Horiba on-board diesel exhaust particulate sampler (OBS-PM) is a filter based partial flow particulate sampling system used for On-board diesel particulate matter (PM) measurement. It takes sample from either raw or diluted exhaust. It can run at constant dilution ratios or at variable dilution ratios with proportional control on the sample flow. The diluted exhaust moves through a pre-weighed 47 mm particulate filter and PM is collected on the filter. By weighing the loaded sample filter, PM emission from the engine or the vehicle can be determined.
The performance of the OBS-PM meets most of requirements for a real-time partial flow sample system (PFSS) recommended by ISO 16183 [2]. The physical size and the power consumption of the instrument are minimized. It is powered with four 12 volts batteries, and can be installed on a vehicle for real-world PM emission evaluation. It is used either as a standalone instrument or as an instrument with a Horiba on-board gaseous instrument (e.g. Horiba OBS-2000).
The OBS-PM has been evaluated at Southwest Research Institute and compared with a CVS tunnel with the secondary dilution for PM correlation. A DDC series 60 heavy-duty diesel engine with a diesel particulate filter (DPF) were operated to evaluate the performance of the OBS-PM at four test cycles, FTP, FTP with DPF by-pass (FTP w/ BP), steady-state test I (SS1), and steady-state test II (SS2) with 7 repeats for each cycle. The diesel engine and DPF were the same ones used in CRC project E-66 phase 3 which aims to evaluate commercially available partial flow samplers [5]. For FTP, FTP w/ BP, and SS1, PM emissions reported based on OBS-PM were 15.2%, 21.9%, and 14.1% lower than those reported based on the CVS, respectively. Due to the fact that the CVS tunnel exhibited high blank PM emissions, it is likely that the PM emission from the CVS is higher than real emissions. For SS2, the OBS-PM shows 10.6% higher emissions than that from the CVS. By comparing the correlation of the OBS-PM vs. the SwRI CVS to correlations of commercially available partial flow samplers vs. the SwRI CVS, it is found that the OBS-PM achieves a similar performance to those of the commercially available laboratory partial flow samplers.