Numerical Analysis of Piloted Ignition Over a Combustible Solid Tzung-Hsien Lin, Chia-Hung Wu Department of Mechanical Engineering Southern Taiwan University of Technology, Yung Kang, Tainan 710, Taiwan This study develops a two-dimensional piloted ignition model of a PMMA solid fuel heated by external radiation in a quiescent, normal gravity environment. The gas phase model consist of two-dimensional, time-dependent continuity, complete elliptic Navier-Stokes, energy and species equations. The combustion is described by a one-step overall chemical reaction with finite rate global kinetics. The solid phase is modeled by an unsteady energy and mass conservation equations, which coupled with the gas phase through the energy feed back term from the gas phase. The solid pyrolysis is described by first-order Arrhenius expression. The model investigated the piloted ignition phenomena and subsequent transition to flame spread behaviors under various igniter, fuel surface temperature and external heat flux. Besides the external radiation source, the piloted ignition needs a high temperature piloted igniter to trigger the thermal runaway in the gas phase. If the piloted igniter located at or near the region which the fuel/air mixture are within the flammable limitation, the flash or piloted ignition will occurs. In this study, the piloted igniter used in the laboratory such as high temperature particle, hot platinum wire and piloted small flame are modeled by the multi-points, linear type and plane type hot region within the raising plume in the gas-phase. Whereas the external radiant heat source used in laboratory is modeled by a Gaussian distribution heat flux in the computation model. This allows the pilot ignition as well as the flash phenomena can be simulated readily. The study parameters used in this work are the piloted igniter type, the location of the piloted igniter, the fuel surface temperature and the intensity of external radiant heat flux. It was found that the fuel surface temperature at the ignition increases with the distance of the igniter to the surface. The trend was compared with the previous experimental correlation. The ignition delay time under various intensity of external radiant heat flux also predicted and compared with experiments data for different igniter distance. Therefore, the piloted ignition is more hazards than the auto-ignition. Corresponding Author: Tzung-Hsien Lin Department of Mechanical Engineering Southern Taiwan University of Technology, 1 Nan Tai Street, Yung Kang, Tainan 710, Taiwan Telephone : 886-6-2533131 Ext 3542 FAX : 886-6-2425092 E-mail : thlin@mail.stut.edu.tw