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[en] Highlights: • Novel volumetric extinction measurement for particles in optically DISI engines. • EGR-dependence on soot formation and oxidation of different fuels was studied. • Increased soot formation for biofuel blends in comparison to the base fuel. • The artificial gasoline Toliso showed higher soot formation for increased EGR-rate. • An EGR increase reduces the soot volume fraction of the Biofuels E20 and B20. - Abstract: The soot formation and in-cylinder soot oxidation in an optically accessible DISI-engine is analyzed for gasoline-ethanol and -butanol mixtures. The volumetric extinction measurement technique used is capable of determining quantitative soot volume fractions and in-cylinder soot oxidation at low gas and soot particle temperatures. Toliso, a fuel mixture containing isooctane and toluene (65 vol% isooctane and 35 vol% toluene) was utilized as a surrogate gasoline fuel. The EGR-dependence (EGR-exhaust gas recirculation) on soot formation and -oxidation of the fuels was studied at part load operation. The studied operating point is characterized by an early injection timing leading to distinct piston wetting and a sooting pool-fire. The measurements without EGR showed a low soot formation for Toliso, while EGR leads to higher soot formation. E20 and B20 showed a strong sooting behaviour without EGR. An EGR increase reduced the soot formation for E20 and B20. It can be concluded that the physical fuel properties determine the spray formation and piston wetting. The fuel dependent evaporation of the liquid wall film as well as local mixing conditions play a major role on soot formation and oxidation.
[en] The post-depositional enrichment of black soot in snow-pack was investigated by measuring the redistribution of black soot along monthly snow-pits on a Tien Shan glacier. The one-year experiment revealed that black soot was greatly enriched, defined as the ratio of concentration to original snow concentration, in the unmelted snow-pack by at least an order of magnitude. Greatest soot enrichment was observed in the surface snow and the lower firn-pack within the melt season percolation zone. Black carbon (BC) concentrations as high as 400 ng g−1 in the summer surface snow indicate that soot can significantly contribute to glacier melt. BC concentrations reaching 3000 ng g−1 in the bottom portion of the firn pit are especially concerning given the expected equilibrium-line altitude (ELA) rise associated with future climatic warming, which would expose the dirty underlying firn and ice. Since most of the accumulation area on Tibetan glaciers is within the percolation zone where snow densification is characterized by melting and refreezing, the enrichment of black soot in the snow-pack is of foremost importance. Results suggest the effect of black soot on glacier melting may currently be underestimated. (letter)
[en] The chief source of smoke-type air pollution in cities is civil coal burning for heating. A typical city with air pollution during heating seasons is Taiyuan in Shanxi Province. Data in this paper are given in UNDP Random Sampling Investigation of Urban Households and Small Energy Consumers in which the writer took part and reports of sampling of air pollution during heating seasons in Taiyuan urban districts in recent years. Multi-objective policy-making technique and minimum cost-benefit analyzing methods are employed here in making ecological economic analysis. Measures and techniques taken in optimizing evaluation of civil coal heating in northern Chinese cities and policy-making analysis of air pollution are discussed
[en] Highlights: • The PaSR-based soot model proposed by the authors’ group has been further improved. • The present model is physically more sound. • The improved model has been implemented into the in-house version of the FireFOAM code. • New formulas have been proposed to compute characteristic time for soot formation and oxidation. • The predictions have achieved improved agreement with the experimental measurements. - Abstract: The extension of the laminar smoke point based approach to turbulent combustion using the partially stirred reactor (PaSR) concept proposed by Chen et al. (2014) has been further improved to overcome the limitation in the formulations of Chen et al. (2014) which assumed infinitely fast soot oxidation chemistry and constant soot formation characteristic time. In the PaSR approach, each computational cell is split into two zones: the reacting zone and the non-reacting zone. Soot formation and oxidation are assumed to take place at finite rates in the reacting zone and computed from the corresponding laminar rates and the mass fractions for soot formation and oxidation, which are evaluated in each computational cell from the characteristic time scales for turbulent mixing, soot formation and oxidation. Since soot would be produced in not only the fine structures but also surrounding fluids in the Eddy-Dissipation-Concept (EDC) model, the average field parameters between the fine structure and surrounding fluid are employed instead of those Favre-averaged values in Chen et al.’s soot formation model. The newly extended model has been implemented in FireFOAM, a large eddy simulation (LES) based solver for fire simulation based on the open source CFD code OpenFOAM®. Numerical simulations of a 30 cm diameter heptane and toluene pool fires tested by Klassen and Gore (1992) were performed for validation. The predicted soot volume fraction and temperature have achieved improved agreement with the experimental measurements in comparison with that of Chen et al. (2014), demonstrating the potential of the improved PaSR-based soot model for fire applications.
