Multiple venting behavior of inner dust explosions

Explosion venting experiments of corn starch are carried out in a small-scale container. With the help of a high-speed camera and a pressure sensor, an interesting multiple venting behavior and its physical mechanism are comprehensively analyzed. The results suggest that the failure of the venting structure could cause three times intermittent explosion venting at most, which is negatively correlated with the opening pressure. Only the first venting significantly changes the internal explosion pressure. The flame behavior changes substantially from one venting to the other, even under the same operating conditions. The first venting flame occurs in an underexpanded jet form (with point sparks at the front), the second one is bright and spherical (without sparks), and the third one is dim and exhibits a striped pattern. In addition, the earlier the venting, the larger the average velocity of the external flame. With the opening pressure increasing, a decrease in the maximum propagation distance and time of the first venting flame is observed; simultaneously, the average flame velocity and the maximum instantaneous flame velocity increase. There is no such a phenomenon in secondary venting, although the flame brightness gradually decreases. Overall, the results may provide a theoretical basis for the safety design of explosion venting and further exploration of the explosion mechanism.