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Fuel injected from multi-hole injector with a small injection angle (100°) is impinged to the multi-impingement-wall head(MIW head), which is located in the center of combustion chamber and is attached to the cylinder head. The fuel is diffused into the piston cavity to form a three-dimensional diffusion spray. The main advantage of diffusion spray is that the effects of the fuel impinging diffusion and the collision between fuel particles can be obtained. Based on the concept of MIW head, the experimental results show that the combustion performance and the fuel consumption have been improved. Besides, the NOx, HC and smoke densities of the exhaust gas of a diesel engine have been reduced.

A three-dimensional diffusing spray using the multi-impingement-wall head (MIW head) has been proposed to form air-fuel mixtures in a simple DI diesel engine. In this paper, effects of the width of the MIW head on spray pattern, distribution and engine performance have been investigated. In the fuel spray and engine performance experiments, an optimal width of MIW head results in the collision of fuel particles to advantageous position in a combustion chamber for obtaining a good fuel spray distribution. The minimum BSFC is almost the same value as that of a single DI diesel engine, the HC and smoke densities are reduced and the NOx density is shown a tendency to some increase under part load and decrease under full load. A relatively slow heat release rate and maximum temperature duration of the MIW head can be obtained by shortening the ignition delay.

The multi-impingement-wall head (MIW head) is designed to be located at the center of combustion chamber and is attached to the cylinder head. In this paper, a new concept of the MIW head has been investigated to obtain a three-dimensional diffusion spray for improving the combustion and performance of a DI diesel engine. Four Types of combustion chambers, the troidal type used in a normal DI diesel engine, and the reentrant types with a projection, with a cutouts, and their combinations (with both projection and cutouts) have been used in the NICS-MH engine experiments. Based on the experimental results of engine performance, it shows that the reentrant type of combustion chamber with a projection and a cutouts has a better fuel consumption and produces lower harmful exhaust gases (HC, NOx and smoke) than those of other NICS-MH engines.