EXPERIMENTAL INVESTIGATIONS ON ADHERED FUEL AND IMPINGING DIESEL SPRAY NORMAL TO A WALL

Since the combustion chamber in a diesel engine is too small to mix injected fuel and surrounding gas perfectly, wall impingement of the spray is considered to be inevitable in the engine. Therefore it is important to understand the basic behavior of impingement spray and the fuel dispersion after impingement. In this paper, the effects of impingement distance, injection pressure, and ambient pressure on the adhering fuel mass of an impinging diesel spray on a normal flat wall were investigated experimentally. Behaviour of diesel fuel spray injected into a high-pressure chamber in cold condition was observed by a high-speed camera. An aluminum circular disk was used as an impingement wall. Adhered fuel mass was measured under conditions of three sizes of circular disk, 20, 30, and 40 mm in diameter. As a result, the adhered mass ratio remarkably increased by an impingement distance increase from 30 to 50 mm. As the injection pressure increased, the adhered mass ratio tended to decrease. Results also showed that less adhering fuel was attained when the height of post-impingement spray increased.