Trends in Environmentally Friendly Diesel Engine Oils

摘要

Diesel engines, which offer thermal efficiency and durability as high as those of internal combustion engines, are widely used in automobiles, construction machines, ships, and power generation equipment. In Europe, in addition to improving the silent operation to the level of gasoline passenger automobiles, a lower emission of CO{sub}2 and higher durability and reliability are reached [1]. In contrast, in Japan and the United States, the proportion of diesel engine-equipped passenger automobiles in the total number of passenger automobiles on the market in 2002 exceeded 40%, and it is believed that the worldwide demand for diesel engines will grow in the future [2]. With such a background, diesel engine makers encounter a problem of significantly lowering the emission level of diesel engines. In short, in addition to such advantages as low fuel consumption and low CO{sub}2 emission, further progress in the technology of reduction of paniculate matter (PM) and nitrogen oxides (NO{sub}x) in gas emission is needed. The emission reduction technology includes an improvement in fuel combustion by high-pressure electronic-controlled fuel injection, crude exhaust gas recirculation (EGR), application of turbo intercoolers and installation of four valves and after-treatment devices. These devices include PM oxidation catalysts, continuous regeneration type diesel particulate filter (DPF), selective catalytic reduction (SCR) by using fuel and urea as a reducing agent, NO{sub}x absorption catalysts, and so on. The development of a stricter control of emission is underway. The technology has already been partially implemented [3].