ID 359

Film Formation Characteristics of N-heptane Spray-wall Impingement at Engine-like Conditions

 

Abstract:

Spray-wall impingement in internal combustion engines is known to affect engine performance and emissions. The combustion of the fuel film deposited during spray impingement on the chamber walls, known as pool fire, promotes the formation of unburnt hydrocarbon and the emission of particulate matter. In this work, the fuel film characteristics are investigated experimentally and numerically. The analysis focuses on morphology, thickness, and evaporation time of the deposited film in a constant volume combustion vessel. In the experiments, n-heptane fuel is injected through a side-mount single-hole diesel injector and impinged on two glass plates characterized by different surface finishing. A high-speed camera with optical access to the spray-wall impingement location is used to capture the effects of the tested injection pressures and ambient densities on the liquid film properties. Side- and bottom-view Mie scattering imaging of the impinged spray on a smooth plate are used to analyze the area, structures, and evaporation time of the film. The liquid film thickness is measured on the rough plate using the Refractive Index Matching (RIM) technique. The experimental data from two representative cases are finally compared against Lagrangian-Eulerian (LE) CFD simulations of spray-wall impingement and film formation. Newly developed post-processing tools are employed to ensure consistency between experimental and numerical quantities. The comparison allowed to identify the state of the art of LE spray simulations, including strengths and weaknesses of the CFD model and opportunities for future improvement.