Study on the Optimal Pre-Chamber Specifications for Active Pre-Chamber Gas Engines with Different Engine Operating Conditions

Pre-chamber engines can realize further fuel dilution and their thermal efficiency can be improved because adding pre-chamber separates the ignition process from the main combustion. On the other hand, it also increases the number of design variables which have a large effect on combustion. Therefore, these parameters must be decided properly. In this study, the candidates of the optimal pre-chamber specifications in an active pre-chamber gas engine were proposed using NSGA-Ⅱ with ANN (Artificial neural network) models. The design parameters were the volume of pre-chamber, the diameter of a nozzle hole, and the number of nozzle holes. Employing ANN models of thermal efficiency, NOx, and CO as objective functions, the optimal geometry of the pre-chamber is obtained as Pareto solutions. The ANN models’ inputs were pre-chamber specifications and engine operating condition. As the models can consider both pre-chamber specification and engine operating condition, the specifications were optimized with varying engine operating conditions. As a result, the optimal pre-chamber specification was obtained for each condition, and they had specific propensities for engine operating conditions. Also, an analysis of the results was conducted using jet intensity.