RevisionC-Developmentofconceptofcompressorforcommercialvehicle

efficiency (Km) of any reciprocating machine will be around 0.75 to 0.8 at rated speed. For the
same speed, the 43KW power required to run the compressor decreases with decrease in mass
of air handled.
2.3.8 Indicated torque
Torque (or often called a moment) can be thought of as a “rotational force” or “angular
force” which causes a change in rotational motion. This force is defined by linear force multiplied
by a radius.
If a force is allowed to act through a distance, it does mechanical work. Similarly, if
moment is allowed to act through a rotational distance, it does work. Power is the work per unit
time. However, the time and rotational distance are related by the angular speed where each
revolution results in the circumference of the circle being travelled by the force that is generating
the torque. This means that, torque causes the angular speed to increase in doing work and the
generated power may be calculated as
P = Torque x Angular Velocity
From the torque calculation at different crank angles, it is possible to find the maximum
torque and maximum indicated power which the compressor absorbs in a cycle.
2.3.9 Volumetric efficiency
Analysis of volumetric efficiency is essential to estimate the suitability of a compressor
for a particular application. The factors affecting volumetric efficiency are
• Clearance volume (Increase in clearance volume decreases Kv)
• Discharge pressure (Increase in discharge pressure decreases Kv)
• Temperature of cylinder (Heating of the cylinder decreases Kv)
• Compressor speed (Increase in speed decreases the increase in Kv)
• Leakage (Leakage past the piston, decreases Kv, but this effect can be
neglected)
2.4 Performance parameters of compressor
The performance of the compressor can be studied by individual parameters, such as
pump up time, delivery air temperature, speed and power. [5]
2.4.1 Pump up time
Pump up time is the time required to develop a delivery pressure in a reservoir of given
volume connected to the compressor air outlet. Pump up time is important as it indicates the
volume flow rate of air inside the compressor under given operating conditions. Mainly the
clearance volume affects pump time performance in addition to the flow area available in the
cylinder head. The flow area available should not be less than the adapter inside flow area.
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