Investigation of condition parameters in each stage of a three-stage helico-axial multiphase pump via numerical simulation

As an important equipment in subsea booster system, helico-axial multiphase pump plays a significant role in subsea oil and gas development. In this study, the variations of condition parameters in each stage of a three-stage helico-axial pump was investigated by using a commercial CFD code. The three-dimensional (3D), steady-state Reynolds-Averaged Navier-Stokes (RANS) equations with standard SST (shear stress transport) turbulence models are solved in ANSYS CFX. The results show that static pressure increases from the inlet to outlet while gas void fraction decreases. Inlet flow angle of shroud in impeller decreases constantly from the first stage to the third stage and the rate of decline tends to be slow. The main parameters effect the inlet flow angle of shroud are inlet volume flow rate, rotational speed of impeller and gas void fraction(GVF). For every stage of the pump, the inlet flow angle of shroud in impeller increases when the inlet volume flow rate rises while the other parameters remain unchanged. And it decreases when the rotational speed of impeller or GVF grows except the first stage of the pump. In order to diminish the effect of variable inlet condition parameters on pump performance, the stage-by-stage design method should be developed. It contains reducing inlet blade angle of impeller which is related to the inlet flow angle of shroud and modifying the import hub ratio, semi-cone angle and other crucial geometry parameters of impeller at the second and third stage of pump.