The principle of fluid transportation determines the performance differences. The rotary vane pump achieves volume changes by relying on the eccentric rotor to push the sliding vanes (the single-stage compression ratio is usually ≤0.8MPa), while the gear pump forcibly conveys the medium through the meshing of teeth (the working pressure can reach 40MPa). In the application of automotive Fuel Pump, the Bosch high-pressure direct injection system adopts an external meshing gear pump, with a single-stage boosting capacity of up to 15MPa (while the rotary vane pump is only 0.3MPa), precisely matching the 200bar rail pressure requirement of in-cylinder injection.
The sealing characteristics affect the adaptability of the medium. The vane-stator clearance of the rotary vane pump is always 0.05mm (requiring oil film lubrication), and the volumetric efficiency is > 92% when transporting gasoline. However, when the ethanol content is greater than 85%, the lubrication fails and the wear rate surges fivefold. In contrast, Mitsubishi Heavy Industries’ corrosion-resistant gear pumps, featuring double D-ring seals and a 0.1μm surface finish, maintain a volumetric efficiency of 86% in a biodiesel environment and extend their lifespan to 100,000 hours.
The pulsation control capability is related to the stability of the system. The measured data shows that the flow rate of the single-chamber rotary vane pump fluctuates by ±18% (frequency 5-50Hz), while the pulsation rate of the 6-tooth external meshing gear pump is compressed to ±2.5%. The gear pump equipped in the Volkswagen EA888 engine has an oil pressure fluctuation of less than 0.5bar at 6000rpm, ensuring that the fuel injection control error is less than 1% and significantly reducing nitrogen oxide emissions by 12%.
The anti-fouling performance determines the maintenance cost. The upper limit of the fouling particle size of the rotary vane pump is 25μm. When the impurity concentration of the fuel reaches 50mg/L, the failure cycle is shortened to 8,000 hours. Cummins technical verification shows that the gear pump, due to its metal meshing structure, can withstand 150μm particles. Under the same contamination conditions, it can operate continuously for 24,000 hours without attenuation, and the major overhaul interval is extended by three times.
The energy consumption comparison reveals the differences in application scenarios. In an 80kW hydraulic station, the peak efficiency of the rotary vane pump set is 82% (flow rate 550L/min@7bar), and the efficiency of the gear pump under the same working conditions is 92%. However, when transporting high-viscosity media (such as 90°C lubricating oil), the viscosive-efficiency curve of the rotary vane pump is more gentle: when the viscosity increases from 46cSt to 220cSt, the efficiency attenuation is only 7%, while the efficiency of the gear pump decreases by 21% due to the sharp increase in frictional loss.
The temperature rise characteristics affect system integration. The mechanical loss power in the high-speed zone of the gear pump accounts for 15%, and the temperature rise of the 75L/min flow pump reaches 35℃ at 1500rpm. Hyundai Motor has adopted a composite rotary vane structure in the hybrid platform, reducing the axial size of the rotor by 40%. Combined with ceramic blades, the full-load temperature rise of the Fuel Pump is controlled within 22℃, contributing to an increase of 1.8 kilometers in the pure electric range.
The full life cycle cost needs to be comprehensively evaluated. Data from the circulation system of a certain petrochemical plant shows that the initial purchase price of the rotary vane pump is 8,500 (with a maintenance cycle of 6 months), and that of the gear pump is 21,000 (with a maintenance cycle of 30 months). Based on a 10-year operation calculation, the total cost of the rotary vane pump is 24,800 yuan, while that of the gear pump is only 19,200 yuan. With the application of digital twin technology to predict failures, the unexpected downtime rate has been reduced to 0.3%.