NUMERICAL SIMULATION OF GAS FLOW PATTERNS AND CHARACTERISTICS OF A CENTRIFUGAL COMPRESSOR

Abstract

The design of compressors based on one- and two-dimensional flow calculations has reached the limit of development by achieving the maximum efficiency of devices. Further development is possible by conducting expensive experiments or by analyzing the results of the modern mathematical models of three-dimensional flow calculations based on the Reynolds-averaged Navier-Stokes equations. To improve the characteristics of the centrifugal compressor and improve the flow part with the subsequent change in the shape and location of the compressor impeller blades, threedimensional flow calculations were performed. Calculations were made using the Ansys CFX software with a student license. The effect of mesh on the integral flow characteristics is analyzed. There is a qualitative coincidence of the compressor performances, as well as gas flow patterns, and separation zones with experimental data. The research uses a sectoral approach to modeling. Calculations based on different turbulence models were compared and it was found that the models based on the "k – ε" model give practically identical results. Compared with the experimental data of the compressor, the Eddy Viscosity Transport Equation turbulence model showed a significant error in determining the total-to-total polytropic efficiency, this value is underestimated by more than 7 %. Due to an increase in the mass flow rate in the compressor, the velocity in the blade diffuser increases significantly and the flow separates from the blades. Based on the comparison of Mach number contours, in addition to flow separation from the diffuser blades, flow separation from the splitter walls and impeller blades are also observed, even at low mass flow rates. The influence of the sector approach on the calculation results and the mutual location of the impeller sector and the blade diffuser sector require further research, which will be the subject of further research.