| Research Abstract |
To reduce tohe unburned HC and SOF emission, the effects of specifications of injection system were investigated at first year. At second year the influences of combustion chamber shapes and thermal insulation, and the exhaust catalyst system were experienced. The main results at second year are following :
(1) The combustion chamber was modified to improve the mixture formation. The fuel spray impinges on a projection attached on the combustion chamber wall and mixes with air. Many kinds of projection shapes were tested. It was found that the unburned HC reduces with the combination of the round projection and the air turbulence.
(2) To increase the wall temperature of combustion chamber, the various combustion chamber material, the insulation spacer between the combustion chamber and the piston base, and the combustion chamber with air gap in the chamber bottom were attempted. The HC emission in a light load condition decreases with increasing of combustion chamber insulation, however, the NO and smoke emission in a high load condition increase with the increasing of thermal insulation. To improve this demerit, the thermal insulation where the fuel spray does not impinge directly is effective.
(3) The unburned HC and SOF emission due to the engine modification exceed our target level, yet. The exhaust catalyst needs to reduce these emissions. In this study it indicates that the pre-catalyst system which is attached the small catalyst in the front of main catalyst is effective to early catalyst reaction.
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