Experimental and numerical flow field investigation through two types of radial flow compressor volutes

Abstract

Being able to optimal design and fabrication of compressors requires understanding of the flow structure through the compressor components. Volutes are commonly the last main component in radial flow compressors. The stream passes through inlet, impeller and diffuser and finally is collected and discharged to the downstream pipeline by a volute. Volute shape has a direct and non-negligible effect on the compressor performance and its stable operating range. This component causes distorted pressure field in the upstream flow passages which could lead to the aero-mechanical forces acting on the impeller. As the flow inside the volute is fully three dimensional and turbulent, better understanding of flow mechanism has priority before modifying the volute design procedure.In this research the experimental and numerical flow investigation through a radial flow compressor volute are performed to recognize the flow structure. The whole compressor components including the inlet, impeller, vane-less diffuser and volute are modeled and the flow structure inside the volute is captured. The three dimensional flow field model of the compressor was obtained numerically solving Navier–Stokes equations with shear stress transport turbulence model. Flow field investigation through volute cross section is performed utilizing a five-hole probe.As the original volute is overhang type volute, the new external type volute is designed and fabricated based on the optimum design procedure. The results which are used for numerical model verification show that stage pressure ratio and total to total isentropic efficiency are increased by 2.5% and 1.9%, respectively at 70,000rpm rotational speed using the new fabricated volute. The flow field inside the volute is also captured and compared to the experimental results obtained from the original volute setup and also for verifying the numerical model.