COMPUTATION OF COMPRESSION LOADS IN TWIN-SCREW COMPRESSORS

The compression mechanism in a twin screw compressor consists of two h elical voters. In this work, a method is presented for computing the f orces and moments induced on each rotor due to gas compression. These are defined as the compression loads. The helical rotor surfaces are d efined by the end profiles, wrap angle and rotor length. The 3D surfac e of each rotor is mapped to 2D integration regions. These regions cor respond to the surfaces associated with individual compression chamber s. The compression loads are completed by integrating the chamber pres sure over the rotor surfaces. The integrals ave evaluated at increment al values of the rotor angular position. The method is presented and i mplemented for a specific compressor configuration. The compression le nds are resolved to forces at the bearing locations. These bearing for ces are presented for operating pressures which represent an under-pre ssure condition. A frequency analysis demonstrates the rich frequency content of the bearing forces due to the sharpness of the compression loads as a function of the rotor angular position. In addition, it is demonstrated that the moment lend about the axis of rotation induced o n the female is approximately 12 percent of that induced on the male. Therefore, the female rotor motion approaches that of an idler gear.