Performance of Laser and Spark Ignition Systems in a Reciprocating Natural Gas Engine

Lean-burn natural gas engines remain attractive as they offer low emissions with simultaneous high engine efficiency. The low carbon to hydrogen ratio in natural gas minimizes the carbon dioxide emission, while the low-temperature operation reduces NOx formation. However, to preserve engine specific power, turbo-charged operation is required, which results in an unfavorable environment for the spark ignition system. In this study, the performance of three ignition systems - Spark Ignition (SI), Laser Ignition (LI), and Prechamber Laser Ignition (PCLI) - were assessed through tests in a single-cylinder natural gas engine. Both λ and ignition timing sweeps were performed while maintaining a constant speed of 1800 rpm and a load of 10 bar BMEP. Emissions and combustion data analysis, while complying with allowable emission regulation and ignition stability requirements, showed the best performance to be achieved with the PCLI system. This is attributed to improved ignition with the use of a laser, volumetric ignition facilitated by spatially distributed flame jets, and increased in-cylinder turbulence. This results in reduced ignition delay and shortened combustion duration.