Calculation of Gas Loads Acting on Screw-Compressor Rotors.

A calculation method of rotor loads and some numerical examples are presented. Gas loads acting on the male and female rotors are calculated from sealing lines which are formed as border lines between working spaces. The procedure is simplified by taking advantage of the property that the sealing lines do not change in shape when the meshing rotors rotate. Axial loads as well as radial loads are obtained from sealing line shapes projected to two planes which are parallel to the rotor axis and intersect perpendicularly. Especially, the axial loads are calculated using the principle of virtual work. The calculation results show that a high operating pressure itself does not necessarily increase the amplitude of the rotor load, but the mismatching between the operating pressure ratio and the built-in pressure ratio makes the amplitude larger.