The Influence of the obstacle position on the explosion characteristics of methane-hydrogen-air premixed gas in a closed 90° bend pipe

Abstract

Abstract Experiment and numerical simulation were combined to reveal the influence of the obstacle position on the combustion and explosion characteristics of methane-hydrogen-air mixture in a closed 90° bend pipe. The results showed that the synergistic effect of the obstacle and the hydrogen addition significantly enhanced the explosion intensity of the mixed gas. Affected by the turbulent vortex near the obstacle, the flame was distorted significantly when it approached the obstacles, thus enhancing the flame instability and accelerating the flame transition from layer to turbulence. The relative position between the obstacle and the elbow in the 90°bend pipe had an obvious influence on the excitation of flame propagation. When the distance between the obstacle and the elbow was more than 6 times the diameter of the pipe, the closer the obstacle was to the ignition end, the stronger the excitation effect. When the distance between the obstacle and the elbow was 2 to 6 times the diameter of the pipe, the excitation effect of the obstacle on the flame propagation gradually increases with the decrease of the distance. When the distance between the obstacle and the elbow was less than twice the diameter of the pipe, because the vortex size was less than the distance between the obstacle and the elbow, the flame easily contacted pipe wall after it entered the vortex area, resulting in partial flame extinguishing,, which was not conducive to the flame acceleration. When the obstacle was located behind the elbow, the excitation effect of the obstacle on the flame propagation was weak. The maximum explosion pressure of the methane-hydrogen-air premixed gas in the barrier bend pipe can be divided into two parts according to obstacle positions. When the distance between the obstacle and the elbow was more than 6 times the diameter of the pipe, the maximum explosion pressure was mainly affected by the obstacle position. However, when the distance between the obstacle and the elbow was less than 6 times the diameter of the pipe, the maximum explosion pressure was comprehensively affected by the combustion characteristics of the mixed gas and the obstacle position.