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Higher pressure and higher precision are required for diesel fuel injection equipment in response to increasingly severe emissions control regulations. Market diesel fuels have become more diversified than in the past. Diesel fuel quality has also been changing, being affected by crude oil slate, extreme lowering of sulfur content, and diesel reformulated from heavy fuel oil, among other reasons. As a result of this, deposits thought to have a fuel origin have been observed within diesel fuel injectors in certain regions. Related changes in fuel injection quantity have also been observed. This paper determines injector deposit production mechanisms. It focuses on the structural changes of deposit causative substances by temperature as well as injector design change improvements to prevent deposits.

As exhaust emissions regulations are becoming increasingly stringent year by year, higher injection pressure and higher injection precision are required for diesel fuel injection equipment. On the other hand, market fuels tend to diversify. From the viewpoint of global warming prevention in particular, biodiesel fuels are attracting attention as renewable fuel and have been launched in many parts of the world. Moreover it is predicted that the concentration of Fatty Acid Methyl Ester (FAME) in biodiesel fuel will be increased and greater diversity of feedstocks will be used in the future. On the other hand there is a concern about deposit adhesion caused by biodiesel fuel to diesel fuel injection equipment. This paper clarifies the biodiesel deposit formation mechanism [1],[2],[3] and describes an accelerated re-production test method, which simulates real-world market condition and enables evaluations with a common rail system.

As exhaust emissions regulations are becoming increasingly stringent year by year, common rail system, which is capable of injecting high-pressure fuel, is already becoming mainstream in the field of diesel injection equipment. On the other hand, market fuels tend to diversify. From the viewpoint of global warming prevention in particular, biodiesel fuels are attracting attention as renewable fuel. Fatty Acid Methyl Ester (FAME) contained in biodiesel fuel is liable to aging and tends to generate deposits, thus, there is a concern about not only deposit adhesion to diesel injection equipment but also corrosion occurrence due to free water presence. This paper reports that an accelerated re-production test method which simulates real-world market environment successfully clarified the effects of DLC coating on control of deposit adhesion to diesel injection equipment as well as its mechanism and the corrosion mechanism was understood.