Electric aerosol spectrometry

http://www.ester.ee/record=b4294315*es

Calibration of PMP Condensation Particle Number Counters - Effect of Material on Linearity and Counting Efficiency

Recently the particle number method was proposed to the light duty regulation, so the proper calibration of Particle Number Counters (PNCs) will be very important. Calibration includes the linearity measurement and the counting efficiency measurement. Labs will have to demonstrate compliance of their PNCs with a traceable standard within a 12 month period prior to the emissions test. Compliance can be demonstrated by: -Primary method: By comparison of the response of the PNC under calibration with that of a calibrated aerosol electrometer when simultaneously sampling electrostatically classified calibration particles, or -Secondary method: By comparison of the response of the PNC under calibration with that of a second PNC which has been directly calibrated by the above method. Compliance testing includes linearity and detection efficiency with particles of 23 nm electrical mobility diameter. A check of the counting efficiency with 41 nm particles is not required. A workshop was organised to investigate the effect of the material on the calibration procedures and the uncertainties of the suggested procedure. GRIMM and TSI provided PNCs and AEA, MATTER, GRIMM, TSI provided five particle generators. The experiments were conducted in the European¿s Commissions laboratories (JRC). Heavy duty diesel engine (w/o aftertreatment) particles were also produced (measurements downstream a thermodenuder) at idle and a medium load mode. The measured data were evaluated by JRC. The results showed that there was an effect of the material used and suggestions were given. In addition the uncertainties of the procedure were quantified. Theoretical calculations showed the corrections that should be applied.JRC.H.4-Transport and air qualit

Design and evaluation of a thermal precipitation aerosol electrometer (TPAE)

A new aerosol electrometer (AE), the thermal precipitation aerosol electrometer (TPAE), was designed for use with particles of sizes less than 300 nm, and its performance was experimentally evaluated. The TPAE combines the thermal precipitator with a microcurrent measurement circuit board (i.e., pre-amplifier) for measuring the current carried by collected particles. The thermal precipitator is in the disk-to-disk configuration. Heating paste and air cooling were adopted to establish the desired temperature gradient in the precipitation chamber. At a sample flow rate of 0.3 L min−1 and a temperature gradient of 264 K cm−1, the precipitation efficiency of 70 nm particles reaches ∼100 %. The measurement range of the designed aerosol electrometer is ±5×105 fA, and the accuracy is ±2 fA (2500 to 6.25×107 cm−3 using a flow rate of 0.3 L min−1 and assuming that only singly charged particles exist in the sample). During the evaluation process, the electrical performance of the TPAE was first tested using sodium chloride (NaCl) and soot particles previously classified by a differential mobility analyzer (DMA) and compared to the reference. The precipitation performance of the TPAE was then characterized as functions of the temperature gradient, sampling flow rate and particle size. It was shown that the particle collection efficiency of the built-in thermal precipitator is inversely proportional to the sampling flow rate and proportional to the temperature gradient. The effect of particle size on the particle collection efficiency was minor for NaCl particles of sizes between 23 and 200 nm. Unlike that which was observed for the NaCl particles, a slightly positive correlation between the collection efficiency and the mobility size for soot particles (in the size range of 30–160 nm) was observed. This observation might be due to the existence of soot agglomerates. Compared to existing electrometers, the TPAE does not require the use of high-efficiency filters and includes the additional feature of the “soft” collection of particles for offline particle characterization as well as aerosol current measurement.</p

