NOx Reduction on Direct Injection Natural Gas Engines 1999-01-3608
Direct injection natural gas engines need to produce in the mixing process between the fuel jet and the air in the cylinder a “stratified” fuel-air mixture, with an easily ignitable composition near the spark plug at the time of ignition.
Stratified-charge engines have a tendency to produce high NOx emissions due to the high temperature of burning areas at the start of combustion since the fuel-air mixture is not uniform. Therefore, it is necessary to reduce NOx emissions from direct injection natural gas engines.
The objective of this study is to investigate measures to reduce emissions, especially NOx emissions, from direct injection natural gas engines. A single cylinder test engine was equipped with a newly developed high-pressure electromagnetic injector and a spark plug.
The possibility of reducing emissions, especially NOx emissions, while maintaining high thermal efficiency was investigated by means of multiple stage injection with a test engine using an electromagnetic injector, and by means of control of oxygen concentrations in intake air by adding nitrogen (a method like EGR control).