Study of the Numerical Solving Methods of the Motion Model of Polydispersed Droplets

Moisture separation is one of crucial devices in PWR power plant for it plays an irreplaceable role in eliminating droplets from steam and supplying dry-saturated for turbines. It would be helpful to design and optimize the structure of moisture separator through analyzing the behaviors of droplets. This paper studies the numerical solving methods of the motion model of polydispersed droplets. The equations of model belong to the field of nonlinear stiff ordinary differential equations, thus backward differentiation formula, a kind of multi-steps methods are used which advance in solving stiff different equations. The coefficients of equations involve the velocity and rotation of flow field in separator, and these parameters are given by the output of Fluent. After solving the differential equations we can get the velocity and angle velocity of droplets in different locations and the movement track of droplets in separator, as well as the separation efficiency of moisture separator for polydispeased droplets with special distribution. Finally through the numerical solving of the motion model of polydispersed droplets in chevron-type separator, we find that multi-steps method improves the numerical stability and reduces the steps of iteration under the same calculation precision compared with classical methods such as fourth-order Runge-Kutta method. So it lays the foundation for development of moisture separator program suit for engineering computing.