The Development of an On-Board Instrument for On-Road Diesel Particulate Measurement

The on-board transient response diesel particulate measurement (OBS-TRPM) instrument measures on-road vehicle particulate emissions. It is a continuation of the Horiba on-board PM sampler (OBS-PM) [5].

The OBS-TRPM measures total diesel particulate emission by collecting diesel particulate matter (PM) on a pre-weighed 47 mm filter while the partial flow sample system (OBS-PM) runs under a proportional control strategy. A real-time diffusion charge sensor (DCS) takes sample upstream of the filter, and measures diesel PM in term of particle length (mm/cm³). By integrating the DCS real-time signal during the filter sampling, the cumulative fraction of diesel PM emission is obtained. Finally, diesel PM mass emission during a specific region, for example a Not-to-Exceed (NTE) zone, is calculated from the fraction of the real-time PM signal. Thus, the OBS-TRPM provides a solution to measure PM emission in NTE zones which are defined by the US EPA.

The performance of the instrument was evaluated on a 1998 VW beetle diesel vehicle and a 1999 Ford Windstar gasoline vehicle. The NEDC (new European drive cycle) was operated for both vehicles. Results show that the OBS-TRPM measures total exhaust PM; in the meantime, the PM emission from each segment can be calculated from the cumulative fraction of the particle length concentration measured by the DCS.