辐射传热对微重力环境下预混火焰传播特性的影响

1引言在火焰中，辐射过程是一种重要的传热方式。对该过程尽可能精确的计算，对于改进燃烧设备的设计、改善设备的运行性能十分有益。在正常重力环境下，与其它的释热现象相比，预混火焰中的辐射热损失十分微弱，因而，过去对预混火焰的分析中，往往忽略了辐射热损失的影响。近年来，对微重力（ug）环境下的预混火焰的研究结果表明，可燃极限与＃s最小点火能无关，自媳灭火焰（SEFs）发生时；其释放的能量比通常观察到的点火极限时的能量大几个数量级山，因此火焰伸张并不能解释“g环境下观察到的实验结果，辐射热损失可能是影响＃g火焰可…

EFFECTS OF RADIATIVE L0SSES ON PREMIXED FLAME PROPAGATION CHARACTERISTICS AT MICROGRWITY

The effects of radiative losses on premixed laminar methane/air flame propagation char-acteristics were simulated in this paper with the detailed chemistry and transport propertiesby using the simplified radiative model which derived by assuming that the flames of interestare opticalIy thin and adopting the grey-medium approximation. Case studied include leanlaminar methane/air flame speed and flame standoff distance relative to the burner surface.The model predictions are compared with experimental data, and agreement is generallyvery good. The results have shown that radiative heat 1oss from the combustion productsare probably the dominant process leading to flame extinction at microgravity. It is importantat the fundamefltal flammability limits. Meanwhile, the flame standoff distance calculationsare also presented in this paper. To include the radiative heat loss, the fiame clearly standoff from the burner surface. This longer flame stand off imp1ies a weaker heat feedback fromthe fiame which is the same as the behavior of the candle flame at microgravity.