On the Development and Characterization of a Reduced Scale Continuous Feed Firebrand Generator

Abstract

A new experimental apparatus, known as the NIST Reduced Scale Continuous Feed Firebrand Generator (the NIST continuous feed Baby Dragon) is presented. This version of the Firebrand Generator is based upon the NIST Dragon, the only experimental device capable of generating controlled firebrand showers. The unique features of the continuous feed Baby Dragon, as opposed to the present NIST Dragon, is the capability to produce a constant firebrand shower in order to expose building materials to continual firebrand bombardment. An experimental series was conducted to determine the range of operating conditions for this device. Wood pieces were fed into the device using a conveyer system, ignited using a propane burner, and a blower was used to loft the generated firebrands. The number flux and mass flux were measured as function of feeding rate to determine optimum conditions to generate steady firebrand showers. It was observed that a feeding rate of 15 pieces (34.6 g/min) provided the most constant and uniform continuous firebrand production. Measurements of heat release rate (HRR) were conducted to make sure the device provided low HRR in order to determine if it may be considered for use by testing laboratories in a safe manner. Finally, the firebrand size and mass produced using the newly developed device presented in this paper are commensurate to those measured from full scale tree burns and actual WUI fires.