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The use of portable emissions measurement systems (PEMS) for testing vehicle emissions while driving on the road has been demonstrated as early as the 1980s. Many users have taken the driving route and repeated the route in a chassis cell with the same vehicle expecting identical results. Emission results can be comparable but there are many factors that need to be considered. This study compares PEMS results for a driving route repeated across seasons and traffic conditions with a single vehicle. The ambient temperature variability and traffic is shown to cause variation in emissions for any individual run. Generating a test cycle to mimic the driving route can be done in a variety of ways. The simplest is to take an individual driving run and translate the time and speed trace directly. This does not address the statistical results from numerous driving runs on the same route.

Direct measurement of dilution air volume in a Constant Volume emission sampling system may be used to calculate tailpipe exhaust volume, and the total dilution ratio in the CVS. A Remote Mixing Tee (RMT) often includes a subsonic venturi (SSV) flowmeter in series with the dilution air duct. The venturi meter results in a flow restriction and significant pressure drop in the dilution air pipe. An ultrasonic flow meter for a similar dilution air volume offers little flow restriction and negligible pressure drop in the air duct. In this investigation, an ultrasonic flow meter (UFM) replaces the subsonic venturi in a Remote Mixing Tee. The measurement uncertainty and accuracy of the UFM is determined by comparing the real time flow rates and integrated total dilution air volume from the UFM and the dilution air SSV in the RMT. Vehicle tests include FTP and NEDC test cycles with a 3.8L V6 reference vehicle.

The application of Selective Catalytic Reduction (SCR) to control nitric oxides (NOx) in diesel engines (2010, Tier 2, Bin5) introduced significant amounts of Ammonia (NH3) and Urea to the NOx exhaust gas analyzers and sampling systems. Under some test conditions, reactions in the sampling system precipitate a white powder, which can accumulate to block sample lines, rendering the exhaust emission sampling inoperable. NOx gas analyzers used for exhaust measurement are also susceptible to precipitation within the sample path and detector components. The contamination requires immediate maintenance for powder removal to restore baseline performance. The results of experiments to eliminate the powder are presented. Analysis of the powder identifies it as ammonium nitrate (NH4NO3) and ammonium sulfate ((NH4)2SO4), which is consistent with the white crystalline precipitate.

Diesel fuel may be blended with ethanol as a bio-fuel extender. However, ethanol is not miscible with diesel fuel, so an emulsifier must be added to a diesel-ethanol blend to prevent the ethanol fraction from separating in a fuel tank. This diesel-ethanol blending and storage problem can be avoided by installing a separate ethanol fuel tank, fuel pump, and ethanol fuel injector that operate in parallel with the standard diesel fuel injection system. A Medium Duty diesel truck has been modified for blending ethanol with the standard diesel fuel consumed by the engine. The ethanol is injected into the intake air so that diesel and ethanol aerosols are blended in the engine cylinder. The ethanol injection is synchronized with the diesel fuel injection, where the proportion of ethanol to diesel fuel is constant. Vehicle tests include EPA FTP procedures on a chassis test cell dynamometer.

Solid particle emissions from a modern gasoline hybrid electrical vehicle (HEV) and a conventional gasoline vehicle were studied under diverse transient drive cycles on a chassis dynamometer. It is found that solid particle emissions from the conventional gasoline vehicle which has a 3.8-liter engine are sensitive to vehicle temperatures. Over 90% of solid particles are emitted during the first 250 seconds of transient cycles. Spikes for solid particle emissions from the HEV during a transient cycle are mainly caused by engine starts, hard accelerations after engine starts, and the engine running harder at high vehicle speeds. The engine and vehicle temperature status on the HEV doesn't show a strong correlation to the solid particle emission.

Engine testing in the United States has been updated with the new centralized testing procedure in 40 CFR 1065. This regulation introduces a variety of new checks and tests required for certification testing. Upgrading existing equipment to run these tests in some cases introduces error or does not follow the spirit of the regulation. The term “good engineering practice” is used within the regulation to insure users make decisions on differences or unclear implementation. This paper addresses some of the recommended modifications and evaluates the differences in the results with and without the modifications.

