minimum Pitch= 19d =73.59 mm
• maximum pitch = 28.5d =110.38 mm
• The pitch of studs is 89.01 mm. it is within the limits of maximum and
minimum pitch. Therefore, the pitch of studs is satisfactory.

36. Piston
•Piston is a reciprocating part of I.C. engine.
•Transmit force due to gas pressure to
crankshaft through connecting rod.
•Compresses the gas in compression stroke.
•Seals inside portion of cylinder from crankcase
by means of piston rings
•Takes side thrust resulting from obliquity of
connecting rod.
•Dissipates large amount of heat from
combustion chamber to cylinder wall.

38. Design requirements of Piston
•Should have sufficient strength
•Should have sufficient rigidity
•Adequate capacity to dissipate heat
•Should have minimum weight
•Form an efficient seal to prevent leakage
•Noiseless operation

39. Piston Materials
•Cast Iron,
•Cast Steel,
•Forged Steel,
•Cast Aluminum Alloy,
•Forged Aluminum Alloy

40. Thickness of Piston Head
• There are two types of piston heads:
❖Flat head
❖Cup type

41. Criteria for calculating piston head
thickness
• Strength
• Heat dissipation

42. Strength criteria
•Piston head is treated as flat circular plate of uniform
thickness.
•Where,
•th= thickness of Piston head (mm),
•D= Cylinder bore (mm),
•Pmax = Max. gas pressure (N/mm2)
•b=Permissible bending stress (N/mm2)
𝑡ℎ = 𝐷
3 × 𝑝 𝑚𝑎𝑥
16 × 𝜎𝑏

43. •Bending stress-
•for C.I. (30-40 N/mm2) &
•for Al. Alloy (50-90 N/mm2).
•Max. gas pressure may rise to 8 N/mm2. but average
value is taken as 4-5 N/mm2.
•Empirical formula to find out piston head thickness
•th =0.032 D+1.5 mm
Strength criteria

44. Heat dissipation criteria
• Thickness of piston head
• Where,
• Th= thickness of piston head (mm),
• H= amount of heat conducted through head (W)
•K= thermal conductivity factor (W/m/0C)
•Tc= temp. at center of piston head (0C)
•Te= temp. at edge of piston head (0C)
𝑡ℎ =
𝐻
12.56𝑘 𝑇𝑐 − 𝑇𝑒
× 103

45. • K values
• C.I.=46.6 (W/m/0C)
•Al. alloy = 175 (W/m/0C)
•Permissible temp. difference( Tc-Te)
• C.I.=2200 C
•Al. alloy = 75 0C
Heat dissipation criteria

46. Amount of heat conducted
•H=[CHCV m BP] 103
•HCV= Higher Calorific Value (kJ/Kg)
•M= mass of fuel per power per second (kg/kW/s)
•BP=brake power of engine per cylinder (kW)
•C= ratio of heat absorbed by piston to heat developed in
cylinder=0.05

47. •HCV values
•For diesel = 44*103 kJ/kg
•For Petrol = 47*103 kJ/kg
•The Avg. consumption of fuel in diesel
engine is 0.24 – 0.30 kg/kW/h
•𝑚 =
0.24 𝑡𝑜 0.3
60×60
kg/kW/s
Amount of heat conducted

48. Piston ribs and cups
•Piston head is provided with a no. of ribs for:
•Strengthening piston head against gas
pressure
•Ribs transmit large portion of heat from
piston head to piston rings.
•Side thrust created by obliquity of connecting
rod is transmitted to piston at piston pin.

49. Guidelines for ribs
•th < 6 mm – no ribs
•th > 6 mm – ribs required.
•No. of ribs = 4 – 6
•Thickness of rib is
•Where,
• tR=thickness of rib
•th= thickness of piston head

50. Piston Cup
•A cup provides additional space for
combustion of fuel.
•Depends upon volume of combustion
chamber.
•And arrangement of valves.

51. Guidelines for cup
•l/D < 1.5 – cup required
•l/D > 1.5 – cup not required
•Radius of cup= 0.7 D

52. Piston Rings
•Compression ring
•Oil scrapper ring

53. Guidelines for design of rings
•Material– Gray C.I. & Alloy C.I.
•No. of piston rings—
•Compression rings for aircraft engine= 3 – 4
•For stationary engine= 5-7
•Oil scrapper rings= 1 – 3

54. Dimensions of c/s
• Rectangular c/s
• 𝑏 = 𝐷
3𝑝 𝑤
𝜎𝑡
• Where,
• b = radial width of ring
• Pw = allowable radial pressure on cylinder wall (N/mm2)
• t=Permissible tensile stress for ring material (N/mm2)
• Pw =0.025 – 0.042 (N/mm2)
• t = 85 – 110 (N/mm2)
• Axial thickness of ring h = (0.7 b ) to b

55. • Gap between free ends
• 3.5 b – 4 b
• Width of top land and ring lands
• h1 = th – 1.2 th
• h2 = 0.75 h -h

56. Piston barrel
• t3 = (0.03 D + b + 4.9
• t3 = thickness of piston barrel at top end
( mm)
• b= radial width of ring ( mm)
• t4 = thickness of piston barrel at open
end ( mm)
• t4 = 0.25 t3 – 0.35 t3

57. Piston skirt
• Acts as
bearing
surface for
side thrust

58. • Max. gas pressure on piston head=
𝜋𝐷2
4
𝑝 𝑚𝑎𝑥
• Side thrust = 𝜇
𝜋𝐷2
4
𝑝 𝑚𝑎𝑥
• Where, µ= coefficient of friction = 0.1
• Side thrust=pbDls
• Where,
• Pb= allowable bearing pressure (Mpa)
• ls =length of skirt (mm)
• Equating above eqns.
• From this length of skirt is obtained
• 𝜇
𝜋𝐷2
4
𝑝 𝑚𝑎𝑥 = pbDls

59. Numerical 5
•The following data is given for a 4 stroke diesel engine:
•Cylinder bore=250 mm, length of stroke = 300 mm,
speed = 600 rpm, Indicated mean effective
pressure=0.6 MPa, Mechanical efficiency =80%,
maximum gas pressure =4 Mpa, fuel consumption =0.25
kg/BP/h, Higher calorific value of fuel =44000kJ/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 FG200 (Sut = 200 N/mm2 and k =46.6
W/m/0C) and factor of safety is 5. the temperature
difference between the center and edge of the piston
head is 2200 C

60. Thickness of piston head by Strength criteria
•The permissible tensile stress is given by
• 𝜎𝑡 =
200
5
=40 N/mm2
•Piston head is treated as flat circular plate of uniform
thickness.
𝑡ℎ = 𝐷
3 × 𝑝 𝑚𝑎𝑥
16 × 𝜎 𝑏
Thickness of piston head = 35 mm

61. Thickness of piston head by Heat dissipation
criteria
• Thickness of piston head
• Where,
• Th= thickness of piston head = 42 mm
• So, thermal consideration is the criteria to decide thickness of piston
head
𝑡ℎ =
𝐻
12.56𝑘 𝑇𝑐 − 𝑇𝑒
× 103

62. Piston ribs and cups
•th > 6 mm – ribs required.
•It is assumed that number of ribs = 4
•Thickness of rib is = 18 mm

63. Requirement of Piston Cup
• l/D=1.2, so a cup is required
• Radius of cup = 0.7D= 250 mm