高速S-CO_(2)向心透平几何参数优化及变工况特性分析

Geometric Parameter Optimization and Off-design Performance Analysis of A High-speed S-CO_(2) Radial-inflow Turbine

透平是热力循环中实现热功转换的核心设备,优化透平几何参数以改善气动性能,是提升系统热效率的关键。该文以面向某船舶主机烟气余热利用的超临界二氧化碳布雷顿循环透平设计参数为基础,给出向心透平主要几何参数,采用耦合CO_(2)真实物性参数的CFX仿真方法,分析几何参数动、静叶包角以及叶轮出口几何角对透平性能的影响规律并进行参数优化,进一步研究非设计工况下的透平运行特性。结果表明:增大静叶包角会使动叶前缘出现扰动涡流并减少余速损失,增大叶轮出口几何角,动叶包角对透平效率的影响规律不变,但效率峰值点会沿动叶包角减小的方向移动;动、静叶包角和叶轮出口几何角分别为49°、21.5°、25°时透平设计点总-静等熵效率高达87.99%,相比优化前,提高0.54个百分点;透平偏离设计点±20%工况下等熵效率大于80%。结果可为超临界二氧化碳高速向心透平设计提供一定参考。

The turbine is the core equipment for realizing heat-power conversion in the thermodynamic cycle.Optimizing its geometric parameters to enhance its aerodynamic characteristics is an efficient approach to boosting the thermal efficiency of the entire cycle system.Drawing from the design parameters of the supercritical carbon dioxide turbine utilized in waste heat recovery for marine main engines,we have achieved the calibration of key geometric parameters for the high-speed radial-inflow turbine.Using the CFX simulation method coupled with the real physical parameters of CO_(2)in the database,the influence laws of geometric parameters rotor,stator blade wrap angle,and impeller outlet geometric angle on the performance of the turbine are analyzed in detail.The operation characteristics of the radial-inflow turbine under the off-design operating conditions are further studied.Simulation results indicate that increasing the wrap angle of stator blade will cause disturbance eddy current at the leading edge of rotor blade and reduce exit loss.With the increase of impeller outlet angle,the influence of the rotor blade wrapping angle on turbine efficiency remains unchanged,but the peak point of isentropic efficiency will move along the direction of the rotor blade wrap angle decreasing.Through optimization analysis,the isentropic efficiency of the turbine design point is 87.99%when the wrap angle of the rotor and stator blades and the geometric angle of the impeller outlet are 49,21.5,and 25,respectively,which is 0.54 percentage points higher than that before optimization.The isentropic efficiency of a radial-inflow turbine is more than 80%when it deviates from the design point by 20%up and down.The results can provide reference for the design of the supercritical carbon dioxide high-speed radial-inflow turbine.