Destruction of Nitric Oxide via Selective NOx Recirculation During Lean Combustion: A Comparison of Various Engines and Fuels 2006-01-3369

A series of experiments were performed using a Yanmar TS180, single cylinder, indirect injection (IDI) diesel engine, a natural gas fueled, Olympian G25F1S, spark-ignited, 25 kilowatt generator, and a two-stroke, multi-fuel, spark ignited engine to provide a diverse research platform for the study of in-cylinder NOx destruction (Conversion of NO). For each type of engine, the NOx recirculation step of the selective NOx recirculation (SNR) cycle was simulated by injecting pure nitric oxide (NO) into the intake air at various concentrations, depending on engine type and operating conditions. Previous researchers have attempted to characterize NOx destruction behavior by simulating the NOx recirculation step in both diesel and gasoline engines. Some prior work has suggested that NOx destruction behavior in diesel engines is not dependent on the amount of NO present in the intake air, and that the NOx destruction efficiency was greatly enhanced by increasing engine load. The results from the present study are not consistent with these past findings for the case of spark-ignited gasoline-fueled engines. Prior findings suggest that NOx destruction is independent of both load and the amount of NO present in the intake air, which is consistent with the present observations. All engine experiments performed during this study demonstrated that SNR can be an effective NOx control strategy for a wide range of combustion systems regardless of fuel type and combustor design. From these experiments, one can infer that the dominant NO reduction pathways and dependencies change with combustor type and in the diesel case, with engine operating conditions.