变几何涡轮可调导叶瞬时转动气动特性研究

Study on Aerodynamic Characteristics of Variable Geometry Turbine Adjustable Guide Vane under Instantaneous Rotation

为探究单级变几何涡轮(VGT)在导叶转动过程中的过渡态性能,对某动力涡轮进行了非定常数值计算,应用动网格技术实现导叶转角的改变,并对导叶通道开大或关小过渡过程中涡轮性能进行了分析。结果表明:导叶转角从0°变化到-5°时,单级涡轮效率逐渐下降1.6%,从0°变化到6°时,效率逐渐提高0.5%;质量流量和导叶出口绝对气流角随转角改变接近线性变化,而动叶出口相对气流角、熵增、效率和导叶出口总压损失等随转角改变呈抛物线型变化;过渡态下导叶流场内损失变化主要受上、下端壁处间隙泄漏涡影响,动叶出口熵增变化规律主要受动叶吸力侧泄漏涡和下部通道涡影响,其中下部通道涡的改变是引起熵增变化的主要原因。

To investigate the transition state performance of single-stage variable geometry turbine(VGT) in the process of guide vane rotation,the unsteady numerical calculation of a power turbine was carried out,the dynamic mesh technology was used to realize the change of guide vane rotation angle,and the turbine performance during the transition process of the guide vane channel opening or closing was analyzed.The results show that when the guide vane angle changes from 0° to-5°,the single-stage turbine efficiency gradually decreases by 1.6%;from 0° to 6°,it gradually increases by 0.5%;the mass flow rate and the absolute flow angle at the outlet of the guide vane change nearly linearly with the change of the rotation angle,while the relative flow angle,entropy increase,efficiency and total pressure loss at the outlet of the rotor blade show parabolic changes with the change of the rotation angle;in the transition state,the change of the loss in the flow field of the guide vane is mainly affected by the leakage vortex at the upper and lower end walls,and the change of the entropy increase at the outlet of the rotor blade is mainly affected by the leakage vortex at the suction side of the rotor blade and the lower passage vortex which is the main reason for the change of entropy increase.