Abstract:
This paper considers the effect of an electric field on the methane flame plume. The main purpose of this study is to determine the characteristic regimes of the effect of an external electric field on the methane combustion, which are characterized by significant changes in the temperature pulsation spectrum. The temperature distribution in the methane flame plume was analyzed by infrared thermography. When the flame was exposed to an electric field up to a voltage of 4.0 kV, the maximum amplitude of temperature pulsation decreased from 20 K to 12 K. At a voltage of 4.5 kV, a significant reduction in temperature pulsation amplitude was observed up to 4 K. In the voltage range of 5.0 - 8.0 kV, the temperature pulsations in the flame plume were minimal, and there were no characteristic frequency maxima in the spectrum. Further increase of voltage up to 10 kV again led to the appearance of frequency maxima, but they were shifted toward lower frequencies by 3 Hz. The maximum amplitude of the temperature pulsations became equal to 10 Hz, as well as three subsequent harmonics (20, 30, and 40 Hz). The temperature change in the flame plume is related to the flow structure and chemical reactions. This is caused by changes in the main hydrodynamic parameters (velocity, pressure, density, etc.), which in turn affect the transfer coefficients. This fact has an impact on the oxidizer entry into the combustion zone and the chemical reactions occurring in the flame. Thus, the presence of an external electric field has a significant effect on the variation of all the above parameters and leads to changes in the shape and height of the flame, as well as in the characteristic temperatures.
Keywords:thermography, temperature pulsations, flame structure, methane, temperature pulsation spectrum.
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