科研之友
微信
新浪微博
Facebook
分享链接
摘要
An unsteady three-dimensional numerical model has been formulated, coded, and solved to study ignition and flame development over a composite solid fuel sample upon heating by a localised radiant beam in a buoyant atmosphere. The model consists of an unsteady gas phase and an unsteady solid phase. The gas phase formulation consists of full Navier-Stokes equations for the conservation of mass, momentum, energy, and species. A one-step, second-order overall Arrhenius reaction is adopted. Gas radiation is included by solving the radiation transfer equation. For the solid phase formulation, the energy (heat conduction) equation is employed to solve the transient solid temperature. A first-order in-depth solid pyrolysis relation between the solid fuel density and the local solid temperature is assumed. Numerical simulations provide time-and-space resolved details of the ignition transient and flame development and the existence of two types of ignition modes: one with reaction kernel initiated on the surface and the other with ignition kernel initiated in the gas phase. Other primary outputs of the computation are the minimum ignition energy (Joule) for the solid as a function of the external heating rate (Watt). Both the critical heat input for ignition and the optimal ignition energy are identified. Other parameters that were varied over the simulations include: sample thickness, ignition heat source spatial shape factor, and gravity level.
- 出版日期2013-12-1