Wet electrostatic scrubbing for high efficiency submicron particle capture

Exposure to fine particulate matter has been associated with serious health effects, including respiratory and cardiovascular disease, and mortality. Very fine inhalable particles can remain suspended in the atmosphere for a long time, travel long distances from the emitting sources and, once inhaled, they can reach the deepest regions of the lungs and even enter in the circulatory system. Therefore, the smaller the particle size, the higher its toxicity. In typical combustion units used in process industry, the end-of-pipe technologies include trains of consecutive abatements devices. Nevertheless, the traditional particle abatement devices are mainly designed and optimized to treat particles with sizes above or around 1µm, and they are far less effective towards the submicron dimensions. Among the end-of-pipe technologies, the Wet Scrubbers (WS) are widely utilized in industry due to their capacity to capture simultaneously gaseous pollutants and particles. The main particle collection mechanisms involved in WS are those related to directional interception and inertial impact, which allow high particle abatement efficiency for particles in micrometric range. Both the mechanisms are instead ineffective in the submicron range, thus resulting in low collection efficiencies. It the past 40 years, it was demonstrated that the presence of electric charge of opposite polarities on the particles and the sprayed droplets can increase the capture efficiency due to Coulomb forces between the two phases. The presence of this additional contribution in a scrubber is an upgrade of the traditional wet scrubbing and the new process is commonly referred as Wet Electrostatic Scrubbing (WES). Experimental investigation of the pertinent literature confirmed the ability of WES to increase the particle capture efficiency respect to the classic wet scrubber, but submicron range is generally not directly investigated so that the best operating conditions to increase submicron particle abatement efficiency is still an unsolved problem. This optimization problem is mainly related to the difficulties to model wet electrostatic scrubbing process due to the high number of the variables involved, resulting in a complex experimental evaluation of the main collection mechanisms that are responsible of the particle capture. Above all, a significant hindrance to the assessment of a proper description of wet electrostatic scrubbing is the complexity of the electro-hydrodynamics of the charged water spray. In this work, a new experimental methodology was adopted to perform experiments in controlled conditions in order to allow an easier investigation of the effects of the main physical variables on the abatement of submicron particles emission. This experimental approach is based on the use of a lab scale batch reactor, in which charged particles produced by combustion are inserted. In the reactor, a train of uniform droplet size and charge is used to remove the suspended particles. This approach has the main advantages to make possible to investigate specific parameters (like the effect of droplet charge or its size) under well-defined conditions and therefore model the particle abatement process. Therefore, the objective of this work is the experimental analysis and the modeling of wet electrostatic scrubbing process for submicron particles with the new methodology developed and the evaluation of the influence of the main physical variables on the capture of submicron particles. The results obtained confirm that the particle abatement is significantly enhanced by charging both particles and droplets, and that the particle abatement rate is directly proportional to the particles and droplet charges and droplet concentration. Furthermore, tests with uncharged particles and charged droplets do not show any relevant increase in the scrubbing efficiency with respect to common wet scrubbing in the investigated conditions. The experimental results obtained were compared with the predictions of classical particle scavenging models valid for ambient temperature and humidity conditions. These models were rarely applied to submicron particles and found a reliable experimental support from the performed experiments. On the other hand, this comparison also confirm the reliability of the experimental methodology in the study of wet electrostatic scrubbing and encourage the development of further tests in experimental conditions more similar to that of industrial scrubbers

Air pollution monitoring instrumentation A survey

Air pollution monitoring instrumentation developed for aerospace uses surveyed for industrial application

Investigation of bipolar charge distribution of pharmaceutical dry powder aerosols using the phase doppler anemometry system

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London.Electrostatic properties of formulation component materials and blends play an important role in dry powder inhalation (DPI) products, and that valid measurement of charge distribution will lead to more precise control of powder behavior in DPI manufacturing processes. Ultra-fine powders are known to be bipolarly charged, have non-spherical shapes and tend to be highly cohesive. Real time, non-invasive techniques need to be developed to obtain a precise and accurate time-history characteristic of electrically charged powders as they aerosolize from a DPI product, and how this measure relates to materials behavior throughout the various steps of a manufacturing process i.e. from drug micronisation, blending with lactose, through to filling dose units. A novel non-invasive technique for simultaneous measurement of size and charge of pharmaceutical powders is considered which employs the Phase Doppler Anemometry (PDA) system. Previous research demonstrated the advantages of this technique in measuring the bipolar charge distribution on a population of particles. These findings led to significant improvements in understanding performance of dry powder formulations, manufacturing processes and development of new platforms for inhaled drug delivery. The main aim of this research is to perform an investigation of electrostatic propertiesof pharmaceutical dry aerosols using the PDA system. The PDA technique was used to track the motion of charged particles in the presence of an electric field. The magnitude as well as the polarity of the particle charge can be obtained by solving the equation of particle motion in DC and AC fields combined with the simultaneous measurement of its size and velocity. The results show the capability of the technique to allow real-time size and charge distribution in the control of dry powder attributes that are critical to fully understanding manufacturing design space. The data obtained from initial investigations of electrical properties of pharmaceutical powders and bipolar charge measurements was used to perform an in-depth study of electrostatic properties of pharmaceutical aerosols dispensed by dry powder inhaler (DPI) devices. The delivery of a drug to the lungs can only be achieved by a combination of inhaler device and drug formulation which is capable of producing an aerosol of an aerodynamic diameter smaller than 5 μm and of appropriate charge. The aerosols generated by these devices are often bipolarly charged and can influence specific site deposition in human lung. By controlling the electrostatic charge generated by tribielectrification, it may be possible to achieve the desired drug deposition in the airways. Bipolary charged dispensed ultrafine particles are inhaled through the extrathoracic and tracheobronchial airways down into the alveolar region. Anatomically realistic respiratory airways and computation fluid dynamics (CFD) models have been created to study airflow structures and predict aerosol deposition within the human respiratory system using visible human data sets, human casts and morphometric data. Many theoretical studies of charged aerosol deposition in human respiratory systems have been developed, however getting real time, non-intrusive data of bipolar charge levels on aerosols dispensed from DPI’s within the human respiratory system represents a challenging issue. This research project presents a simplified human upper airway model which combined with the modified Phase Doppler Anemometry (PDA) system is able to provide real time bipolar charge distributions of aerosols delivered from several commercially available DPI devices. A three dimensional (3D) reconstruction of the upper respiratory system was performed from two dimensional (2D) images obtained from computerized tomography (CT), magnetic resonance imaging (MRI) and cryosectioned images available from Visible Human Server data set (Ecole Polytechnique Fédérale de Lausanne). The resulting dimensions of the model were consistent with morphometric data from the literature from which the simplified upper airway model consisting of two connected segments, i.e., the oral airways from the mouth to trachea (Generation G0), was created. The findings of this study provided a better understanding of the interaction between specific active ingredients and DPI devices. These results may be used in designing future generation DPI devices and a better understanding of aerosol transport and deposition efficiency within the human airways.Engineering and Physical Sciences Research Council. Pfizer team, U

