1. Top dead center
(T.D.C.)
In a reciprocating engine the piston moves to and fro motion
in the cylinder. When the piston moves upper direction in the cylinder, a point
at which the piston comes to rest or change its direction known as top dead
center. It is situated at top end of cylinder.
2. Bottom dead center
(B.D.C.)
When the piston moves in downward direction, a point at
which the piston come to rest or change its direction known as bottom dead
center. It is situated in bottom side of cylinder.
3. Stroke (L)
The maximum distance travel by the piston in single
direction is known as stroke. It is the distance between top dead center and
bottom dead center.
4. Bore (b)
The inner diameter of cylinder known as bore of cylinder.
5. Maximum or total
volume of cylinder (Vtotal)
It is the volume of cylinder when the piston is at bottom
dead center. Generally, it is measure in centimeter cube (c.c.).
6. Minimum or clearance
volume of cylinder (Vclearance)
It is the volume of cylinder when the piston is at top dead
center.
7. Swept or displace
volume (Vswept)
It is the volume which swept by the piston. The difference
between total volume and clearance volume is known as swept volume.
Swept volume = Total volume - Clearance volume
8. Compression ratio
The ratio of maximum volume to minimum volume of cylinder is
known as the compression ratio. It is 8 to 12 for spark ignition engine and 12
to 24 for compression ignition engine.
Compression ratio = Total volume / Clearance volume
9. Ignition delay
It is the time interval between the ignition start (spark
plug start in S.I. engine and inject fuel in C.I. engine) and the actual
combustion starts.
10. Stroke bore ratio
Stroke bore ratio is the ratio of bore (diameter of
cylinder) to length of stroke. It is generally equal to one for small engine
and less than one for large engine.
Stroke bore ratio = inner diameter of cylinder / length of stroke
11. Mean effective
pressure
The average pressure acting upon the piston is known as mean
effective pressure. It is given by the ratio of the work done by the engine to
the total volume of engine.
Mean effective pressure = Work done by engine / Total volume of cylinder