Abstract

The paper presents a comparison of flow types, which occur in rotational and volumetric machines. Leak paths in multivane rotational machines are indicated and their characteristics, i.e. length, width and height of their associated gaps, given. Formulae are also presented, which allow to calculate the individual gas mass related to the gaps. Based on the formulae, the gas mass contained in the working chamber is given for an arbitrary chamber position.
This gas amount fluctuates strongly when the chamber is being filled or evacuated, although, in theory, it should remain constant in a closed chamber, As can be seen from the diagram that recapitulates the calculations by the author, the gas mass present in the working chamber during decompression decreases down to even 70% of its initial mass. Therefore, laws of the variable-mass thermodynamics have to be used to analyze thermodynamic processes performed by the gas, which is contained in the working chamber of a multi-vane rotational machine.