诱导轮快速启动过程的瞬态水力特性研究

The hydraulic performance and the flow instability in an inducer have a vital impact on the safety and operating efficiency of the liquid rocket engine fuel transportation system. According to the transient characteristics of the inducer during the rapid start-up process, the standard k -ε turbulence model and the Zwart cavitation model are applied to simulate the unsteady flow process inside the inducer numerically. The numerical simulation results were verified by the experimental data. It is found the head coefficient and the cavity shape obtained by numerical calculation were in good agreement with the experimental results. At the rated speed of 5 000 r/min, the synchronous rotating cavitation phenomenon was captured by the numerical results when cavitation number σ=0.035. The unsteady characteristics of rotating cavitation were analyzed based on the data of cavity shape and pressure fluctuation of the inducer. The results indicate that the occurrence of synchronous rotating cavitation is the main reason for the rapid decline in the cavitation performance of the inducer. During the rapid start-up process, the head coefficient and axial force of the inducer have obvious impact characteristics, and the response of head coefficient and flow coefficient lags behind the speed. In the initial stage of the start-up acceleration, a significant backflow phenomenon is observed. The size and quantity of the vortex structure in the flow passage decrease with the increase of the rotation speed. The inception cavitation is dominated by the leakage vortex cavitation, and then expands to the blade surface and moves to the trailing edge of the blade. After reaching the rated speed, the flow inside the inducer tends to be stable. Compared with the condition at rated speed, cavitation always exists in the trailing edge, and the cavity shape of the three blades is similar. The cavitation is mainly blade-attached cavitation, and the stable flow coefficient and head coefficient are respectively 1.176 times and 0.6 times of the flow coefficient and head coefficient under rated speed conditions. The results can provide a reference for the stability analysis of the inducer under rapid start-up and variable operation conditions.