A comparative study the spray and combustion of diesel and ammonia engine under cross and horizontally-opposed dual direct injection

Abstract

Ammonia is increasingly recognized as a promising zero-carbon renewable energy source for internal combustion engines. The dual direct injection combustion method, which utilizes diesel to ignite ammonia, represents a highly effective strategy for employing ammonia as an engine fuel. This study investigates the spray and combustion characteristics of diesel and ammonia at injection angles of 90° and 180° using optical diagnostic techniques in a constant volume combustion chamber. The results indicate that, compared to the 90° injection angle, the 180° injection angle enhances the axial diffusion and evaporation rates of the collision spray while inhibiting both radial diffusion and evaporation rates. An increase in injection pressure further promotes both axial and radial diffusion and evaporation rates, significantly improving the atomization characteristics of the collision spray. At the 180° injection angle, the collision spray exhibits greater turbulence, facilitating thorough mixing of fuel and air. This results in prolonged ignition delays and combustion durations, an increased flame area, and reduced soot emissions. Specifically, compared to the 90° injection angle, soot emissions from the 180° injection angle at 60 and 100 MPa decreased by 32.03 % and 5.43 %, respectively. Similarly, while increasing injection pressure effectively mitigates soot emissions, this improvement is inhibited at the 180° injection angle.