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This paper illustrates a method to determine the experimental uncertainties in the measurement of tailpipe emissions of carbon dioxide, carbon monoxide, nitrogen oxides, hydrocarbons, and particulates of medium-, and heavy-duty vehicles when tested on a heavy-duty chassis dynamometer and full-scale dilution tunnel. Tests are performed for different chassis dynamometer driving cycles intended to simulate a wide range of operating conditions. Vehicle exhaust is diluted in the dilution tunnel by mixing with conditioned air. Samples are drawn through probes for raw exhaust, diluted exhaust and particulates and measured using laboratory grade emission analyzers and a microbalance. At the end of a driving cycle, results are reported for the above emissions in grams/mile for raw continuous, dilute continuous, dilute bag, and particulate measurements.

Diesel exhaust aftertreatment systems are required for meeting both EPA 2010 and final Tier 4 emission regulations while meeting the stringent packaging constraints of the vehicle. The aftertreatment system for this study consists of a fuel dosing system, mixing elements, fuel reformer, lean NOx trap (LNT), diesel particulate filter (DPF), and a selective catalytic reduction (SCR) catalyst. The fuel reformer is used to generate hydrogen (H₂) and carbon monoxide (CO) from injected diesel fuel. These reductants are used to regenerate and desulfate the LNT catalyst. NOx emissions are reduced using the combination of the LNT and SCR catalysts. During LNT regeneration, ammonia (NH₃) is intentionally released from the LNT and stored on the downstream SCR catalyst to further reduce NOx that passed through the LNT catalyst. This paper addresses system packaging and exhaust flow optimization for heavy-duty line-haul and severe service applications.

Diesel engine exhaust has been an area of research since the early 80's because of their harmful nature. The upcoming EPA regulations require substantial reductions in NOx and Particulate Matter (PM) and an aftertreatment system will likely be needed to meet these regulatory emissions levels. A more advanced technology in Aftertreatment system uses in-line fuel reformer to convert injected diesel fuel to hydrogen-rich reformates. It is used as the rich component for regenerating the Lean NOx Trap (LNT). The LNT regeneration process produces ammonia (NH3) that enables further NOx reduction in a downstream Selective Catalytic Reduction (SCR). A Diesel Particulate Filter (DPF) provides PM reduction capability in the system. The high conversion efficiency of regeneration cycle demands complete vaporization and uniform distribution of the injected fuel. Computational Fluid Dynamics simulation is effective in optimizing geometrical parameters to achieve the above requirements.