Influence of the In-Cylinder Flow Field (Tumble) on the Fuel Distribution in a DI Hydrogen Engine Using a Single-Hole Injector

This paper examines the interaction of bulk flow and jet-induced fuel convection in an optically accessible hydrogen-fueled engine with direct injection. Planar laser-induced fluorescence (PLIF) of gaseous acetone as a fuel tracer was performed to obtain quantitative images of the hydrogen mole-fraction in the operating engine. With the engine motored, fuel was injected into inert bulk gas from a centrally located injector during the compression stroke. The injector had a single-hole nozzle with the jet angled at 50 degrees with respect to the vertical injector axis. Two parameters were varied in the experiments, injector orientation and tumble intensity, and for each of these, the injection timing was varied. Image series of the mean fuel mole-fraction between injection and near-TDC crank angles capture the mixture-formation process for each configuration and injection timing. Variation of the injector orientation shows that with the unmodified low-tumble engine-head the influence of bulk flow on fuel convection is subtle, but clearly detectable. Counter-flow from tumble-enhancing, modified ports retards the progress of injection-induced fuel convection and thereby causes significant changes in the final mixture distribution.