During the report period the research, work on open fires
has been directed, mainly, to the study of fire burning rates. A theoretical model of the process of the combustion of a liquid fuel contained in a vessel has been developed. This model gives stationary as well as transient burning rates of the fuel and tenperature distributions within the vessel as a function of the amount of heat received through the fuel surface. Dimensionless results are shown as well as several numerical applications for n-heptane, iso-octano, benzene, ethyl-alcohol and dioxane. An extense research program is being carried out in order to verify the theoretical conclusions and in oder to obtain basic
information on the conbustion process. The research facilities are, essentially, the same ones described in First Annual Report, although they have boon improved
and several radiometers have been installed. Several experimental results are shown as well as a comparison between theoretical and experimental results. Some interesting conclusions are obtained on the Open Fires
program which are included at tho end of the Report.
Theoretical and experimental studies on the problem of
transport of firebrands have shown that an excellent approximation of the process is obtained by assuming that the firebrands fly at their terminal or final velocity of fall. By means of numerical integrations of tho differential
equations of the process and by means of analytical calculations it is shown that in a matter of seconds the firebrands reach values of their velocities very close to tho terminal velocity of fall. Therefore, flight paths are calculated, under such assumption, and the experimental tests in the wind tunnel are carried out at wind speeds equal to tho firebrand terminal velocity of fall.
This is achieved "by reducing continuously tho wind speed in the tunnel during the test, in order to keep equal the values of the aerodynanic drag and the weight of the particle. This is controlled by the position of the wire holding the firebrand or else by the recorded curves of such weight and drug.
An extense research program is also being carried out,with
firebrands of several kind of woods (pinus pinaster, picer excelsa, quercus sessiliflora, populus tremuloides and ochrona lagopus) with spherical and cylindrical shapes and for different moisture contents. The small wind tunnel described in First Annual Report is being used. A large wind tunnel has been deaigned and constructed and it will be soon utilized.
Several results are shown and discussed, including flight
paths of the firebrands for several wind conditions.
Some important conclusions are obtained on the transport
of firebrands progran which at the end of the report.