Fuel Spray Analysis Near Nozzle Outlet of Fuel Injector During Valve Movement

Reducing the exhaust emissions of gasoline engines is important for the global environment. Coarse droplets during valve moving, late fuel during valve closing of a fuel injector, and fuel films stuck on the wall around the nozzle outlets are all sources of particulate matter (PM). In this work, we analyze these fuel sprays during valve moving timing by means of fuel spray simulation and direct measurement of valve movement. We developed a fuel spray simulation near the nozzle outlets of a fuel injector during valve opening and closing and simulated fuel flow within the flow paths of the fuel injector by a front capturing method while the fuel breakups near the nozzle outlets were mainly simulated by a particle method. The inlet boundary of the fuel injector was controlled to affect the valve motions on the fuel behavior. We developed a technique for directly measuring the valve movement by measuring the valve lift using a thin diameter Doppler laser method and an optical window with high pressure resistance. The simulation results were validated by comparing the simulated fuel breakup near the nozzle outlets with the measured ones, revealing a good agreement between them. By using the valve movement measurement and fuel spray simulation, we found that fuel spray at the valve opening/closing timing had coarse droplets. Moreover, we found that the late fuel had several types of fuel spray that were generated by low speed fuel flow through the nozzles during the bounds of the valve. The effect of the bounds of the valve on the fuel around the nozzle outlets was also clarified by means of experimental results showing the decreasing bounds of the valve. The late fuel of the nozzle outlets decreased with the decreasing bounds of the valve.