An on-board diesel particulate measurement (OBS-TRPM) instrument is developed to measure on-road exhaust PM emission at Horiba. It is used to characterize particulate matter (PM) emission from a gasoline vehicle, the 1999 Ford Windstar with California Ultra Low Emission (ULEV) certification. PM emissions from three test cycles, EPA FTP 72, SFTP-US06, and new European drive cycle (NEDC), are evaluated. It is found that the PM emission from the SFTP-US06 with the cold start is roughly two times higher than PM emissions from the cold FTP 72 and the cold NEDC. This may be due to aggressive drive patterns for the US06 while the vehicle is still cold. The aggressive drive pattern for the US06 makes the gasoline vehicle emit a much higher fraction of elemental carbon (EC), and lower fraction of organic carbon (OC). Fractions of the EC from the vehicle are 9.1% for the FTP 72, 6.3% for the NEDC, and 56.6% for the US06.

A partial-flow sampling system, namely a Bag Mini-Diluter (BMD) is an accepted alternative to Constant Volume Sampling (CVS) for obtaining mass emissions in a chassis test cell. Our equipment delivers equivalent CVS and BMD emission results with gasoline engines of 2.0 to 5.6 liter displacement. However, while testing a vehicle with a 1.3 liter engine, CVS and BMD CO2 mass differences greater than 9% were observed during cold-start tests. This paper describes the modifications made to obtain BMD and CVS mass emissions that match within 2% during cold-start tests with a 1.3 liter vehicle.

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.

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.

A new on-board portable emission measurement system (PEMS) for gaseous emissions has been designed and developed to meet CFR Part 1065 requirements. The new system consists of a heated flame ionization detector (HFID) for the measurement of total hydrocarbon, a heated chemiluminescence detector (HCLD) for the measurement of NOx, and a heated non-dispersive infra-red detector (HNDIR) for the measurement of CO and CO2. The oxygen interference and relative sensitivity of several hydrocarbon components have been optimized for the HFID. The CO2 and H2O quenching effect on the HCLD have been compensated using measured CO2 and H2O concentration. The spectral overlap and molecular interaction of H2O on the HNDIR measurement has also been compensated using an independent H2O concentration measurement. The basic performance of the new on-board emission measurement system has been verified accordingly with CFR part 1065 and all of the performances have met with CFR part 1065 requirement.

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.

This paper is a continuation [1] of the discussion of data collected during an effort in comparing on-board systems (Horiba OBS 1000 and MEMS built by West Virginia University) of Test Cell Equipment during Dynamometer runs (FTP) and on road routes (Sabraton-Bruceton Mills cycle). The OBS data in general, agreed within 6-11% of the lab equipment. In addition, data and installation experience on a heavy duty vehicle, a snow plow, will be presented.

A vehicle-mounted emissions measurement system that continuously measures CO, CO2, HC, NOx, and A/F as concentrations and also measures exhaust gas flow rate, mass emissions and fuel consumption is presented. The limitations of the accuracy and precision of the on-board emissions system are characterized using a vehicle exhaust emissions simulator. The simulator provides accurate simulated exhaust flows in the range of 10-120 SCFM. The simulator has demonstrated in tests of injected versus recovered CVS mass emissions an overall accuracy of approximately 0.5% of the requested values. The simulated exhaust tests include both fixed and transient concentrations, as well as simulations of an EPA-75 test for a typical vehicle..

Automotive emissions have been regulated to very low mass emissions. Various collection techniques have been utilized to measure the emitted gases. Some sample collection techniques utilize dilution gases that have concentrations below ambient air background values. For these applications analyzers with very low ranges have been produced. When using analyzers with ranges below 10 ppm, gas accuracy and impurities become very critical to the successful operation of these analyzers. A general demonstration of analyzer accuracy will be presented for various ranges. The availability and accuracy of the reference gases will be discussed. The relationship between the accuracy of the gas labeling and the analyzer's calibration accuracy will be evaluated. Gas delivery components can also affect the purity of zero gases and the accuracy of gas mixtures. Oxygen cleaned gas cylinder regulators will be compared to standard regulators for THC background contribution.

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.

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.