水滴迷宫式调节阀空化特性计算与结构改进

针对超(超)临界机组中水滴迷宫式调节阀在高温高压工况下引起的严重气蚀问题,基于计算流体力学理论和空化机理,选用标准k-ε湍流模型、Mixture模型和Schnerr-Sauer空化模型,比较了改进前后调节阀在典型开度下的压力、速度、气相体积分数等结构性能。计算结果表明:原始碟片结构压降大,最大可至19.95 MPa,流速高,最高可达237 m/s,从而导致了严重的空化现象,气相体积分数甚至高达1;增加围堰后,碟片流道内最大压降降低了52.5%,最大速度减小了38.8%,最大气相体积分数降低至0.18;证明增加围堰可有效控制阀内压降和流速,减小气蚀破坏程度。此外,适当增加围堰高度有利于抑制空化发生,但高度过大会使空化区域向围堰处转移,同时形成不稳定流场影响阀门启闭特性。

Numerical simulation and structural improvement of cavitation characteristics of water droplet labyrinth control valve

For the problem of the severe cavitation caused by the water droplet labyrinth regulating valve in the super-(super-)critical unit under high temperature and high pressure conditions,based on the theory of computational fluid dynamics and cavitation mechanism,the standard k-εturbulence model,Mixture model and Schnerr-Sauer cavitation model were selected to compare the structural performance of the control valves before and after improvement at typical openings in terms of pressure,velocity,gas volume fraction,etc.The calculation results show that the original disc structure has a large pressure drop,up to 19.95 MPa at maximum,and a high flow rate,up to 237 m/s at maximum,which leads to severe cavitation,and the gas phase volume fraction is even as high as 1.The maximum pressure drop in the disc flow passage was reduced by 52.5%,the maximum speed was reduced by 38.8%,and the maximum gas phase volume fraction was reduced to 0.18.It was proved that increasing the cofferdam can effectively control the pressure drop and flow velocity in the valve and reduce the degree of cavitation damage.In addition,appropriately increasing the height of the cofferdam is conducive to suppressing the occurrence of cavitation,but an excessively high height will cause the cavitation area to shift to the cofferdam,and at the same time,an unstable flow field will be formed,which will affect the valve opening and closing characteristics.