Procedure of validated CFD-modeling of a two-stage screw-centrifugal pump

The article presents a CFD-modeling technique of the kerosene pump work flow. Various methods of improving CFD models have been investigated in the course of work to improve the reliability of simulation results: the selection of the type of boundary conditions, the extension of inlet and outlet pump connections, the estimation of the influence of the grid size and turbulence models. The advantage of boundary conditions of the «Opening» type with the «Opening Pressure» subtype is revealed. Rational lengths of additional pipes for correct modeling are determined:  ½ of the inlet diameter size at the inlet, 4 diameters of the outlet diameter at the outlet for rated operating conditions and 7 diameters for all other conditions. The best combination of turbulence model and mesh sizing have been identified: it is better to use the k-omega turbulence model for a fine grid with the size of the first element equal to 1 micron and the k-epsilon turbulence model for coarser grids. The convergence of solutions is evaluated by the changes of integral parameters of the pump from iteration to iteration. The amplitude of efficiency fluctuations in the process of calculation amounted to 1 % even in the case of the most accurate model. The model reliability is assessed by comparing the design characteristics obtained and the experimental data. The radial load on the impeller bearing is estimated by using the verified CFD model, which also showed qualitative agreement of the calculated and experimental data. Thus, the proposed modeling technique makes it possible to create adequate CFD pump models with the lowest computational costs. CFD-models developed according to the technique can be used for optimization studies of multistage screw centrifugal pumps.