Study of Lean Burn Gas Engines using Pilot Fuel for Ignition Source

Lean burn gas engines are expected to reduce NOx emission while improving engine performances such as output and thermal efficiency. Recently, an ignition method using a small quantity of diesel fuel (pilot fuel) as an ignition source for lean-burn gas engines has introduced further improvement of their performance. Generally, this method has been used for pre-chamber engines because it could not successfully lead to reduce NOx and Particulate emissions when adopted for open-chamber engines. However, the possibility of improvement of performances of open-chamber engines with this ignition method has also been expected⁽¹⁾. An experimental study was conducted to investigate the performance of an open-chamber gas engine with pilot fuel for ignition source. Experiments were conducted by using a single cylinder gas engine equipped with a common-rail injection system. Main gas fuel is supplied to the engine cylinder, and then a small quantity of diesel fuel (approximately 0.4∼1 % of total fuel energy input) was injected into the main chamber for ignition. This open-chamber gas engine has demonstrated superior performance, such as, a shaft-end thermal efficiency of 39.1 % with NOx level of 1.20 g/kW-h and 36.7 % with 0.40 g/kW-h, while maintaining COVimep within 2 %, which equals those of conventional spark ignited pre-chamber lean burn gas engines.