Thermodynamic effects of the generation of H*/OH*/CH2O* on flammable gas explosion

Abstract

To establish the relationship between energy diffusion and intermediate generation during the gas explosion, a mathematical model of the maximum explosion pressure and the free radical concentration was built according to the explosive chain reaction mechanism and the laws of thermodynamics. A 20-L spherical closed explosion experimental system and spectral measurement system were used to collect the pressure and flame emission spectra characteristics during the explosion process of five typical gases (CH4, C2H6, C2H4, CO, and H2). The experimental results verified the reliability of the model by mathematical fitting. And the weight ratio of three free radicals (H*, OH* and CH2O*) to promote maximum explosion pressure was calculated. Results show that the explosion pressure can be linearly expressed by the sum of the concentration of all free radicals containing the same element. As the equivalent ratio increases, the peak of explosion pressure and radical emission intensity rise simultaneously; there is a piecewise linear relationship between them. When the equivalent ratio is less than 1, the promotion of the three free radicals to the maximum explosion pressure is equal; when the equivalent ratio is more than 1, the effect of the three free radicals on the maximum explosion pressure in descending order is H*, CH2O* and OH*. This is significant to the selection of chemical explosion suppression media, which provides a theoretical basis for the prevention and control of gas explosion.