A diesel particulate filter (DPF) can be used to reduce the particulate matter (PM)
emissions from a vehicle. However, when these devices fail the tailpipe emissions can
change. The main goal of this project was to determine if a soot sensor provided by
Honeywell could detect a failed filter, defined as an exhaust aerosol concentration
downstream of the DPF greater than the current US heavy duty PM standard of 13
mg/kWh (10 mg/bhp-hr). In this study a DPF failure was first simulated on an engine
dynamometer test stand using an exhaust bypass valve. Then the valve was removed and
the filter was actually failed in a series of steps by drilling out individual channel end
Exhaust was cooled and diluted using a partial flow air ejector dilution tunnel, and
dilution ratios were determined using raw and dilute nitric oxide (NO) measurements.
Dilute diesel exhaust aerosol was characterized upstream and downstream of a DPF.
Filter samples and an AVL photo-acoustic soot sensor were used to estimate PM mass
emissions, and TSI aerosol instruments were used to measure aerosol size distributions
and total number concentrations. An electrostatic precipitator, DMA, electrometer and
CPC were used to evaluate the aerosol charge distribution. Downstream measurements
were repeated as the filter was progressively failed in a series of steps.
These measurements were then used to evaluate the response of the Honeywell
exhaust soot sensor. Under certain steady state conditions the sensor output showed a
statistically significant increase as the filter was failed but the output was susceptible to interference from mechanical vibration and was dependent on engine operating
conditions, and the exhaust system used. Exhaust aerosol charge measurements showed
the concept is viable but further work is required to refine the sensor.
University of Minnesota M.S. thesis. December 2010. Major: Mechanical Engineering. Advisor: David B. Kittelson. 1 computer file (PDF);vii, 56 pages; appendices A-D.
Ragatz, Adam C..
Characteristics of particles downstream of a partially failed diesel particulate filter..
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