The core component of modern electronic Fuel injection engines, the Fuel Pump, is mainly responsible for delivering fuel at a specific pressure, and its performance parameters have a crucial impact on the atomization quality. Take the common low-pressure vane fuel pump as an example. Its working range is usually under a pressure of 3 to 5 bar, providing a fuel flow rate of approximately 80 to 120 liters per hour. If the output pressure fluctuates by more than ±0.2 bar or the flow rate attenuation reaches 15%, the injection system will be unable to maintain the preset precise control of 14.7:1 air-fuel ratio, resulting in an excess air coefficient deviation of more than 8%, directly causing a decrease in combustion efficiency and deterioration of emissions. Research institution AVL tests have found that a pressure reduction of 0.5 bar can increase the average droplet diameter by 10 to 15 micrometers, significantly deteriorating the uniformity of atomization.
The design differences of different types of fuel pumps lead to significant performance disparities. The working pressure of the roller pump relied on by the traditional manifold injection system is approximately 3-4 bar, and the average diameter of the fuel droplets formed by it is usually within the range of 120-150 micrometers. The pressure of the plunger pump used in the high-pressure direct injection system (GDI) can reach 200-350 bar, and the droplet diameter generated through the multi-hole injector can be controlled at 15-20 microns, significantly increasing the liquid phase surface area. Volkswagen’s technical report shows that the 200bar high-pressure pump used in its EA888 engine, in combination with piezoelectric fuel injectors, has shortened the evaporation time of fuel droplets by nearly 50%, increased combustion efficiency by more than 10%, and especially reduced hydrocarbon emissions by 70% during the cold start stage. In comparison, the efficiency of mechanical fuel pumps is usually only 40-50%, while the high-efficiency electric design can reach over 75%.
High-pressure output directly enhances the dynamics of the atomization process. Experimental data from Bosch Company confirm that when the injection pressure is increased from 100 bar to 300 bar, the oil droplet breakage can be increased by approximately 9 times, and the initial liquid filament breakage time is shortened by about 50%. At this point, the Reynolds number exceeds 40,000, and the turbulence intensity increases by more than 120%, prompting the fuel beam to enter the combustion chamber at a speed of 20-30 meters per second and form an injection cone Angle of more than 80°. The Ferrari 488 Pista engine, with the help of a 350 bar system and an optimized fuel injection strategy, can still ensure atomization quality when the engine speed reaches 8000 rpm, achieving a thermal efficiency of 40% and a power output of 710 horsepower.
The long-term performance and reliable maintenance of the fuel pump are important factors in ensuring the atomization quality. According to the 2020 SAE report, approximately 90% of fuel pump failures are related to filter clogging or internal wear, resulting in a flow rate drop of more than 35%. Tests conducted by a major automaker show that after running 100,000 kilometers with contaminated fuel (with particulate matter concentration >5mg/L), the volumetric efficiency of the pump decreases by approximately 12%, while the variance of the injector flow rate increases to 5%, causing the temperature difference in the cylinder combustion to expand by more than 60 degrees Celsius. It is recommended in the industry that the fuel system be maintained, cleaned or key components replaced every two years or 40,000 kilometers on a regular basis to keep the fuel flow fluctuation within 2% and avoid a decline in combustion efficiency of more than 5%.