Prechamber NO{sub}x formation in low BMEP 2-stroke cycle natural gas engines

摘要

Precombustion chambers (PCCs) are an ignition technology for large bore, natural gas engines enabling increased combustion stability while extending the lean limit of operation. A PCC is a small chamber, typically 1-2% of the clearance volume, in which a near-stoichiometric mixture of fuel and air is ignited by a standard spark plug. After the mixture in the PCC is ignited, its pressure rises and expels a flame jet of hot gas mixture into the main chamber. The amount of energy a typical PCC produces is roughly one million times that of a conventional spark plug. In this work the role that the PCC plays in the formation of oxides of nitrogen (NO{sub}x) is investigated. Previous research indicates that the PCC is responsible for a significant part of engine-out NO{sub}x, especially near the lean limit of engine operation. Experimental results are presented from a large bore lean-burn 2-stroke cycle engine. The data shows that the PCC is responsible for a significant part of engine-out NO{sub}x emissions. However, the PCC NO{sub}x does not form in the PCC. Rather it forms within the gas jet after it penetrates into the main chamber combustion gases.