PR-457-14201-R01 Variable Natural Gas – Composition Effects and Control Methods for Two-Stroke Engines

Literature is reviewed for the impacts of variable natural gas composition on two-stroke lean burn pipeline compressor engines. Information gathered for these engines can be simplified for development of control algorithms in four-stroke and richer burning engines. Data shows that geospatial, geological, and transient hydraulic effects cause composition variations that adversely affect engine emissions, efficiency, rated performance, and operational safety considering auto-ignition effects. In order to compensate for these changes in composition, better engine control schemes can help meet desired performance goals. For specific gas compositions combusting at a fixed air-fuel ratio, the laminar flame speed, adiabatic flame temperature, and ignition delay relate to and allow the prediction of the mixture’s reactivity, thermal availability, and auto-ignition tendency. Predicting changes in these combustion parameters, as caused by changes in fuel composition, is essential to the success of control development for variable composition engine operation. In addition to addressing the associated combustion effects resulting from variable fuel composition, an overview of sensor technologies is presented for use in control applications.