True density of soot particles: A comparison of results highlighting the influence of the organic contents

International audienc

Development of a portable reference aerosol generator (PRAG) for calibration of particle mass concentration measurements

International audienceThe tapered element oscillating microbalance with filter dynamics measurement system (TEOM-FDMS) is an instrument commonly employed by the French air quality monitoring network. This instrument is currently calibrated with calibration weights traceable to SI but having value and mass differences between each of them that are not representative of real atmospheric particle mass measurements. Moreover, these calibration weights do not allow detection of any technical problems associated with either the TEOM-FDMS sampling system upstream of the mass measurement or the intrinsic TEOM-FDMS filtration system. Therefore, a calibration method was developed using a portable reference aerosol generator (PRAG) that produces known and stable particle mass concentrations over time. Here, we present the characterization of the PRAG system in terms of a reference range of particle masses between 30 ± 10 and 3456 ± 83 μg at three sampling times. Its coupling with the TEOM-FDMS and a global comparison between the defined reference range of particle masses and the measured masses obtained with each TEOM-FDMS implicated in this study are also presented. © 2017 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Science

Characterization of aerosols generated from nine nanomaterial powders reliability with regard to in vivo inhalation toxicology studies

International audienceIn experimental toxicology, when simulating human exposure to aerosols in the working environment, inhalation is the route of administration of choice for evaluating the toxicity of a given material (in aerosol form) in animals. In this context, this work aimed to contribute to the establishment of recommendations concerning the characterization of aerosol tests in inhalation toxicology studies. In particular, the work consisted of experimentally characterizing test aerosols using a given generation method to be used for inhalation toxicology studies. Nine nanomaterial powders have been investigated (four types of TiO2, two types of SiO2, ZnO, CeO, and BaSO4). The aerosols produced cover the particle size range from a few tens of nanometers up to several micrometers and are mainly composed of aggregates and/or agglomerates. The work carried out shows that generation and characterization of test aerosols for inhalation toxicology studies is a complex but essential element of inhalation studies, for which the conditions required (stability, repeatability, level of concentration) are sometimes difficult to obtain. Moreover, this study highlights the necessity to carry out preliminary tests to ascertain the performances of the chosen devices and their suitability for inhalation toxicology. © 2018, Springer Nature B.V

Airflow and particle transport simulations for predicting permeability and aerosol filtration efficiency in fibrous media

International audienceIn this work, synchrotron X-ray microtomography was used to produce high spatial resolution images of two kinds of binderless and monodisperse fibrous filter media, made of fiberglass and sintered stainless steel respectively. Representative computational domains were created based on these images. Both flow and collection efficiency simulations were then carried out using the flow and particle transport modules of the GeoDict® code. An image analysis program based on Matlab® was used to determine the structural properties of the computational domain, namely the thickness, the solid volume fraction and the fiber size distribution. In parallel, permeability and collection efficiency measurements were performed on the same media, to provide an experimental comparison. Very good agreement was found between the experimental and the simulated permeability values. We showed that, in order to compare collection efficiency from experiments with those simulated with GeoDict®, it was necessary to take into account the difference between the thickness of the fibrous structures that were used to create the calculation domain, and the averaged experimental thickness characterized by SEM. Using this way of comparison, we obtained the first experimental validation of the GeoDict® code on both permeability and efficiency aspects for aerosols filtration. © 2017 Elsevier Lt

Specific surface area of fire emitted particles: impact of primary particle diameter and organic content

International audienc

Specific surface area of fire emitted particles: impact of primary particle diameter and organic content

International audienc

Specific surface area of fire emitted particles: impact of primary particle diameter and organic content

International audienc

Influence of Pleat Deformation on Pressure Drop for a High-Efficiency Particulate Air Filter: A Small-Scale Experimental Approach

International audienceFor industrial or domestic applications, the wide range of use of pleated filters makes the understanding of their airflow behavior a major issue for designer and users. In all industrial installations dealing with radioactive matter, the containment of pollutants must be ensured. High-efficiency particulate air (HEPA) filters are used as the last purification stage before the air is rejected in the environment. These filters can be used either alone, in the case of nonsensible installation, or coupled with other filtration devices disposer before it where contamination level could be important. The prediction of their pressure drop is very important in nuclear safety to be able to anticipate any dysfunction or rupture of these devices. It has been observed that geometry of the medium has an influence on the pressure drop of a pleated filter. In the case of HEPA filters, no convincing explanation has been brought to explain their airflow behavior. The pressure drop evolution of the filtre during the clogging remains difficult to explain by assuming constant pleat geometry. Some studies show that deformation occurs during the filter use, which could induce an increaseof the available volume in the pleat and a reduction of the efficient filtration surface. The increase in computation capacity introduces nowadays the possibility to perform complex simulation, taking into account the effect of fluids on sensible devices. This can be the case for simple structural analysis or for more complex analysis such as vibration induced by gas or fluid flow. It is mostly applied to avoid breaking or deformation of safety devices,and this can also be applied to anticipate the fluid behavior of some special devices such as filters. In classical filtration application, properties of the filter are coupled with particle deposition (e.g., changes in geometry and permeability depend on the thickness of the deposit). The studies concerning mechanical properties of filters are mainly perfore for liquid filtration and clean filters. For pleated filters, the complexity of this kind of analysisremains the modification of the link between geometry, pressure drop, mechanical strength, and particle transport and accumulation inside the pleat. As a first approach, it has been chosen to combine an experimental and a numerical approach to improve the understanding of filter behavior. In this paper, the pleat deformation will be investigated using a direct nonintrusive laser measurement performed on a single pleat experiment.The rate of filtration surface lost will be estimated using these data and taken into account to evaluate the pressure drop against the filtration velocity. Results obtained show that the pleat deformation is an important parameter, which influences the geometry of the pleat

True density of soot particles: A comparison of results highlighting the influence of the organic contents

International audienc

True density of combustion emitted particles: A comparison of results highlighting the influence of the organic contents

International audienc