Investigations on Pre-Chamber Spark Plug with Pilot Injection 2007-01-0479
Combustion concepts for future SI engines try to meet CO2 emission commitments and legislation all over the world. Where the diesel engine has an advantage by principle, the efficiency of the SI engine has to be improved significantly, while of course there must be no deterioration in exhaust emissions. Another approach is to switch from gasoline to gaseous fuels such as compressed natural gas (CNG) or liquefied petroleum gas (LPG) with more appropriate C/H ratios in order to reach the CO2 targets.
Both methods of using liquid and gaseous fuels in an SI engine take into account that the air/fuel mixtures in the combustion chamber turn to a lean air/fuel ratio to increase engine efficiency, whether by stratification or air dilution. The challenge in this case is to solve the conflict between high efficiency and low raw emissions, especially in the field of NOx emission. Ignition itself increasingly becomes a relevant parameter to reach the most efficient combustion, with common ignition systems being limited in terms of energy and spark position.
There are currently two competing systems offering potential for igniting a greater mixture volume and lead from local dependency of the spark; these are laser ignition on the one hand and plasma torch systems on the other.
IAV has studied the potential of a plasma torch system, using a pre-chamber for mixture preparation to generate an optimized jet flame. This paper presents results from numerical simulation, optical investigations and engine testing to give an overview of the ignition system's potential regarding engine operation under lean burn conditions.