To study the coupled relationship between the flame propagation and the pressure built-up of gas explosions

the test was carried out in a 5 L quartz duct with different concentrations of NaHCO3. The results showed that the pressure waveform of gas explosions gradually changed from a single-peak curve to a bimodal curve with the increase of the mass concentration. Moreover

there are more small particles per unit volume as the suppressant concentration was large enough

which would inhibit the flame propagation firstly and then prolonged the endothermic time of larger powders

making the flame front be further inhibited. In the middle and late stages of the flame propagation

the settlement of large particles resulted in the uneven distribution of powders in space

which significantly affected the inhibition efficiencies. The distribution of powders in the duct can be divided into three regions:the combustion zone with low powder concentration

the sedimentation and collection zone of large particles with high mass concentration and the suspension zone of small particles with low powder concentration. The time dependence of the flame front velocity was similar to that of overpressure. Although the flame front velocity can reflect the intensity of the combustion to some extent

the rise and fall of the overpressure cannot determine entirely by the trend of the flame front velocity. The explosion overpressure wouldn't decrease immediately with the transient reduction of the flame front velocity when the flame front velocity was large enough.