Explosion limit evolution of low calorific value coalbed methane and its response to fuel blending

Low-calorific-value coalbed methane (LCVCBM), defined by a low methane concentration and substantial dilution with inert gases, presents significant challenges for clean and efficient combustion due to its narrow flammability range and limited chemical reactivity. In this study, the explosion limit (EL) characteristics of LCVCBM are systematically examined through numerical simulations employing detailed chemical kinetic mechanisms. Three representative LCVCBM compositions from distinct mining areas are selected to evaluate the effects of compositional variations, particularly C₃ and C₄ hydrocarbon content, on explosion behavior. The results indicate that the presence of higher hydrocarbons broadens the explosion region and promotes negative temperature coefficient (NTC) behavior, particularly in the intermediate temperature range (600-800 K), thereby enhancing overall reactivity, although the marginal contraction of explosion-limit boundaries gradually converges as the C₃/C₄ content increases. Variations in equivalence ratio demonstrate distinct temperature-dependent behaviors. While a higher equivalence ratio does not monotonically enhance explosion sensitivity, the high-temperature region above approximately 945 K exhibits nonlinear evolution of explosion-limit boundaries, including a plateau-like response between approximately 950 and 1100 K, arising from suppression of effective chain-branching reactions under oxygen-limited conditions. Furthermore, dimethyl ether (DME) exhibits superior performance compared with methanol in promoting explosion reactivity, primarily through low-temperature chain-initiation pathways involving CH₂O and H₂O₂ intermediates. This study provides new insights into the explosion behavior of LCVCBM within multicomponent synergistic reaction systems and offers theoretical support for optimizing oxygenated-fuel blending strategies for LCVCBM, laying a foundation for its clean and efficient utilization.