Analysis and Control of Off-Design Turbulent Flow in a Centrifugal Pump

Centrifugal pumps are ubiquitous in industrial and domestic flow systems, yet their performance is significantly impacted by complex turbulent flows at off-design conditions. Understanding and controlling these flows are crucial for enhancing their efficiency and ensuring robust performance. This study focuses on the highly turbulent flow within the volute of a centrifugal pump operating at a high above-nominal flow rate condition. Large eddy simulation of a model problem is performed to reveal distinct flow features of the volute under the overloaded operation. At this off-design condition, the flow near the volute tongue exhibits particularly high unsteadiness, characterized by a dominant reverse flow on its volute side and large-scale vortex shedding on its upper side. Furthermore, the blade-tongue interactions are found to induce large fluctuations and exhibit strong three-dimensionality on the discharge side of the tongue. To mitigate these adverse flow phenomena, active flow control strategies are considered. Specifically, we explore the effectiveness of wall-normal jet blowing and suction near the volute tongue. Our findings demonstrate that the unsteady jet on the volute side of the tongue modulates the total pressure on both sides of the tongue. A jet placed on the discharge side of the tongue modulates the total pressure on its same side. At the same time, we observe an increase in turbulent kinetic energy near the tongue. This research provides valuable groundwork for improving their performance through flow control.