Small centrifugal compressor performance trend prediction based on computational fluid dynamic

Abstract

Centrifugal compressors (impeller), sometimes termed radial compressors, are a sub-class of dynamic axisymmetric turbomachinery device. The idealized compressive dynamic turbo-machine achieves a pressure rise by adding kinetic energy/velocity to a continuous flow of fluid through the rotor or impeller. This kinetic energy is then converted to an increase in potential energy/static pressure by slowing the flow through a diffuser. Small Centrifugal compressor now is commonly used for mini turbojet engine which applications are in rapid drone among others. The usage of small centrifugal compressor in the mini turbojet has several advantages. One of them is that it can give higher pressure ratio than axial compressor (for example common single stage small centrifugal compressor can give 3-4 in pressure ratio at 80000-98000 rpm). The purpose of this paper is to assess the effect of geometry parameters, such as fillet radius, number of splitter and blades, to the pressure ratio. In this paper, typical small centrifugal compressor with diameter of 6.6 cm will be simulated using NUMECA, a CFD software and their results will be discussed to map the effect of each geometry parameter to pressure ratio hence compressor performance. Different geometry parameters are calculated and compared at several boundary conditions and flow setting to explore the trend of pressure ratio evolution with the change of those parameters. Based on the simulation result is indicated that there is similiar effect on the applying spplitter and adding blade number in the impeller configuration to increase the pressure ratio. In another case, adding fillet at the end of impeller hub wall give tendency to reduce compressor pressure ratio.