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The subject of engine emissions is expected to be at the forefront of environmental regulations and consumers’ concerns for years to come. As technology develops to comply with new and different requirements in various regions of the world, understanding the fundamental principles of how engine emissions occur, and how they can be properly measured, is vitally important. Engine Emissions Measurement Handbook, developed and co-authored by HORIBA Automotive Test Systems team addresses the main aspects of this subject. Written with the technical user in mind, this title is a must-have for those involved in engine development and testing, and environmental researchers focusing on better ways to minimize emissions pollution.

Fuel efficiency is one of the most important parameters in advanced vehicles. Therefore, the measurement of fuel consumption in-situ and in real-time is obviously demanded in development and evaluation processes of new engines and vehicles. This paper describes a new concept for measuring fuel consumption in real-time, which utilizing raw exhaust gas flow rate and exhaust air-to-fuel ratio (AFR). The AFR is defined as the mass ratio of air and fuel supplied to the engine, and the mass flow rate of exhaust gas can be regarded as the summation of the mass flow rate of air and fuel. This means the fuel consumption can be calculated from exhaust flow rate and AFR. To realize in-situ, real-time measurement, we used an ultrasonic exhaust flow meter which can measure a wide flow range accurately with no pressure loss, and a fast response zirconia sensor which can be installed onto the exhaust pipe directly without any sampling system.

A Solid Particle Counting System (SPCS) has been developed according to the ECE draft regulation proposed by the particle measurement program (PMP). In the previous report the basic performance of the SPCS has been mentioned in detail [1, 2, 3, 4, 5 and 6]. It has been reported that the SPCS demonstrates very stable dilution of sample with air and the error of real time dilution factor is less than 6% up to the total dilution factor of 1000. Penetration of solid particles through the SPCS is over 95% and volatile particles removal efficiency is over 99%. In this study the SPCS has been used to investigate the soot emission behavior from different vehicles with different after-treatment technologies. Direct injection (DI) diesel vehicles without diesel particulate filter (DPF), and with different DPFs (catalyzed and non-catalyzed) have been tested. Direct injection gasoline (DIG) vehicle with oxidation and NOx reduction catalysts have also been tested.

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.

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.

Measurements of soot and SOF emitting from automobile engines by conventional gravimetric method and soxhlet extraction method are difficult and time-consuming processes. The composition in the filter substrate may change during time-consuming analysis. Therefore an accurate and real time measurement method for particulate matter is the key demand for automobile industry. This paper describes a new concept for analyzing PM, which includes measurement of soot and SOF separately, as well as the total PM emission from automobile engine continuously. The concept comprises of the real-time measurement of soot emission with a diffusion charger (DC) combined with a specific dilution system. A differential flame ionization detector with separate sample line temperatures (47°C and 191°C), have been applied for the SOF measurement. The total PM is then expressed as the sum of soot and SOF mass.

In response to the appearance of formal regulations, CFR part 1065 subpart J, a new in-use emission measurement system was developed, the OBS 2000. The OBS 2200 uses partial-vacuum analyzers. The heated flame ionization detector (HFID), heated chemiluminescence detector (HCLD) and heated non-dispersive infrared analyzer (HNDIR) are all upstream of the sample pump. This design decreases the response time of the analyzers, lowers power consumption and minimizes the overall dimensions of the system by avoiding the use of a heated sample pump. The size of the heated zones is also minimized to reduce power usage. Typical power consumption of analyzer unit is less than 500 W. The overall dimension of the main unit is 350mm (W) × 330mm (H) × 500mm (D). Analyzer linearity checks as required by new regulations [1] for all available ranges will be presented along with cut point accuracies relative to full scale and percentage of point.

A sulfur analyzer utilizing an ultraviolet fluorescent (UVF) detector has been developed to measure sulfur components in vehicle emissions. Generally, it is considered that an UVF detector cannot be used to measure sulfur components in vehicle emission due to a significant interference from NO in sample gases. In this study, an O3 injection technique has been developed to eliminate NO interference. Using this technique, the interference from NO has been reduced to less than 0.01 ppm with 3000 ppm NO. These result show a capability of utilizing UVF with this O3 injection technique to measure sulfur components in vehicle emissions including emissions with high concentrations of NO. An oxidation catalyst has also been evaluated to measure total reduced sulfur, TRS.

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.

Continuous measurement of dilute exhaust gas from the CVS system, which provides gas concentrations proportional to the mass of emissions, is widely used for modal mass analysis of exhaust emission. Recently, exhaust gas flow rate measurement devices have become commercially available. Cost-effective raw exhaust modal mass analysis will be feasible with a combination of the new exhaust gas flow meters and fast response gas analyzers. In this paper, the benefits of raw exhaust modal mass measurement and the impacts of response time for the gas analyzer on the accuracy of exhaust mass calculations are discussed. Gas analyzer system with enhanced speed of response has been developed by hardware modification applied to the existing conventional bench system. De-convolution or inverse digital filter techniques that compensate the delay in the exhaust sampling system and the gas analyzer are described with comparisons to the hardware modifications.

