Dual-fuel dual-direct injection: An efficient and clean combustion technology for diesel engines

Abstract

The reduction of pollutant emissions from diesel engines and achievement of a carbon-neutral transportation sector requires the improvement of traditional diesel engine combustion. Dual-fuel combustion modes have been introduced to promote the application of renewable fuels in diesel engines accordingly. However, traditional dual-fuel combustion is limited by poor stability, low renewable fuel substitution rate, narrow operating conditions, and high pollutant emissions. Dual-fuel direct injection (DFDI) has been proposed to address these problems. This paper critically reviews the latest research on and compares the advantages of DFDI combustion with those of other combustion modes and evaluates the performance, combustion, and emissions characteristics of diesel–gasoline, diesel–natural gas, diesel–methanol, diesel–ammonia, and diesel–hydrogen DFDI engines. When using DFDI, the fuel injection strategy is more flexible, the concentration and activity distributions of the different fuels in the cylinder can be effectively controlled, and there is considerable potential for combustion optimization. Furthermore, the DFDI engine exhibits a higher power output, better thermal efficiency, and significantly improved combustion stability compared to the conventional diesel engine. These advantages broaden the engine working conditions, increase the replacement rate of diesel with renewable fuels, and reduce the emissions of carbon monoxide, hydrocarbons, nitrogen oxides, particulate matter, soot, and other pollutants.