The impact of rear cover plate cutting on the degree of gas–liquid mixing in centrifugal pumps

To enhance the conveying capacity of semi-open gas–liquid centrifugal pumps under high inlet gas volume fraction (IGVF), a systematic investigation was conducted to reveal the mechanisms by which different rear cover plate cutting designs affect the gas–liquid mixing degree. At low IGVF (≤9%), the performance of the original pump Y1 outperforms the modified rear cover plate pumps SL1 (Slice Plan 1) and SL2 (Slice Plan 2). In contrast, at high IGVF (>9%), the performance of pumps SL1 and SL2 was found to be significantly better than the pump Y1. The analysis of gas–liquid mixing degree (λ) showed that, at IGVF = 12%, the λ value of pump SL1 reached 0.86. For pumps SL2 and Y1, the λ values were 0.76 and 0.846, respectively. It was thereby demonstrated that the rear cover plate cutting configurations enabled more thorough gas–liquid mixing. At different blade heights (Span), the energy dissipation degree (σ) of pump SL1 was found to be the lowest. That of pump SL2 was higher than SL1 but still lower than Y1. The energy dissipation degree of the original pump Y1 was significantly higher than those of the two optimized models. Compared to the original model, at an IGVF of 12%, SL1 shows increases in pump head and hydraulic efficiency by 7.01 m and 12.7%, respectively, with corresponding increases of 6.47 m and11.8% for SL2. This study provided valuable implications for improving the mixing uniformity, pump head, and hydraulic efficiency of centrifugal pump operating under high IGVF conditions.