EFFECTS OF ASPECT RATIO AND IGNITION LOCATION ON VENTED EXPLOSION PRESSURES

A three-dimensional gasdynamic model with constant burning velocity is applied for the prediction of the maximum pressure rise from gaseous combustion in vented enclosures with variable aspect ratios and ignition locations. A series of calculations for vented enclosures with aspect ratio varied between 0.5 and 8 are presented as well as a series of calculations for three different ignition locations. In addition to the aspect ratio and ignition location, the flame speed and the vent size were also parameters of the study. A solution for the evaluation of the flame surface area from the model output is developed. This solution is used for the determination of a quantity known as the “vent parameter”, which is widely used in analytical models for prediction of the maximum reduced explosion pressure. Results of calculations are compared with an ideal analytical solution for spherical vessels, with results from a previous study using the same 3D gasdynamic model and with the NFPA 68 guidelines for vent sizing. It is shown that both changes in aspect ratio and changes in the ignition location result in shifts along the same reduced pressure rise- vent parameter curve. The results of the analysis have been summarized by a formula for the practical evaluation of the effects of aspect ratio on the maximum explosion pressure