Effects of pre-chamber specifications on lean burn operation in a pre-chamber engine with fuel reformed gas

Lean combustion has been well known to be an effective method to improve the thermal efficiency. However, leaner mixture is prone to cause the unstable combustion and poorer unburned hydrocarbon (UTHC) emissions. Pre-chamber turbulent jet combustion has been proved to enhance the combustion stability under ultra-lean conditions. However, more NOx is formed during the combustion, resulting in the fact that the tailpipe NOx emission is too high to be still not available for the real application. In this report, in order to achieve a higher air excess ratio while keeping lower UTHC emissions, and especially NOx emission, a new combustion technique which combined pre-chamber jet combustion with fuel reforming was proposed and experimentally demonstrated on a pre-chamber engine.