With a baseline urea SCR and CDPF emission control system, over 80% NO(x) reduction was achieved on a 6000 lbs light-duty truck on the FTP-75 cycle, and tailpipe NO(x) was below the Tier 2 Bin 8 emission standard (0.2 g/mi NO(x)). Good mixing of aqueous urea in the exhaust gas was essential for full utilization of the reductant by the SCR catalyst, thus improving NO(x) conversion. Rapid warm-up of the exhaust system during cold-start was found to be critical to achieve the 90+% NO(x) conversion required to meet the light-duty Tier 2 Bin 5 standards. The objective of 0.07 g/mi NO(x) and 0.01 g/mi PM on an engine dynamometer over the FTP-75 was met with an improved fresh emission control system of Urea SCR and a CDPF. System improvements were required to lower engine-out NO(x) and enable rapid exhaust system warm-up. The improved Urea SCR and CDPF system was aged successfully on the engine dynamometer for the equivalent of 50k mi on the Ford High Speed Cycle. Evaluation of the aged system on the LDT resulted in HC, CO & PM emissions that met Tier 2 Bin 5 standards at 50k mi. However, NO(x) emissions were 0.09 g/mi and were predicted to be 0.05 g/mi (Bin 5) if rapid warm-up during cold-start was functional. The improved Urea SCR and CPDF system was aged successfully for another 70k mi on the engine dynamometer using the same aging cycle, bringing the total aging time to about 2500 engine hours or an equivalent total mileage of 120k mi. The CDPF was regenerated a total of 643 times, with each regeneration typically lasting ten minutes, including six minutes with the SCR at high temperature (over 600 deg C). In all, the SCR spent approximately 64 h at high temperature during the durability phase, similar to the lab aging time. PM, NMOG and CO emissions were within Tier 2 Bin 5 limits, but Bag 1 NO(x) emissions were higher than expected due to the lack of a reliable rapid warm-up strategy during cold start. Overall FTP-75 NO(x) conversion was 74% conversion with 0.128 g/mi at the tailpipe, exceeding the Tier 2 Bin 5 standard at 120k mi of 0.07 g/mi NO(x). This result was improved by using a fresh DOC upstream of the 120k mi SCR (0.091 g/mi); therefore, the durability of the DOC had a significant impact on SCR performance. An improved SCR catalyst was ovenaged and tested with the 120k mi DOC resulting in 0.08 g/mi NOx, and 0.06 g/mi NO(x) with a fresh DOC. Again the importance of DOC durability for long-term NO(x) reduction was shown.


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    Titel :

    Urea SCR and CDPF system for a Tier 2 Light-Duty Truck


    Weitere Titelangaben:

    Harnstoff SCR und CDPF System für einen Light-Duty-Truck


    Beteiligte:
    Lambert, Christine (Autor:in) / Williams, Scott (Autor:in) / Carberry, Brendan (Autor:in) / Koehler, Erik (Autor:in) / Tomazic, Dean (Autor:in)


    Erscheinungsdatum :

    2006


    Format / Umfang :

    14 Seiten, 11 Bilder, 6 Quellen


    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Print


    Sprache :

    Englisch




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