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The measurement of solid particles down to 10 nm is being incorporated into global technical regulations (GTR). This study explores the measurement of solid particles below 23 nm by using both current and proposed particle number (PN) systems having different volatile particle remover (VPR) methodologies and condensation particle counter (CPC) cutoff diameters. The measurements were conducted in dynamometer test cells using ten diesel and eight natural gas (NG) engines that were going under development for a variety of global emission standards. The PN systems measured solid PN from more than 700 test cycles. The results from the preliminary campaign showed a 10-280% increase in PN emissions with the inclusion of particles below 23 nm.

Euro VI regulations in Europe and its adaptors recently extended the regulation to include Particle Number (PN) for in-use conformity testing. However, the in-use PN Portable Emissions Measurement System (PEMS) is still evolving and has higher measurement uncertainty when compared against laboratory-grade PN systems. The PN systems for laboratory require a condensation particle counter (CPC). Thus, in this study, a CPC-based Horiba PN-PEMS was selected for performance evaluation against the laboratory-grade PN systems. This study was divided into four phases. The first two phases’ measurements were conducted from the Constant Volume Sampler (CVS) tunnel where the brake-specific particle number (BSPN) levels of 1010-12 and 1013 (#/bhp-h) were measured from the engines equipped with diesel particulate filter (DPF) and without DPF, respectively. In comparison against PN systems, PN-PEMS, on average, reported 14% lower BSPN from 82 various tests for the BSPN levels of 1010-11.

The US Code of Federal Regulations (CFR) Title 40 Part 1065 and 1066 require gravimetric determination of automobile Particulate Matter (PM) collected onto filter media from the diluted exhaust. PM is traditionally collected under simulated driving conditions in a laboratory from a full flow Constant Volume Sampler (CVS) system, where the total engine exhaust is diluted by HEPA filtered air. This conventional sampling and measurement practice is facing challenges in accurately quantifying PM at the upcoming 2025-2028 CARB LEVIII 1 mg/mi PM emissions standards. On the other hand, sampling a large amount of PM emitted from large size high power engines introduces additional challenges. Applying flow weighting, adjusting the Dilution Ratio (DR) and Filter Face Velocity (FFV) are proposed options to overcome these challenges.

Light-duty vehicle emission measurement test protocols defined in the Code of Federal Regulation (40 CFR Part 1066) allow sampling particulate matter (PM) of all phases of Federal Test Procedure (FTP-75) on a single PM sampling filter by means of flow-weighted sampling in order to increase PM mass loaded on the filter. A technical challenge is imposed especially for partial flow dilution systems (PFDS) to maintain a precise dilution ratio (DR) over such a wide sample flow range due to the subtraction flow determination method of dilution air and diluted exhaust flows, because the flow difference is critical at high DR conditions. In this study, an improved flow weighting concept is applied to a PFDS by installing a bypass line with a flow controller in parallel with the PM sampling filter in order to improve DR accuracy during flow-weighted sampling.

Automobile Particulate Matter (PM) Emission regulation requires gravimetric determination of PM collected on filter media under simulated driving conditions in the laboratory traditionally in a full flow Constant Volume Sampling (CVS) dilution tunnel. There have been discussions about whether current sampling and measurement practices are sufficiently accurate in quantifying PM at the upcoming 1mg/mi PM emissions standards of CARB LEV III. Sampling technique alternative to a CVS such as a Partial Flow Dilution (PFD) system has already been developed and is acceptable for certification testing. Lower dilution ratios and higher filter face velocity (FFV) are options to load traceable amount of PM on filter in case of light duty vehicle (LDV) testing. On the other hand higher dilution ratios and lower FFV are required for heavy duty engine (HDE) testing to keep the PM loaded on filter <400μg.

In the engine and vehicle test procedures described in Parts 1065/1066 of Title 40 of the Code of Federal Regulations (CFR), the United States Environmental Protection Agency (US-EPA) allows for the measurement of N2O emissions from sample storage bags, from a continuous dilute stream or a raw exhaust stream. Typically, batch (Bag) sampling has better accuracy and repeatability, but continuous sampling is more efficient in terms of test cell running time and provides test-mode emissions with good correlation to bag measurements. In this study, correlations between bag sampling and continuous dilute exhaust sampling were investigated using a fleet of vehicles with a wide range of N2O emission levels. Very good correlation between these two sampling methods was observed for the majority of tests conducted. In the best cases, differences in average N2O concentration levels measured by these two methods were less than +/− 1%.

