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

VVV c

wallpch AAAA

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