Effects of reduced oxygen levels on flame propagation behaviors of starch dust deflagration

An experimental investigation of reduced oxygen levels on flame behaviors of starch dust deflagration is studied in a half-closed dust explosion tube. Six kinds of nitrogen/air ratio mixtures are prepared as the experimental atmosphere for flame propagation. A high-speed photography is used to record flame propagation behaviors and luminous features. The characteristics of flame temperature and deflagration pressure are measured by fine thermocouple and pressure sensor, respectively. The influence of reduced oxygen concentration on flame propagation characteristics are discussed in different conditions. The results show that reducing the oxygen content can effectively retard the flame propagation process and weaken the dust combustion reaction. Compared with air atmosphere, flame acceleration process under reduced oxygen atmosphere is suppressed and the luminous intensity of flame post-combustion zone is greatly diminished. The characteristic parameters of flame velocity, flame temperature and deflagration pressure are all influenced by the reduction in oxygen concentration. Furthermore, effective partial inerting suppression can be achieved for starch deflagration flame, when the oxygen concentration is lower than 18.90%. This study is helpful for dust explosion prevention and mitigation. Additionally, the dust cloud concentration changes the flame velocity characteristic at low oxygen levels and higher dust concentration is more limited the flame acceleration.