Investigation On The Mechanism Of The Enhanced Fuel/Air Mixing Of A New Diesel Injector

Fuel injector is one of very important fuel injection parts of diesel’s fuelsupplement systems. It’s function is to break liquid fuel into tiny fuel drops and injectthem into the intended chamber’s positions according to the mixture requirements of adiesel engine. Fuel injector should meet different demands of injection characteristicsfor different chamber types. Generally, injection should achieve certain injectiondistance and spray angle, good vaporized quality, and the drip shouldn’t happen at endof the injection.In this paper, a new self-excited oscillation injection nozzle for diesel engines isstudied to reveal the mechanism of the enhanced fuel atomization of the new injector byperforming simulation analysis on the injector’s inner fluid field with FLUENT. Thenthe influence of new nozzle’s structure parameters on the vortex ring in the oscillationchamber is investigated by orthogonal experimental method. Finally, simulationanalysis on the injector’s fuel injection process is conducted and a free injectionexperiment is performed on a self-made injector test bench. The main study content andconclusions of this paper are shown as follows:1) Mechanisms of the enhanced fuel atomization of the new injector are revealedby combining numerical simulation of inner fluid field of the new injector and fluidboundary theory and vortex theory.2) Effects of nozzle’s structure parameters, diameter and length of oscillationchamber, diameters of upper injector and lower injector, on injector’s vortex ring aresystematically analyzed by orthogonal experimental method. The results show that thelower injector’s diameter has the greatest influence on injector’s inner pressures, and thelength of oscillation chamber and chamber diameter of oscillation chamber showsmaller and smallest effects on injector’s chamber pressure, respectively.3) The multiphase flow simulation of the injector’s inner and outer flow isperformed on the basis of multiphase flow theory of fluid mechanics. The results showthat the self-excited oscillation happens whenthe fuel with high pressure and high speedpasses through the new injector, and fuel is broken inside the injector’s nozzle, andfuel’s vortex disturbance is caused at the expansion shaped exit. As a result, fuel isbetter atomized due to the self-excited oscillation4) Free injection experiments are conducted for the injectors equipped with new nozzles on a self-made injector test bench. The results prove that the new nozzle haslonger injection distance and bigger spray angle, and comparable fuel atomization witha conventional nozzle.