Notes

The piston engine is known as an internal-combustion
heat-engine. The concept of the piston engine is that
a supply of air-and-fuel mixture is fed to the inside of the
cylinder where it is compressed and then burnt. This
internal combustion releases heat energy which is then
converted into useful mechanical work as the high gas
pressures generated force the piston to move along its
stroke in the cylinder. It can be said, therefore, that
a heat-engine is merely an energy transformer.
To enable the piston movement to be harnessed, the
driving thrust on the piston is transmitted by means of
a connecting-rod to a crankshaft whose function is to
convert the linear piston motion in the cylinder to
a rotary crankshaft movement (Fig. 1.1-1). The piston
can thus be made to repeat its movement to and fro, due
to the constraints of the crankshaft crankpin’s circular
path and the guiding cylinder.
The backward-and-forward displacement of the
piston is generally referred to as the reciprocating motion
of the piston, so these power units are also known as
reciprocating engines.