Predictive NOx Emissions Modeling for a Large Bore, Lean-Burn, Integral Compressor Engine

The ultimate goal of this work is to aid in the improvement of emissions control methods for compressor engines used in the natural gas transmission pipeline industry. The work presented here contributes to that larger goal by adding onto the capabilities of a previously-developed model of a Cooper-Bessemer GMWH-10C intended to simulate the effects of varying natural gas composition on engine behavior. This work targets the implementation and tuning of NOx emissions predictions in the engine model, with the expectation that it can be used in the future to inform the development of controller improvements needed for fuel composition variability. Though the nature of combustion within a lean-burn engine is complex, with many spatial dependencies, the approach taken in this work utilizes a simple 0D/1D, two-zone engine model which lacks rigorous physical accuracy, but produces acceptable engine performance results in a short amount of time. The unique operating conditions of these engines also results in NOx formation characteristics which are different and more complicated than those in the more common four-stroke, spark-ignited engine commonly used in automotive applications. Thus, special considerations must be taken into account when simulating NOx formation in a lean-burn engine. NOx prediction capabilities were added to the engine model through implementation and assessment of various methods including different pathways of NOx formation. The best method was tuned to obtain acceptable agreement with experimental data and was tested for its ability to predict emissions for other operating conditions. Finally, a preliminary fuel sweep was performed with the full engine model