Effect of airflow velocity on flame propagation and pressure of starch dust explosion in a pneumatic conveying environment

To investigate the flame propagation and pressure characteristics of dust explosions during the airflow transportation of dust particles, a 2 m transparent pipeline, supplied with a constant airflow from a fan, was constructed as a dust explosion testing apparatus. The distribution patterns of airflow velocity were measured using an anemometer and subjected to statistical analysis. Dust explosion experiments were conducted with airflow velocities of 5, 10 and 15 m/s, and an ignition energy of 1 kJ was applied to the transported dust particles. The results revealed that the flame propagation of starch explosions undergoes distinct stages: ignition, slow propagation, accelerated propagation. The flame propagation speed and explosion pressure initially increased and subsequently decreased as the airflow velocity was raised. As the airflow velocity increased from 5 m/s to 10 m/ s, the maximum flame propagation speed rose from 53.2 m/s to 67.7 m/s, and the maximum explosion pressure increased from 25.62 kPa to 31.96 kPa. At an airflow velocity of 15 m/s, both the maximum flame propagation speed and explosion pressure decreased, reaching 32.6 m/s and 19.67 kPa, respectively. In contrast to conventional closed container powder injections, chemical igniters in the pneumatic conveying environment exhibit elongated flames, with the airflow influencing the timing of dust deflagration flame appearance and accelerating flame propagation. Due to the connectivity of the airflow transport pipeline, the explosion pressure tends to be lower. Influenced by non-uniform airflow and temperature differentials, dust deflagration flames within the airflow transport pipeline manifest a spiral propagation structure.