Fuel-Spray Simulation With Valve Motion Perpendicular to Closing Direction

Particulate matter (PM) in exhaust gas from automotive engines causes air pollution. Multiple injections of fuel into the combustion chamber is one of the solutions to decrease PM; a uniform air/fuel mixture and short fuel-spray duration by using multiple injections are effective to decrease PM. To form the uniform air/fuel mixture, fuel sprays from fuel injectors needs to be uniform during injections. Unsteady valve-motions, especially those perpendicular to the closing direction, cause spray swings that form un-uniformity of air/fuel mixture. It is difficult to measure valve motions in the space of a few micrometer within a stainless steel body during fuel injections. Fuel-spray simulation is useful to study the effect of valve motion on the un-uniformity of fuel sprays. In fuel-spray simulation, jets passing through nozzles need to be simulated with the valve motion. We previously developed a particle/grid hybrid method that integrated the inner flow simulation using a grid method with a fuel breakup simulation using a particle method. In this study, we studied the effects of valve motions perpendicular to the closing direction on fuel sprays in order to decrease the un-uniformity of air/fuel mixture. First, we observed fuel-spray behaviors during measurements; a fuel injector with multi-holes was selected, and spray patterns were recorded by a CCD camera with a Xenon flash lamp. The jets passing through the nozzles changed their profiles over time, and the widths of the jets changed from thin to thick at almost the same time. The simulated spray behaviors with valve motion in the front-to-rear direction showed the same trends as those in measurement. It is assumed that because the positions of the six nozzles on the orifice cup were assigned asymmetrically in the front-to-rear direction, asymmetric flow distribution caused the valve motion.