Hochschule für Technik und Umwelt FHNW
Dauerhafte URI für den Bereichhttps://irf.fhnw.ch/handle/11654/35
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8 Ergebnisse
Bereich: Suchergebnisse
Publikation Growth and structural change of combustion aerosols at high relative humidity(American Chemical Society, 01.12.1995) Weingartner, Ernest; Baltensperger, Urs; Burtscher, Heinz01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Hygroscopic properties of carbon and diesel soot particles(Elsevier, 08/1997) Weingartner, Ernest; Burtscher, Heinz; Baltensperger, UrsLaboratory experiments were performed in order to study the hygroscopic properties of freshly produced carbon and diesel soot particles at subsaturations (i.e. at relative humidity < 100%). Wetted carbon aggregates collapsed to a more compact structure. In contrast, the diesel combustion particles exhibited a much smaller restructuring combined with condensational growth. The hygroscopicity of the diesel particles was enhanced when the sulfur content of the fuel was increased or when the particles were subjected to an ozone and UV pre-treatment. By extrapolating the data with a Köhler model critical supersaturations were calculated. Freshly emitted combustion particles are unlikely to act as cloud condensation nuclei whereas an aging of the particles will enhance their nucleation ability.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Aerosol emission in a road tunnel(Elsevier, 02/1997) Weingartner, Ernest; Keller, Christian; Stahel, Werner; Burtscher, Heinz; Baltensperger, UrsContinuous measurements of aerosol emissions were performed within the scope of emission measurements in the Gubrist tunnel, a 3250 m long freeway tunnel near Zürich, Switzerland, from 20 September to 26 September 1993. The particles in the respirable size range (d < 3 μm) were found to be mainly tail pipe emissions with very small amount of tire wear and road dust. The calculated PM3 emission factor for diesel engines was about 310 mg/km, where the main part (63%) of the diesel vehicles were heavy-duty vehicles. Thirty-one percent of the PM3 emissions from diesel vehicles were black carbon and 0.86% particle bound PAR Due to the high fraction emitted by diesel engines the contribution of gasoline engines could not be evaluated by the statistical model. During their residence time in the tunnel the particles undergo significant changes, resulting in a more compact structure. It is concluded that this is mainly due to adsorption of volatile material from the gas phase to the particle surface.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Separation of volatile and non-volatile aerosol fractions by thermodesorption. instrumental development and applications(Elsevier, 04/2001) Burtscher, Heinz; Baltensperger, Urs; Bukowiecki, Nicolas; Cohn, P.; Hüglin, Christoph; Mohr, Martin; Matter, Urs; Nyeki, Stephan; Schmatloch, Volker; Streit, Niklaus; Weingartner, ErnestAn instrument to remove volatile material from aerosol particles by thermal desorption is presented. The thermodesorber consists of a heated tube, where volatile material is desorbed from the particles, and a water- or air-cooled tube, consisting of activated charcoal. This last tube removes desorbed material and thus prevents it from re-adsorbing onto particles. Although designed for measuring particulate emissions from combustion processes it can also be applied to atmospheric aerosols. After theoretical and experimental determination of thermodesorber operating characteristics (temperature profile, losses, removal of desorbed material), examples of applications in several fields are given. Examples of atmospheric measurements at several remote and urban sites are presented. In combustion technology, the thermodesorber is applied to remove all volatile materials, allowing separation of volatile species and the non-volatile core (mainly elemental carbon) of combustion particles. Finally, the thermodesorber is used to study adsorption and desorption processes of polycyclic aromatic hydrocarbons on particles.