Experimental study on characteristics of methane-coal dust explosions and the spatiotemporal evolution of flow field in early flame

Abstract

To understand the explosion characteristics of methane-lignite coal dust mixtures and the spatiotemporal evolution of the early flame flow field, explosion pressure, OH* emission spectra, and early flame schlieren images were captured in a 60L constant volume combustion bomb. Schlieren image velocimetry was used to obtain the instantaneous velocity distribution of the methane-coal dust flame front. The results indicate that adding coal dust causes a nonlinear increase in explosion pressure, particularly at low methane concentrations. At a 5 % methane concentration, adding coal dust can increase the maximum explosion pressure by up to 39 % (190 kPa). The trend of the OH* emission spectra corresponds with the maximum explosion pressure. A slight increase in coal dust significantly enhances the OH* emission spectra, especially at lower concentrations, potentially increasing it by nearly five times. However, at higher coal dust concentrations, the OH* emission spectra are significantly reduced. Additionally, within the considered concentration range (≤58.14 g/m³), larger turbulent integral length scales in initial conditions consistently result in the fastest flame acceleration. These findings provide experimental evidence for further exploration of the explosion mechanisms of methane-coal dust mixtures and the development of chemical reaction kinetic models.