ARB Research Seminar
This page updated June 19, 2013
Demonstration of Particulate Matter (PM) Sensor in Post-DPF Environment
Brian Krafthefer, P.E., Honeywell Laboratories Plymouth, Minnesota
April 07, 2010
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA
After-treatment and engine control systems for diesel engines are being required to achieve lower emissions and also to verify that these systems are functioning while the vehicle is operating. This is preferred to conducting system checks with the vehicle pulled off-road. The California Air Resources Board (CARB) also requires certification that recommended on-board diagnostic (OBD) levels are not being exceeded. Moreover, there is a need for rapid determination of a failed diesel particulate filter (DPF), especially during engine operation, to indicate that maintenance or replacement is needed. As DPF failure occurs, higher particle mass concentrations begin to exit the after-treatment systems. Failures of the DPF may occur where these particle mass concentrations begin to exceed the EPA emissions certification levels of 0.01gm/bhp-hr and ultimately the higher OBD level of 0.05 gm/bhp-hr. Current methods of determining DPF failure rely on monitoring the pressure drop across the DPF due the decrease in flow restrictions within the DPF itself. A method of directly measuring particle mass would ultimately be preferential since the failure conditions could be directly determined by the amount of mass passing through the DPF and would be directly correlated to the standard.
The intent of the PM sensor demonstration program is to test a developed particulate mass (PM) sensor concept for operation in the post-DPF environment of the after-treatment system for diesel engines. This sensor will have the capability of determining particle mass concentration within this environment and will, hopefully, be able to detect the failure of the DPF to maintain the OBD criteria for emissions. At this point in time, there is an incomplete understanding of the particle-charge characteristics in this environment. Since the detection mechanism of the PM sensor relies heavily on the charge particle characteristics, a better understanding of the charge nature of these particles in the post DPF environment is also needed. In the ICAT project, Honeywell evaluated the sensors in an on-engine application using both a functional as well as a failing DPF to provide the conditions resulting in post-DPF particle mass concentrations that approached the 5x certification levels of 0.05 gm/bhp-hr. The project examined the probe's time response and signal accuracy by comparing measurements with calibrated particle measuring equipment and with gravimetric measurements.
Brian Krafthefer, P.E., B.C.E.E., is a research scientist with Honeywell's Sensors and Wireless Laboratory at Honeywell Automation and Control Solutions and is the project manager on this program. His main areas of research are gas and particle sensors for ambient air and harsh environments. These programs conduct both modeling on, and experimental development of gas and particle sensors. Current projects include high temperature gas sensing of combustion gases.