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  • 1.
    Garami, Attila
    et al.
    University of Miskolc, Hungary.
    Toth-Pal, Zsolt
    RISE - Research Institutes of Sweden (2017-2019), Bioeconomy, ETC Energy Technology Center.
    Csordas, Bernadett
    University of Miskolc, Hungary.
    Palotas, Arpad
    University of Miskolc, Hungary.
    Reaction zone monitoring in biomass combustion2018In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 74, p. 95-106Article in journal (Refereed)
    Abstract [en]

    In this work we demonstrate the utilization of a machine vision-based combustion monitoring system in biomass combustion. The proposed system monitored the location of the reaction zone in a 3 MW, grate-fired biomass boiler operated at varying loads and with fluctuating fuel quality. The system can help guarantee equal primary air supply to different regions of the grate and avoid the elutriation of fly ash by providing information on the location of the reaction zone. Strong correlation was found between the reaction zone boundary location and most process parameters, indicating that the location of the reaction zone can be a useful metric in monitoring and control by providing supplementary measurements to already existing monitoring to avoid over-emissions and improve economics.

  • 2.
    Toth-Pal, Zsolt
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea KIMAB.
    Hammam, Tag
    RISE - Research Institutes of Sweden, Swerea, Swerea KIMAB.
    Pressure dependence of thermal contact resistance between copper heat sink and copper DBC surfaces in SiC power device packages2014Conference paper (Refereed)
    Abstract [en]

    Thermal contact resistances have been measured in an experiment emulating heat transfer from a SiC die to a cooled heat sink through a heat spreader and a DBC structure. The major surfacedependent parameters are the surface roughness, surface hardness, and planarity. The measured thermal contact resistances are in agreement with theoretical values. When investigating DBC copper surfaces a second interface between the bonded Cu to AlN has to be taken into account. © (2014) Trans Tech Publications, Switzerland.

  • 3.
    Toth-Pal, Zsolt
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, KIMAB.
    Zhang, Ya Fan
    RISE, Swedish ICT, Acreo.
    Nee, Hans Peter
    KTH Royal Institute of Technology, Sweden.
    Bakowski, Mietek
    RISE, Swedish ICT, Acreo.
    Investigation of pressure dependent thermal contact resistance between silver metallized SiC chip and molybdenum substrate and between molybdenum substrate and bulk copper2016In: Materials Science Forum, 2016, Vol. 858, p. 1061-1065Conference paper (Refereed)
    Abstract [en]

    Thermal contact resistances between a silver metallized SiC chip and a Molybdenum substrate and between the Molybdenum substrate and bulk Copper were measured in a heat transfer experiment. An experimental method to separate thermal contact resistances in a multilayer heat transfer path was used to extract the layer-specific contact resistances. The experimental results were compared with theory based calculations and also with 3-D computational fluid dynamics (CFD) simulation results. The results show significant pressure dependence of the thermal contact resistance and the results show higher thermal contact resistance per unit area between the bulk SiC chip and Molybdenum than between Molybdenum and bulk Copper.

  • 4.
    Toth-Pal, Zsolt
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea KIMAB.
    Zhang, Yafan
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Hammam, Tag
    RISE - Research Institutes of Sweden, Swerea, Swerea KIMAB.
    Nee, Hans Peter
    KTH Royal Institute of Technology, Sweden.
    Bakowski, Mietek
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Thermal improvement of press-pack packages: Pressure dependent thermal contact resistance with a thin silver interlayer between molybdenum substrate and silicon carbide chip2017In: 2017 IEEE International Workshop on Integrated Power Packaging, IWIPP 2017, 2017Conference paper (Refereed)
    Abstract [en]

    In typical press-pack, free-floating packages the thermal contact resistance between chip and substrate is a major limiting factor for the cooling ability of the power module. We report an introduction of a new, thin Silver interlayer between Molybdenum substrate and chip, and how it improves the thermal contact. The thermal contact resistances were measured with and without a Silver interlayer at different pressures. The surface roughness of the SiC chip and the Molybdenum substrate were characterized. The thermal contact resistances were measured at three different heating power levels. The results show a significant reduction of the thermal contact resistance with only a few micrometer Silver interlayer. The improved cooling effect of a Silver interlayer was also demonstrated with a fluid dynamics type of 3 D simulation comparing temperature distributions with and without a Silver interlayer. These results project a possible thermal improvement in press-pack packages.

