Mechanism of gas blockage suppression and parametric optimization in tandem cascades for oil–gas multiphase pumps

Mitigating intermittent gas blockage in helical axial-flow multiphase pumps under high gas void fraction conditions is crucial for improving pump efficiency and ensuring pipeline safety. This study applies the jet flow field control concept, using a tandem cascade structure to suppress the gas-blocking phenomenon and enhance pump performance. Employing a Latin hypercube sampling-based experimental design methodology, the research investigates the influence of tandem cascade configuration and geometric parameters on pump performance. Special emphasis is placed on three critical factors: the front blade camber angle, the rear blade camber angle, and the approximate attack angle of the rear blade. A mathematical model for the pump head under tandem cascade jet flow is established, along with a newly defined parameter that characterizes the gas aggregation scale at the trailing edge. Results show that pump efficiency exhibits higher sensitivity to front blade camber angle, whereas changes in rear blade angle predominantly affect head characteristics. The tandem cascade configuration demonstrates particularly pronounced efficiency improvements under high gas volume fraction conditions. Increasing front blade camber angle reduces pressure gradient in the rear impeller section, thus alleviating gas-phase aggregation; however, the enlarged front blade wake region introduces additional flow losses downstream. The rear blade's approximate attack angle significantly influences flow impingement on both pressure and suction surfaces of the rear blade by altering inflow conditions. When the rear blade's approximate attack angle is negative and its value is smaller, the loss of work performed by the front blade increases, with the optimal pump efficiency occurring when the value is zero.