Frictional drag and turbulent dissipation in a water-ring vacuum pump

The water-ring vacuum pump is a crucial piece of negative pressure extraction equipment, extensively utilized in gas extraction and wind tunnel applications. While water-ring vacuum pumps offer numerous advantages, including safety and reliability, they also present drawbacks such as low efficiency and high energy consumption. The operational efficiency of these pumps is one of their most significant performance indicators and serves as the foundation for evaluating their energy consumption. Enhancing the operational efficiency of water-ring vacuum pumps is currently at the forefront of research and a significant area of interest. The efficiency of these pumps is influenced by multiple factors. This article focuses on two critical factors that impact the operational efficiency of water ring pumps: casing friction and turbulent dissipation. This study employs theoretical analysis and simulation to compare the casing friction of the pump under both rotating and non-rotating conditions, thereby analyzing the power loss associated with turbulent dissipation and friction within the water ring. At an ideal impeller speed of 3000 r/min, the corresponding characteristic Reynolds number is Re = 1.88 × 105. The results indicate that (1) the power consumed by casing friction is 0.4 kW, while the power lost due to turbulent dissipation amounts to 1.2 kW; (2) when the pump casing rotates with the water ring at a speed of 1000 r/min, the power consumption of the casing decreases to 0.16 kW, representing a reduction of approximately 60%; the power loss from turbulent dissipation also drops to 0.16 kW, reflecting an 87% decrease; and (3) when the pump casing rotates with the water ring at a speed of 2000 r/min, the power consumption of the casing further decreases to 0.056 kW, reflecting a reduction of 86%. The power loss due to turbulent dissipation further drops to 0.046 kW, indicating a reduction of 96%. This study presents a significant finding that rotation of the pump casing can markedly weaken friction and turbulent dissipation, providing valuable insights for the design of high-efficiency water ring pumps.