Emissions from DME combustion in diesel engines and their implications on meeting future emission norms: A review

•Detailed review of DME combustion and emissions in a diesel engine is carried out.•UFPM and PM emissions from DME combustion are not studied in detail yet.•Use of fuel additives and lubricants can also contribute to emissions.•Systems like EGR, DPF, catalytic converter, etc. are effective for emissions control.•Fuel injection strategies and new combustion methods can help reduce emissions.

Dimethyl Ether (DME) is an alternative liquid fuel developed mainly from coal and natural gas that can be used in compression ignition (CI) engines without major modifications to the diesel configuration. One of the advantages of DME combustion is the low emission levels of nitrous oxides (NOx) and particulate matter (PM) when compared to diesel combustion. Research so far were largely focused on tackling issues due to less viscosity and low heating capacity of DME as compared to diesel and in developing DME specific fuel system to overcome its incompatibility with rubber seals. In this paper, the body of experimental and numerical research on gaseous and PM emissions from DME combustion is reviewed, with the objective being to identify promising methods for emission control in DME engines. Gaseous emissions from DME combustion is a well-researched topic, while PM emissions has not yet been explored in detail. PM emissions, especially ultra-fine particulate matter (UFPM), are expected to become a major concern with the implementation of future emission norms. This review paper critically evaluates some of the novel methods of emission control in CI engines to meet future emission regulations using fuel injection strategies, combustion after-treatment and suggests future direction for DME research.