Experimental study on the effects of venting area on the structural response of vessel walls to methane-air mixture deflagration

To investigate the effects of venting areas on the structural response of the vessel walls to an explosion, a series of vented explosion experiments of a 10% methane-air mixture were carried out in a 1 m3 rectangular vessel with different venting areas. The adjustable area explosion vent was on the top of the rectangular container, and a piece of aluminum membrane bolted with a flange was used as a vent cover. The vibration acceleration rates and internal overpressures were recorded by an acceleration sensor and a pressure sensor, respectively, the flame propagation images were captured by a high-speed camera during deflagration and the frequency-time distributions of signals were obtained by using the short-time fast Fourier transform. The following conclusions could be obtained by analyzing acceleration rates, internal overpressures, flame propagation images and frequency-time distributions of signals. (1) The change trends of vibration acceleration and internal overpressure are similar, and both have obvious double peaks, but the vibration acceleration peak appears slightly later than the overpressure. As the dimensionless coefficient increases, the first peak of internal overpressure and vibration acceleration increases, and the second peak first decreases, then increases, and finally decreases. (2) Two types of structural response with different amplitudes and frequency distributions were observed. The low-amplitude vibrations are triggered by the combined effects of flame initial propagation, Helmholtz-type oscillations, and Taylor instability, while the high-amplitude vibrations are triggered by the coupling of sound waves and flames. (3) Before the flames are ejected from the vent, the average velocities of the upper flames decrease with the increase of the dimensionless coefficient and the flames are ejected from the vent earlier when the dimensionless coefficient is smaller. (4) Under the current experimental conditions, the thermoacoustic coupling phenomenon is the most violent when the dimensionless coefficient is 25.00, as characterized by the maximum amplitude vibration response and maximum energy high-frequency oscillation. As the dimensionless coefficient further increases or decreases, the thermoacoustic coupling phenomenon gradually attenuates. © 2022, Editorial Staff of EXPLOSION AND SHOCK WAVES. All right reserved.