水下S-CO_(2)循环部分进气轴/径向涡轮机对比研究

Comparison of Partial Admission Axial and Radial Inflow Turbines for Underwater S-CO_(2) Power Cycle System

将超临界二氧化碳(S-CO_(2))循环动力系统合理应用于无人水下航行器(UUV),有助于解决现有UUV蒸汽动力循环系统尤其是针对小功率等级应用效率低的问题。为合理选型水下S-CO_(2)系统涡轮机,结合损失模型的一维方法获得了设计空间内的最佳几何参数,并基于RANS方程的三维数值仿真方法验证了一维设计方法的合理性,进一步对比分析了轴/径向涡轮机的气动性能及流动特性。结果表明,设计工况下径向涡轮机内效率比轴向涡轮机高5.41%,但尺寸较大,约为轴向涡轮机的2倍;径向涡轮机的主要损失集中在喷管和转子非工作段,而轴向涡轮机则主要为转子处产生的二次流损失。通过变工况分析发现,轴向涡轮机更适用于低速比工况,但在同一转速下径向涡轮机效率更高。文中研究结果可为应用于UUV的S-CO_(2)系统动力主机的研制提供参考。

The reasonable application of supercritical carbon dioxide(S-CO_(2))power cycle systems to unmanned undersea vehicles(UUVs)can help address the problem of low efficiency for the existing UUV steam power cycle systems,especially for small-power applications.In order to select the optimal turbine for the underwater S-CO_(2)system,the one-dimensional approach combined with the loss model was used to obtain the best geometric parameters within the design space.In addition,the three-dimensional numerical simulation method based on the RANS equation was adopted to verify the rationality of the one-dimensional design method.The aerodynamic performance and flow characteristics of the axial/radial turbine were further compared.The results show that the internal efficiency of the radial turbine is 5.41%higher than that of the axial turbine under the design conditions,but the size of the radial turbine is larger,about twice that of the axial turbine.The main loss of the radial turbine is from the nozzle and the rotor non-working section,while that of the axial turbine is mainly concentrated in the secondary flow losses generated at the rotor.Through the analysis of variable operating conditions,it is found that the axial turbine is more suitable for the low velocity ratio operating conditions.Nevertheless,the radial turbine has higher efficiency at the same speed.This research can provide a reference for the development of the S-CO_(2)system power unit applied in UUVs.