  • 5.
    Winikka, Henrik
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Toth, Pal
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. University of Miskolc, Hungary.
    Jansson, Kjell
    Stockholm University, Sweden.
    Molinder, Roger
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Broström, Markus
    Umeå University, Sweden.
    Sandström, Linda
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Lighty, JoAnn S.
    University of Utah, USA.
    Weiland, Fredrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Particle formation during pressurized entrained flow gasification of wood powder: Effects of process conditions on chemical composition, nanostructure, and reactivity2018In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 189, p. 1339-1351Article in journal (Refereed)
    Abstract [en]

    The influence of operating condition on particle formation during pressurized, oxygen blown gasification of wood powder with an ash content of 0.4 wt% was investigated. The investigation was performed with a pilot scale gasifier operated at 7 bar(a). Two loads, 400 and 600 kW were tested, with the oxygen equivalence ratio (λ) varied between 0.25 and 0.50. Particle concentration and mass size distribution was analyzed with a low pressure cascade impactor and the collected particles were characterized for morphology, elemental composition, nanostructure, and reactivity using scanning electron microscopy/high resolution transmission electron microscopy/energy dispersive spectroscopy, and thermogravimetric analysis. In order to quantify the nanostructure of the particles and identify prevalent sub-structures, a novel image analysis framework was used. It was found that the process temperature, affected both by λ and the load of the gasifier, had a significant influence on the particle formation processes. At low temperature (1060 °C), the formed soot particles seemed to be resistant to the oxidation process; however, when the oxidation process started at 1119 °C, the internal burning of the more reactive particle core began. A further increase in temperature (> 1313 °C) lead to the oxidation of the less reactive particle shell. When the shell finally collapsed due to severe oxidation, the original soot particle shape and nanostructure also disappeared and the resulting particle could not be considered as a soot anymore. Instead, the particle shape and nanostructure at the highest temperatures (> 1430 °C) were a function of the inorganic content and of the inorganic elements the individual particle consisted of. All of these effects together lead to the soot particles in the real gasifier environment having less and less ordered nanostructure and higher and higher reactivity as the temperature increased; i.e., they followed the opposite trend of what is observed during laboratory-scale studies with fuels not containing any ash-forming elements and where the temperature was not controlled by λ.

  • 6.
    Ögren, Yngve
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Toth, Pal
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. University of Miskolc, Hungary.
    Garami, Attila
    University of Miskolc, Hungary.
    Sepman, Alexey
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Development of a vision-based soft sensor for estimating equivalence ratio and major species concentration in entrained flow biomass gasification reactors2018In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 226, p. 450-460Article in journal (Refereed)
    Abstract [en]

    A combination of image processing techniques and regression models was evaluated for predicting equivalence ratio and major species concentration (H2, CO, CO2 and CH4) based on real-time image data from the luminous reaction zone in conditions and reactors relevant to biomass gasification. Two simple image pre-processing routines were tested: reduction to statistical moments and pixel binning (subsampling). Image features obtained by using these two pre-processing methods were then used as inputs for two regression algorithms: Gaussian Process Regression and Artificial Neural Networks. The methods were evaluated by using a laboratory-scale flat-flame burner and a pilot-scale entrained flow biomass gasifier. For the flat-flame burner, the root mean square error (RMSE) were on the order of the uncertainty of the experimental measurements. For the gasifier, the RMSE was approximately three times higher than the experimental uncertainty – however, the main source of the error was the quantization of the training dataset. The accuracy of the predictions was found to be sufficient for process monitoring purposes. As a feature extraction step, reduction to statistical moments proved to be superior compared to pixel binning.

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