Evaluation of Partial Flow Dilution Systems for Very Low PM Mass Measurements

Abstract

Particulate matter (PM) mass measurement methodologies were improved considerably with the application of Title 40 Code of Federal Regulations Part 1065 for the 2007 standards for heavy-duty engines that emphasized PM. However, there is still a need to improve the understanding of and the confidence in mass measurements for light-duty vehicles, which are now being subjected to more stringent PM standards. The purpose of this study is to evaluate commercially available partial flow dilutors (PFDs), with a particular focus on their equivalency with the standard constant volume sampler (CVS) tunnel method and the ability to provide reproducible measurements at low PM emission levels. For the main PFD comparison, simultaneous testing was conducted with the three PFDs, over federal test procedure (FTP) and US06 tests. The results of the calibrations and proportionality tests all showed good performance for the PFDs. The exhaust flow meters (EFMs) for the PFDs showed measurements within 2% or less of a calibration source. The PFDs also showed good level proportionality and can easily meet the CFR 1066 requirements for light-duty vehicles and 1065 requirements for all tests performed. Larger differences were seen for the main comparisons between the CVS and the different PFDs during the FTP testing, with the relative difference of PM emissions between the PFDs and the CVS varying from − 16.5 to − 0.6%, with an average pooled difference of − 8.5%. These FTP differences only represented 0.00 to 0.11 mg/mile on an absolute basis, however, and could be attributed to difficulties making and weighing filter mass measurements at such low levels. For the US06 cycle, the differences between the PFDs and the CVS were not statistically significant and ranged from − 6.7 to − 0.7% and up to 0.07 mg/mile.

Impacts of Exhaust Transfer System Contamination on Particulate Matter Measurements

“…The results of the direct PFD comparisons showed an absolute difference of − 0.046 mg/mi vs − 0.12 mg/mi for the FTP and − 0.11 mg/mi vs − 0.17 mg/mi for the US06. These absolute differences were actually less than those found during a more systematic evaluation of PFD and CVS differences that was conducted in conjunction with this study and is presented elsewhere [13]. Additionally, the PM emissions comparison did not seem to improve as the cleaning steps were performed, suggesting a bias between CVS and PFD remained even though the tunnel blank for the CVS decreased (15 to 3 μg) at cycle #3, as discussed in greater detail in the next section.…”

“…The stability of the weighing conditions was also monitored with 5 Teflon reference filters, which were weighed at least daily and sometimes hourly, which showed standard deviations of between 1.0 and 2.0 μg. The PM emission results were background corrected based on average tunnel blank filter masses collected periodically over the course of the project, which included other separate studies that are discussed elsewhere [13]. Tunnel blanks were collected over a test with the same duration as the cumulative or individual FTP phases or US06 tests, but without exhaust flow.…”

“…These have included studies to evaluate different methodologies to better quantify the light-duty PM mass emissions through lowering CVS dilution ratios, combining filters, and increasing filter face velocity (FFV). The use of partial flow device (PFDs) as an alternative to the constant volume sampling (CVS) system for PM sampling method has also been investigated [10,[13][14][15][16][17][18][19]. PFDs are of particular interest to quantify very low PM mass because of their potential to reduce the artifact from exhaust transfer system, such as exhaust transfer line and CVS.…”

Polylactic acid/hydroxyapatite/yttria-stabilized zircon synthetic nanocomposite scaffolding compression and flexural characteristics

“…To mix nanomaterials, the subject of implant applications had previously been established. The author is trying to say zirconium (YSZ) is a biodegradable, neutral ceramic with good compression, twisting, and hardness 6 . Because pressure causes the transition from a rhombohedral to a tetragonal structure, YSZ has a high execution strength.…”