The demand for gas engines running on natural gas and sewage gas has been increasing in recent years as the key of the cogeneration systems which are now being put into commercial use. At the same time, the regulations aimed at reducing air pollution from exhaust gases are becoming more and more stringent in line with the public interest in environmental protection.
In response to these demands, the authors have developed the mediumsized, medium-speed gas engines “26HXG” series.
The developed engine realizes a very low NOx emission and high efficiency by an Ultra Lean Burn with an excess air ratio exceeding 2.0. This Ultra Lean Burn has been realized by means of a pre-chamber combustion system and a lot of efforts for optimizing design parameters.
As a result of the optimization of the design parameters, a low NOx emission of 200 ppm in O2 0% equivalent together with a high thermal efficiency as high as 38 %, which is competitive to the diesel engines, has been achieved.