Distinguishing fuel and lubricating oil combustion products in diesel engine exhaust particles

The main sources of particulate emissions from engines are fuel and lubricating oil. In this study, particles emitted by a medium speed diesel engine for locomotive use were characterized chemically by using a soot particle aerosol mass spectrometer (SP-AMS). Additionally, positive matrix factorization (PMF) was applied to the SP-AMS data for the separation of fuel from lubricating oil and/or oil additives in diesel engine emissions. The mass spectra of refractory species, i.e., metals and rBC, were included in the PMF input matrix in addition to organics in order to utilize the benefit of the SP-AMS to measure non-refractory and refractory species. In general, particulate matter emitted by the diesel engine was dominated by organics (51%) followed by refractory black carbon (rBC; 48%), trace metals and inorganic species (1%). Regarding the sources of particles, PMF indicated four factors for particle mass of which two were related to lubricating oil-like aerosol (LOA1, 29% and LOA2, 24%) and two others to diesel-like fuel aerosol (DFA1, 35% and DFA2, 12%). The main difference between LOA1 and LOA2 was the presence of soot in LOA1 and metals in LOA2 factors. DFA factors represented burned (DFA1) and unburned fuel (DFA2). The results from the PMF analysis were completed with particle size distributions, volatility measurements and particle morphology analyses.

Copyright © 2019 American Association for Aerosol Research     

Power boiler fuel augmentation with a biomass fired atmospheric circulating fluid-bed gasifier

The successful experience in developing the advanced Foster Wheeler atmospheric circulating fluidized-bed (ACFB) combustion system subsequently led to the development of the ACFB gasification (ACFBG) Technology in the early 1980s. The driving force for the development work was the dramatic increase in oil price during this period. The primary advantage of the ACFBG technology is that it enables the substitution of expensive fuels (e.g. oil or gas) with cheaper solid fuels. Prior to this Lahti project, Foster Wheeler had supplied four waste wood fired commercial scale ACFBGs in the mid-1980s to the pulp and paper industry with capacities from 17 to 35 MW_th based on fuel input. These units are still in successful operation today. Lahden Lämpövoima Oy (LLOy) is a Finnish power company producing power and district heat for the City of Lahti. The company is jointly owned by the city of Lahti and by Fortum Oy, the largest utility power company in Finland. LLOy operates the Kymijärvi Power Plant located nearby the city of Lahti in Southern Finland. To keep the energy prices as low as possible, Plant personnel are continuously looking for the most economical fuel sources, and simultaneously, trying to improve the environmental aspects of the energy production. Currently, about 300 GW h/a of different types of biofuels and refuse fuels are available in the Lahti area. On an annual basis, the available amount of biofuels and refuse fuels is enough to substitute for about 15% of the fuels burned in the main boiler, equaling up to 30% of the coal typically used. The aim of the LLOy Kymijärvi Power Plant gasification project is a commercial scale demonstration of direct gasification of wet biofuel and the use of hot, raw and very low calorific gas directly in the existing coal fired boiler. The gasification of biofuels and co-combustion of gases in the existing coal-fired boiler offers many advantages such as: recycling of CO₂, decreased SO₂ and NO_x emissions, efficient way to utilize biofuels and recycled refuse fuels, low investment and operation costs, and utilization of the existing power plant capacity. Furthermore, only small modifications were required in the boiler and process upsets in the gasifier do not shut down the power plant. The first two years of operation (1998 and 1999) have been excellent with good availability for the gasifier and its related components. During 1998 several measurements and tests with different fuel combinations were performed. This paper presents the project in detail as well as the most important results of the first measurements. The EU Thermie program has supported this project.     

Technology beats algorithms (in exact string matching)

More than 120 algorithms have been developed for exact string matching within the last 40 years. We show by experiments that the naïve algorithm exploiting SIMD instructions of modern CPUs (with symbols compared in a special order) is the fastest one for patterns of length up to about 50 symbols and extremely good for longer patterns and small alphabets. The algorithm compares 16 or 32 characters in parallel by applying SSE2 or AVX2 instructions, respectively. Moreover, it uses loop peeling to further speed up the searching phase. We tried several orders for comparisons of pattern symbols, and the increasing order of their probabilities in the text was the best.     

