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In resent years,lower noise has been in high demand in small diesel engines for agricultural and industrial uses as well as automotive engines. Furthermore,emission regulations becomes more severer due to environmental concerns. In order to satisfy these objects,diesel engine combustion needs to be improved. Especially fuel injection system is the key element to control engine combustion and should be improved dramatically. This research is to pursue the ideal fuel injection system to realize optimized diesel engine combustion which creates low combustion noise and clean exhaust emission. Recent progress will be reported in fuel injection technology including injection pressure pattern, injection rate pattern, injection timing and spray pattern, etc.

In recent years, diesel engine exhaust gas regulations become more severe due to environmental concerns. Especially, particulate reduction is one of the biggest concern, and the reduction through high injection pressure has been studied.(1), (2) and (3) However, much is not yet known about the influence of changes in fuel flow inside the nozzle tip on atomization and engine performance, and there would exist a lot of room for exhaust gas reduction through the nozzle modification. In this research we found that changing the shape of the nozzle tip showed a remarkable difference in the smoke emission at low engine speed, analysis showed that difference in the flow rate at the nozzle orifice cause difference in the fuel spray droplet size and therefore the difference in the smoke emission.

A large number of problems for which solutions must be found have come to the surface recently in regards to heavy duty diesel engines. These begin with the strict emission regulations, and also include the questions of improved fuel econoray, better engine output and lower noise levels. One indispensable element in the solution to these problems is an improvement in engine combustion, a factor which must include modifications in the fuel injection system. Another critical question is that of improving engine and vehicle control technology. The improvement of fuel injection performance-which must include control performance as well-is hence extremely important to the purification of diesel engine emissions, and research in this area roust progress at ever increasing rates.