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In recent years, since the demands for comfortable operation and low fuel consumption are increasingly enhanced on the industrial machines, non-road engines as power sources on agriculture, landscape and construction applications are required to be achieved high power, low fuel consumption and low noise. Also, even for small engines, it is necessary to keep up with the trend of electronic control devices on these machines. Based on such backgrounds, we developed new non-road direct injection diesel engines with common rail system to satisfy those demands. This paper reviews the technologies to achieve the adoption of common rail system onto such small displacement industrial engines and to optimize the combustion system and injection characteristics.

The simulation techniques play important role on contemporary engine design. In this study, computer fluid dynamics approach (CFD) was focused to design the intake and combustion system of the direct injection diesel engine for versatile use. A practicality was stressed as much as an accuracy to correspond to designer and researcher's requirements, such as close relationship to the engine performance and short period of computation. The correlation of the trapping efficiency and the swirl ratio was mainly focused. A steady flow rig tests and engine operation data were combined to improve their quality mutually.

Very wide ranging applications or versatility are required to industrial diesel engines. Moreover, engines should be fitted the market trends, that are such as high reliability, low fuel consumption, and/or compact size with high output power (high power density). In addition, in recent years, exhaust emissions regulations have been getting strict; hence the further emission reduction is required in keeping and improving the above mentioned demands. From such backgrounds, we developed new direct injection turbo diesel engine for industrial use, that satisfies the market needs with a high level by adopting the new concept engine structure and the emission reduction devices.

Because of recent strong demands for environmental protection, all nonroad engines for agricultural and construction equipment should be conformed to the exhaust emission regulations in Japan, the United States and Europe. Some regulations include transient smoke standard at free acceleration in addition to exhaust emissions at steady state condition such as nitrogen oxides (NOx), hydrocarbon (HC) and particulate matter (PM). Therefore, especially a turbo charged diesel engine needs a countermeasure to reduce the smoke level at free acceleration. This study confirms a mechanism of the smoke discharge at free acceleration and realizes that the injection pattern of the PFR injection pump with timer function reduces the smoke level at free acceleration. As a result, we could develop the engine complied with the transient smoke standard without boost compensater, with which it is very difficult for small engines to make a fine adjustment of proper fuel delivery.