Search Results

On-board Particulate Matter (PM) mass calibration (OB-PMMC) is an approach to calibrate a real-time PM sensor with the gravimetric PM mass being collected on a conventional filter. The real-time PM sensor is integrated in a PM sample system and takes sample upstream of the sample filter. The PM mass collected on the filter is determined either by weighing the filter or by using analytical approaches. A unique calibration coefficient for each sample filter is generated for converting the PM real-time signal to the real-time PM mass emission. This calibration approach can be used to modify Constant Volume Samplers (CVS) and laboratory Partial Flow Sample Systems (PFSS), etc., into real-time PM mass measurement instruments for engine or vehicle exhaust PM measurement. The same technique may also be used to measure real-time PM concentration in the atmosphere under some circumstance.

Two Euro 4 light-duty diesel vehicles were retrofitted with Diesel Particulate Filters (DPF). One was retrofitted with a low efficiency flow-through DPF. And, the other was retrofitted with a high efficiency wall-flow DPF. PM emissions from both vehicles were evaluated under the new European drive cycle (NEDC) on a chassis dynamometer. Several instruments were used to measure particulate matter (PM) emissions simultaneously from different aspects for two retrofitted vehicles. The PM mass emission from the vehicle retrofitted with the low efficiency DPF is close to 5.0 mg/km Euro 5 mass emission standard. However, the solid particle number emission is about 30 times higher than the Euro 5 solid particle number emission standard. Mass and number emissions from the vehicle retrofitted with the high efficiency DPF are well below Euro 5 emission standards.

The on-board transient response diesel particulate measurement (OBS-TRPM) instrument measures on-road vehicle particulate emissions. It is a continuation of the Horiba on-board PM sampler (OBS-PM) [5]. The OBS-TRPM measures total diesel particulate emission by collecting diesel particulate matter (PM) on a pre-weighed 47 mm filter while the partial flow sample system (OBS-PM) runs under a proportional control strategy. A real-time diffusion charge sensor (DCS) takes sample upstream of the filter, and measures diesel PM in term of particle length (mm/cm3). By integrating the DCS real-time signal during the filter sampling, the cumulative fraction of diesel PM emission is obtained. Finally, diesel PM mass emission during a specific region, for example a Not-to-Exceed (NTE) zone, is calculated from the fraction of the real-time PM signal. Thus, the OBS-TRPM provides a solution to measure PM emission in NTE zones which are defined by the US EPA.

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.

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.

The applicability of several popular diesel particulate matter (PM) measurement techniques to low temperature combustion is examined. The instruments' performance in measuring low levels of PM from advanced diesel combustion is evaluated. Preliminary emissions optimization of a high-speed light-duty diesel engine was performed for two conventional and two advanced low temperature combustion engine cases. A low PM (<0.2 g/kg_fuel) and NOx (<0.07 g/kg_fuel) advanced low temperature combustion (LTC) condition with high levels of exhaust gas recirculation (EGR) and early injection timing was chosen as a baseline. The three other cases were selected by varying engine load, injection timing, injection pressure, and EGR mass fraction. All engine conditions were run with ultra-low sulfur diesel fuel. An extensive characterization of PM from these engine operating conditions is presented.

The prototype solid particle counting system (SPCS) has been used to study solid particle emission from gasoline and diesel vehicles. As recommended by the PMP draft proposal, exhaust is diluted by a Constant Volume Sampler (CVS). The SPCS takes the sample from the CVS tunnel. Transient test cycles such as EPA FTP 75, EPA HWFET (EPA Highway Fuel Economy Cycle), and NEDC (New European Driving Cycle) were tested. The repeatability of the instrument was evaluated on the diesel vehicle for three continuous days. The instrument exhibits good repeatability. The differences for the EPA ftp 75, the EPA HWFET, and the NEDC in three continuous tests are ± 3.5%. The instrument is very sensitive as well and detects the driving differences. A large number of solid particles are found during the hard acceleration from both the gasoline and the diesel vehicles. Solid particle emissions decrease quickly at deceleration and when vehicles approach constant speed.

