i.c. engine parts
DESCRIPTION
Design of Parts of I.C. EnginesShankar SehgalTRANSCRIPT
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Design of I.C. Engine Parts
By:Er. Shankar Sehgal
Faculty of Mech. Engg., UIET,Panjab University, Chandigarh
Website: http://shankarsehgal.weebly.com
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I.C. Engine
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Design of Cylinder
• Types of stresses:– Stresses due to Gas Pressure
• Longitudinal Stresses
• Circumferential Stresses
– Stresses due to Piston Side Thrust
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Design of Cylinder
• Bore and Length of Cylinder:
• Where, – ; I.P. = Indicated Power, B.P. = Brake Power
– pm is indicated mean effective pressure– l is length of stroke = 1.5 D– A is cross-sectional bore area of cylinder– n is number of working strokes per minute
• Length of Cylinder = 1.15 l
60.. lAnpPI m
mech
PBPI
....
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Design of Cylinder
• Thickness of Cylinder Wall:
• Based upon thin cylinder formula
• Where C is allowance for reboring
CpDtc
2
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Design of Cylinder Flange
• Cylinder flange thickness = 1.4 t• Considering tensile failure of cylinder flange
bolts:
• Use bolts of diameter greater than 16 mm only
2
2
4
4
cdn
pD
AF
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Design of Cylinder Head
• Cylinder head thickness:
• Considering tensile failure of cylinder head bolts:
ch
pCDt.
2
2
4
4
cdn
pD
AF
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Design of Piston
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Piston of I.C. Engine
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Design Considerations for Piston
• High strength to withstand the high gas pressure and inertia forces.
• Low weight density
• Low coefficient of thermal expansion
• High heat conductivity
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Materials for Piston
• C.I.
• Cast Aluminium
• Cast Steel
• Forged Aluminium
• Forged Steel
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Design of Piton Head
• Considering tensile strength requirement:– Using Grashoff’s Formula
tH
Dpt16.3 2
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Design of Piton Head
• Considering heat dissipation requirement:
• Where, – H is heat flow rate
– k is coefficient of thermal conductivity
– TC is Temperature at centre of the piston
– TE is Temperature at edges of the piston
ECH TTk
Ht
56.12
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Design of Piton Rings
• Compression Rings– Three to seven in number– Transfer heat from piston to cylinder liner– Absorb side thrust on piston– Cross-section is rectangular– Diameter is slightly larger than cylinder bore– Diagonal or step cut is provided
• Oil Control Rings– Help in lubrication of liner
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Design of Piston Rings
ringsnDt
102 t
wpDt
31
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Design of Piston Rings
• Width of top land
• Width of other ring landsHtb 1
22 tb
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Design of Piston Barrel
9.4100
313 tDt
34 41 tt
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Design of Piston Skirt
• Considering bearing failure of piston skirt:
skirtb Dl
Dpp
2
4101
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Design of Piston Pin
• Considering bearing failure of piston pin:
• Where,
10
2
4ld
Dppb
Dl 45.01
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Design of Piston Pin
• Considering bending failure of piston pin:
64
4222
2
44
12
ioo dd
lPlP
d
IM
y
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Design of Connecting Rod
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Connecting Rod
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Ratio
• l = length of connecting rod
• r = radius of crank
• Small
– small and compact engines– large angular motion of connecting rod– large side thrust of connecting rod– rapid wear and tear of cylinder liner
5__4 torl
rl
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