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Real-time characterization of ultrafine and accumulation mode particles in ambient combustion aerosols(Elsevier, 08/2002) Bukowiecki, Nicolas; Kittelson, David B.; Watts, Winthrop F.; Burtscher, Heinz; Weingartner, Ernest; Baltensperger, UrsThe diffusion charging sensor (DC), photoelectric aerosol sensor (PAS) and condensation particle counter (CPC) are real-time particle instruments that have time resolutions < 10s and are suitable for field use. This paper shows how the relative fraction of nuclei mode particles (D ≤ 50nm) in ambient combustion aerosols can be determined, along with the coverage degree of the respective accumulation mode particles with a modal diameter of ~ 100nm. Main tools for interpretation are the diameter of average surface DAve,S (obtained from CPC and DC measurements) and PAS/DC versus DAve,S scatter plots. Compared to the scanning mobility particle sizer (SMPS), which is a standard instrument for aerosol particle size distribution measurements, the presented method has a limited accuracy, but is substantially faster. Additionally, it is experimentally less demanding than SMPS measurements, especially for field applications.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Development of an airborne sensor for reliable detection of volcanic ash(IEEE, 2016) Weingartner, Ernest; Jurányi, Zsofia; Egli, Daniel; Steigmeier, Peter; Burtscher, HeinzThis sensor detects volcanic ash particles and distinguishes them from cloud droplets. Operated on an airplane, this detector can quantify the exposure to hazardous refractory ash and the in-situ measurement is not biased by the presence of cloud particles. A volcanic eruption emits a significant amount of hazardous ash particles into the air. If the event is strong enough, the volcanic ash plume can reach high altitudes and can be a serious security risk for airplanes. We have developed a new prototype aerosol sensor for the reliable detection of volcanic ash. The envisaged application is the employment of this new technique on board of passenger aircraft. It allows in-situ monitoring of the airplane's exposure to volcanic ash. The challenge of this development is the requirement that the sensor can distinguish cloud droplets (or ice crystals) from the hazardous refractory ash particles. At aviation altitudes, water droplets and ice crystals are often present in the particle size region of the ash (1-20 micrometer) and their concentrations can reach the levels that are considered as the limits of the different volcanic ash contamination zones. Therefore, it is crucial that the sensor can differentiate between volcanic ash and water or ice particles. The sensor measures the scattered light intensities from individual particles outside of the airplane cabin through a glass window. The desired discrimination is achieved with two lasers operating at different wavelengths. Ash concentrations (in terms of number and mass) are derived, and the exposure of the airplane is recorded and transmitted in real time to the pilot. The volcanic ash detector was tested in the laboratory with various test aerosols and micrometer-sized water droplets. Then, ground-based outdoor measurements were conducted and the instrument response to mineral dust (a surrogate for volcanic ash) and natural cloud droplets (and ice crystals) was investigated. In a next step, this new technique will be tested in summer 2016 on-board of a research aircraft.04B - Beitrag KonferenzschriftPublikation Characterizing particulate emissions from wood burning appliances including secondary organic aerosol formation potential(Elsevier, 31.08.2017) Keller, Alejandro; Burtscher, HeinzBiomass burning is a major contributor to environmental particulate matter pollution and should therefore be contemplated by emission control legislation. However, policy decisions for improving air quality by imposing emission limits are only as good as the selected metric. We discuss an approach that incorporates recent scientific results and is compatible with type-approval testing and field measurements. We include potential secondary organic aerosol (SOA) by aging emissions in an oxidation flow reactor. Quantification is done by particle-bound total carbon analysis. Total carbon is the fraction relevant to combustion quality and a better marker for toxicity than total particulate matter, which also includes salts and ashes. The data is complemented by on-line size distribution measurements. We exemplify our approach by showing measurements performed on a variety of appliances. Our measurements suggest that non-methane hydrocarbons (NMHC) species with very low volatility are responsible for most of the SOA. Condensing and precipitating this fraction significantly reduces SOA potential but has no noticeable impact on total NMHC. Thus, key precursors of SOA may be a much smaller subset than previously thought. Targeting this fraction could be a straightforward SOA mitigation strategy. These results could not have been derived using the current standard emission control metrics.01A - Beitrag in wissenschaftlicher Zeitschrift
