A Study on the Mechanism of New Conceptual Mixture Formation of Lean Diffusion Combustion in the Bump Combustion Chamber of a Diesel Engine

TLDR: Based on a self-made optical experimental facility and a CFD numerical analysis code, experimental investigations and numerical simulations of the mixing process of an impinging diesel fuel spray were carried out.

Abstract: Based on a self-made optical experimental facility and a CFD numerical analysis code, experimental investigations and numerical simulations of the mixing process of an impinging diesel fuel spray were carried out The computed results were in good agreement with the experimental ones obtained by planar laser-induced fluorescence (PLIF) method by comparison Both measured and computed results with a plane or an actual combustion chamber wall indicated that the wall-impingement jet would stripped off the wall and formed a secondary space jet when it met with the bump on the wall This resulted in the rises of space mixing volume and mixing rate of the wall-impingement jet with the surrounding air, and a "flash mixing" phenomenon appeared with rapid mixing of diesel fuel and air And the amount of fuel accumulated on the wall was reduced The computational results also showed that the bump on the chamber wall changed the flow field structure of in-cylinder gas motion, and that the counter-flow "two-vortex-structure" near the BUMP significantly enhanced entrainment of the secondary jet to the surrounding air and thus promoted the mixing of fuel with air And it was the key to the formation of lean mixture and lean diffusion combustion in the bump combustion chamber