Flow-Feedback Method for Mitigating the Vortex Rope in Decelerated Swirling Flows
Flow-Feedback Method for Mitigating the Vortex Rope in Decelerated Swirling Flows
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DOI：
10.1115/1.4023946
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发表时间：
2013-06
影响因子：
2
通讯作者：
C. Tănasă;R. Susan-Resiga;S. Muntean;A. Bosioc
中科院分区：
文献类型：
--
作者：
C. Tănasă;R. Susan-Resiga;S. Muntean;A. Bosioc
当反动式水轮机远离设计运行工况运行时，特别是在部分泄流时，在转轮下游的泄流锥中会产生旋流不稳定性，并产生旋进螺旋涡流及其相关的严重压力波动。Bosioc等人（2012年，“Unsteady Pressure Analysis of a Swirling Flow With Vortex Rope and Axial Water Injection in a Discharge Cone，”ASME J. Fluids Eng.，134（8），p.081104）表明，这种不稳定性可以通过沿轴线沿着注入水射流而成功地减轻。然而，喷射流量太大，不能提供绕过转轮的高压水，因为这种流量与体积损失有关。在本文中，我们证明了控制射流注入的锥形扩散器的入口处，实际上可以提供与水收集从排放锥出口，从而引入了一个新的概念，流量反馈。在这种情况下，射流由反馈蜗壳所在的锥形壁与射流喷嘴出口处的压力之间的压差驱动。为了达到所需的射流流量阈值，我们还引入了喷射泵来部分补偿回水管中的水力损失。广泛的实验研究表明，对于典型的部分负荷涡轮机运行状态，当射流达到主流流量的12%时，壁面压力波动被成功地减轻。约10%的喷射流量由普通流量反馈提供，只有2%的增压由喷射泵提供。因此，这种新方法为在真实的水轮机中的实际应用铺平了道路。
When reaction hydraulic turbines are operated far from the design operating regime, particularly at partial discharge, swirling flow instability is developed downstream of the runner, in the discharge cone, with a precessing helical vortex and its associated severe pressure fluctuations. Bosioc et al. (2012, “Unsteady Pressure Analysis of a Swirling Flow With Vortex Rope and Axial Water Injection in a Discharge Cone,” ASME J. Fluids Eng., 134(8), p. 081104) showed that this instability can be successfully mitigated by injecting a water jet along the axis. However, the jet discharge is too large to be supplied with high pressure water bypassing the runner, since this discharge is associated with the volumetric loss. In the present paper we demonstrate that the control jet injected at the inlet of the conical diffuser can actually be supplied with water collected from the discharge cone outlet, thus introducing a new concept of flow feedback. In this case, the jet is driven by the pressure difference between the cone wall, where the feedback spiral case is located, and the pressure at the jet nozzle outlet. In order to reach the required threshold value of the jet discharge, we also introduce ejector pumps to partially compensate for the hydraulic losses in the return pipes. Extensive experimental investigations show that the wall pressure fluctuations are successfully mitigated when the jet reaches 12% of the main flow discharge for a typical part load turbine operating regime. About 10% of the jet discharge is supplied by the plain flow feedback, and only 2% boost is insured by the ejector pumps. As a result, this new approach paves the way towards practical applications in real hydraulic turbines.