Multi-Control-Volume Analysis of the Compression Process in a High-Temperature Root's Type Compressor

Abstract

In this study we have modeled a high-temperature Root's type compressor and compared predicted results with measurements. Compression process is modeled using multiple control volumes. Initially, there are two control volumes connected by an “expansion nozzle” naturally formed by the rotor tip and the blower casing. The “nozzle” has time-varying geometry and is modeled to allow transition from choked to non-choked flow. The well-filling process is modeled via expansion of the compressed gas from the high-pressure reservoir into the well through this “nozzle.” When the pressures in the well and reservoir equalize, the “passive” part of the compression process is taken to be complete. At this point, the gas in the well is assumed to be fully-mixed and the two control volumes are subsequently considered as one. Then the “active” part of compression takes place. Numerical computations are shown to agree well with the experimental data.