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The existence of branch pipelines is very common in industry. And the angles between the pipes are different. For studying the influence of inclined crossed pipe and different equivalence ratios on the flame propagation dynamics of premixed methane/air, a high-velocity camera and pressure sensor were used to record the flame propagation images and the changes of pressure inside the pipe on the basis of experiments. The results show the maximum flame propagation velocity and the maximum overpressure increased with the increase of equivalent ratios. Since the crossover pipe was set up with three outlets, the obtained results showed the maximum overpressure value in the straight pipeline was higher than that in the cross pipeline, 0.1553 bar and 0.1142 bar, respectively. Nevertheless, the maximum flame propagation velocity in cross pipe was much higher than that in straight pipe, 65.6 m/s and 25.6 m/s, respectively. The existence of branch pipe can greatly improve the flame velocity. [ABSTRACT FROM AUTHOR]

To further investigate the flame dynamics inside the special tubes, experiments were carried out in a T-type tube to investigate the effect of the equivalence ratio and the opening ratio on the deflagration of the methane-air premixed mixture. The changes of flame structure, propagation velocity and overpressure during flame propagation are analyzed. The experimental results shown when equivalence ratio was 1.0 and the outlets was fully open, the mixture burned completely, the flame propagation velocity was the highest, it taken only 51 ms for the flame to spread to the exits at both ends and the flame shape was more symmetrical. Under the same equivalence ratio, the increase of the opening ratio would cause the flame propagation velocity to increase, but the overpressure would decrease. When the opening ratio was 0.25, the resistance encountered during the flame propagation process was the largest, and the turbulence at the fork also increased, the interaction between the two caused the maximum overpressure of 0.58 bar at this time. The coupling effect of overpressure and flame front velocity could also clearly show that the two were positively correlated, and the velocity of the flame propagating to the left and right ends of the horizontal tube was symmetrical. When the equivalence ratio was 1.0, as the opening ratio increases, the time to reach the maximum overpressure peak shown a linear downward trend. These findings add to our knowledge of the deflagration dynamics of special tubes. [ABSTRACT FROM AUTHOR]