报告内容：关于池火燃烧和辐射特性的专题报告
报 告 人：John de Ris博士（中科院外国专家特聘研究员）
报告时间：12月7日下午3:00
报告地点：火灾实验室多媒体会议室
参加人员：欢迎感兴趣的师生参加！
报告摘要：
The talk presents a model for the radiant fraction, incompleteness of combustion,
and effective radiation temperature with its associated absorption coefficient for
buoyant turbulent diffusion flames characteristic of fires. Effects of heat loss
(gain) to nearby surfaces are included.
The combustion of the turbulent diffusion flames is driven by the local Rayleigh
instability of the flamelets. It results in the: (1) volumetric heat release rate,
(2) radiant fraction, and (3) incompleteness of combustion all being constants
independent of the fire size.
Radiation comes primarily from luminous soot. The radiative heat loss from flamelets
causes their local extinction with release of soot. Radiative extinction occurs in both
buoyant turbulent diffusion flames as well as laminar “candle” flames at their
smoke point. It results in a close correspondence between turbulent and laminar
flames for their soot formation rates and dependence on dependence on the flame
adiabatic stoichiometric temperature.
The correspondence produces a simple empirical relationship between the incompleteness of
combustion of turbulent flames to the fuel’s laminar-flame smoke point flame-height.
The effective flame radiation temperature rise above ambient is estimated to be 75% of the
effective convective temperature rise. Conservation of energy then provides a simple
expression relating the radiant fraction, convective fraction and incompleteness of
combustion.
The expression produces a simple correlation of over 300 measurements for the radiant fraction
from burning hydrocarbon gases (CH4, C2H6, C3H8, C2H4, C3H6 and C4H8) in terms of their
enthalpy available for radiation and their oxidant to fuel stoichiometric mass ratio.
Fuels appear to divide into two classes: moderately sooty and extremely sooty flames.
Each has its own relationship between radiant fractions and incompleteness of combustion.
In summary, the model provides the radiant fraction, incompleteness of combustion,
effective flame radiation temperature and absorption coefficient in terms of tabulated
fuel properties.
