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Wyszukujesz frazę "ion current" wg kryterium: Temat

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    Wyświetlanie 1-2 z 2
    Tytuł:
    Application of Ion Current Measurement to Identification of Combustion Parameters in a Homogeneous Charge Compression Ignition Engine
    Autorzy:
    Hunicz, J.
    Filipek, P.
    Sobiesiak, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/221670.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    HCCI
    ion current
    heat release rate
    combustion control
    Opis:
    This study examines the application of ion current measurements to the identification of heat release parameters inside the combustion chamber of a homogeneous charge compression ignition (HCCI) engine fuelled with gasoline. HCCI combustion was achieved with the use of exhaust gas trapping. Combustion parameters derived from the in-cylinder pressure and ion current measurements were compared and analysed. Ion current measurements were accomplished using the existing spark plug and a dedicated electronic circuit. The experiments were performed at a variable excess air ratio and a variable amount of trapped residuals. The results showed a good correlation between peak values of the ion current and heat release rate, except for the cases where a fuel-rich mixture was burnt. The computed ion current integral over the volume of the combustion chamber showed a good agreement with the heat released in the combustion chamber, however this parameter was found to be affected by the amount of trapped residuals. Combustion timing characteristic values computed using heat release and ion current were found to be correlated, however the relationship was not linear.
    Źródło:
    Metrology and Measurement Systems; 2018, 25, 1; 223-234
    0860-8229
    Pojawia się w:
    Metrology and Measurement Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Leakage Current Degradation Due to Ion Drift and Diffusion in Tantalum and Niobium Oxide Capacitors
    Autorzy:
    Kuparowitz, M.
    Sedlakova, V.
    Grmela, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/221515.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    niobium oxide capacitors
    tantalum capacitors
    leakage current
    ion diffusion
    ion drift
    Opis:
    High temperature and high electric field applications in tantalum and niobium capacitors are limited by the mechanism of ion migration and field crystallization in a tantalum or niobium pentoxide insulating layer. The study of leakage current (DCL) variation in time as a result of increasing temperature and electric field might provide information about the physical mechanism of degradation. The experiments were performed on tantalum and niobium oxide capacitors at temperatures of about 125°C and applied voltages ranging up to rated voltages of 35 V and 16 V for tantalum and niobium oxide capacitors, respectively. Homogeneous distribution of oxygen vacancies acting as positive ions within the pentoxide layer was assumed before the experiments. DCL vs. time characteristics at a fixed temperature have several phases. At the beginning of ageing the DCL increases exponentially with time. In this period ions in the insulating layer are being moved in the electric field by drift only. Due to that the concentration of ions near the cathode increases producing a positively charged region near the cathode. The electric field near the cathode increases and the potential barrier between the cathode and insulating layer decreases which results in increasing DCL. However, redistribution of positive ions in the insulator layer leads to creation of a ion concentration gradient which results in a gradual increase of the ion diffusion current in the direction opposite to the ion drift current component. The equilibrium between the two for a given temperature and electric field results in saturation of the leakage current value. DCL vs. time characteristics are described by the exponential stretched law. We found that during the initial part of ageing an exponent n = 1 applies. That corresponds to the ion drift motion only. After long-time application of the electric field at a high temperature the DCL vs. time characteristics are described by the exponential stretched law with an exponent n = 0.5. Here, the equilibrium between the ion drift and diffusion is achieved. The process of leakage current degradation is therefore partially reversible. When the external electric field is lowered, or the samples are shortened, the leakage current for a given voltage decreases with time and the DCL vs. time characteristics are described by the exponential stretched law with an exponent n = 0.5, thus the ion redistribution by diffusion becomes dominant.
    Źródło:
    Metrology and Measurement Systems; 2017, 24, 2; 255-264
    0860-8229
    Pojawia się w:
    Metrology and Measurement Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-2 z 2

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