Turbulence generated by dust dispersion in the standard 1 m3 vessel

Abstract

The standard 1 m3 vessel is an apparatus recommended for an assessment of dust explosion indices by ISO, European and American Standards. However the definition of the vessel construction given in the Standards leaves some room when designing it. That may lead to significantly different results obtained in vessels built in different laboratories even when all of them meet the requirements of the Standards. One of key parameters that should be controlled in the tests is turbulence. Several authors reported measurements of turbulence intensity in the 1 m3 vessel. However, all of those results were obtained for pure air dispersed from the dust dispersion system. The paper presents results of turbulence measurements performed in the 1 m3 vessel built and used at Experimental Mine Barbara of Central Mining Institute, Poland. In previous measurements transient flow velocity in the vessel was generated by dust injection from the dust dispersion system. For the measurement the Bi-Directional Velocity Probe developed by McCaffrey and Heskestad ((McCaffrey B.J. (1976)) was used. The construction of the probe was modified to improve its performance in the dusty conditions. The tests were performed for several nominal dust concentrations of two dusts. From the measurements the root-mean-square of instantaneous velocity (u'rms) was calculated. The results were compared with the results obtained for pure air in the dust dispersion system. The presence of dust modifies turbulence in the vessel. Its intensity is reduced and the flow development is delayed.