全冠与部分冠轴流涡轮流动的数值模拟

采用数值模拟方法对某1.5级轴流带冠涡轮的流场进行了研究,分析了全冠、部分冠以及改进的部分冠密封的流场及总体参数。研究结果表明,相对于全冠密封,未改进的部分冠密封降低了涡轮的效率,而改进的部分冠使效率提高到与全冠基本相等。由于叶冠容腔泄漏流周向速度与主流速度不同,导致90%以上叶展出口气流角小于主流的出口气流角,与未改部分冠相比,改进的部分冠减小了这种气流角差别和掺混损失。未改部分冠前部存在压力面向吸力面的横向流动,这种流动造成很大的损失,而改进的部分冠密封减弱了这种横向流动。

Numerical Simulation of the Flow in a Fully-and-partially-shrouded Axial Flow Turbine

By using a numerical simulation method,studied was the flow field in a 1.5-stage axial flow shrouded turbine with the flow field sealed by using a full-shroud,partial-shroud and improved partial-shroud and its overall parameters being analyzed.The calculation results show that relative to the fully-shrouded seal,the partially-shrouded seal not yet improved may lower the efficiency of a turbine while the improved partial shroud can enhance such an efficiency to one basically identical to that of the full shroud.A difference in the circumferential velocity of the leakage flow in the blade shroud cavity and the main stream will lead to a smaller gas flow angle at the outlet than the main stream one in more than 90% span of the blade.Compared with the partial shroud not yet improved,the improved partial shroud can reduce such a difference in the gas flow angle and the mixing and dilution losses.There exists a transversal flow from the pressure surface to the suction one in the front of the partial shroud,which can result in a very big loss.The seal by using the improved partial shroud,however,can weaken such a transversal flow.