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Supersonic jet / resonance enhanced multi-photon ionization (Jet-REMPI) technique was focused on the analyzing method for gas mixture like exhaust gas from automobiles. In this method, when the mass number and wavelength of excitation laser are determined adequately, the target compound can be monitored selectively. We developed a new analyzer utilizing REMPI method. Using this analyzer, real-time monitoring of exhaust gas from a motorcycle and diesel vehicles was conducted. As a result of real-time monitoring test of the vehicles, concentrations of aromatic compounds like benzene toluene etc. were quantified and real-time changes of their concentrations were observed.

Real-time analysis of benzene in automobile exhaust gas was performed using the Jet-REMPI (supersonic jet / resonance enhanced multi-photon ionization) method. Real-time benzene concentration of two diesel trucks and one gasoline vehicle driving in Japanese driving modes were observed under ppm level at 1 s intervals. As a result, it became obvious that there were many differences in their emission tendencies, because of their car types, driving conditions, and catalyst conditions. In two diesel vehicle, benzene emission tendencies were opposite. And, in a gasoline vehicle, emission pattern were different between hot and cold conditions due to the catalyst conditions.

Recently, particulate matter (PM) emission from internal combustion engines, especially particles having the diameter of less than 100 nm (Nano-particles) are being considered for their potential hazards posed to human health and the environment. Nano-particles are unstable and easily influenced by the conditions of engine operation and measurement techniques. In this study, the influences of cooling and dilution processes on nano- particles are presented to understand the generation and dilution mechanisms, and to further development of an accurate measurement method. It is found that the thermo-dilurter is necessary for measuring the nano-particles with higher accuracy. Accurate measurement of nano-particles requires immediate dilution of the exhaust gases by hot air.

The authors have developed a new partial flow dilution tunnel (hereafter referred to as PPFT), whose principal device is a flux splitting gas divider, as a new means of measuring particulate emissions which can be applied to transient cycle testing of diesel engines. The advantage of this system is that it can achieve perfect constant velocity splitting by means of its structure, and theoretically can also maintain high splitting performance despite fluctuations in the exhaust flow rate, including those due to engine exhaust pulsation. We compared this system with a full tunnel by analyzing the basic performance of the system and measuring particulate matter (PM) using an actual vehicle engine.

The use of a Thermo-Denuder (TD) is proposed to suppress the nano-particle measurement fluctuations caused by the volatile components in the available techniques. The problems encountered during the use of thermo-denuder for nano-particle measurement and their respective solutions are suggested. The behavior of nano-particles in the TD itself is not clearly understood but the thermo-denuder influences both the volatile and solid particles. As a first report, only the effect of TD dimension on solid nano-particle measurements is presented. It is concluded that the TD influences the nano-particles i.e. loss of particles occurs even the sample gas contains no volatile fractions. A sharp temperature gradient between the low temperature wall of the absorption part of TD and hot sample gas causes particle losses due to thermophoresis effect. Especially the smaller particles are affected significantly.

Conditioning of diluted exhaust gas by Thermo-Conditioner prior to measurement has been proposed by the GRPE/PMP Research Council of the United Nation in order to achieve stability in nano-particle measurement. In this study the effect of thermo-conditioner on the thermo-physical behavior of nano-particle under different conditions have been clarified. Stability in measurement was also attempted depending on the characteristics of nano-particles. Quality of the raw exhaust gas, the dilution ratio and temperature, and the thermal conditioning temperature were considered as the main parameters. Exhaust gas from a medium duty DI diesel engine was used for analysis. Scanning Mobility Particle Sizer was used for measuring the concentration of nano-particles. It was concluded that the concentration of nuclei-mode particles within the size range of 15∼30 nm are significantly influenced by the thermal conditioning temperature.