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This paper aims at improving the combustion efficiency of direct injection diesel rotary engine (DI-DRE) by adjusting the injection strategy. An experimental validated 3D-dynamic simulation model coupled with chemical kinetics mechanism was established. A high-pressure direct injection mode was used to investigate the effect of diesel fuel injection timing (IT) and injection angle (IA) on fuel-air mixing and combustion process in a DI-DRE with spark ignition. Results showed that increasing IA changed the fuel distribution position from front to back of the combustion chamber, delayed IT and the fuel distribution area also became narrower and more concentrated. For combustion process, the fuel concentrated at partial central position towards the back of the combustion chamber was better for ignition. The distribution of more continuous mixture between the two spark plugs and concentration of more fuel near the trailing spark plug (TSP) was conducive to the improvement of combustion efficiency. The preferable combustion rate and emission performance were obtained when the IT was 80°CA (BTDC) and IA was 90°. Compared to the original scheme, maximum combustion pressure increased by16.82% while crank angle for maximum combustion pressure reduced by 8.19%. Soot and CO emissions reduced by 41.48% and 32.87% respectively. However, NO and CO 2 emissions increased slightly. [ABSTRACT FROM AUTHOR]

• 3-D dynamic simulation model based on chemical kinetics reaction is established. • Simulation models based on biodiesel fuel is validated by experimental data. • Equivalence ratio, injection and spark timing effect on rotary engine are analyzed. • Preferred injection and spark timing are 80°CA(BTDC) and 35°CA(BTDC) respectively. • Preferred equivalence ratio is 0.8 under the computational condition. Rotary engine has a flat combustion chamber that results in high unburned fuel leading to fuel inefficiency and emissions. Biodiesel regarded as a clean source of energy is an alternative fuel due to its ability to minimize environmental pollution resulting from unwanted emissions. In this regard, the improvement of combustion efficiency of a direct injection rotary engine fueled with biodiesel was numerically investigated. Experimental data was used in validating the established three-dimensional computational fluid dynamics (3D-CFD) model. On this basis, investigation of various biodiesel injection timing (IT) (100, 80, 60) °CA before top dead center (BTDC), spark timing (ST) (35, 30, 25, 20) °CA BTDC and equivalence ratios (∅) (0.6, 0.8, 1.0, 1.2) on mixture formation and combustion process was carried out. Results revealed that when IT retarded fuel distribution narrows and the mixture formed is concentrated. Conversely when ST retarded there is broad and dispersed fuel distribution. For lean condition the mixture formed is less concentrated compared to rich condition. For combustion process, when biodiesel was concentrated at the middle of in-cylinder at 30 mm (X-axis) and 15 mm (Z-axis) from the centerline in opposing directions it was better for spark-on. Also, the in-cylinder pressure and temperature reduced with advanced IT, retarded ST and decreased ∅. When ∅ leaned, flame development and propagation periods decreased. The suitable rate for combustion considering emissions was obtained when IT was 80°CA (BTDC) and ST 35°CA (BTDC) at a ∅ of 0.8 because when compared to the original scheme (case B4), maximum combustion pressure increased by 28.57% and increase of CO 2 , CO, soot and NO emissions were reasonable due to increase in temperature and fuel evaporation. [ABSTRACT FROM AUTHOR]