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Spray-wall impingement is an unavoidable physical process in homogeneous charge compression ignition (HCCI) diesel engines using early injection strategy which is the main source for the hydrogen carbon (HC) and monoxide (CO) emissions. Dimethyl ether (DME) is a potential fuel additive to decrease HC and CO emissions due to its higher oxygen content. However, issues relating to structural design and early injection timing mean spray-wall impingement still occurs when using the diesel-DME blended fuels, which directly affect the fuel-air mixture formation in the near wall region and further influence the emission characteristics. The better understanding for the effects of spray-wall impingement parameters on fuel-air mixture formation in near wall region for diesel-DME blended fuels is helpful for the improvement of HC and CO emissions for HCCI diesel engines.

With the rapid expansion of the automotive market in China, air quality in the major cities has become a severe concern. Great efforts have been made in introducing new emission regulations; however, fuel and lubricant qualities, emissions aftertreatment system durability and in-use compliance to the emissions regulations still require significant improvement. China follows the European Union (EU) emission regulations in general, but different levels of standards exist. This paper gives a comprehensive overview of the current and near-future heavy-duty diesel emission regulations, as well as fuel and lubricant specifications.