[en] Widespread use of tributyltin (TBT) poses a serious environmental problem. Adsorption by black carbon (BC) may strongly affect its behavior. The adsorption of TBT to well characterized soot and two charcoals with specific surface area in the range of 62-111 m2 g-1 have been investigated with main focus on pH effects. The charcoals but not soot possess acidic functional groups. TBT adsorption reaches maximum at pH 6-7 for charcoals, and at pH > 6 for soot. Soot has between 1.5 and 15 times higher adsorption density (0.09-1.77 μmol m-2) than charcoals, but charcoals show up to 17 times higher sorption affinities than soot. TBT adsorption is successfully described by a new pH-dependent dual Langmuir model considering electrostatic and hydrophobic adsorption, and pH effects on TBT speciation and BC surface charge. It is inferred that strong sorption of the TBTOH species to BC may affect TBT toxicity. - Tributyltin adsorption to black carbon increases at increasing pH but charcoal exhibits electrostatic and hydrophobic adsorption, whereas soot only adsorbs hydrophobically.
[en] In this study, the microstructure and oxidation behaviour of soot from the raw exhaust of a Euro IV test heavy duty (HD) diesel engine are investigated and compared to that of spark-discharge soot and hexabenzocoronene (HBC, C42H18). We find a microstructure-controlled reactivity towards oxidation of all three samples in 5% O2 in N2. The spark-discharge soot with its fine primary particles and fullerenoid structure has an onset temperature of 423K for combustion, while the HBC with its well-ordered crystallites has a high onset temperature of 773K. Due to an improved combustion process in the Euro IV HD diesel engine, the emitted soot consists of more fullerenoid- or onion-like particles agglomerated in a chain-like secondary structure. The onset temperature of the Euro IV HD engine soot combustion is 573K. Oxidation of the three samples produces only CO2 and H2O. The different H2O production profiles can be assigned to the functionalised surface of the samples and depend on the soot structure and preparation route
[en] Contrails and contrail-cirrus may be the largest source of radiative forcing (RF) attributable to aviation. Biomass-derived alternative jet fuels are a potentially major way to mitigate the climate impacts of aviation by reducing lifecycle CO2 emissions. Given the up to 90% reduction in soot emissions from paraffinic biofuels, the potential for a significant impact on contrail RF due to the reduction in contrail-forming ice nuclei (IN) remains an open question. We simulate contrail formation and evolution to quantify RF over the United States under different emissions scenarios. Replacing conventional jet fuels with paraffinic biofuels generates two competing effects. First, the higher water emissions index results in an increase in contrail occurrence (∼ +8%). On the other hand, these contrails are composed of larger diameter crystals (∼ +58%) at lower number concentrations (∼ −75%), reducing both contrail optical depth (∼ −29%) and albedo (∼ −32%). The net changes in contrail RF induced by switching to biofuels range from −4% to +18% among a range of assumed ice crystal habits (shapes). In comparison, cleaner burning engines (with no increase in water emissions index) result in changes to net contrail RF ranging between −13% and +5% depending on habit. Thus, we find that even 67% to 75% reductions in aircraft soot emissions are insufficient to substantially reduce warming from contrails, and that the use of biofuels may either increase or decrease contrail warming—contrary to previous expectations of a significant decrease in warming. (letter)
[en] Mazut is used in the process of start-up of the power units at the thermal power plants in the complex Maritza East. The threat which the presence of mazut soot poses causes a restraint on the operation of the electrostatic precipitators, which on its part leads to the emergence of problems such as the excessive contamination of the environment and the abrasive wearing out of the blades of the ID fans. Considering these matters, we had to measure the dust concentration in the flue gases at the time of the start-up of one of the boilers of type P-62. The present document offers the results of this scrutiny
[en] We studied the distribution function of particle sizes by an aerosol particle counters with different meteorological conditions of atmosphere. The concentration of particles of size 0.3-0.4 micron range from 25 to 300 particles/cm3, 0.5-0.8 micron particles - from 1 to 10 particles/cm3, the particle size about 1.0 microns - from 0 to 2 particles/cm3. Simultaneously we measured the soot content in the atmospheric aerosol by means of soot aerosol meter. (author)