Characteristics of nano-PMMA dust explosion through the vented tube

Abstract

The explosion venting experiments of 150 nm polymethyl methacrylate (PMMA) dust with different lengths (L) and diameters (D) of the vent tube are conducted. The effect of tube size on overpressure and flame propagation behavior is explored. High-frequency and low-frequency Helmholtz oscillations are observed on the overpressure curves in the chamber. The (dP/dt)max in the chamber is increased with high-frequency oscillations, while the maximum flame width is also visible with low-frequency Helmholtz oscillations. As the L increases from 0 m to 2 m, the Pred,max increases by 29.2–145.1% and the (dP/dt)max increases by 38.4% − 127.7%. With the increase of the D, the Pred,max in the chamber and vent tube decreases, and the flame transforms from an under-expansion jet flame to a subsonic jet flame. Due to the interaction between the external flow field and the concentration of unburned particles, the maximum external overpressure increases alongside with the incease of the tube length and diameter. In addition, the maximum calculation error of EN14491 is 1100%, while NFPA68 seriously underestimates the explosion venting pressure. A modified prediction model is established to provide a design method for a safe vent through the vent tube of the nano-dust explosion.