A prototype solid particle counting system (SPCS) has been developed in Horiba. It measures the engine exhaust solid particle number emissions in real-time. The instrument is designed to follow the recommendation in the PMP proposal for solid particle number emissions measurement on Light-duty diesel vehicles. Two wide range continuous diluters, which were developed during this project, have been used as cold and hot diluters, respectively. The accuracy of the dilution ratio is normally ± 4% for the designed range. The instrument has low particle losses, and exhibits over 95% penetration for solid particles. The new instrument has functions such as, normal measurement, dilution ratio control, daily calibration for condensation particle counter (CPC), etc. These functions have been automated to make the instrument's operation simple.

The regulated level of particulate mass for 2007 heavy duty diesel on-road engines is 0.01 g/bkhp-hr. Measurement of this low level of particulate by weighing is costly and time consuming. The weighing method must measure 100 μg or less of particulate on a filter that weighs about 100 mg with a resolution of ± 2.5 μg or better. This means that the microbalance and sampling handling procedure must be accurate within ±25 ppm by mass or ±1/40,000. It requires a microbalance with 0.1 μg precision housed in a special environment. Moreover, the weighing method involves a lengthy process. The filter must be equilibrated, and then pre- and post-weighed, usually with repeat measurements. An alternative to gravimetric analysis is a thermal mass analyzer that measures the semi-volatile organic fraction (SOF), as well as soot and sulfate fractions of the particulate matter (PM) collected on a cleaned quartz filter. The calibration of the thermal mass measurement is discussed in detail.

While developing one of the first commercialized Super Ultra Low Emission Vehicles, one vehicle manufacturer also improved the method for measuring low level hydrocarbons [1]. This was accomplished by enhancing the Constant Volume Sample System, and correcting hydrocarbon measurements from the Flame Ionization Detector hydrocarbon analyzer for the effect of oxygen quench. Based on the manufacturer's results, it appears that the variation in oxygen content of the calibration gas, span gas, zero gas, and sample gas can affect the accuracy of low level hydrocarbon measurement. Within the last couple of years, the United States Environmental Protection Agency and the California Air Resources Board approved the Bag Mini Diluter method for emission sampling [2,3]. This method was developed by the American auto industry in cooperation with government agencies within the American Industry/Government Emissions Research Consortium.

With the need for emission measurements of super ultra low emission vehicles (SULEV), analyzer manufacturers have been required to produce more precise and accurate analyzers. In order to compare analyzers, the customer must understand the different specifications used by the analyzer manufacturers. One specification that some manufacturers have used is the limit of detection (LOD) to indicate the reliability of the analyzer output at low concentrations. There are various methods for determining the LOD for a given analyzer. The authors will demonstrate how variations in methodology can produce different LOD values for a specific analyzer and what it means for the automotive emission analyzers. It is also demonstrated that the standard deviations of a zero signal, which is related to LOD, can be heavily influenced by data processing, such as data length in use and/or data smoothing. The LOD values obtained will be compared to the limit of quantification (LOQ) for that analyzer.

For the past several years, manufacturers have been developing emission measurement systems for Super Ultra Low Emission (SULEV) measurements. The Bag Mini-Diluter (BMD) with an advanced exhaust flow measurement device is designed as an alternative to the traditional method for sampling vehicle exhaust, the constant volume sampler (CVS). Exhaust sampling instruments require system verification tests. The system verification test described and mandated for the CVS in the Code of Federal Regulations (CFR) §86.119-90(c) is a simulated test with propane. The very low concentration measurements required for SULEV regulations demand a more enhanced and accurate verification technique and procedure than the method described in the CFR. This investigation focuses on the technique and necessary equipment for verifying system integrity of the entire emission sampling system, including the Bag Mini-Diluter and the exhaust flow measurement device in the test cell.

