Fluid Flow Characteristics of Twin and Gerotor Screw Compressors

Abstract

Abstract The study explores variations in fluid flow characteristics between two types of screw compressors: the twin-screw compressor (TSC) and the gerotor screw compressor (GSC). After generating rotor profiles using mathematical models, 3D fluid analysis models for both screw compressors are constructed using computational fluid dynamics (CFD). To facilitate comparison, the cross-sectional areas in the TSC chamber and the outer rotor of the GSC are designed to be the same, with identical area efficiency and screw rotor helix angles. Under consistent design conditions, the study examines three different rotor lengths (120mm, 180mm, and 240mm) for both GSC and TSC to assess the impact of screw compressor design on output performance and compare their flow characteristics. The evaluation includes output mass flow rate, pressure, temperature, and their fluctuation properties to discern the advantages and disadvantages of the two screw compressor designs. Simulation results indicate that increasing the length of the screw compressor enhances the mass flow rate. However, higher lengths lead to power losses and increased leakage, potentially negatively affecting compressor efficiency. Furthermore, the GSC exhibits a higher outlet average pressure compared to the TSC for the same length, with relatively smaller pressure fluctuations in a suitable rotor length. Additionally, the GSC design achieves a lower stable temperature through a smoother compression process. This smoother compression process ensures a steady fluid flow, resulting in reduced friction and stable temperatures. Overall, the GSC demonstrates several advantages, including a higher flow rate, greater operating stability, lower leakage, reduced power loss, and improved efficiency compared to the TSC across all three rotor lengths.