双通道蜗壳径流涡轮的设计与流动机理研究

低负荷下的扭矩对于小型发动机十分重要,其决定了汽车的驾驶性能。配有双通道蜗壳的涡轮已被证实在瞬态性能和气缸扫气方面具有极大优势。本研究通过数值方法,比较了不同部分进气条件下双通道径流涡轮的性能。设计了一个双通道径流涡轮,以达到某国外混流涡轮(带有可变喷嘴的涡轮A)的流通能力。借助软件ANSYS-CFX,采用稳态数值模拟方法来实现全部进气和部分进气条件下涡轮的性能预测。基于不同进气条件(叶根进气HI和叶尖进气SI)的性能比较结果进行流动机理分析。结果显示SI比HI具有更好的性能,且传递到叶轮的流动在通道内产生了完全不同的涡流结构。对于HI进气,产生于叶轮叶根处的涡流逐渐迁移到叶尖区域,而SI进气正好相反,这即是HI进气较SI进气具有更高流动损失和更差性能的原因。

Design and Flow Mechanism Analysis of Radial Turbine with Twin-entry Volute

The torque at low load which determines the drivability of automobile is an important performance characteristic of a downsized engine.Twin-entry volute turbine has been proved to have great advantages in terms of transient performance and cylinder scavenging.The performances of radial turbine with a twin-entry volute at different partial intake conditions were compared by the numerical method.A baseline radial turbine with a twin-entry volute was first designed to achieve the flow capacity of foreign mixed flow turbine with variable nozzle.Then the steady numerical simulation was carried out for the performance prediction of designed turbine at full and partial intake conditions with ANSYS-CFX software.Based on the performance comparison between HI and SI intake conditions, the flow mechanism was analyzed.The results show that the performance of SI is superior to that of HI.The flow fed to the rotor produces different vortex structures in the passage.The vortex generated at the root of impeller migrates gradually to the tip region for HI, but it goes an opposite direction for SI, which is the reason for the high flow loss and poor performance of HI.