Abstract:
With the continuous improvement of coal mine intelligence, the number of underground wireless communication and electromagnetic equipment has increased significantly, and the complex electromagnetic environment may induce new risks of gas explosion. To break through the limitations of traditional research on thermal effect and electric spark ignition, this study focuses on the low-ionization weak plasma environment in mines and constructs a micro-dynamic analysis framework collaboratively driven by electromagnetic fields and weak plasma. It analyzes the physical mechanism of the cold ignition of gas induced by electromagnetic waves from the initial stage of the explosive chain reaction. By quantitatively simulating the acceleration process of free electrons in a time-varying electric field and their inelastic collision with methane molecules, this paper mainly investigates the coupling conditions of electron energy accumulation and molecular resonant dissociation. The results show that when the kinetic energy of free electrons accumulates to the threshold range of 5-10 eV, it can induce the dissociation of methane molecules and generate methyl and hydrogen radicals, thereby triggering the subsequent gas chain reaction process. Based on the complex scaling theory, calculation results indicate that the characteristic energy for low-energy electron impact on methane to form negative ion resonance states is concentrated in the range of 5-6 eV. Considering safety and adopting the most explosive working conditions, a quantitative comparison of the disaster-inducing characteristics of multi-band electromagnetic waves is carried out. The results show that the electric field strength required for very high frequency bands to drive electrons to critical energy is much lower than that of ultra-high frequency bands, showing obvious risk sensitivity. Combined with the geometric characteristics of underground roadway space and equipment structures, the field convergence effect caused by roadway wall reflection, equipment diffraction and multipath superposition is deeply simulated. The result displays that sharp metal components, periodic structures or parabolic-like morphologies can lead to local electric field strength distortion amplification by 10-100 times. Typical case verification shows that for a mine wireless device with a transmitting power of 0.5 W and a frequency of 150 MHz, the near-field electric field strength can exceed the safety threshold under the coupling effect of specific obstacles, which further explains that complex electromagnetic environments pose a substantial threat to gas safety.