Design Space for Prechamber Gasoline Engine Modelling

Lean air–fuel mixture combustion is an effective way to reduce HC/CO/NOx emissions significantly in premixed gasoline and gas engines. Slower flame speeds of lean mixture impact cycle-to-cycle IMEP variation and thereby emissions. This becomes much more challenging with large-bore gasoline and gas engines, leading to significant HC and CO emissions with lower efficiencies. This can be overcome with a prechamber combustion design which generates hot burning gas (and radicals) jets that come into the main chamber and provide higher ignition energy and turbulence along with a higher surface area for entraining and propagating flames which can engulf the premixed mixture in the main chamber much better. The prechamber spark-ignited engines are knock-tolerant and provide robust ignition. An active prechamber (which involves the introduction of fuel/ fuel and air directly into the prechamber) is more effective in providing the required prechamber jets compared to a Passive prechamber (premixed prechamber charge introduced from the main chamber). With proper optimization of prechamber volume, air–fuel mixing, and strength (Air–fuel ratio) in the prechamber and the pressure rise in the prechamber (thereby the ΔP across the prechamber nozzle), it is possible to achieve a significant reduction in emissions and improvement in thermal efficiency. The current scope is to review the state-of-the-art active prechamber spark-ignited engines, analyse the parameters studied, and present key observations on the parameters of importance and their range for designing prechamber engines which need to be investigated through Modelling and experiments.