Browse Publications Technical Papers 2012-01-1659
2012-09-10

Simulation of the μMist ® Fuel Injection System's Fine Droplet Spray Air-Entrainment from Injection Point, within the Intake Manifold, to the Cylinder 2012-01-1659

The entrainment of the fine spray of the μMist® fuel injection system (patented technology) with induction air within the intake port of a test engine (Lotus single-cylinder thermodynamic engine) has been simulated using a commercial CFD package. Moving mesh complexities have been avoided via a steady state simplification of the induction air flow within the intake manifold and the cylinder, and the induction air flow rate is set to its average (over the intake stroke) at 2000 rev/min for that engine under WOT. Since this engine has two intake valves, previous experiments had a μMist® injector with two orifices, each aimed at the back of one of the two intake valves. In this study, the wall wetting effect of the two different injection angles between the dual sprays, that were previously experimentally tested on the aforementioned engine, have been compared numerically. The modelling showed that the experimental configuration was still suboptimal with some demonstrable wall wetting, which could be minimised by alteration of the port injection angles, including the bifurcation angle between the two streams. Finally, the experimentally developed increased mass flow (by 50%) injector was simulated to predict its anticipated experimental performance as regards to wall wetting. It was found that the increased flow rate, despite also increasing the injection velocity by ∼50%, can be configured to reduce wall wetting, since it produces smaller droplets that are better air entrained than the conventional larger droplets that were simulated earlier.
This modified μMist® injector shows virtually no wall wetting, and this performance is independent of the injection angles, which is a great advantage for applying the design to various engine configurations - it is anticipated to further improve the engine emissions and performance compared to previous engine experiments which already had shown significant advantages over state-of-the-art PFI and to some extent over DI injectors (injecting into the cylinder in homogenous DI mode, not into the intake port) [3].

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