Methods of study of electrical processes in gases and aerosols = Методы исследования электрических процессов в газах и аэрозолях

• Contents • Содержание • M. Aints, A. Haljaste, K. Kudu, V. Sobek. Breakdown dynamics in uniforn HF electric field • Резюме • M. Laan, P. Paris. Streamer initiation by X-гау pulse • Резюме • E.T. Protasevich. Air-discharge peculiarities at variable humidity and pressure 1-20 Torr (Self-organisation of supercooled HF- discharge plasma) • Резюме • J. Salm. Electrostatic dispersion of air ions with a normal mobility distribution • Резюме • Luts. Chemical kinetics of tropospheric ions at higher ionization rates • Резюме • T. Parts. The effect of some alkylamines on mobility spectra of small air ions • Резюме • Я. Й. Сальм. Зависимость подвижности иона от его массы • Summary • Ü. Kikas. The identification of particle sources by aerosol spectra measurements • Резюме • E. Tamm, L. Langus. The neutralization of aerosol • Резюме • Я.Й Сальм, И.Я. Сергеев. Измерения распределения высокодисперсных аэрозольных частиц по размерам • Summary • V. Tamme. Practical operational problems of vibrating orifice aerosol generator • Резюме • M. Kaasik, L. Visnapuu and R. Priiman. Deposition of electrically charged and uncharged aerosols in chamber • Резюме • M. Kaasik. Electrostatic dispersion of air ions generated by a pneumatic sprayer in a chamber • Резюме • R. Matisen, F. Miller. Air ion meters of small air ions UT-9007 • Резюме • М.Э. Роос, О.В. Сакс. Быстродействующий измеритель малого тока УТ-9003 • Abstract • O. Saks, J. Hämaalov. Measurement of disturbances caused by the operation of the needle-contact on electrometer input • Резюме • J. Hämmalov. Dependence of surface noise on the number of adsorbed gas molecules • Резюмеhttp://tartu.ester.ee/record=b1077788~S1*es

Development and Characterization of Microfabricated Device for Real-Time Measurement of the Size and Number of Airborne Ultrafine Particles

Ultrafine particle emissions in motor-vehicle exhaust are associated with cardiopulmonary health impacts and increased mortality. The emission, evolution, and exposure-uptake of these particles, one hundred nanometers and smaller in diameter, are fundamentally quantified by the number concentration as a function of particle size. Ultrafine particle number distributions are widely varying and fast changing as they are strongly influenced by local environmental conditions and variation in vehicle operation and maintenance. Research and regulation to quantify and control such emissions rely on measurement of the number distribution of ultrafine particles in vehicle exhaust and by the roadside. Instruments to make such measurements are commercially available, but they are expensive, non-portable, and have slow response times. A new instrument, the NanoAPA, is being developed for these in-situ applications as an inexpensive, portable, and real-time instrument. The instrument is designed to perform ultrafine particle sizing and counting through electronic control of a microfabricated device that charges sampled airborne particles with a corona ionizer and then incrementally size-separates, collects, and counts the number of particles in the aerosol. The focus of this thesis was the development and characterization of the smallest device known that can perform these sizing and counting functions. The device miniaturizes a classical instrument from the aerosol field, the double-condenser of Whipple (1960) used for the sizing and counting of atmospheric ions, into a microfabricated device designed to utilize voltage-and-flowrate-variable electrophoresis to measure ultrafine particle aerosols. Performance characterization of the microfabricated device required development of an apparatus for the generation and conditioning of aerosols appropriate to this application. This Standard Aerosol apparatus was demonstrated to produce repeatable, temperature and humidity stable, charge-neutral, monodisperse exhaust-analog aerosols of particles 10 to 100 nanometer in diameter. The microfabricated device was characterized with the Standard Aerosol apparatus for the operating conditions of 0.1 to 1.5 liter per minute flow rate and 0 to 3000 volt separator voltage. Results of the characterization demonstrated effective selection and collection of solvent droplets in the diameter range 10-100nm. The selection and collection results for engine-exhaust analog particles were inconclusive, likely due to particle re-entrainment. Repeatable measurements of particle number proved elusive, likely due to electrical field interference, the limited particle concentration obtainable from the Standard Aerosol apparatus, and signal-to-noise and temporal stability issues with the electrometer electronics. Recommendations are made for approaches likely to overcome these issues