The Internal flow mechanisms and windage loss in impeller back gap of a supercritical carbon dioxide (sCO2) radial inflow turbine with scallops are comprehensively investigated in this paper. The study emphasizes the effects of scallop depth and leakage outlet pressure. The results indicate that scallop structures lead to a degradation in overall turbine performance. Under design conditions, a turbine with a scallop depth ratio of 0.5 exhibits a 3.7 % reduction in efficiency and a 3.4 % decrease in total power compared to no scallop configuration. Furthermore, as scallop depth increases, the skin friction coefficient decreases in the disk gap while it increases for the seal in the impeller back gap. Increasing leakage outlet pressure reduces the leakage flow rate and skin friction coefficient. Fitted models for skin friction coefficient are proposed respectively. The conclusions providing valuable insights for designing and optimizing sCO2 radial inflow turbines with scallops.

中文翻译：

---

带叶轮扇形的 sCO2 径向流入式涡轮机的流机机理和背隙风阻损失


本文全面研究了扇形超临界二氧化碳 （sCO2） 径向流入式涡轮机的内部流动机理和叶轮背隙中的风阻损失。该研究强调了扇贝深度和泄漏出口压力的影响。结果表明，扇形结构会导致涡轮机整体性能下降。在设计条件下，与无扇形配置相比，扇形深度比为 0.5 的涡轮机的效率降低了 3.7%，总功率降低了 3.4%。此外，随着扇形深度的增加，圆盘间隙中的蒙皮摩擦系数减小，而叶轮背隙中密封件的蒙皮摩擦系数增加。增加泄漏出口压力会降低泄漏流量和表皮摩擦系数。分别提出了蒙皮摩擦系数的拟合模型。结论为设计和优化带扇贝的 sCO2 径向流入式涡轮机提供了有价值的见解。