Effects of initial temperature on CH₄/H₂ mixtures deflagration dynamics in slender confined pipelines

To evaluate the explosion hazards of CH₄/H₂ mixtures under different initial temperatures, this study investigates the influence of initial temperature (T₀) and hydrogen blending ratio (λ) on the dynamic evolution of deflagration shock waves and flames using a multi-component gas explosion test platform. The results show that the initial temperature is inversely related to the maximum explosion pressure (P_max), but positively correlated with the maximum rate of pressure rise (dP/dt)_max, average shock wave velocity (V_a), and average flame velocity (V_fa). Increasing the initial temperature reduces the energy density of the CH₄/H₂ mixtures while accelerating the chain-branching reactions, thereby promoting free-radical formation and enhancing the laminar flame speed. A higher hydrogen blending ratio leads to an exponential increase in P_max, (dP/dt)_max, and V_fa. This trend is attributed to the hydrogen component effect, which suppresses cumulative heat loss and strengthens the positive feedback mechanism between the flame and the shock wave. Furthermore, the growth rates of V_a and V_fa decrease with increasing initial temperature, as elevated temperatures diminish the inherent differences in deflagration flame characteristics between CH₄ and H₂. The evolution of flame morphology exhibits multi-coupling behavior involving thermal, flow-field, and shock-wave interactions, wherein the coupling between reflected pressure waves and the flame front governs the secondary acceleration of the flame. This process also displays temperature-dependent differentiation. These findings expand the knowledge base on the explosion characteristics of CH₄/H₂ mixtures and provide an important reference for assessing deflagration hazards under varied initial temperatures, as well as for formulating corresponding safety measures and emergency response protocols.