Search Results

The performance of a soft ionization mass spectrometer (MS) has been investigated using nearly one hundred hydrocarbon components and nine inorganic components. Based on a list of typical hydrocarbon emissions from automotive exhaust, synthesized samples have been used to discuss the cross-sensitivity of the target components. The system has been shown to measure hazardous air pollutants (HAPs) such as 1,3-butadiene, benzene and toluene in the vehicle exhaust. As a result, the technique will prove to be very useful in emissions monitoring in the development of low emissions vehicles.

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.

The accuracy and precision of exhaust gas mass emission measurement has recently come under close scrutiny as the absolute mass emission level has become lower. The uncertainty of the mass emission measurement can not be defined simply as it is a combination of many parameters in the measurement system. This paper lists and reviews the major factors that affect the accuracy in super-low emission measurement when using a constant volume sampler (CVS), such as analyzer performance, HC contamination, excessive dilution of sample gases, error in DF calculations and the variation of vehicle emission itself. Additionally, an alternative sampling system, using the bag mini-diluter (BMD) technique, is investigated in comparison with the enhanced CVS system, i.e. use of dilution air refiner, and heating of the whole system. Some ideas for reducing the HC contamination are also described as it is an important parameter that affects measurement accuracy in both the CVS and BMD systems.

The European Union has announced the next term emission regulations for light-duty vehicles which include particle number (PN) emission standards. The protocol for PN counting for the regulation is described in UNECE Regulation No.83. The PN counting system required for this regulation should consist of a Volatile Particle Remover (VPR) and a Condensation Particle Counter (CPC). The regulation also requires calibration of the VPR's Particle Concentration Reduction Factor (PCRF) periodically. Since the PCRF is directly used in the calculation of PN emission, an improper calibration of the factor can cause a significant error of PN emission result. This paper investigates propriety to use NaCl particles generated by atomizing method in the PCRF calibration as reference particles. As a result, it is shown that the NaCl particles can be used in PCRF calibration because of the sufficient stability when appropriate thermal treatment is applied.