Scaling the turbulent jet by active pre-chamber

Recently, pre-chamber turbulent jet ignition technology has attracted many attentions as a means of improving combustion efficiency in alternative fuel engines. Pre-chamber engines span a wide range of bore diameters and power outputs, and scaled model experiments based on similarity theory can promote the intensification of research and development for pre-chamber engines with different sizes. While the similarity of turbulent jet development plays the most important role in the entire scaled model experiments, relevant research in this area is scarce. In this paper, for the first time, the theoretical analysis of pre-chamber turbulent jet similarity is carried out based on the similarity theory and gas jet theory. Then, the constant-volume combustion chamber and the high-speed double-pass schlieren imaging are implemented to study the similarity of turbulent jets from two pre-chambers with the orifice diameters of 2.12 mm and 1.50 mm. The results show that controlling the spark timing is an effective method to ensure the same jet ejection timing and pressure building processes during the development of the turbulent jet. Finally, it is found that the jet penetration, jet angle and projection area can be well scaled using the proposed similarity law. These results agree well with the theoretical analysis.