(57w) Revisions to the Qmefs Vapor Cloud Explosion Model

The Quest model for estimating flame speeds (QMEFS) was introduced in 2007, has since been published, and has been used by Quest and other companies to provide a detailed method for vapor cloud explosion (VCE) predictions. QMEFS provides a set of parameters that predict a flame speed, which then is used with the Baker-Strehlow-Tang (BST) blast curves to predict overpressure and impulse. The original intent of the QMEFS model was to provide better characterization of confined or congested areas, as well as fuel reactivities, that fit between the low, medium, and high categories offered by the BST model, so that the large differences in predictions between categories could be eliminated. In this way it provided a more refined system for predicting the consequences of a VCE, while remaining anchored within the flame speeds provided by the BST matrix.

In the years since QMEFS’ publication, there have not been a great deal of advancements in the understanding and simulation of vapor cloud explosions. However, use of the model has highlighted some of the areas where the model could be improved. This paper serves to refresh the reader on the basic construction of the model, and shows several ways in which the model has been enhanced to encompass more conditions than are covered by the BST model.