Influence of Pre-Chamber Nozzle Orientation on Dilution Tolerance in a Constant-Volume Optical Engine

This study presents an analysis of the effects of pre-chamber nozzle orientation on dilution tolerance in a light-duty, optical, single-cylinder, constant-volume optical engine. Seven different nozzles with varying nozzle orientation to area-to-volume (A/V) ratio were studied using a combination of experimental and numerical methodologies. The findings reveal that the swirling nozzles were found to have lowest dilution tolerance of 6% tolerance due to the complexity of their internal flow dynamics and increased heat loss through nozzle surfaces. whereas straight nozzles with varying A/V ratio were stable up to 15% dilution. Pre-chambers combining swirling and straight nozzle orientations fail to synergize the benefits of each type, and instead, exacerbate challenges such as heat loss, flame quenching, and unfavorable flow dynamics. Furthermore, an increase in the number of nozzles, for a fixed area-to-volume ratio, tends to enhance ignition performance and stability across a range of dilution scenarios, primarily due to an increase in ignition points and a larger ignition surface area. These findings emphasize the complexity and nuanced trade-offs involved in optimizing pre-chamber design for improved dilution tolerance and suggest potential directions for future research in this area. These findings emphasize the complexity and nuanced trade-offs involved in optimizing pre-chamber design for improved dilution tolerance and suggest potential directions for future research in this area.