The Vehicle Exhaust Emissions Simulator was developed to evaluate the performance of vehicle emissions sampling and analytical systems. The simulator produces a representative tailpipe volume flow rate containing up to five emission constituents, injected via mass flow controllers (MFCs). Eliminating the variability of test results associated with the vehicle, driver, and dynamometer makes the simulator an ideal quality control tool for use in commissioning new test cells, checking data correlation between test cells, and evaluating overall system performance. Earlier vehicle emissions simulators being used in the industry were primarily for checking Constant Volume Samplers (CVSs) and Bag Benches but they did not have the ability to properly simulate tailpipe volume.

As automakers begin to develop and certify vehicles that meet the California Air Resources Board LEV II and Environmental Protection Agency Tier II Regulations, emissions test cells must be designed and implemented that are capable of accurate low-level measurements. A new test cell has been installed at Ford Motor Company for use in testing vehicles that meet the stringent Partial Zero Emission Vehicle tailpipe requirements (NMOG = 10 mg/mile, NOx = 20 mg/mile). This test cell includes a redesigned Bag Mini-Diluter (BMD), improved analytical benches, an ultrasonic exhaust flow meter with an integrated tailpipe pressure control system, a conventional constant volume sampler (CVS), and a moveable electric dynamometer. The Bag Mini-Diluter will be used as the primary sampling system for the tailpipe measurements. The moveable electric dynamometer enables the test cell to be configured so that the vehicle is moved to the test equipment rather than moving the test equipment to the vehicle.

As automakers begin to develop and certify vehicles that meet the California Air Resources Board LEV II and Environmental Protection Agency Tier II Regulations, the study/usage of the Bag Mini-Diluter (BMD, or Mini-Diluter) sampling system continues to increase. Previous papers have provided an overview of the BMD and compared the measurements from the BMD to the measurements from a traditional constant volume sampler (CVS). These papers have suggested that the BMD approach offers new opportunities to improve the quality of vehicle exhaust measurement at very low levels, which will be crucial for accurate measurements on vehicles meeting LEV II SULEV standards (NMOG = 10 mg/mile, NOx = 20 mg/mile). This paper continues the effort to study and implement the BMD sampling system as the optimal sampling system for SULEV measurements. Based on the results from previous testing, a number of investigations have been initiated to improve the quality and understanding of BMD measurements.

The Bag Mini-diluter (BMD) is a proportional exhaust sampling system that is being studied as an improved measurement system for ultra-low level vehicle exhaust emissions. The traditional method for sampling vehicle exhaust has been the constant volume sampler (CVS) technique. This method dilutes the entire exhaust output from the vehicle, meters the mixture, and then takes a proportional sample for measurement. In contrast, the Mini-diluter sampling method meters a small sample of raw exhaust, and then dilutes this sample to a fixed dilution ratio. This approach offers new opportunities to improve the quality of the sample measurement at very low levels, which will be crucial for accurate vehicle exhaust emission measurements on vehicles that meet the ULEV and SULEV standards. A number of test programs have compared the performance of the Mini-diluter to the CVS on vehicles certified to Tier 1 and LEV standards, and the results demonstrated favorable correlation.

The traditional method for sampling vehicle exhaust has been the constant volume sampler (CVS) technique as described in the Code of Federal Regulations (CFR). This method dilutes the entire exhaust output from the vehicle, meters the mixture, and takes a proportional sample for measurement. The Mini-diluter sampling method reverses this process by first metering a small sample and then diluting to a fixed dilution ratio. This approach offers new opportunities to improve the quality of the sample measurement. This is especially interesting considering the lower emissions levels from ULEVs. The usefulness of this idea will depend on the development of stable and repeatable devices to implement it. This paper describes the operation of and presents results from a Mini-dilution system that uses critical flow venturis to provide a stable and repeatable dilution.