耦合火焰不稳定的爆炸超压预测

Explosion pressure prediction considering the flame instabilities

基于火焰不稳定和爆炸超压的耦合机制,通过向光滑火焰模型中引入褶皱因子,建立了褶皱火焰模型和湍流火焰模型,对密闭燃烧室内爆炸超压进行理论预测,且对比了绝热压缩和等温压缩对爆炸超压预测的影响规律。结果表明:在增强的流体动力学不稳定作用下,膨胀火焰失稳加剧,且在定容燃烧阶段形成胞状火焰;光滑火焰模型忽略了火焰不稳定,爆炸超压理论预测值比实验值偏低,且等温压缩下超压预测值低于绝热压缩下的预测值;湍流火焰模型高估了火焰褶皱程度,超压预测值远高于实验值;褶皱火焰模型可成功预测丙烷/空气爆炸压力和燃烧室体积V=25.6 m3的甲烷/空气爆炸压力;对于甲烷/空气爆炸,燃烧室体积V≤1.25 m3时,实验压力值介于褶皱火焰模型和绝热光滑火焰模型预测值之间。

This paper is aimed at revealing the couplings of flame instabilities and explosion pressure. By introducing flame wrinkling factor into the smooth flame model, the wrinkled flame model and turbulent flame model are developed to predict explosion pressure evolution. The effects of adiabatic and isothermal compression on explosion pressure prediction are also compared. The results demonstrate that the expanding flame tends to be more unstable under enhancing hydrodynamic instability and the cellular flame will be formed in the constant-volume stage. Since the smooth flame neglects the flame instabilities, the predicted explosion pressure is lower than experimental value. For the smooth flame model, the predicted pressure in the adiabatic condition is higher than that in the isothermal condition. The explosion pressure behavior could be overpredicted significantly using the turbulent flame model due to the fact that the turbulent flame model overestimates the flame wrinkling level. When the wrinkled flame model is considered, the explosion pressure behavior could be reproduced relatively satisfactorily for stoichiometric propane-air mixture and stoichiometric methane-air mixture in V=25.6 m3. When V≤1.25 m3, the experimental explosion pressure is lied within the predicted value using wrinkled flame model and adiabatic smooth flame model.