Optimized inducer design for transporting air–water two-phase flows in centrifugal pumps: Outperforming traditional inducers

Abstract

This study investigates the impact of different inducer designs on centrifugal pump performance during air–water two-phase flow pumping. A semi-open impeller with elliptical blades was tested with three configurations: no inducer, a traditional industrial inducer, and a novel optimized inducer. Experiments were conducted at a relevant rotational speed of 1450 rpm. The experimental analysis explores the performance for constant gas volume fraction, constant air flow rate, performance degradation, surging (flow instabilities), and two-phase flow regimes. High-speed cameras captured flow behavior to identify and categorize the flow regimes present during operation for each configuration. The results reveal that the industrial inducer could only provide limited performance improvements at part-load for the gas volume fraction range of 5%–6%. In contrary, the optimized inducer effectively delayed the sharp performance degradation to 7% gas volume fraction. Additionally, it provided almost constant performance near optimal flow conditions, showing a flat behavior up to 7% gas volume fraction. Performance improvements are still noticeable up to 11% air content. While the industrial inducer negatively advanced the onset of pump surging and increased its intensity, the optimized inducer strongly delays pump surging and maintains it at low intensity. The use of the industrial inducer leads to unstable curves for a wide range of flow rates for the performance with constant air flow rate at the inlet. However, the optimized inducer could improve that performance along the entire flow range, with almost no reduction near the optimal flow up to 100 L/min flow of air. The recorded flow regimes show the improved two-phase mixing and higher gas accumulation resistance when using the optimized inducer. Accordingly, the use of such an optimized inducer is highly recommended to keep robust two-phase pumping with minimal flow instabilities. the optimized inducer demonstrates remarkable effectiveness in enhancing pump performance. Based on our own experimental comparisons and findings, these improvements strongly outperform the capabilities of other traditional techniques commonly used to transport two-phase flows, including impeller modifications, tip clearance adjustments, and the use of a standard inducer.