Experimental study on the effect of concentration gradient on explosion dynamics and flame propagation in a methane-filled pipeline

Traditional studies on gas explosions are typically conducted under uniform conditions. However, in practical scenarios, gas distribution is often non-uniform, a factor that significantly influences the explosion process. To further explore the impact of such non-uniform distributions on the deflagration and detonation characteristics of combustible gases, this study designs and establishes an experimental platform capable of accurately quantifying concentration gradients during gas explosion and propagation. The experiments demonstrate that the most severe impact of shock waves and flame propagation occurs under conditions of uniform gas distribution, where the maximum overpressure reaches 395.28 kPa and the average flame propagation velocity reaches 214.74 m/s. The presence of concentration gradients mitigates the overpressure hazard of explosions and suppresses flame propagation and development. Moreover, positive concentration gradients (fuel-lean to fuel-rich) exhibit a weaker inhibitory effect on explosion characteristics compared to negative concentration gradients (fuel-rich to fuel-lean). When the volume of methane injected into the pipeline remains constant, a 4 % variation in concentration gradients results in a 57 % and 79 % reduction in maximum overpressure under positive and negative gradient conditions, respectively. These experimental findings can offer valuable theoretical guidance and data support for the design of explosion resistance and venting systems in combustible gas installations.