Faculty of Mechanical Engineering

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Gas Shielded Metal Arc Brazing of Surface Zinc Coated Thin Steel Sheet
(25 Jubilee Scientific Conference, MTF 2007, 14-16 September, Sozopol Bulgaria, Proceedings, Vol. 1, pp. 182-187, 2007-09-15)
Runchev Dobre, Dorn Lutz
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Radiation Heat Transfer Modelling and CFD Analysis of Pulverised-Coal Combustion with Staged Air Introduction
(PAN - Polish Academy of Sciences, 2009-10)
Risto V. Filkoski
Modelling of fossil fuel utility and industrial boilers has reached a remarkable development in recent years. Particular attention in optimisation of a utility boiler furnace operation, is given to the flame geometry and position. Combustion chamber designers endeavour to achieve optimum operating conditions that give maximum combustion efficiency, as well as minimum pollutant formation rate. The application of computational fluid dynamics (CFD) modelling technique and other advanced mathematical methods offer opportunities for analysis, optimisation and options examination in order to increase the overall efficiency of the energy facilities. The main purpose of the present study was to investigate how the results obtained with two radiative heat transfer methods, the P1 approximation method and the discrete ordinates (DO) method, fit temperature field in a boiler furnace on pulverised coal, with implemented over-fire air (OFA) ports. The framework of the CFD modelling approach is described. The numerical modelling results for boiler baseline operating conditions are compared with a test matrix of local temperature measurements. An accuracy analysis of the P1 and DO methods is done on a basis of a comparison between the numerically obtained and measured temperature profiles.
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Computational fluid dynamics technique as a tool for description of the phenomena occurring in pulverized coal combustion systems
(SAGE Publications, 2007-05-01)
Filkoski, R. V.
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Belosevic, S. V.
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Petrovski, I. J.
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Oka, S. N.
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Sijercic, M. A.
<jats:p> The paper presents the overall frame, principal steps, and some results of a numerical model of a power boiler furnace that uses pulverized coal, with tangential disposition of the burners. This model demonstrates the application potential of the computational fluid dynamics (CFD) technique and of the computational thermal analysis. Complex three-dimensional furnace geometry, two-phase turbulent flow, coal combustion, and heat transfer have been examined. Two numerical modelling approaches were employed in the investigation, both based on the Euler-Lagrangean two-phase flow concept and on the gas-phase semiempirical k-ɛ turbulence model. The first approach is based on a specially developed comprehensive model of processes in a pulverized coal furnace. In the second case, a commercial CFD code is used to create a three-dimensional furnace model. Some distinctive results concerning the performance of the boiler that was examined are presented graphically. On the basis of a comparison between the simulation predictions and available site measurements, a conclusion can be drawn that these two numerical codes provide realistic insight into furnace processes. Qualitative agreement indicates that the calculations are reasonable and validates the submodels employed. </jats:p>
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Optimization of pulverised coal combustion by means of CFD/CTA modeling
(National Library of Serbia, 2006)
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Petrovski, Ilija
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Karas, Piotr
<jats:p>The objective of the work presented in this paper was to apply a method for handling two-phase reacting flow for prediction of pulverized coal combustion in large-scale boiler furnace and to assess the ability of the model to predict existing power plant data. The paper presents the principal steps and results of the numerical modeling of power boiler furnace with tangential disposition of the burners. The computational fluid dynamics/computational thermal analysis (CFD/CTA) approach is utilized for creation of a three-dimensional model of the boiler furnace, including the platen superheater in the upper part of the furnace. Standard k-e model is employed for description of the turbulent flow. Coal combustion is modeled by the mixture fraction/probability density function approach for the reaction chemistry, with equilibrium assumption applied for description of the system chemistry. Radiation heat transfer is computed by means of the simplified P-N model, based on the expansion of the radiation intensity into an orthogonal series of spherical harmonics. Some distinctive results regarding the examined boiler performance in capacity range between 65 and 95% are presented graphically. Comparing the simulation predictions and available site measurements concerning temperature, heat flux and combustion efficiency, a conclusion can be drawn that the model produces realistic insight into the furnace processes. Qualitative agreement indicates reasonability of the calculations and validates the employed sub-models. After the validation and verification of the model it was used to check the combustion efficiency as a function of coal dust sieve characteristics, as well as the impact of burners modification with introduction of over fire air ports to the appearance of incomplete combustion, including CO concentration, as well as to the NOx concentration. The described case and other experiences with CFD/CTA stress the advantages of numerical modeling and simulation over a purely field data study, such as the ability to quickly analyze a variety of design options without modifying the object and the availability of significantly more data to interpret the results. .</jats:p>