Nitrous oxide (N₂O) emission reduction has gained large prominence recently due to its contribution to the climate change as a greenhouse gas. The United States Environment Protection Agency (US-EPA) together with the United States Department of Transport (DOT) has already regulated the N₂O emissions from light-duty vehicles (LDV) to 0.010 g/mile. For LDV, N₂O measurement should be done from sample storage bags over the light-duty FTP drive cycles. N₂O emission standard of 0.10 g/bhp-hr for heavy-duty engines (HDE) is also finalized. The final N₂O standard becomes effective in 2014 model year for diesel engines. Usually raw or diluted exhaust is measured for HDE emission testing. Therefore, an analyzer capable of measuring N₂O from bag and from diluted sample continuously is required to support both LDV and HDE regulations.

The United States Environmental Protection Agency (EPA) has finalized a reporting rule for the Greenhouse Gases (GHGs) emissions including Nitrous Oxide (N₂O) from all sectors of the economy. In addition, EPA and the National Highway Traffic Safety Administration (NHTSA) have been working together on developing a National Program of harmonized regulations to reduce GHGs emissions and improve fuel economy of light-duty vehicles (LDV). As a consequence, the limiting value for N₂O emission from LDV is set to 0.01 g/mile. Considering this regulatory limit of N₂O emission from LDV, if the exhaust gas is diluted and stored in a sample storage bag, the concentration of N₂O becomes very low which requires a highly sensitive analyzer for accurate measurement. In the previous study, an instrument based on Quantum Cascade Mid-IR Laser (QCL-Mid IR) Spectroscopy has been developed for measuring ultra-low level of N₂O in automobile exhaust gas sampled in a sample storage bag.

An analyzer based on Quantum Cascade Laser (QCL) has been developed for chemical sensing of gaseous nitrogen compounds (NO, NO₂, N₂O and NH₃). The QCL can emit coherent lights in the Mid-infrared (Mid-IR) region where these nitrogen compounds exhibit strong absorption tendency. Therefore, it is possible to detect very low concentration gas. QCL can also give a super fine resolution of the spectrum in this region. Therefore, utilization of this spectrometer can reduce the interference caused by the spectral overlap of coexisting gases in automobile engine exhaust. In the previous study, the fundamental concept of development along with some basic performance of the analyzer had been reported. In this study, improvement of performance has been attempted. Especially, the cell design, response time of NH₃, broadening the measurement ranges, and increasing the data sampling speed have been considered.

An analyzer based on Quantum Cascade Laser (QCL) has been developed for chemical sensing of gaseous nitrogen compounds (NO, NO2, N2O and NH3). The QCL can emit lights in a mid-infrared (Mid-IR) region where these nitrogen compounds have strong absorption. This laser optics configuration can give a super fine resolution of the mid-infrared spectrum. Therefore, utilizing this spectrometer can reduce the interference caused by the spectral overlap of co-existing gases in engine exhaust. The developed analyzer has been evaluated using actual engine exhaust to confirm the influence from coexisting gases and the measurement accuracies and stabilities. Very low detection limit (less than 1 ppm) and quick response time (less than 2 sec) have been achieved even with the newly developed analyzer.

Monodisperse and polydisperse Sodium Chloride (NaCl) particles were used to calibrate the solid particle penetration for the Volatile Particle Remover (VPR) in a Horiba prototype Solid Particle Counting System (SPCS). Prior to the calibration, dilution ratios on the SPCS are verified carefully with a flame ionization analyzer (FIA). Size distributions for polydisperse aerosols upstream and downstream of the Volatile Particle Remover (VPR) were measured with a Scanning Mobility Particle Sizer (SMPS). It is found that overall penetrations for polydisperse aerosols are larger than 95%. Geometric standard deviations from the raw and the diluted by the VPR are within ±1.5% difference. Thus, shapes of size distributions aren't changed after dilution. Geometric mean diameters shift a little, on average ±5% after dilution. Therefore, the VPR doesn't change the aerosol characteristics after the aerosol is diluted and heated up to 320 °C.