To understand the deflagration phenomenon of combustible gas in gas pipelines and improve the design of pipeline structural strength, this work adopted the self-developed experimental platform with a length of 12 m and a diameter of 90 mm to simulate the transportation process of urban variable-caliber gas pipelines. Experiments were conducted in a 9.5% methane/air premixed gas environment using a high-voltage ignition system, high-resolution data acquisition system, multiple piezoelectric sensors, fiber-optic flame speed sensors, ultra-high-speed laser schlieren system, and laser texture technology. The effects of blocking ratios of 0.4, 0.6, and 0.8 on the evolution characteristics of the deflagration wave system and the acceleration effect of combustible gas flames were comprehensively investigated. The blocking ratio was varied by placing an annular block somewhere along the pipeline. The results reveal that: (1) As the blocking ratio increased from 0 to 0.8, the pressure peak of the flow field did not appear near the ignition location. Comparing different blocking ratios, 0.4 blocking ratio had the maximum pressure, reaching 302 kPa, 0.6 blocking ratio reached the pressure peak position earliest, and the maximum pressure occurred at 83 times the cross-sectional diameter; (2) The blocking ratio of 0.6 had the most obvious effect on the flame acceleration, it could accelerate nearly three times within a range of 2 m, with a peak velocity of 130 m/s and an acceleration of 829 m/s; (3) By identifying the laser schlieren image, the flame acceleration process and the coupling relationship between the reflected wave and the flame were able to be clearly understood, and the obtained flame speed was consistent with the measurement speed of the fiber optic sensors. The research results can provide a basis for urban variable-caliber gas pipeline accident prevention and structural design, and provide new ideas for re-understanding the gas deflagration mechanism.

中文翻译：

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变口径管道内可燃气体爆燃波系演化特征及火焰加速效应

为了解燃气管道中可燃气体的爆燃现象，提高管道结构强度设计，本工作采用自主研发的长12 m、直径90 mm的实验平台，模拟城市变量的输送过程。口径燃气管道。实验在9.5%甲烷/空气预混合气体环境中进行，采用高压点火系统、高分辨率数据采集系统、多个压电传感器、光纤火焰速度传感器、超高速激光纹影系统和激光纹理技术。综合研究了0.4、0.6、0.8阻隔比对爆燃波系统演化特性和可燃气体火焰加速效果的影响。通过在管道沿线某处放置环形块来改变阻塞率。结果表明：（1）随着阻塞率从0增加到0.8，点火位置附近没有出现流场压力峰值。比较不同堵塞比，0.4堵塞比压力最大，达到302 kPa，0.6堵塞比最早达到压力峰值位置，最大压力出现在83倍截面直径处； (2)阻塞比为0.6对火焰加速影响最明显,在2 m范围内可加速近3倍,峰值速度为130 m/s,加速度为829 m/s; (3)通过识别激光纹影图像，可以清楚地了解火焰加速过程以及反射波与火焰之间的耦合关系，并且获得的火焰速度与光纤传感器的测量速度一致。研究成果可为城市变口径燃气管道事故预防和结构设计提供依据，为重新认识燃气爆燃机理提供新思路。