A Constant-Volume Rapid Exhaust Dilution System for Motor Vehicle Particulate Matter Number and Mass Measurements

Abstract

An improved version of the constant volume sampling (CVS) methodology that overcomes a number of obstacles that exist with the current CVS dilution tunnel system used in most diesel and gasoline vehicle emissions test facilities is presented.

A Comparative Investigation of Ultrafine Particle Number and Mass Emissions from a Fleet of On-Road Diesel and CNG Buses

“…Table gives a concise summary of the Z ratio values determined in this study. In agreement with previous studies – , it is confirmed that the particle mass emission from CNG buses is significantly less than from diesel buses (8.8%). CNG buses emit large concentrations of particle numbers when in the accelerating mode.…”

“…CNG-powered vehicles emit virtually no visible particulate matter (PM) or black soot at the tailpipe and consistently show significantly less PM emissions than diesel vehicles. Associated reductions are often over 90% – . However, there is still a lot of uncertainty about the particle number emissions from vehicles using CNG in relation to diesel, with many studies showing apparently contradictory results.…”

The effective density and fractal dimension of soot particles from premixed flames and motor vehicle exhaust

“…Only the steady-state idle test showed a small nucleation mode (smaller than the soot mode), which was deemed to be vehicle generated owing to the low exhaust temperature. Second, comparison measurements are reported that use a prototype constant-volume rapid exhaust dilution (CVRED) system, where the dilution occurs immediately at the tailpipe (Maricq, Chase, Xu, & Podsiadlik, 2003a). These yield e ective densities in good agreement with those from the conventional dilution tunnel.…”

Multipollutant Air Quality Management

“…It makes no sense to climb the smokestack with 1950s-era glass impingers to separately measure NO x , SO 2 , PM 10 , etc., as required by EPA's certification source testing methods. 166 It is time to replace these antiquated practices with a dilution system, similar to that used for mobile sources, 109,[167][168][169][170][171][172] to which ambient sampling and analysis methods can be coupled. 173 …”