Abstract
FDS (Fire Dynamics Simulator) is the open-source software developed by NIST of USA. Pyrolysis is considerd to solve the one-dimensional heat conductivity equation in three directions respectively. FDS is applied widely for building fires, tunnel fires and so on. Since combustion analysis is significant for proactive measures, we have acquired enough skill to use for science programs. We have executed fire spread simulations of small plastic gears with a diameter of 30 mm and 10 mm in thickness in a closed duct to evaluate the capability of FDS as a development tool. In this report, we have investigated the combustion characteristics of an upper gear for the distance between two gears and aperture ratio of upper surface of the duct. We prepared an analytical model with 2.5 mm mesh size to compare time variation of temperature with the experimental results. Our numerical calculations correlated well with our experimental results. In addition, the time variation of concentration of a fuel gas showed a physically reasonable behavior. For the small distance between gears, the fuel gas generated from an under gear mainly plays an important role in ignition of the upper gear. We understand the effect of temperature and fuel concentration generaterd by the under gear. FDS Ver. 6 is applicable to solid combustion phenomena for 10 mm size plastics.
