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Average concentration of a diesel impingement spray and characteristics of fuel adhering on a flat wall were investigated experimentally. Spray tip penetration and spray volume before and after impingement were measured on high speed photographs of the spray which was injected into a high pressure chamber of cold state. Further, the adhered fuel on the wall was directly measured by a precision balance. To clarify the characteristics of the impingement spray at various wall distances, pre-impingement spray and post-impingement spray were individually analyzed. Based on the entrainment air and fuel mass which was corrected by the adhered fuel, the air-fuel ratio was derived at various wall distances. As the results, the wall impingement of the diesel spray caused lean mixture spray concentration in comparison with the free spray. As the wall distance increased, the fuel film diameter to spray width ratio decreased.

Characteristics of fuel adhering after wall impingement of diesel spray were investigated experimentally. A flat wall, a recessed-wall which has a conical opening at impingement point, and a rugged-wall which has many concentric circular grooves, were used as an impingement wall. Diesel spray was impinged vertically to the wall in a high pressure chamber under a cold state. The spray behavior impinged on each of the three types walls was observed using a drum camera, which allowed high speed photographs. The spray after impingement on the recessed-wall was reflected from the wall with rolling-up motion, while the spray impinging on the flat wall was expanded along the wall surface to the radial direction. So, the recessed-wall might be expected to control the spray attitude in real engines. The spray height on the recessed-wall was higher than that on a flat wall. The amount of fuel stuck on each wall was measured by a precision balance.