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Diesel engines have been the major power source for medium- to heavy-duty ground vehicles due to superior fuel efficiency and durability over gasoline engines. However, Diesel engines are the main contributors for non-renewable Diesel fuel consumption and NOx and particulate matter (PM) emissions. Biodiesel fuel has been considered as a promising alternative fuel and can be directly fed into Diesel engines without major modifications. In addition, biodiesel has demonstrated lower hydrocarbon (HC), carbon monoxide (CO), and PM emissions than Diesel fuel. Nevertheless, the NOx emissions of biodiesel are generally higher. To meet stringent NOx emission regulation, urea-based selective catalytic reduction (SCR) systems have been widely utilized in Diesel-powered vehicles. The application of biodiesel fuel to Diesel engines can significantly change the exhaust condition and thus increase the complexity of SCR design and controls.

Diesel engines have been widely adopted in medium- to heavy-duty ground vehicles, due to high engine efficiency, high power output, and superior reliability. However, as Diesel engine emission regulation has been significantly tightened in the past decade, emission control has become a major barrier for Diesel engine efficiency improvement. Integrated Diesel engine and aftertreatment system controls are very important for modern Diesel engines to further improve fuel efficiency while facing increasingly stringent NOx and particulate matter (PM) emission regulations. In this paper, a real-time implementable, integrated engine-aftertreatment control framework was proposed to coordinate a modern Diesel engine with the coupled urea-based selective catalytic reduction (SCR) system for achieving close-to-optimal engine efficiency while meeting tight tailpipe NOx and NH3 slip requirements.

Oxygen storage capacity (OSC) is one of the most critical characteristics of a three-way catalyst (TWC) and is closely related to the catalyst aging and performance. In this study, a dynamic OSC model involving two oxygen storage sites with distinct kinetics was developed. The dual-site OSC model was validated on a bench reactor and a natural gas engine. The model was capable of predicting temperature dependence on OSC with H2, CO and CH4 as reductants. Also, the effects of oxygen concentration and space velocity on the amount of OSC were captured by the model. The validated OSC model was applied to simulate lean breakthrough phenomena with varied space velocities and oxygen concentrations. It is found that OSC during lean breakthrough is not a constant for a particular TWC catalyst and is dependent on space velocity and oxygen concentration. Specifically, breakthrough time exhibits a non-linear, inverse correlation to oxygen flux.