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Solid Particles

Physico-chemical study of solid particles formation
and their evolution in the exhaust line vehicles:

Modeling and Experimentation
Dr. Nguyen Thi Thanh Xuan

For vehicle emissions,  particles are shown to harm the health. Indeed, the fine particles with size lower than 2,5 µm are likely to penetrate deeply in the respiratory system and to release toxic products. The vehicle manufacturers and the oil companies need precise information concerning particle formation and prediction. Developing computer code is really essential. The size distribution emitted by the vehicles is particularly studied; however, the used methodologies, the tested vehicles and the operating conditions are so different from one study to another, that is very difficult to compare the results. Certain assumptions were advanced concerning particle formation, the nucleation (conversion gas-liquid) of the sulphuric acid-water mixture could be an important process, without excluding the participation of some hydrocarbons.


A simulation model has been developed, taking into account the various phenomena induced in the particle formation: nucleation, growth by condensation, coagulation etc. as well as the variations in temperatures and concentrations along the exhaust line and the sample line (dilution, catalyst, filter particles). We have demonstrated that liquid aerosols could only appear after dilution of the exhaust gas. This model was validated, successfully, by comparison with the results of measurement campaign. The sensitivity studies allow to evaluate the influence of the parameters "fuel" (sulphur content), "motor" (speed, fuel consumption,…), and "conditions of measurements" (temperature, dilution ratio, humidity, residence time,…). This thesis work has increase our knowledge to better interpret results of particle measurements, to give true information to legislators, to predict vehicle emissions and to  propose possible future standards.

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