Computational analysis of spray angle effects on combustion and emissions in methane-diesel dual-fuel engine

A diesel methane dual fuel engine appears as a potential means for lowering emissions while retaining useful thermal efficiency. Ansys Forte 2023 R1 CFD software was employed to analyze the combustion parameters, performance attributes, and emissions characteristics of a methane-diesel dual-fuel engine at various spray angles of 100°, 105°, 110°, 115°, and 120°. Simulation is performed under 0.44 MPa load, 50% methane energy share, and −7° after TDC start of injection. Methane is injected into the intake manifold for premixing with air. Peak cylinder pressure increased as the spray angle (SA) raised to 110°. Thereafter, it slightly decreased to 120° SA. Lower combustion duration is obtained at 14.98° at 110° SA. The maximum thermal efficiency was found to be 32.04% with a low indicated specific fuel consumption of 289.43 g/kWh at 105° SA. Comparative performance is obtained from 110° SA. UHC and VOC is found to be minimum in 100° and 105° SA; thereafter, Unburned Hydrocarbons (UHC) and Volatile organic compounds (VOCs) increase rapidly. NO_X emission trends first increased up to 110° SA and then decreased. Higher CO emissions were observed at 100° SA and then decreased with increasing spray angle up to 110°; however, CO emissions increased slightly. Fuel vapor mass fraction and temperature contours ensured low diffusion burning for 115° and 120° SA, resulting in unmixed remaining unburned methane and a sharp increase in UHC emissions. O and OH radical formation is hindered for converting by CO₂ from CO at 120° SA due to quenching. The optimal spray angle was determined as 110°, which provided an excellent balance of efficient burning, consistent pressure progression, and acceptable emissions.