Research and optimization of the mechanism of centrifugal compressor

As the core component of an aeroengine, a compressor significantly affects the flow and power of the engine. Compared with the axial compressor, the centrifugal compressor is characterized by structural simplicity, manufacturing convenience, and high single-stage pressure ratio. Therefore, the compressor is highly suitable for turboshaft engines with low flow rates and low total pressure ratios. However, the piston engine plays a more important role in the market. Accelerating the research on centrifugal compressors used in small turboshaft engines is essential.

The design methods currently used in this project include experimentation, theoretical analysis, and numerical simulation. The numerical simulation method can eliminate the requirements of experimentation, overcome measurement difficulties, and eliminate the costs associated with the experiment process. Therefore, it is a relatively accurate and efficient method for flow and transfer analysis. In this paper, according to the theory of numerical simulation, the impeller and diffuser of the centrifugal compressor are designed under specified working conditions. A three-dimensional numerical simulation of the centrifugal compressor is conducted. The influence of typical parameters on the centrifugal compressors is studied, and the parameters of the preliminary design model are optimized to obtain the ideal model of the centrifugal compressor under the design conditions.

The results of this study were obtained according to the static pressure distribution cloud map and the total pressure distribution cloud map of the meridional channel surface at the highest efficiency of the centrifugal compressor and design speed conditions. The efficiency of the optimized centrifugal compressor was 0.831; the corresponding pressure ratios was 8.771, which was 3.68% higher than that of the preliminary design; and the working margin was 18.44%, which was 4.79% higher than that of the preliminary design centrifugal compressor.

Through the numerical simulation results of an Eckardt impeller and comparison of the simulation with reference experimentation results, the reliability of the numerical simulation of a centrifugal compressor by FINE/Turbo is proved. The results demonstrate that the kinetic energy of the gas at the impeller outlet of the centrifugal compressor is basically transformed into pressure energy and that the supercharging effect is relatively good. The entropy increase mainly occurs at the tip clearance, where the leakage flow is relatively critical. The static pressure distribution of the B2B (blade to blade) section is compared with that of the meridional flow channel. The meridional section is a contraction channel along the flow direction caused by the large turning angle of the hub. Owing to the effect of centrifugal force, a low-speed zone is developed in the flow channel to form a separation zone and result in energy loss. The separation area can be reduced through the reduction of the inlet flow angle to improve the overall performance of the compressor. The research shows that properly reducing the inlet hub ratio and the inlet angle of the impeller blade root and reasonably selecting the blade tip clearance value and the relative width of the impeller outlet are beneficial to improving the efficiency and pressure ratio of the compressor.