Light-off temperature shift as a detection method of catalyzed diesel particulate filter nonmethane hydrocarbon oxidation efficiency degradation
Abstract
California Air Resources Board emissions regulations for 2013 require that heavy duty diesel on-board diagnostic (OBD-II) systems light the malfunction indicator lamp if tailpipe nonmethane hydrocarbon levels are ever greater than 2.0 times the legal limit, or if the catalyst in the catalyzed diesel particulate filter (CDPF) is no longer active with respect to NMHC. This study focused on the serial diesel oxidation catalyst (DOC) to CDPF aftertreatment system found on Cummins ISB products and detecting when the CDPF is no longer catalytically active. Investigation into catalyst aging showed no statistically significant trends as a filter aged from degreened to effectively end of useful life. Light-off temperature shift was chosen as the method to be used to detect catalyst activity. An aged CDPF has a light-off temperature more than 50°C higher than a degreened CDPF, but also loses its ability to light- off easily at low flowrates, despite crossing what would otherwise be considered its light-off temperature. Using light-off temperature shift as a diagnostic method on this system requires CDPF light-off independent of DOC light-off. Ultimately, the proposed diagnostic strategy's solution space is exceedingly small: ISB engine power levels below 43 hp. Testing at highway speed and load, idle, and in the OBD solution space never produced independent CDPF light-off; spatially nonuniform DOC bed temperature distributions always caused the DOC to light-off before the CDPF. Cool- down times to drop the DOC below its light-off temperature to attempt independent CDPF light-off are too long to allow this to remain a viable detection strategy.
Degree
M.S.M.E.
Advisors
Meckl, Purdue University.
Subject Area
Mechanical engineering
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