超临界二氧化碳迷宫密封内摩擦损失数值研究及流动特性分析

In order to clarify the influence factors of windage loss in labyrinth seal and build a predicting model of friction coefficient, based on the experiment device constructed by Vannini, et al., the influence relations of Reynolds number, pressure ratio, and radius ratio on friction coefficient and leakage flow with supercritical CO₂are investigated by numerical method in this paper. The results show that the friction coefficient decreases as Reynolds number increases, and it almost keeps constant with the pressure ratio. The leakage flow is almost constant when Reynolds number is less than 10, but it decreases with the increase of Reynolds number when it is larger than 10⁴, and it increases with the increase of pressure ratio. Under the different conditions, the friction coefficient and the leakage flow linearly increase with the increase of radius ratio. The slope of friction coefficient is basically constant, but that of leakage flow increases with the increase of pressure ratio. When Reynolds number is larger and pressure ratio is lower, there arc larger vortexes in the inlet regime of seal, which is beneficial to decreasing the leakage flow but reduces slightly the prediction accuracy of leakage model. When the radius ratio is lower, the windage loss is mainly from the flow in gap. When the radius ratio is larger, the interaction between fluid and wall is the primary reason for windage loss. Finally, a predicting model of friction coefficient is proposed based on numerical results, and its predicting accuracy is validated. The research results will provide referance for improving the design of supercritical CO₂labyrinth seal and turbo-machinery.