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It was shown in our previous study that the air-jet in the late combustion period reduces the diesel exhaust soot effectively. However, the plunger-pump type air-jet generator used in our previous study has a big power-loss. In this paper, the reduction of soot emission with a newly designed air-accumulation type air-jet generator is investigated using an experimental single cylinder engine. The optimum design parameters, such as the spring constant and the air outlet diameter, are examined experimentally. The effectiveness of the air-accumulation type air-jet generator for the reduction of soot and NOx emission is about a half of that of the plunger-pump type. It is confirmed that the disappearing speed of the luminous flame region accelerates with the increase of the heat-release in the late combustion period.

A new spray/wall impingement model for gasoline engines has been developed. The model is based on experimental analysis of impinging spray droplets using a phase doppler particle analizer (PDPA). Three new equations were obtained in terms of droplet size, Weber number and the angle from a wall for droplets which were splashed after impinging or created by the impact of a droplet on the liquid film layer on the wall. The three-dimensional calculation results using the model agree very well with the experimental data. The model is also applied to the fuel mixture formation process in a lean-burn gasoline engine.

Compression ratio of newly developed gasoline engines has been increased in order to improve fuel efficiency. But in-cylinder pressure around top dead center (TDC) before spark ignition timing is higher than expectation, because the low temperature oxidization (LTO) generates some heat. The overview of introduced calculation method taking account of the LTO heat of unburned gas, how in-cylinder pressure is revised and some knowledge of knocking prediction using chemical kinetics are shown in this paper.