Investigation of leakage flow in compressor clearances

• Main Author: Lim, Li Ying
• Other Authors: Chan Weng Kong
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Engineering::Mechanical engineering::Fluid mechanics; Engineering::Aeronautical engineering
• Online Access: https://hdl.handle.net/10356/141487
• Institution: Nanyang Technological University

Rising global temperatures and lower-middle class income levels in recent years have fuelled the energy demand for cooling, which is projected to become a necessity as temperatures continue to rise. It is thus more important than ever to develop sustainable and energy efficient cooling systems. To do so, one of the key areas of improvement is reducing volumetric inefficiencies in the compressor, which arise as a result of leakages within the compressor chambers. Thus, in this project, leakage flow through clearances in a swing compressor was investigated with the use of Computational Fluid Dynamics (CFD) simulations. The two dominant leakage paths were identified as the end face clearance and radial clearance, which were modelled according to the geometry of the swing compressor of interest. Simulations were conducted at different crank angles and the results were compared to those obtained from a mathematical approach. In addition, for the end face clearance leakage, the effect of additional step clearances was investigated, which was found to increase leakage flow rates by approximately 28%. Parametric studies were also conducted to investigate the effect of varying rotor geometry and pressure ratio on end face leakage, as well as the effect of varying radial clearance height and pressure ratio on radial clearance leakage. Empirical equations were derived for both end face and radial clearance leakages which were found to perform well within the valid range of parameter values investigated. The overall leakage flow rates for the swing compressor was also computed and it was found that the radial clearance was the dominant leakage path in the compressor of interest due to the large clearance heights. Hence, special care should be taken to minimise radial clearances as far as possible to improve overall compressor efficiency.