1. The numerical analysis of flame stability in case of premixed hydrogen-air combustionMarc Jaeger, Matjaž Hriberšek, Niko Samec, Yang Guo, Xuebin Wang, Filip Kokalj, 2025, original scientific article Abstract: This study addresses the urgent need for decarbonization of heating sector, focusing on the potential of hydrogen-air combustion in gas condensing boilers. In the field of gas condensing boilers, groups of holes or slits can be used in perforated burner surfaces, providing a possible solution to the challenge of hydrogen air combustion. Real burners are always adjacent to an area with non-existent combustion, which can lead to a disturbed flame pattern. For this reason, a comparison between single-slit and multi-slit perforated flame holders with a significantly reduced structure temperature with a hydrogen-air premix is carried out as part of this study. Using Ansys Fluent, a 2D simulation approach is employed to analyze laminar flame stability behind a perforated flame holder. Inlet conditions consider fully premixed and homogenous distributed mixtures as well as nonhomogeneous premixed mixtures, with variations in pressure, velocity, and mixing degree. The model examines various slit-burner configurations and flashback behaviors based on an actual geometric shape used in a gas heating device. It has been found that with finite multi-slit burners, the bulk flow rates at the critical flashback point are 30–50% higher compared to infinitely symmetrical burners. A further deterioration of 32% is to be expected due to real mixture quality fluctuations and inhomogeneous inflow conditions. Finally, the findings demonstrate the model’s potential for designing efficient surface-stabilized burners and lay the groundwork for future 3D simulations in the pursuit of sustainable heating solutions.
Keywords: hydrogen combustion, flashback, flame stability, perforated flame holder, gas condensing boiler
Published in DKUM: 19.05.2025; Views: 0; Downloads: 6
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2. Comparison of emissions depending on the type of vehicle engineVladimír Rievaj, Ján Gaňa, František Synák, 2019, original scientific article Abstract: Road transport is showing growth in the period of globalization. Its task is to transport cargo as well as people to the required location within the shortest possible time and at the lowest price. Thus, road transport plays a crucial role in enabling the globalization to be developed and improved. However, the internal combustion engine hat prevail among the vehicles of freight and passenger transport are the producers of gaseous emissions from the exhaust gases. Many developed countries of the world has committed themselves, inter alia also trough the Paris Agreement, to reduce global warming, and thus to reduce the production of harmful gaseous emissions. The result is the endeavour to replace the internal combustion engine vehicles that burn carbon fuels with the vehicles powered by electric motors consuming electric energy. The reason of such trying claims that road transport using the internal combustion engine vehicles is environmentally aggressive, and the problem would not be solved by implementation of the vehicles with electric motors. Such claim is based on the fact that an electric car does not produce any of primary emissions. From an overall perspective, it is also necessary to take into account secondary emissions that are produced during the electric energy production by which is the vehicle with electric motor powered. The purpose of this article is to assume the possibility of reducing global pollution by replacing the internal combustion engine vehicles with the vehicles powered by electric motors in dependence with producing the emissions during the production of electric energy.
Keywords: electric energy, emissions, electric vehicle, internal combustion engine, global pollution
Published in DKUM: 22.08.2024; Views: 43; Downloads: 8
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3. Converting waste into products and energy using complete circular economy and the hydrogen effect technique to reduce dependence on natural gasAnita Kovač Kralj, 2023, original scientific article Abstract: Conversion of waste into products and energy has the potential to reduce CO2 emis-sion through implementation of a complete circular economy and utilisation of the hy-drogen effect technique. This study considers the novelties of the hydrogen effect tech-nique, which incorporates an upgraded input unit mathematical model. It includes real-simulated results obtained using an Aspen Plus & REG; simulator, and enlarged production. This technique is developed for optimal municipal solid waste (MSW) combustion, gas-ification, and reforming, presented as an upgraded input unit for syngas production, which can reduce CO2 emissions by 3 & BULL;106 kmol a-1. This approach is exemplified by utilizing existing methanol and dimethyl ether production processes from natural gas, as they can be achieved and exceeded using MSW with varying hydrogen amounts. The optimal upgraded methanol and dimethyl ether production processes can increase pro-duction by 47 % and 16 %, including only the upgraded input unit, as well as decrease the temperature in the product reactors by 30 & DEG;C.
