Real-Time, Real-World Measurement of Particulates Demonstrated at Sandia
April 16, 2004
A team led by researchers at the U.S. Department of Energy's (DOE's) Sandia National Laboratories' Combustion Research Facility (CRF) has demonstrated the ability to measure "real world" particulate emissions from a vehicle under actual driving conditions. Onboard measurements of gaseous emissions are routine, while real-time particulate measurements have been far more elusive, yet are essential for validating federal emissions guidelines for vehicle compliance. The ability to measure on-board particulate tailpipe emissions is of growing environmental interest because of the desire to validate current U.S. Environmental Protection Agency (EPA) vehicle certification procedures.
Sandia's CRF engine combustion department recently collaborated with Artium Technologies, Chevron Oronite, and the National Research Council (NRC) Canada to demonstrate the feasibility of obtaining on-board measurements of vehicle particulate emissions using laser-induced incandescence (LII) technology. LII is a nonintrusive diagnostic technology that can perform real-time measurements of particulate emissions produced by internal combustion engines. Funding for Sandia's portion of the effort came from DOE's FreedomCAR and Vehicle Technologies Program.
The most notable result during the recent tests was that although vehicle speed and engine rpm were reasonably steady for the period from 470 to 600 seconds, the particulate emissions suggested that fuel injection cycled on and off intermittently. The average particulate emissions measured by LII during this period were 8.4 ppb, as compared to 10-11 ppb during steady-state idle. This suggested that the engine control module had been programmed to minimize fuel consumption during a descent while maintaining idle-like particulate emission levels. The researchers believe the ideal fueling strategy would be to turn off injection for the entire descent, but they suspect that fueling is being cycled on-and-off to keep the oxidation catalyst at a functioning temperature.