As a positive displacement hydraulic machinery, the circular arc swing internal meshing gear pump has an inner rotor tooth profile that is an equidistant curve of a continuous short amplitude epitrochoid, and an outer rotor that uses a conjugate circular arc as the tooth profile curve. Due to its simple structure, smooth operation, low noise, long lifespan, good rotational speed characteristics, and high volumetric efficiency, it has been widely used in fields such as aviation and aerospace that require high overall weight. Due to the fact that the lubricating oil at the inlet of the gear pump has completed its mission of lubricating and cooling the engine bearings, its pressure is much lower than that at the outlet of the booster pump, which can easily lead to the precipitation of gases that were originally dissolved in the lubricating oil, resulting in a deviation in the actual volumetric efficiency of the gear pump Low. At present, many scholars have conducted research on the factors affecting the volumetric efficiency of gear pumps. Regarding the volumetric efficiency of the circular arc swing internal gear pump, numerical calculations were conducted to study the flow characteristics within a certain speed range and the variation of volumetric efficiency at different speeds. Using dynamic grid technology, numerical calculations were performed on a circular arc oscillating internal meshing gear pump for a certain vehicle, and the flow rate and volumetric efficiency variation curves of the pump under different operating conditions were obtained. The influence of the volume efficiency of the angle between the inlet and outlet chambers of a circular arc oscillating internal meshing gear pump was analyzed using the fluid simulation software Pumplinx. Based on the fluid simulation software Pumplinx, the influence of the inlet and outlet oil grooves of the circular arc swing internal meshing gear pump on the flow characteristics and volumetric efficiency was studied. Based on experimental research and CFD numerical calculation analysis, the influence of geometric parameters of the rotor of the circular arc swing internal meshing gear pump on its performance was studied. In terms of studying the volumetric efficiency of external gear pumps, numerical simulation calculations were conducted to obtain the transient flow rate changes inside the pump, and the factors affecting the volumetric efficiency were analyzed. The calculation formula for the flow pulsation coefficient of an external gear pump was derived, and the influence of gear teeth, pressure angle, and radial clearance on flow pulsation was analyzed. A three-dimensional simulation of the internal flow of an external gear pump was conducted using numerical simulation software CFX, and the effects of radial clearance and end clearance on flow rate and volumetric efficiency were studied. Based on the fluid simulation software Pumplinx, the internal flow of the external meshing gear pump was simulated and analyzed, and the effects of pressure, suction port size, speed, and other factors on the volumetric efficiency of the external meshing gear pump were further studied. Taking the high-speed aviation circular arc swing internal meshing gear pump as the object, the computational fluid dynamics software Pumplinx was used to study the influence of different operating conditions such as different speeds and different inlet oil to gas ratios on the volumetric efficiency of circular arc swing internal meshing gear pumps with different structures, in order to obtain the influence law of the structure and operating parameters of the circular arc swing internal meshing gear pump on the pump volumetric efficiency under oil and gas two-phase conditions.
When the circular arc swing internal meshing gear pump is in operation, the inner and outer rotors and end face devices such as the end cover undergo relative motion, so there must be a certain end face gap between the rotor and the end cover, resulting in end face leakage. In order to study the effect of end face gap on the volumetric efficiency of the circular arc swing internal meshing gear pump and maintain other operating conditions unchanged, three sets of end face gaps of 0.08, 0.10, and 0.12 mm are set respectively on the basis of a speed of 8500 r/min and an inlet section oil content of 30% and 70%. The curve of the volumetric efficiency of the circular arc swing internal meshing gear pump conveying lubricating oil with the variation of end face clearance under different oil content conditions is given. From Figure 9, it can be seen that under different inlet section oil content conditions, the volumetric efficiency of the circular arc swing internal meshing gear pump decreases with the increase of end face clearance. This is because the increase of end face clearance leads to an increase in end face leakage and a decrease in lubricating oil flow rate. At this time, the theoretical flow rate is independent of the end face clearance, so the volumetric efficiency decreases accordingly. As the oil content increases, the volumetric efficiency of the mixed medium decreases less significantly, from 20.42% when the end clearance is 0.06 mm to 15.72% when the end clearance is 0.12 mm.
Under different rotor thicknesses, the volumetric efficiency of the circular arc oscillating internal meshing gear pump decreases with the increase of oil content in the inlet section, and the larger the rotor thickness, the more obvious the decrease in volumetric efficiency with the increase of oil content from 0.3 to 0.7, from 12.59% when the rotor thickness is 6.5 mm to 35.51% when the rotor thickness is 19.5 mm. Therefore, at the same speed, the effect of rotor thickness on the volumetric efficiency of the circular arc oscillating internal gear pump is higher when the oil content is high than when the oil content is low. This is because the rotor speed remains constant, and the increase in rotor thickness increases the volume of the cavity between the inner and outer rotors, while the end face leakage is relatively reduced, resulting in an increase in oil flow rate with the increase in rotor thickness. After the thickness of the rotor increases to a certain extent, since the rotational speed has not changed at this time, the centrifugal force acting on the lubricating oil remains unchanged and cannot The cavity between the inner and outer rotors is well filled, so the effect of the oil flow rate increasing with the thickness of the rotor is weakened. When the operating conditions of the circular arc swing internal meshing gear pump are determined, in order to increase the oil flow rate, the increase in rotor thickness needs to be controlled within a certain limit, especially in the case of high oil content. Excessive rotor thickness can easily cause oil accumulation inside the rotor, leading to difficulties in oil recovery.
Conclusion
Taking the high-speed aviation circular arc swing internal meshing gear pump as the research object, the valve pump simulation analysis software Pumplinx was used to conduct simulation analysis of its gas-liquid two-phase performance under multiple structures and operating conditions. The following laws were obtained regarding the influence of the structure and operating parameters of the circular arc swing internal meshing gear pump on the pump volumetric efficiency under oil and gas two-phase conditions.
1) Under different inlet section oil content, the lubricating oil flow rate of the circular arc swing internal meshing gear pump increases with the increase of rotor speed. As the speed increases, the increasing effect of lubricating oil flow rate produced by the same speed increment becomes less and less significant. When the oil content in the inlet section is low, the volumetric efficiency of the circular arc swing internal meshing gear pump increases first and then decreases with the increase of rotor speed. After the oil content in the inlet section increases, the volumetric efficiency decreases with the increase of rotor speed. The maximum decrease amplitude reaches 27.79% when the oil content is 70%.
2) The volumetric efficiency of the circular arc oscillating internal gear pump decreases with the increase of end face clearance under different inlet section oil content; As the oil content increases from 30% to 70%, the volumetric efficiency decreases from 20.42% when the end face clearance is 0.06 mm to 15.72% when the end face clearance is 0.12 mm.
3) When the oil content in the inlet section is low, the volumetric efficiency of the circular arc swing internal gear pump decreases with the increase of rotor stages; When the oil content in the inlet section is high, the volumetric efficiency of the circular arc swing internal gear pump increases with the increase of rotor stages; As the oil content increases from 30% to 70%, the volumetric efficiency decreases from 12.59% when the rotor stage is 1 to 6.51% when the rotor stage is 3.
4) The volumetric efficiency of the circular arc oscillating internal gear pump decreases with the increase of rotor thickness under different inlet section oil content; As the oil content increases from 30% to 70%, the magnitude of the decrease in volumetric efficiency increases from 12.59% when the rotor thickness is 6.5 mm to 35.51% when the rotor thickness is 19.5 mm.