Fuel cell is one of the promising candidates for low emission and high efficiency power plant for the next generation vehicles. Currently, general discussions are focused on from where and how to supply hydrogen to the fuel cell stack in a vehicle. Two major concepts are presented; (1) storing pure hydrogen on-board and (2) use of hydrocarbon as a fuel in combination with on-board fuel reformer system to extract hydrogen. Although the reformer idea seems to be rather complicated than the pure hydrogen, the fuel reformer system is very much demanded, due to the energy density of liquid fossil fuel and availability of fuel supply infrastructure. In the development of the fuel reformer system, gas composition measurements are required to achieve (1) efficient hydrogen extraction, (2) low carbon monoxide concentration to protect PEM stack, and (3) low emission.

Due to a need for a robust measurement system for on-board real-world vehicle emission measurement, a heated ND-IR(h-NDIR) technique has been developed and evaluated for its potential. The h-NDIR is capable of measuring CO and CO2 under wet-based condition by correcting interference from co-existing gas with an algorithm specially developed for the present study. The resulting H2O interference to the CO2 measurement is less than 0.01vol% for zero point and less than ±1% for span points and that of CO measurement is less than 0.001vol% for zero point and less than ±2% for span point against 0 to12vol% H2O. An on-board emission measurement system using the h-NDIR in combination with an Annubar® flow meter and an air to fuel ratio sensor has been evaluated. The result reveal correlation between the present system and a chassis test system to be within 7% for fuel consumption, within 5% for CO mass emission, and within 6% for CO2 mass emission.

A new hydrogen analyzer using a magnetic sector mass spectrometer (MS) has been developed to perform continuous analysis of hydrogen gas concentrations in exhaust gas. This method is insensitive to substances other than hydrogen gas ions and so is not easily affected by the presence of other molecules. In addition, this analyzer has a fast response compared to conventional hydrogen analyzers, which employ other measurement principles. The T90 response time is about 1 second. The minimum sensitivity is few tens of ppm. Because of these characteristics, the sector MS method has significant potential for analyzing hydrogen concentrations in exhaust gas continuously. In this study, the authors performed continuous emissions measurement of several kinds of gasoline engine vehicle in a chassis test cell using the hydrogen gas analyzer in combination with other gas analyzers.

For the purposes of environmental protection, regulations of particulate matter are becoming more stringent year by year. Accordingly, engine systems have been improved and particulate emissions are much lower compared to those of previous engine systems. The automotive industry generally uses a gravimetric method to quantify particulate emissions. It is becoming increasingly difficult to quantify particulate emissions using a conventional gravimetric balance because the amount of particulates continues to decline. In order to overcome this problem, a new method has been developed that uses gas analyzers to measure potentially as much as several micrograms of particulates. Furthermore, with this method, it is possible to simultaneously analyze volatile organic fraction (VOF), soot, and sulfates. The particles collected by a quartz filter are placed in a furnace at a specific temperature, and VOF and sulfates are vaporized in an inert atmosphere.

In previous multi-dimensional modeling on spray dynamics and vapor formation, single component fuel with pure substance has been analyzed to assess the mixture formation. Then it should be expected that the evaporation process could be performed for the multicomponent fuel such as actual Gasoline and Diesel gas oil. In this study, vapor-liquid equilibrium prediction was conducted for multicomponent fuels such as 3 and 10 components mixed solution with ideal solution analysis and non-ideal solution analysis. And the computation of distillation characteristics was conducted for the steady state fuel condition fuel condition to understand the evaporation process. As a result, calculated distillation characteristics are consistent well with experiment results. And the evaporation process of a multicomponent droplet in the combustion chamber has been calculated with the variation of ambient pressure and temperature.

Numerical models of three kinds of mass emission measurement systems, i.e. the constant volume sampler (CVS) system, the mini-diluter system and the direct modal-mass measurement system have been built on PC using a software called Mathematica®. The models are capable of simulating gas compounds concentration in the CVS bags and mass emitted during a test, using the time trend exhaust emission patterns, the exhaust gas flow rate pattern, and initial setting values like dilution ratio. Major error factors in the measurement systems, such as H2O condensation, gas compounds present in ambient air, delay and smoothing of the gas stream, and performance of the analyzers, can also be introduced to the calculation. Using the models, various techniques to optimize the sampling system are quantitatively compared.