Recent developments with pre-chamber spark ignition system for lean burn combustion engines: a review

Lean or ultra-lean combustion mode is an effective strategy to enhance the characteristics of conventional engines. However, lean burn spark ignition engines have several drawbacks, such as combustion instability, lower flame speed, cycle-to-cycle variability, and engine misfire. Hence, several advanced high-energy ignition concepts have recently evolved to assist lean combustion, in which the pre-chamber spark ignition systems offer potential benefits, which include improved combustion stability, higher engine efficiency, and reduced engine out emissions. The current review includes a detailed discussion on the fundamentals of pre-chamber spark ignition mechanisms, the various types, and the factors that influence their performance. Numerous researchers have reported that the performance of pre-chamber spark ignition systems is primarily governed by turbulent flame jets that rely on the operating conditions and pre-chamber structural parameters. Therefore, this review mainly summarizes the effect of different operating parameters, including intake air pressure and temperature, equivalence ratio, spark timing, and fuel injection parameters, on the characteristics of the pre-chamber system. Further, the influence of pre-chamber structural parameters, like pre-chamber volume, internal shape, throat diameter, nozzle hole diameter, numbers, patterns, and orientations, on the pre-chamber system characteristics are also explored. Finally, the pre-chamber spark ignition system's critical concerns and future research directions are discussed. The current review provides in-depth knowledge of various operating parameters and pre-chamber design considerations, which can be utilized for the optimum design of pre-chamber spark ignition systems for high-efficiency engines.