Thermal Design and Analysis of Oil Injected Screw Compressor

Abstract

In a screw compressor air is compressed by means of two rotating rotors of the male and female screws in a compressor chamber. While rotating, the compressor chamber volume decreases and thus the air is compressed. For optimizing the fluid leakage, the clearance between the two rotors is kept minimum; this in turn results in higher friction between the rotors thus leading to heat generation. So for cooling the compressor rotors, chamber and the compressed air and for providing proper sealing and lubrication to the rotating meshing rotors, lubricating oil at an optimized position is injected during a compression process into the compression volume. The major objective in designing an oil flooded screw compressor is increasing its volumetric and isentropic efficiencies. Therefore, initially thermodynamic analysis is performed, which incorporates the analysis of the force applied on the rotors. By the results obtained from the thermodynamic analysis and force analysis, the profiles of the male and female screws are designed and optimized and also the geometric structure of the case are performed and optimized.

Thus, a thermodynamic analysis of oil flooded twin-screw compressor is performed, which incorporates the use of basis of the laws of perfect gas and standard thermodynamic equations. During the solving of the mathematical model generated, the five steady boundary conditions and the periodic convective are calculated using the steady heat fluxes and the convective heat-transfer coefficient. Also a setup of experiment is proposed to calculate the temperature and pressure distribution in the compressor chamber for validating the calculated results. Further a CFD analysis is done to know the pressure and temperature distribution in the flow regions. The change in pressure and temperature in the clearance path is analysed and modification suggested.