Design optimisation of a screw compressor with a focus on rotor depth: A computational fluid dynamics approach

The increasing demand for enhanced performance and reliability in twin-screw compressors necessitates the application of advanced optimisation tools to improve performance. This study employs response surface methodology (RSM) to optimise the profile parameters of a standard 5/6 compressor, specifically targeting reduction in specific power. Key factors such as axis distance between rotors and female rotor outer diameter, which define the rotor depth, were included in the present optimisation process. Following the optimisation of the rotor profile, port optimisation was also conducted using the same methodology. A multi-chamber thermodynamic analysis was performed with SCORG™ software, which allowed for the calculation of geometric values and thermodynamic quantities. The results of the rotor optimisation revealed notable improvements: a 4.30 % reduction in specific power, a 2.73 % increase in volumetric efficiency, a 3.93 % enhancement in adiabatic efficiency, and a 2.88 % rise in volumetric flow rate compared to the reference design. After port optimisation, both volumetric and adiabatic efficiencies of the optimised rotor profile remained comparable, while specific power was further reduced by 1.37 %. To validate the performance of the optimised compressor, computational fluid dynamics (CFD) analysis was conducted using a conformal mesh generated by SCORG™ and ANSYS CFX multiphase solver. The maximum deviation between the optimal results from SCORG™ and CFD was only 0.19 %, indicating strong agreement between the two methodologies. This study highlights the significant impact of optimisation techniques on the performance of twin-screw compressors.