Dresser Waukesha’s 275GL engine series, released in 2009, included an Engine System Manager (ESM) to manage and control critical engine operations. These engines are typically used in mechanical drive applications for natural gas compression as well as power generation at 2500 to 3300 kWb (3400–4500 bhp). The 275GL is now being offered in a low NOx configuration designated the 275GL+, that features a NOx based Air/Fuel Ratio (AFR) control. Market analysis determined that an engine with lower NOx output emissions while maintaining peak performance is of high importance. Utilizing a traditional oxygen based AFR system has limitations when controlling emissions at extreme low NOx values. In order to meet these needs and maintain a consistent low NOx level, development of a control system that allows an engine to achieve these requirements was essential. A NOx sensor based control system was developed to control extremely low NOx values while accounting for engine wear, humidity and fuel changes. An oxygen based AFR system has limitations that make it difficult, if not impossible, to use this approach for extremely low NOx levels. Some of these limitations can be attributed to sensor signal masking due to exhaust gases and having to correlate O2 to NOx for the specific application. This new NOx sensing functionality enables robust control of specific NOx emissions at varying engine and environmental conditions, yielding a powerful addition to the ESM engine control system applied on the 275GL engine. The NOx control running with ESM allows for the engine to achieve 0.5 g/bhp-hr NOx levels while maintaining fuel efficiency, fuel tolerance, and turndown range. This paper discusses the key testing, results and performance of this development when implemented on the 275GL+ engine.

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