TY - JOUR
TI - Numerical investigation of the effect of fuel injection mode on spray/wall interaction and emission formation in a direct injection diesel engine at full load state
AU - Jafarmadar Samad
AU - Shafee Sina
AU - Barzegar Ramin
JN - Thermal Science
PY - 2010
VL - 14
IS - 4
SP - 1039
EP - 1049
PT - Article
AB - The effect of three injection rate modes on fuel spray-wall impingement and  combustion process in a direct injection diesel engine is investigated in  present work. A three-dimensional computational fluid dynamics model for flow  field, spray, spray-wall interactions, combustion, and emission formation  processes have been used to carry out the computations. The optimized omega  combustion chamber geometry was used in the diesel engine model instead of  baseline cylindrical geometry and the results were verified for this improved  combustion chamber geometry. Results for different injection modes indicate  that using the ramp injection rate curve, the spray-wall impinging is  increased due to higher injection rate at the end of injection duration. Also  the increased in-cylinder temperature, piston surface temperature and higher  turbulence intensity leads to enhanced wall-film evaporation. Soot mass  fraction also decreases due to improved air-fuel mixing and evaporation of  wall-film by reduction of the fuel rich zones especially in the impingement  regions. Results for different injection modes indicate that using the ramp  injection rate shape slightly retards the combustion process and improves  combustion characteristics while maintaining lower NOx and considerably lower  soot emissions compared to the boot and rectangle injection modes. Also, in  this injection mode, because of the high pressure injection, higher spray  droplet velocities (higher Weber number) and increased wall spray height than  the other modes, it could be said that the dominant impingement regime may be  the splashing regime. The results of model for baseline diesel engine are  compared with the corresponding experimental data and show good levels of  agreement.