核主泵变流量过渡过程瞬态水力特性研究

Transient Hydraulic Characteristics of Nuclear Reactor Coolant Pump in Variable Flow Transient Process

为研究核主泵从设计工况向非设计工况过渡过程的瞬态水力特性及内部流动机理,应用计算流体力学软件CFX对核主泵叶轮流道内的变流量瞬态流动特性进行数值模拟计算。研究结果表明:变流量过渡时,核主泵的压力脉动沿圆周方向分布并不均匀,其变化趋势是逐渐上升到最大值后又降低,基本呈正弦变化规律,瞬态压力波动变化次数等于叶片与导叶片数之间的动静干涉次数,监测点越靠近叶片与导叶交界面,压力波动越大;由于冲角的存在造成叶轮流道内的速度呈先下降后上升的变化趋势;导叶不仅具有将动能转换为压能的功能,同时也具有有效减缓压力脉动幅度的功能;向小流量过渡时,由于流量减少,在靠近叶轮出口处出现二次回流,造成叶轮流道内速度变化幅度随流量的减少而增大。

For the study on the transient hydraulic characteristics and internal flow mechanism of the nuclear reactor coolant pump in the transient process from design operation conditions to off-design conditions,the variable flow transient characteristics of centrifugal pump impeller passageway were simulated by using CFX software.The results show that during the variable flow transition,the distribution of pressure pulsation of the nuclear reactor coolant pump along the circumference direction is non-uniform.The pressure pulsation trends to rise gradually to reach the maximum value and then fall,basically following a sine-shape changing law.The times of transient pressure fluctuation change are equal to the times of rotor-stator interference between the vane and the guide vane.The closer monitoring point to the intersection surface between the vane and the guide blade is,the greater the pressure fluctuation is.Because of the attack angle,the speed of the impeller passageway first falls and then rises.The guide vane not only transfers the kinetic energy to pressure energy,but also effectively reduces the pressure pulsation amplitude.During the transition to small flow,flow reducing causes the secondary backflow to occur near the outlet of impeller and in turn leads the amplitude of flow velocity variation in the flow channel of impeller to increase with flow decrease.