Everything you need to know about compressed air:
summarized by netinform and our partner BAUER KOMPRESSOREN GmbH München
If, for example, the counterpressure and thus also the pressure ratio p2/p1 in a single-stage compressor is increased, compression decreases.
The compressor's volumetric efficiency decreases, piston forces increase and since compression is almost isentropic under maximum cooling of the cylinder, the final compression temperature rises.
As the temperature increases, oil lubricity decreases and there is the risk of partial oxidation on contact with air, which would result in the breathing air becoming contaminated with CO or too much CO2.
Last but not least, the ratio of real to ideal, isothermal compression work becomes less favorable.
As soon as it exceeds a certain value, therefore, the pressure ratio is divided up into several stages and the gas is cooled down after every stage, if possible back to the intake temperature.
However, since flow losses and the purchasing price of the compressor rise as the number of stages increases, there is a limit to the number of stages possible.
BAUER KOMPRESSOREN GmbH München