A novel air management system for a large bore two-stroke naturally aspirated gas engine to reduce emissions

The oil and gas industry operates by reciprocating natural gas engines which must comply with regulated emission standards for hazardous air pollutants, including NOx, CO, and volatile organic compounds (VOCs). These pollutants are regulated by Environmental Protection Agency, and each engine is regularly tested for compliance with national emission standards. A general emissions control strategy in combustion engines is to control the air-to-fuel ratio. However, stationary reciprocating engines, especially two-stroke engines, rarely have any mechanisms to control air and fuel parameters at various operating conditions. This article discusses a novel air management system that is invented to control the air-to-fuel ratio for a large bore two-stroke naturally aspirated gas engine, that is, AJAX™ brand model number 2802. The method can also be used for other engines with the same working principle. This novel air management system has been developed through comprehensive computational analyses of the gas exchange process inside the engine and is presented here. Pilot tests have also been conducted to validate the computational model results. The results show that this air management system can significantly reduce the engine emissions to the standard level at various operating conditions, including partial loads and speeds. In the case of VOCs emissions, up to a 75% reduction is observed.