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VERIFICATION OF METHOD FOR ESTIMATING COMBUSTION EFFICIENCY IN A BUBBLING FB COMBUSTOR
(Vinča Institute of Nuclear Sciences, Belgrade, 2000-11)
Risto V. Filkoski
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Longin Przybylski
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Ilija J. Petrovski
The article refers to a mathematical method for estimating the efficiency of the combustion process in bubbling fluidised bed conditions. The calculation procedure used in this work is given elsewhere [1, 2] and, here, it is only briefly described. The objective of the present investigation is to validate the mentioned method when using brown coal as a fuel in a laboratory fluidised bed combustor. Particular attention is devoted to the subject of elutriation of fuel particles out of the combustor, considering the fact that it is one of the most important factors limiting the combustion efficiency and the furnace design as well. The work presented here contains the conditions and some results of experimental research in heat losses resulting from the phenomenon of elutriation of combustible particles [3]. Experiments were carried out in a combustor with an inner diameter of 200 mm and a height of 1200 mm. A numerical testing of the method for estimating the combustion efficiency was accomplished within a bed temperature range from 780 °C to 900 °C and a fluidising velocity from 1.20 to 1.32 m/s. The results achieved were compared with the experimentally obtained data. Besides the appearance of some deviations, it may be stated that the results are reasonable and in line with the expectations.
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Истражување на заварувањето со цврст Nd:YAG-ласер на аморфни кобалт легури во форма на фолии
(1996-11-18)
Добре Рунчев
Истражувано е заварувањето со цврст ласер на аморфни фолии, метални стакла, легури на кобалт.
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Environmental protection and industry: Parameters necessary for environmentally related decision making
(Part of the NATO Science for Peace and Security Series C: Environmental Security book series (NAPSC) © Springer Science + Business Media B.V. 2009, 2009)
Nošpal A., Lazarevska A. M.
Industry, as one of the economy pillars, is to be accounted for the development and improvement of a certain country's well-being. Unfortunately, the prosperity has and still is accompanied with direct and/or indirect negative environmental impact, especially in the Western Balkans countries with economies in transition. In this chapter, we focus on the parameters necessary to identify, describe, parameterize, monitor and prevent pollution deriving from industry for the purpose of alleviating the process of decision making relevant to environmental protection. Illustrated are examples from several industrial sectors including energy generation, public transportation, cement industry and ferrous metallurgy
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A Multi-Criteria Decision Making Conceptual Approach to optimal Landfill Monitoring
(Part of the NATO Science for Peace and Security Series C: Environmental Security book series (NAPSC) © Springer Science + Business Media B.V. 2009, 2009)
Lazarevska A. M., Fischer N., Münnich K., Haarstrick A.
In this chapter, we introduce a novel conceptual approach to determining an optimal landfill monitoring procedure by using the Multi Criteria Decision Making (MCDM). Selecting an optimal landfill monitoring procedure is identified as a complex and multifold problem encompassing parameters related to conflicting demands. It should result in identifying possible landfill monitoring alternatives that have to comply with predefined relevant criteria and offer landfill operators a powerful tool when raised in front of the problem of selecting the most appropriate monitoring alternative for their particular landfill. A decision having to be delivered in such a multidimensional and complex environment, seeks the utilization of the MCDM theory, in particular when the problem is new and complex, existing experience is insufficient, economic implications are significant. It is justified to define an algorithm due to frequent incidence of the problem and intuition is not an option, all of which is the case for the herein defined problem: determining optimal landfill monitoring procedure
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Emerging issues in regulations and standards: Sampling considerations within market surveillance actions
(IEEE, 2009-10)
Hendrikx, Ivan
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Starlikeness and convexity of a class of analytic functions
(Hindawi Limited, 2006)
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Irmak, Hüseyin

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