固定锥形阀特性参数及流动特征的仿真分析

固定锥形阀应具备良好的水力特性以满足管线系统中不同工况的调流和消能要求,以DN1200锥形阀为研究对象,利用计算流体力学(computional fluid dynamics,CFD)方法分析不同开度下的稳态工况及开、关阀过程的瞬态工况,通过对比流量系数、流阻系数、排放系数、汽蚀系数、消能率等阀门特性参数及套筒闸的动静态不平衡力和阀内流场分布等,全面分析了固定锥形的水力特性。结果表明,流量系数和排放系数具有较好的线性特性,其过流能力随开度增大而线性增加。流阻系数和消能率曲线的变化趋势相同,小开度时对水流的流动阻碍和能量损耗作用明显,开度增大后流阻系数和消能率迅速减小。汽蚀系数表征实际工况中的汽蚀可能程度,在设计流量工况下,各开度对应的汽蚀系数呈抛物线变化趋势。另外,由于流动和启闭同在轴向,故套筒闸主要受到轴向的不平衡力;稳态不平衡力与水流方向相同,而开关阀过程的瞬态不平衡力均与水流方向相反,且关阀力略大于开阀力。最后,分别以各开度下的压力、流速、湍动能和湍流耗散率等流场分布对固定锥形阀的流动规律进行说明。

Hydraulic Characteristics Analysis of Fixed-cone Valve

The fixed-cone valve should be good enough in hydraulic characteristics to meet the flow regulating and energy dissipating requirements of different working conditions in the pipeline system. In this research, the DN1200 fixed-cone valve was investigated by CFD method in steady-state conditions under different openings and transient conditions during opening as well as closing processes. To analyze hydraulic characteristics of the fixed-cone valve thoroughly, characteristic parameters of the valve, such as flow coefficient, resistance coefficient, discharge coefficient, cavitation coefficient and energy dissipation rate, were compared as well as the unbalanced forces exerted on the sleeve gate in steady-state and transient working conditions. And the flow field distribution of the valve was also discussed. Results indicate the flow coefficient and discharge coefficient have good linear characteristics that the flow capacity of fixed-cone valve increases linearly with the increase of opening. The variation trends of resistance coefficient and energy dissipation rate are the same. The flow resistance and energy loss are obvious in small opening, and both of the resistance coefficient and energy dissipation rate decrease rapidly while the opening increases. The cavitation coefficient characterizes the possible degree of cavitation in the actual working condition. In the design flow condition, the cavitation coefficient, corresponding to each opening, changes in a parabolic trend. In addition, as the fluid flows in axial direction as well as the opening and closing valve processes, the sleeve gate is mainly subject to axial unbalanced force. The steady-state unbalanced force acts in the same direction of fluid flow, while the transient unbalanced force of both opening and closing act in the opposite direction, and the closing force is slightly greater than the opening one. Finally, flow pattern of the fixed-cone valve is illustrated by the flow field distribution of pressure, velocity, turbulent kinetic energy and turbulent dissipation rate at each valve opening.