Experimental investigation on the effect of injector hole number on engine performance and particle number emissions in a light-duty diesel engine

Particle number emissions need to be monitored and controlled in order to comply with the latest emission legislations for gasoline and diesel engines. This research focuses on performance and emission analysis of a light-duty diesel engine with various injector hole numbers. A 500cc single-cylinder diesel engine was used for this purpose, and injectors with hole numbers varying from 7 to 10 were analyzed. Different operating conditions were selected to test the engine at all types of loading conditions. Start of injection and exhaust gas recirculation swings were carried out at all the test cases to see the variation of particle number and other emissions. Increasing injector hole number from 7 to 9, in-cylinder pressure heat release rate and combustion duration increased while ignition delay was shortened. Soot-NOx and ISFC-NOx trade-offs also improved with decreasing hole diameter for these hole numbers. Particle number emissions reduced significantly with increasing hole number. However, the 10-hole injector exhibited a different behavior than the other injectors. For low loading case, cylinder pressure and heat release rate were higher than those of the 9-hole injector but for medium and high loading cases, in-cylinder pressure, heat release rate, and combustion duration of the 10-hole injector were found to be lesser than the 9-hole injector. For medium and high loading cases, particle number emissions from the 10-hole nozzle also increased as compared to the 9-hole injector. Optical engine investigation revealed a higher flame-flame interference in case of the 10-hole injector which resulted in degraded combustion performance and higher particle number emissions. © IMechE 2020.