Influences of three types of sediment diffusion coefficient model on the calculation of solid-liquid two-phase flow in double suction centrifugal pump

Euler-Euler models can be used to describe the fluid and particulate phase suitable for the two-phase flow in a double-suction centrifugal pump. The sediment diffusion coefficient is one of the most important moduli to express the interaction between the solid-liquid phases. There are the commonly-used three models of the semi-empirical sediment diffusion coefficient. In this study, the NON-DC, Diffusion-in-VOF, and DC-PDPC models were used separately to numerically simulate the solid-liquid two-phase flow field in the double suction centrifugal pump. A systematic analysis was also made to clarify the effects of the three models of sediment diffusion coefficient on the steady and unsteady solid phase concentration and velocity at different flow rates under three particle sizes of 25, 100, and 200μm. The results show that there was a similar steady calculation of solid-liquid two-phase flow in the double-suction centrifugal pump using different models of sediment diffusion coefficient under different particle sizes and rated operating conditions. However, there was a greatly different unsteady distribution in the solid phase concentration using different models of sediment diffusion coefficient. Specifically, the difference increased gradually under low flow conditions with the increase of particle size. Different models of sediment diffusion coefficient shared little influence on the steady solid-liquid two-phase flow for the small diameter particle no more than 100μm, but there was a great influence on the large diameter particle greater than 100μm under low flow conditions. Meanwhile, the steady solid-liquid two-phase flow was basically the same, when the particle size ds was less than or equal to 100 μm. Once the particle size was more than 100μm, the difference of steady increased gradually with the increase of particle size. The greatly different unsteady solid-liquid two-phase flow field was found under the conditions of different particle sizes, where the difference increased gradually with the increase of particle size. Therefore, the basic same was observed for the steady calculation of solid-liquid two-phase flow with the small diameter particle no more than 100 μm. However, there was quite difference both between the steady calculation with a large diameter particle greater than 100μm and the unsteady calculation under different sediment conditions. Therefore, it is necessary to optimize the suitable model of sediment diffusion coefficient for these conditions.