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.

Simulation of the Gas Filling and Evacuation Processes in an Inertial Confinement Fusion (ICF) Hohlraum

In indirect inertial confinement fusion (ICF), the prediction of gas pressures and mass flow rates in the hohlraum is critical for fielding the hohlraum film and the support tent. To this end, it is desirable to understand the gas filling and evacuation process through the microcapillary fill tube and the support tent. In this work, a unified flow simulation of the filling and evacuation processes through the microcapillary fill tube and the support tent in an ICF hohlraum was conducted to study the gas pressure and mass flow rate in the hohlraum. The effects of the support tent size and the microcapillary fill tube size on the critical pressure variation and pressure difference across the hole on the support tent are examined. The results indicate that an increase in the diameter of the hole and the hole number leads to a smaller pressure difference across the hole on the support tent. If the diameter of the hole on the support tent is larger than 0.06 mm, the critical pressure variation rate is nearly independent of the diameter and the hole number. Increases in the diameter and decreases in the length of the microcapillary fill tube induce a larger critical pressure variation rate and pressure difference across the hole, which is conductive to fielding the hohlraum film.