Abstract
A self-developed gas explosion experimental system was used to detonate methane/air mixtures of different concentrations by different ignition methods, and the propagation processes of spherical flames and irregular flames formed by the explosions were recorded using a high-speed camera. Based on image processing and the fractal interpolation method, the propagation velocity of the explosion-stretched flame was calculated. The flame image was processed in MATLAB to optimize the traditional calculation method. Based on fractal theory, a fractal interpolation function was constructed to calculate the propagation velocity at each point on the front of the spherical stretched flame, and then, the laminar combustion velocity of the methane/air mixed balloon flame was obtained. Compared with the numerical simulation and empirical formula, the error in the laminar flame velocity was less than 0.2%, which verifies the correctness of the image processing and fractal interpolation method to calculate the flame propagation velocity. Using this method, the propagation velocity of the irregular fold stretching flame of the methane/air mixture was calculated, and the propagation velocity at each point along the flame front was obtained. The reason why the flame speed of the gas explosion with a high-temperature source was higher than the flame speed of the gas explosion with an electric spark was preliminarily explained.
Highlights
IntroductionMethane is the main component of natural gas, and as an alternative fuel for automotive internal combustion engines, methane is widely used in many countries worldwide. With its excellent combustion performance, methane serves many fields, such as home cooking, heating, and medicine. In the process of storage and transportation, due to the low explosion limit of methane, explosion accidents occur. The explosion shock wave and high-temperature flame generated by methane will cause severe casualties and property losses. Explosion accidents caused by gas outbursts in coal mines occur frequently in various countries.17–25Flame velocity is the main characteristic parameter for describing the propagation law of explosions and can represent the variation in an explosion in a certain time and space. The size of the explosion is closely related to the degree of flame expansion in the explosive reaction zone, the maximum explosion pressure, the rate of pressure increase, and the temperatures in the reaction zone and unreacted zone. For example, Andrews found that the flame propagation speed increases with increasing temperature in the unreacted zone. Metghalchi concluded that the flame propagation velocity is negatively correlated with the pressure
(3) The contour of the outer edge of the flame propagation image at different times is accurately extracted based on the image processing method of MATLAB. (4) The flame contours at different times are divided by selecting 48 points of the extracted flame contour at different times
(2) Compared with the results of the empirical formula method and numerical simulation, the combustion velocity of the spherical propagating flame at 11 positions was calculated by using image processing and the fractal interpolation method
Summary
Methane is the main component of natural gas, and as an alternative fuel for automotive internal combustion engines, methane is widely used in many countries worldwide. With its excellent combustion performance, methane serves many fields, such as home cooking, heating, and medicine. In the process of storage and transportation, due to the low explosion limit of methane, explosion accidents occur. The explosion shock wave and high-temperature flame generated by methane will cause severe casualties and property losses. Explosion accidents caused by gas outbursts in coal mines occur frequently in various countries.17–25Flame velocity is the main characteristic parameter for describing the propagation law of explosions and can represent the variation in an explosion in a certain time and space. The size of the explosion is closely related to the degree of flame expansion in the explosive reaction zone, the maximum explosion pressure, the rate of pressure increase, and the temperatures in the reaction zone and unreacted zone. For example, Andrews found that the flame propagation speed increases with increasing temperature in the unreacted zone. Metghalchi concluded that the flame propagation velocity is negatively correlated with the pressure.. Methane is the main component of natural gas, and as an alternative fuel for automotive internal combustion engines, methane is widely used in many countries worldwide.. In the process of storage and transportation, due to the low explosion limit of methane, explosion accidents occur.. The explosion shock wave and high-temperature flame generated by methane will cause severe casualties and property losses.. Explosion accidents caused by gas outbursts in coal mines occur frequently in various countries.. Flame velocity is the main characteristic parameter for describing the propagation law of explosions and can represent the variation in an explosion in a certain time and space.. Andrews found that the flame propagation speed increases with increasing temperature in the unreacted zone.. Metghalchi concluded that the flame propagation velocity is negatively correlated with the pressure.
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