Abstract
The accuracy of a nozzle diameter directly affects the difference of the injection characteristics between the holes and productions of a GDI (gasoline direct injection) injector. In order to reduce the difference and guarantee uniform injection characteristics, this paper carried out a CFD simulation of the effect of nozzle diameter which fluctuated in a small range on single-cycle fuel mass. The sensitivity of the fuel injection quantity to the injector nozzle diameter was obtained. The results showed that the liquid phase ratio at the nozzle outlet decreased and the velocity of the outlet increased with the increase of the nozzle diameter. When fluctuating in a small range of nozzle diameters, the sensitivity of the single-hole fuel mass to the nozzle diameter remained constant. The increase of the injection pressure lead to the increase of the sensitivity coefficient of the single-hole fuel mass to the nozzle diameter. The development of cavitation in the nozzle and the deviation of the fuel jet from the axis were aggravated with the increase of the injection pressure. However, the fluctuation in a small range of nozzles had little effect on the near-nozzle flow.
Highlights
The internal flow characteristics of injector nozzle and the mechanism of spray fragmentation in gasoline engine are complex, and their characteristics directly affect the mixing process in the cylinder
In order to reduce the differences of the fuel injection characteristics between injectors and the inhomogeneity of each cylinder, it is necessary to analyze and study the differences caused by the machining accuracy of the injection nozzle diameter
Through the comparison and analysis of that the gas phase and liquid phase flow velocity in the injection hole increased and the injection the velocity field and cavitation development process, we found that the gas phase and liquid phase rate quickly the increase the injection pressure.During stablewith period, flowbecame velocitystable in themore injection hole with increased and theof injection rate became stable morethe quickly the the steady injection rate increased withthe the increase of the thesteady injection pressure, and the increase increase of the injection pressure
Summary
The internal flow characteristics of injector nozzle and the mechanism of spray fragmentation in gasoline engine are complex, and their characteristics directly affect the mixing process in the cylinder. The structure of a GDI injector nozzle has an important influence on its internal cavitation and flow state, which greatly affects the velocity, mass flow rate, and turbulent kinetic energy distribution at the outlet of the nozzle [6,7]. In order to reduce the differences of the fuel injection characteristics between injectors and the inhomogeneity of each cylinder, it is necessary to analyze and study the differences caused by the machining accuracy of the injection nozzle diameter. The sensitivity of the single-hole cycle fuel mass to the nozzle diameter is studied, and the influence of the injection pressure on its sensitivity strength is analyzed. Our findings could be used to guide machining technology and the precision of the injection hole diameter of the GDI injector under different injection pressures
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