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Apparatus, system, and method for NOx signal correction in feedback controls of an SCR system

  • US 8,201,394 B2
  • Filed: 04/30/2009
  • Issued: 06/19/2012
  • Est. Priority Date: 04/30/2008
  • Status: Active Grant
First Claim
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1. An apparatus for reducing NOx emissions in an engine exhaust gas stream of an engine system, comprising:

  • a NOx reduction target module configured to determine a NOx reduction requirement, the NOx reduction requirement comprising an amount of NOx in the exhaust gas stream to be reduced on a selective catalytic reduction (SCR) catalyst;

    a tailpipe NOx module configured to determine a sensed amount of NOx exiting the engine system and a predicted amount of NOx exciting the engine system, the predicted amount of NOx exiting the engine system being based at least partially on an analytical model;

    a signal correction algorithm module configured to determine a corrected amount of NOx exiting the engine system based at least partially on the sensed amount of NOx exiting the engine system and an ammonia correction factor, wherein the ammonia correction factor is adjustable by dithering, and wherein dithering comprises comparing the sensed amount of NOx exiting the engine system with the predicted amount of NOx exiting the engine system adjusting the ammonia correction factor accordingly;

    a feedback ammonia target module configured to determine a feedback ammonia addition requirement, the feedback ammonia addition requirement comprising an amount of ammonia added to the exhaust gas stream to achieve the NOx reduction requirement, wherein the feedback ammonia addition requirement is based at least partially on the corrected amount of NOx exiting the engine system; and

    a reductant target module configured to determine a reductant injection requirement, the reductant injection requirement comprising an amount of reductant added to the exhaust gas stream to achieve the feedback ammonia addition requirement.

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