The Role of Cylinder Geometry on Thermo-mechanical Process in I.C. Engines-1
P M V SubbaraoProfessor
Mechanical Engineering Department
Geometry is an Universal Solution of All the Issues….
The Geometrical Description of Engine Cylinder
Selection of Cylinder Geometry
B/L= 1.4B/L= 1.0 B/L= 0.7
The Kinematic Description of Engine Cylinder
Geometry of Cylinder : A Primary Signature
• An engine is described as a square engine when it has equal bore and stroke dimensions, giving a bore/stroke value of exactly 1.
• By custom, engines that have a bore/stroke ratio of between 0.95 and 1.04 can be considered "square".
• An engine is described as under-square or long-stroke if its cylinders have a smaller bore than its stroke - giving a ratio value of less than 0.95.
• An engine is described as over-square or short-stroke if its cylinders have a greater bore diameter than its stroke length, giving a bore/stroke ratio greater than 1.04.
Geometry must respect Heat Transfer: Else Get Extinct…
Indian ElephantAfrican Elephant
Mammoths
Geometrical Features of Survived Non-biological Animals
Bore – to –Stroke Ratio
Ability to Transfer Heat : A Signature of Survival
Geometrical Details at any Crank Angle
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Instantaneous volume of the Thermodynamic system
Instantaneous Surface area of the Thermodynamic system
For a givendisplacement volume, Vd& squareness, RBS
31
2
4,
BS
d
R
VLStroke
31
4,
BS
d
R
VBBore
Displacement Volume at Any Crank Angle
Displacement Volume at Any Crank Angle
Relative location of piston center w.r.t . Crank Axis at any crank angle
Instantaneous Engine Cylinder Volume
Instantaneous Displacement Volume
2
22
sin2cos12
81 L
lL
l
V
LB
V
V
cc
31
2
4,
BS
d
R
VLStroke
3
1
4,
BSdRVBBore
2
2sin2cos1
2
21 L
lL
l
V
V
V
V
c
d
c
Define Rod ratio
2
2sin2cos1
2
21 L
lL
l
V
V
V
V
c
d
c
22 sincos12
1 RRV
V
V
V
c
d
c
31
4
2
BSdRV
lL
l
a
lR
22 sincos12
11
RRr
V
V
c