Children's hedonic response to berry products: Effect of chemical composition of berries and hTAS2R38 genotype on liking

The hedonic response of 104 healthy children, recruited from day-care centres and schools, to 12 different berry products with varying content of added sugar was studied. The berries used as ingredients were blackcurrant (Ribes nigrum), sea buckthorn (Hippophaë rhamnoides), bilberry (Vaccinium myrtillus), and lingonberry (Vaccinium vitis-idaea). Another aim of the study was to study the effects of the chemical composition of berries as well as children’s hTAS2R38 taste receptor genotypes on liking. The most liked product was bilberry with yoghurt, followed by bilberry juice, dried bilberries, and lingonberry rye bread. The most disliked products were sea buckthorn juice, sea buckthorn berries with yoghurt, and oatmeal with blackcurrant powder and berry oil. High total organic acid concentration was strongly related with a poor average liking score of the berries/berry products. A total of four different alleles of hTAS2R38 gene were observed in the study. Of the genotyped children, 45% were bitter taste insensitive individuals of the genotype AVI/AVI, and 40% were of the genotype PAV/AVI. Children of the genotype PAV/AVI were reported using more vegetables, but not berries, than the AVI/AVI children. The results also show that the liking scores of the children of the AVI/AVI, PAV/AVI, and PAV/PAV genotypes differed from each other, and that the familiarity of a berry product is likely to be an important factor in liking.     

Nucleation mode particles with a nonvolatile core in the exhaust of a heavy duty diesel vehicle

The characteristics of the nucleation mode particles of a Euro IV heavy-duty diesel vehicle exhaust were studied. The NOx and PM emissions of the vehicle were controlled through the use of cooled EGR and high-pressure fuel injection techniques; no exhaust gas after-treatment was used. Particle measurements were performed in vehicle laboratory and on road. Nucleation mode dominated the particle number size distribution in all the tested driving conditions. According to the on-road measurements, the nucleation mode was already formed after 0.7 s residence time in the atmosphere and no significant changes were observed for longer residence times. The nucleation mode was insensitive to the fuel sulfur content, dilution air temperature, and relative humidity. An increase in the dilution ratio decreased the size of the nucleation mode particles. This behavior was observed to be linked to the total hydrocarbon concentration in the diluted sample. In volatility measurements, the nucleation mode particles were observed to have a nonvolatile core with volatile species condensed on it. The results indicate that the nucleation mode particles have a nonvolatile core formed before the dilution process. The core particles have grown because of the condensation of semivolatile material, mainly hydrocarbons, during the dilution.     

Effect of engine load on diesel soot particles

This study concentrates on characterization of nonvolatile fraction of diesel particles. These particles have an impact on earth's radiation balance as well as on health effects of vehicle emissions. In addition to composition and size distribution of particles, an important factor affecting their health effects and properties and lifetimes in the atmosphere is their morphology. The effect of engine parameters on soot particle size distributions and also on particle morphology has been studied. It was found that the shape of the size distribution and also the structure of diesel particles depend on engine load. The number distributions were found to obey log-normal assumption. The width of the distribution increased with increasing engine load. The geometric standard deviations of measured distributions varied from 1.7 to 2.1. Simultaneously, the fractal dimension of particles decreased with increasing engine load. The values for mass fractal dimensions based on sealing of particle mass and mobility size were between 2.6 and 2.8. Both electron microscopy and measurements of aerodynamic size versus mobility size suggest that the morphology of particles in different size regimes vary, with the large particles being less compact than the small ones.     

Defect aggregates in the Sr_2MgSi_2O_7 persistent luminescence material

The crystal and electronic structure of the Eu2+ doped and defect containing Sr2MgSi2O7 persistent luminescence material were studied using the density functional theory(DFT) .The defects may act as energy storage or even luminescence quenching centres in these materials,however their role is very difficult to confirm experimentally.The probability of vacancy formation was studied using the total en-ergy of the defect containing host.Significant structural modifications in the environment of the isolated de...     

Fountain-inspired erasure coding for real-time traffic

An erasure correction strategy based on fountain coding is proposed for traffic with real-time requirements. A sliding window marks the range of non-expired data. Each new block entering the window is once sent as such, followed by probabilistically sending a repair packet. The repair packets are formed as a random combination of the blocks in the current window using a degree distribution as in LT coding. The performance of the method with a given channel loss probability is analyzed using a Markov chain model. The state space, however, has to be truncated for computational tractability. The truncation error is verified to be small enough by simulations. By using the analytical model the optimal degree distribution is found to be of single-degree type. The performance of the proposed scheme is compared with deterministic settings, in which repair packets are sent after fixed number of systematic packets. Further comparison is made against Raptor coding, and we note that using the presented strategy can result in better performance in some situations.     

Analysis of aircraft impact to concrete structures

Analysis of aircraft impact to nuclear power plant structures is discussed utilizing a simplified model of a “fictitious nuclear building” to perform analyses using LS-DYNA software, representing the loading: (i) by the Riera force history method and (ii) by modeling the crash by impacting a model of a plane similar to Boeing 747-400 to the structure (i.e., “missile–target interaction method”). Points discussed include: (1) comparison of shock loading within the building as obtained from the Riera force history analysis versus from the missile–target interaction analysis, (2) sensitivity of the results on the assumed Riera force loading area, (3) linear versus nonlinear modeling and (4) on failure criteria.