Keywords: waste gasification, flue gas, syngas, hydrogen, circular economy, combustion
Published in DKUM: 13.02.2024; Views: 320; Downloads: 36
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4. Impacts of zero-emission powertrains based on hydrogen technologies in public transportNiko Natek, Boštjan Krajnc, 2020, original scientific article Abstract: This article reviews the development potentials and environmental impact of introducing category M3 vehicles (for passenger transport/buses) with fuel cell electric powertrains to an urban and inter-urban public transport service (PTS) to be operated in the Savinjsko-Šaleška region. The main focus is the demonstration of the PTS modelling and preliminary environmental impact assessment of the operation compared to conventional (modern) diesel-powered internal combustion engines.
Keywords: Hydrogen, Fuel Cell, Transport, Energy efficiency, Green-house gas emissions, Energy transition, Environment, Public transport service, Internal combustion Engine, CO2
Published in DKUM: 15.11.2023; Views: 415; Downloads: 31
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6. Small wood pellet boiler 3-D CFD study for improved flue gas emissions employing flue gas recirculation and air stagingFilip Kokalj, Tomas Zadravec, Aleksandar M. Jovović, Niko Samec, 2023, original scientific article Keywords: CFD, combustion, wood pellets, air staging, flue gas recirculation
Published in DKUM: 05.09.2023; Views: 391; Downloads: 17
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7. Analysis of the effect of the swirl flow intensity on combustion characteristics in liquid fuel powered confined swirling flamesMarko Klančišar, Tim Schloen, Matjaž Hriberšek, Niko Samec, 2016, original scientific article Abstract: This article examines the implementation of CFD technology in the design of the industrial liquid fuel powered swirl flame burner. The coupling between the flow field and the combustion model is based on the eddy dissipation model. The choice of the LES (Large Eddy Simulation) turbulence model over standard RANS (Reynolds Averaged Navier-Stokes) offers a possibility to improve the quality of the combustion-flow field interaction. The Wall Adapting Local Eddy-Viscosity (WALE) sub-grid model was used. The reaction chemistry is a simple infinitely fast one step global irreversible reaction. The computational model was setup with the Ansys-CFX software. Through the detailed measurements of industrial size burner, it was possible to determine the natural operational state of the burner according to the type of fuel used. For the inlet conditions, axial and radial velocity components were calculated from known physical characteristics of both the fuel and air input, with the initial tangential velocity of the fuel assumed as 18% of the initial axial fuel velocity. Different swirl number (S) values were studied. Addition of a surplus (in comparison to conventional flame stabilization) of tangential air velocity component (W), the rotational component increases itself with a considerably high magnitude, contributing to the overall flame stabilization. The level of S especially influences the turbulent energy, its dissipation rate and turbulent (Reynolds) stresses. In the case of high swirl number values (S > 0,65) it is possible to divide the flow field in three principle areas: mixing area (fuel-air), where exothermal reactions are taking place, central recirculation area and outer recirculation area, which primarily contains the flow of burnt flue gases. The described model was used to determine the flow and chemical behavior, whereas the liquid atomization was accounted for by LISA (Linear Instability Sheet Atomization) model incorporating also the cavitation within injection boundary condition. The boundary conditions were determined based on the data from the experimental hot water system. Depending on system requirements, especially with continuous physical processes as well as the results of experimental measurements, the paper reports on determination of the mixing field and its intensity in the turbulent flow, the description of heat release and interaction of turbulent flow field and chemical kinetics in the case of confined swirling flames.
Keywords: CFD, fluid dispersion, combustion, industrial burner, confined swirling flame, two-phase flow
Published in DKUM: 04.08.2017; Views: 1455; Downloads: 403
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8. Experimental investigation review of biodiesel usage in bus diesel engineBreda Kegl, Marko Kegl, 2017, original scientific article Abstract: This paper assembles and analyses extensive experimental research work conducted for several years in relation to biodiesel usage in a MAN bus Diesel engine with M injection system. At first the most important properties of the actually used neat rapeseed biodiesel fuel and its blends with mineral diesel are discussed and compared to that of mineral diesel. Then the injection, fuel spray, and engine characteristics for various considered fuel blends are compared at various ambient conditions, with special emphasis on the influence of low temperature on fueling. Furthermore, for each tested fuel the optimal injection pump timing is determined. The obtained optimal injection pump timings for individual fuels are then used to determine and discuss the most important injection and combustion characteristics, engine performance, as well as the emission, economy, and tribology characteristics of the engine at all modes of emission test cycles test. The results show that for each tested fuel it is possible to find the optimized injection pump timing, which enables acceptable engine characteristics at all modes of the emission test cycles test.
Keywords: bus diesel engine, fuel injection, fuel spray, combustion, emission, engine performance, tribology characteristics, optimized injection pump timing
Published in DKUM: 07.07.2017; Views: 1657; Downloads: 423
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