Unsteady Flow Loss Mechanism and Aerodynamic Improvement of Two-Stage Turbine under Pulsating Conditions
Unsteady Flow Loss Mechanism and Aerodynamic Improvement of Two-Stage Turbine under Pulsating Conditions
复制标题
脉动工况下两级涡轮非定常流动损失机理及气动改进
DOI：
10.3390/e21100985
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发表时间：
2019-10-10
期刊：
影响因子：
2.7
通讯作者：
Zhang Y
中科院分区：
文献类型：
--
作者：
Zhao R;Li W;Zhuge W;Zhang Y
两级涡轮增压和涡轮复合技术的发展促进了两级涡轮系统在内燃机上的应用。由于涡轮受到脉动排气的影响，其性能在稳态状态下明显恶化。本文分析了两级水轮机的脉动流动损失，提出了一种提高水轮机性能的控制方法。应用商业计算流体动力学软件ANSYS CFX求解三维非定常流动问题。通过各水轮机的实验数据验证了仿真方法的准确性。首先，研究了脉冲幅值对两级水轮机各部件暂态损耗的影响。然后进行流场分析，了解非定常流动的细节。研究发现，低压涡轮叶尖处的入射角变化明显大于轮毂处的入射角变化，导致前缘附近流动损失严重。结果，LPT性能显著下降。为了提高LPT性能，对叶尖形状进行了改进。对三种不同形状的涡轮在高、低负荷脉动流工况下的气动性能进行了评价。结果表明，增大进口叶片角度和介质厚度可获得较好的气动性能。在高负荷脉动工况下，转子平均效率提高了2.27%。
The developments of two-stage turbocharging and turbocompounding promote the application of the two-stage turbine system in internal combustion engines. Since the turbine suffers from the pulsating exhaust, the performance deteriorates significantly from steady conditions. In the paper, the pulsating flow losses in the two-stage turbine are analyzed and a control method is proposed to improve the turbine performance. ANSYS CFX, which is a commercial software for computational fluid dynamic, is applied to resolve the three-dimensional unsteady flow problem. The accuracy of the simulation method is verified by the experimental data from each turbine. Firstly, the impacts of pulse amplitudes on transient loss of each component of the two-stage turbine are studied. Then flow field analysis is carried out to understand details of the unsteady flows. It is found that the variation of incidence angle at the low-pressure turbine (LPT) rotor tip is significantly larger than that at rotor hub, which causes severe flow loss near leading edge. As a result, the LPT performance drops down significantly. To improve the LPT performance, the blade shape at tip is modified. The aerodynamic performances of turbines with three different shapes under high- and low-load pulsating flow conditions are evaluated. It is found that increased inlet blade angle and medium thickness achieves good aerodynamic performance. The rotor averaged efficiency is improved by 2.27% under high-load pulsating condition.
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