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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.

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.

Two new techniques have been applied to FTIR emission analysis which add significant potential to automotive emission measurement. One of these is the use of the mathematical multivariate analysis which is called the partial least squares method. This spectrum discrimination technique, in combination with high resolution spectrum data, enables superior analysis for heavy-overlapping species in the emission. The other technique is a flow conditioned gas sampling cell which is designed especially for real time emission measurement. The flow in the gas cell has been analyzed with computer simulation and the gas cell has a flow conditioner inside with a 10 meter optical path. Seven seconds of 90 percent gas replacement time can be achieved with this cell. As a result, highly accurate realtime data can be obtained with relatively fast response. In this paper, spectrum factors extracted from overlapping species and quantification simulations are shown using standard gases.

An approach for raw exhaust gas sampling, different from the conventional diluted exhaust gas sampling method, has been adopted for a solid particle counting system developed in the previous study. The system has been applied for evaluating solid particle emission from a DI diesel engine with DPF. In addition the filtration efficiency of the DPF has been tested from the real time concentrations, measured at upstream and downstream of the DPF. High accuracy and stability of measurement of the system against high exhaust gas pressure condition have been confirmed. The system response satisfies the requirement of ISO 8178-11. Excellent correlation of direct sampling and diluted gas sampling has been achieved with this system. It is found that the filtration efficiency changes during the engine test cycle and is strongly affected by the pre-conditioning of DPF.

A high speed gas chromatography system has been developed for automotive emissions measurement. The system is capable of quantifying hydrocarbons from C2 to C12 compounds. The separation time required for an analysis is only five minutes. Major technical challenges were (1) tandem quick heat cold traps, (2) four parallel ovens design, and (3) the mid-point back flush technique. Demonstrations of the system have been done using FTP75 cold transient phase. The results indicate that the system is well suited for hydrocarbon speciation measurement with very simple and quick operations.

Investigation of operating parameters have been carried out for an FTIR system dedicated for emission analysis. Discussions are focused on the key parameters, such as spectral resolution, gas cell dimensions, quantification algorithm, and sample gas treatment. The spectral resolution has to be determined so that the scan rate is high enough to make transient analysis, the minimum detection limit is low enough to carry out high sensitivity measurement, and no cross sensitivity can be recognized. A trade-off relationship between the response and the sensitivity exists for the gas cell design. Small volume of the cell is desirable when gas replacement is considered. On the other hand, the sensitivity can be increased by enlarging the cell volume to obtain long optical path. Both quantification algorithm and the sample gas treatment have to be well arranged to obtain accurate concentration values of the gas compounds sampled from the tailpipe.

A detailed description of flow rate measurement technique for automotive exhaust is presented. The system consists of a sector field mass spectrometer for continuous analysis of helium concentration in the exhaust gas and a mass flow controller which injects pure helium at a constant rate into the intake manifold of an engine. The exhaust flow rate can be calculated by helium injection flow rate dividing by the concentration since the concentration value is a measure of the ratio of helium dilution taking place in the engine. The advantages of the technique consist of (1) no disturbance from strong pulsed flow present when an engine is idling, (2) easy time alignment with gas analyzers, and (3) measurement of dry based flow rate that can be directly multiplied by dry based gas concentration to obtain mass emission rate.

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.

This report describes a new, maintenance-free exhaust gas analysis system for automobile quality control. It incorporates non-dispersive infrared. (NDIR) gas analyzers employing a cross-flow modulation method which provides virtually drift-free performance and eliminates the need for optical adjustment, Analyzer modulation is by means of alternating the flow of sample gas and reference gas into two cells with a rotary valve of simple construction. Microcomputers are used for system control and to process the data. This system measures oxides of nitrogen (NOx), total hydrocarbon (THC) and carbon monoxide/dioxide (CO/CO2) with three analyzers. Full scale ranges of 50 ppm for NOx and 20 ppm for THC are feasible with cells merely 35 mm long. In each case the signal-to-noise ratio is 100. In actual operation, the system drift was so low that it required no span calibration over a period of three months.

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.