超细水雾增强与抑制甲烷/空气爆炸的机理分析

通过数值模拟方法对密闭容器内部超细水雾与甲烷/空气爆炸火焰的相互作用机理进行研究。采用大涡模型和部分预混燃烧模型分别对爆炸火焰流场和甲烷/空气燃烧过程进行计算;利用欧拉-拉格朗日方法对连续相和离散相方程进行耦合求解,实现气液两相间的质量、动量和能量的传递。通过实验验证了模型的准确性,并详细分析了水雾导致爆炸增强与抑制的机理。结果表明:水雾吸收的汽化潜热大于显热,且两者均远大于液滴的动量吸收作用;水雾吸热和汽化膨胀两种效应的共同作用导致增强和抑制爆炸两种相反的结果,液滴粒径、速度和水雾质量浓度将影响火焰面的温度、导温系数、脉动速度和湍流尺度,进而影响火焰传播速度和容器内部的热增速率。

Analysis on the enhancement and suppression of methane/air explosions by ultrafine water mist

The interaction mechanism of ultrafine water mist and methane/air explosion flame in a closed vessel was numerically modeled.Large eddy model and partially premixed combustion model were used to calculate the explosion flow field and the methane/air combustion.In order to describe the mass，the momentum and energy exchanges between the gas and liquid phases，the Euler-Lagrange model was used to couple the continuous and discrete phase equations.The calculation result was verified and the enhancing and suppressing mechanism of water mist on explosion was analyzed in detail.Results show that the latent heat absorption is the dominant mechanism followed by the sensible heat absorption by water vapor，and relative to the momentum absorption by water mist；the two opposite results of enhancement and suppression on explosion can be attributed to the combined effect of heat absorption and vaporizing expansion of mist；and the droplet size，velocity and mist concentration have an obvious effect on the temperature，thermal diffusivity，fluctuation velocity and turbulence scale of flame front，and further affect the flame speed as well as the thermal increasing rate of the vessel.