Analysis of Volumetric Efficiency of External Gear Pump Under Deep-Sea Conditions Considering the Influence of Oil Viscosity

External gear pump are the most popular pumps used in modern hydraulic systems. They feature compact structure, strength and long useful life. Due to the shortages of gear pump, e.g., internal leakage and encapsulation, the application of gear pump under deep-sea conditions is limited. Furthermore, the volumetric efficiency of the external gear pump will change with the change of seawater pressure. In order to investigate the impact of sea depths on the volumetric efficiency of the external gear pump, different viscosity media are used, the cavitation characteristics of the rotor domain and the outlet volume flow rate of the external gear pump are studied through numerical calculation and simulation, and the factors affecting the volumetric efficiency of the gear pump are analyzed. The results show that as the sea depth increases, the volumetric efficiency of the gear pump decreases significantly. Among them, the volumetric efficiency of the gear pump with 46# hydraulic oil is the highest, with an average volumetric efficiency of about 11.48% higher than that of 22# hydraulic oil at sea depth of 0–2000 meters. This paper provides some reference and data support for the application of gear pump under deep sea conditions.