Browsing by Author "Zlateva P."

Now showing 1 - 6 of 6
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    CFD-based analysis of wood pellet combustion in a domestic boiler (small-scale)
    (2025-01-01) Krumov K.; Zlateva P.; Mileva N.
    This study presents a numerical analysis of the wood pellet combustion process in a domestic hot water boiler using computational fluid dynamics (CFD) methods. The aim is to assess the impact of primary and secondary air distribution on the temperature field, flow behavior, and pollutant formation. A three-dimensional model of the combustion chamber in code ANSYS CFX was developed. Two air supply configurations were analyzed: 40% primary / 60% secondary air and 60% primary/40% secondary air. The solid fuel was represented by an equivalent gas mixture to simulate the volatile components released during combustion. The simulation results demonstrate that the air distribution ratio substantially influences flame morphology, thermal field uniformity, and the generation of pollutants. The 40/60 air ratio supply configuration promotes improved air-fuel mixing, enhanced combustion stability, and reduced emissions of carbon monoxide (CO) and methane (CH4). In contrast, the 60/40 air ratio configuration yields higher flame temperatures but favors incomplete oxidation, leading to increased emission levels. The proposed numerical model represents a useful basis for optimizing air supply regimes in domestic pellet-fired boilers to achieve improved combustion efficiency and reduced environmental impact.
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    Cost analysis at different energy sources for heating of an air-supported dome for indoor tennis
    (2021-07-12) Gavrilov V.; Penkova N.; Zlateva P.; Mladenov B.
    Numerical analyses of the energy supply for heating of air supported structure for indoor tennis in Sofia via district heating, gas and liquid fuels are performed. The computational procedures are implemented through thermal balances of the structures, calibrated on the base of in situ measurements of the indoor temperature and the amount of the fuel, consumed at heating of an air supported balloon for tennis in University of Chemical technology and Metallurgy. The profitability of the different heating variants is estimated using the price of the energy and the systems.
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    IMPROVEMENT OF FIRING CURVE OF CERAMIC WARE VIA MODELLING AND NUMERICAL SIMULATION OF THE COUPLED THERMO-MECHANICAL PROCESSES IN THE MATERIAL
    (2021-01-01) Penkova N.; Krumov K.; Zlateva P.
    A mathematical model of coupled heat transfer and mechanical processes in ceramic ware at firing is developed. It is based on information about the thermo-mechanical behaviour of the material at sintering, obtained experimentally. The model is solved numerically for massive bodies of technical ceramics to estimate and prevent the reasons for cracks appearance at their firing in chamber kilns. The transient thermo-mechanical processes in the fired mass are simulated varying with the heating rate of the firing curves. The investigated thermal regimes are analysed on the base of the results about the temperature and stresses fields in the articles. Approaches for improvements of the fired curve are discussed in order to prevent defects of the products.
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    Influence of the polyester non-wovens production type on their thermal and flammability properties
    (2022-12-01) Petkova-Slipets R.; Zlateva P.; Staneva D.
    In recent years, non-wovens have become the main segment of textile production because they can find applications in different areas. Thermal insulation properties, fire resistance, and flexibility make them cost-effective and efficient insulation panels for buildings. This paper aims to study the influence of the production method and surface treatment on the thermophysical characteristics and behavior under direct fire of two polyethylene terephthalate non-woven fabrics. The fibers have been bonded with polyacrylate adhesive or thermal and coated with silicone. Infrared spectroscopy, optical microscopy, and thermal analyses were applied to compare the non-wovens’ morphology, composition, and thermal properties. It founds that the non-woven polyester with acrylic additives and adhesive bonding has a higher thermal conductivity value and high flammability with complete combustion. In contrast, thermosetting siliconized polyester materials have limited flammability with limited droplet release. The silicone-based finish protects the polyester fibers leading to self-extinguishing and stopping the complete combustion of the sample.
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    Numerical and Experimental Analyses of Flue Gas Emissions, from Biomass Pellet Combustion in a Domestic Boiler
    (2025-10-01) Mileva N.; Zlateva P.; Ivanov M.; Krumov K.; Terziev A.; Comarla A.
    This study explores the combustion behavior of three biomass pellet types—wood (W), sunflower husk (SH), and a mixture of wood and sunflower husks (W/SH)—in a residential hot water boiler. Experiments were carried out under two air supply regimes (40%/60% and 60%/40% primary to secondary air) to measure flue gas concentrations of oxygen (O2), carbon monoxide (CO), and nitrogen oxides (NOx). The results indicate that SH pellets generate the highest emissions (CO: 1095.3 mg/m3, NOx: 679.3 mg/m3), while W pellets achieve the lowest (CO: 0.3 mg/m3, NOx: 194.1 mg/m3). The mixed W/SH pellets produce intermediate values (CO: 148.7 mg/m3, NOx: 201.8 mg/m3). Overall boiler efficiency for all tested fuels ranged from 90.3% to 91.4%. Numerical simulations using ANSYS CFX (2024 R2 (24.2)) were performed to analyze temperature distribution, flue gas composition, and flow fields, showing good agreement with experimental outlet temperature and emission trends. These findings emphasize that both pellet composition and air distribution significantly influence efficiency and emissions, offering guidance for optimizing small-scale biomass boiler operation.
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    REDUCING THE CARBON FOOTPRINT IN THE CONSTRUCTION SECTOR BY REPLACING CERAMIC BRICKS WITH ALTERNATIVE MATERIALS
    (2024-01-01) Tashkov L.; Zlateva P.; Penkova N.
    The use of non-fired materials with additives of vegetable waste instead of traditional building ceramics reduces the energy input and the carbon footprint in the construction sector. This applies to one- and two-story buildings due to the lower load-bearing capacity of non-fired bricks. A possibility for substitution of the fired ceramics with non-fired clay bricks with additives of straw at the building of the walls of a single-family house is analyzed. The subsequent reductions of the embodied energy, carbon dioxide, and thermal losses of the buildings are determined.