Mechanism of tandem cascade slot jet control for gas–liquid separation in multiphase pumps

The intermittent gas retention and blockage phenomenon observed in helical axial-flow multiphase pumps under high gas volume fraction conditions not only reduces pump efficiency but also poses significant safety risks to oil and gas transportation pipeline systems. Addressing this issue is critical for the widespread engineering application of such pumps. This study investigates the influence mechanism of slot jet control on gas–liquid separation phenomena and pump performance under high gas volume fraction conditions by examining the temporal and spatial evolution of slot jet sources and the principle of jet controlling flow field in tandem blade cascades. The findings reveal that there exists an optimal axial overlap that maximizes both pump head and efficiency. The optimal pump performance is achieved when the axial overlap is negative, with higher gas volume fractions shifting the optimal solution toward greater axial overlap. Additionally, under varying gas volume fractions, a circumferential overlap of 0.2 demonstrates the most significant performance improvement. The effectiveness of tandem cascade slot jets in mitigating gas-phase accumulation is influenced by jet flow rate and jet source pressure stability. As the impact of the front blade wake flow on the working surface of the rear blade varies, the blade work capacity is optimized at a circumferential overlap near 0.2.