CFD Simulation of a Centrifugal Compressor using Star-CCM+
Examensarbete för masterexamen
Applied mechanics (MPAME), MSc
Ravichandran, Sai Anirudh
With anthropogenic greenhouse gas every year, its effect on the climate change is higher than ever and the need to curtail the emission of greenhouse gases is high. Decarbonization of district heat pumps is a step in the right direction to reduce the effects of such machines on climate change. In this case, the working fluid in the heat pump is replaced from R134a which has a GWP of 1430 to R1234ze(E) which has a GWP of 6. The main aim of this work is to perform CFD simulations of a centrifugal compressor using Star-CCM+. The compressor is tested for different outlet pressure conditions to create a compressor map with in-depth analysis of the impact of various factors on the performance. The working fluid is R1234ze(E) which is a low GWP refrig erant. The results obtained from the simulations would then be compared with the in-house and ANSYS CFX results. The process starts from acquiring the geometry and preparing it for meshing. The main task was to add the inlet part and the diffuser part to the compressor. The diffuser dimensions were provided which was added to the impeller. The final geom etry is then meshed appropriately and the physics models required are added. The fluid and thermodynamic properties of the refrigerant are obtained from REFPROP and are added to the material database. With all the prerequisites set, simulations are performed. The outlet pressure is changed for every case and the important compressor characteristics are noted. Properties of the flow are recorded at different boundaries and are used to evaluate the compressor performance using appropriate equations. The effect of different turbulence models and real gas equations are studied. Also, the effect of the diffuser on the compressor is studied by analysing the efficiency curve. The difference be tween the polytropic efficiency and the isentropic efficiency for a compressor is also observed as expected. Finally, the operation analysis at design point and off-design are performed by looking at the flow through the compressor at different spanwise locations.
CFD, centrifugal compressor, isentropic efficiency, polytropic efficiency, pressure ratio.