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Journal Article

A New Approach for Very Low Particulate Mass Emissions Measurement

Pending reductions in light duty vehicle PM emissions standards from 10 to 3 mg/mi and below will push the limits of the gravimetric measurement method. At these levels the PM mass collected approaches the mass of non-particle gaseous species that adsorb onto the filter from exhaust and ambient air. This introduces an intrinsic lower limit to filter based measurement that is independent of improvements achieved in weighing metrology. The statistical variability of back-up filter measurements at these levels makes them an ineffective means for correcting the adsorption artifact. The proposed subtraction of a facility based estimate of the artifact will partially alleviate the mass bias from adsorption, but its impact on weighing variability remains a problem that can reach a significant fraction of the upcoming 3 and future 1 mg/mi standards. This paper proposes an improved PM mass method that combines the gravimetric filter approach with real time aerosol measurement.
Journal Article

Sampling of Non-Volatile Vehicle Exhaust Particles: A Simplified Guide

Recently, a particle number (PN) limit was introduced in the European light-duty vehicles legislation. The legislation requires measurement of PN, and particulate mass (PM), from the full dilution tunnel with constant volume sampling (CVS). Furthermore, PN measurements will be introduced in the next stage of the European Heavy-Duty regulation. Heavy-duty engine certification can be done either from the CVS or from a partial flow dilution system (PFDS). For research and development purposes, though, measurements are often conducted from the raw exhaust, thereby avoiding the high installation costs of CVS and PFDS. Although for legislative measurements requirements exist regarding sampling and transport of the aerosol sample, such requirements do not necessarily apply for raw exhaust measurements. Thus, measurement differences are often observed depending on where in the experimental set up sampling occurs.
Technical Paper

Accuracy of Particle Number Measurements from Partial Flow Dilution Systems

The measurement of the particle number (PN) concentration of non-volatile particles ≻23 nm was introduced in the light-duty vehicles regulation; the heavy-duty regulation followed. Based on the findings of the Particle Measurement Program (PMP), heavy-duty inter-laboratory exercise, the PN concentration measurement can be conducted either from the full dilution tunnel with constant volume sampling (CVS) or from the partial flow dilution system (PFDS). However, there are no other studies that investigate whether the PN results from the two systems are equivalent. In addition, even the PMP study never investigated the uncertainty that is introduced at the final result from the extraction of a flow by a PN system from the PFDS. In this work we investigate the uncertainty for the three possible cases, i.e., considering a constant extracted flow from the PFDS, sending a signal with 1 Hz frequency to the PFDS, or feeding back the extracted flow to the PFDS.
Technical Paper

Measurement of Dry Soot and Particulate Matter from Two-Stroke and Four-Stroke Snowmobiles

Recent increases in emissions regulations within the snowmobile industry have led to significant advancements in fuel, exhaust, and control systems on snowmobiles. However, particulate matter is currently an unregulated exhaust component of snowmobile engines. The measurement of dry soot as well as particulate matter from snowmobiles is the focus of this paper. Two industry-representative snowmobiles were chosen for this research which included a 2006 Yamaha Nytro carbureted four-stroke and a 2009 Ski-Doo MX-Z direct-injected two-stroke. Measurements for each snowmobile included gaseous emissions (CO₂, CO, NOx, O₂, and THC), particulate matter collected on quartz filters, and dry soot measured using an AVL Micro Soot Sensor. Each snowmobile was tested over the industry-standard five-mode emissions certification test cycle to determine the emissions, dry soot, and particulate matter levels from idle to wide open throttle (full-load).
Technical Paper

CMS - An Evolution of the CVS - A Full Flow, Constant Mass Flow, Sampling System

The CMS system commissioned by EPA and built by AVL, is a “start from a clean sheet of paper” approach to a full flow sampling system for aerosol matter from engine exhaust. The challenge of measuring 2007 level post DPF type particulate matter and polyaromatic hydrocarbons led to this re-thinking of sampler design. Previously used CVS designs had evolved to include elements that were not ideally suited for scaling up to large flow rates, and had mixing tunnels that were less than ideal for the sampling of complicated aerosols. The solution presented in this paper used ultrasonic time-of-flight flowmeters in place of the usual Venturi flow tubes, reducing the size and cost of air handling components. Acoustically designed dampeners were used to reduce pulsation disturbances to the flow measurement.
Technical Paper

DVE - Direct Vehicle Exhaust Flow Measurement using Head-type Flowmeters

When exhaust emissions from a vehicle are measured, a flow rate is needed in addition to pollutant concentrations in order to calculate the mass emitted. The highly unsteady flow from an internal combustion engine presents measurement challenges to exhaust flowmeters, especially at idle. Mass measurement methods used in the past have gotten around this problem by a variable dilution scheme (CVS) that measures a different, more favorable flow, but reduces and can contaminate exhaust gas concentration levels. The flow measurement system described here makes possible a more accurate measure of the vehicle exhaust flow by means of a number of design features. This improves considerably the cost effectiveness and accuracy of emissions measurement techniques such as the Bag-Minidiluter sampling system and raw modal analysis.