Diesel Particulate Matter Sensor: Insights into the Effect of Corona Discharge on Signal Amplification

Master of Science, Graduate Program in Mechanical Engineering
University of California, Riverside, June 2015
Dr. Heejung Jung, Chairperson

In  2016,  in-situ  on-board  diagnostic  system  for  on-road  vehicles  is  required  to  monitor particulate filter failure. The design of particulate matter (PM) sensors vary by company (e.g., Honeywell,  Bosch,  Emisense,  and  Delphi)  in  addition  to  method.  The  method  under investigation  in  this  study  is electrical  charge  migration  along  with  corona  discharge generation.

Equilibrium charge state of particles (i.e., particle charging) is  estimated  using  Boltzmann’s Equilibrium  Charge  Distribution.  The  PM  sensor  design  in  this  study  is  understood  to generate a signal that is amplified higher than can be theoretically explained by the migration of  oppositely  charged  particles.  Signal  amplification  is  hypothesized  to  be  attributed  to  the presence of excess ions due to the presence of corona discharge, besides charged particles in an  electric  field.  A  fundamental  study  probing  into  the  effects  of  corona  discharge  on  PM sensor signal amplification is necessary to understanding the underlying operational principles of the sensor. This study will provide qualitative insights into the operating principles of the PM sensor by varying key parameters during testing. The influence of temperature, residence time, and particle concentrations were investigated to understand the behavior of the senor.

This  is  performed  by  correlating  sensor  response  to  varying  physical  conditions  of  PM.  A model  of  the  sensor,  without  the  corona  discharge  effect,  will  also  be  tested  in  comparable conditions  to  characterize  the  effects  that  are  attributed  to  signal  amplification  of  the  PM sensor. Understanding the operational principles of this design could lead to the development of a relatively inexpensive PM sensor with unprecedented high signal sensitivity.