Tank fires threaten the lives of people and pollute the environment for their intense radiant heat, rapid fire spread and explosion hazard. Compressed air/nitrogen foam (CAF/CNF), a cleaner fire extinguishing technique used for the tank fire suppression because halogen-based agents were prohibited for environmental reasons. In this work, the influence of foaming gas in CAF/CNF on extinguishing the n-heptane tank fire was firstly investigated. Firstly, it was found that CNF spreads faster with rapid increase in foam thickness, mainly due to its better stability and less evaporation. Secondly, after foam was discharged, there existed a short increase of the combustion intensity, associated with three monotonous regions and two time delays in the whole extinguishing time. The two time delays were caused by Rayleigh–Taylor instability and flame sheet shift, respectively, and the shift distance was larger for CNF. Finally, the influential factors contributing to flame extinction were exhibited to be mainly related to the decrease in liquid burning rate and gas-phase Damkohler number. Among these factors, foam spreading rate and thickness dominated due to coupled chemical and physical extinguishing effects. Resulted from some competitive effects, CNF was slightly more efficient at extinguishing tank fires than CAF.

坦克大火以其强烈的辐射热，迅速的火势蔓延和爆炸危险威胁着人们的生命并污染环境。压缩空气/氮气泡沫（CAF / CNF），一种较清洁的灭火技术，用于灭火，因为出于环境原因禁止使用卤素类灭火剂。在这项工作中，首先研究了CAF / CNF中发泡气体对扑灭正庚烷罐着火的影响。首先，发现CNF随着泡沫厚度的快速增加而散布更快，这主要是由于其更好的稳定性和更少的蒸发。其次，泡沫排出后，燃烧强度有短暂的增加，与整个灭火时间的三个单调区域和两个时间延迟有关。这两个时间延迟分别是由瑞利-泰勒不稳定性和火焰片位移引起的，而CNF的位移距离更大。最后，导致火焰熄灭的影响因素主要与液体燃烧速率和气相Damkohler数的降低有关。在这些因素中，由于化学和物理灭火作用的耦合，泡沫的扩散速率和厚度占主导地位。由于一些竞争效应，CNF在扑灭坦克火灾方面比CAF稍微更有效。由于耦合的化学和物理灭火作用，泡沫的扩散速率和厚度占主导地位。由于一些竞争效应，CNF在扑灭坦克火灾方面比CAF稍微更有效。由于耦合的化学和物理灭火作用，泡沫的扩散速率和厚度占主导地位。由于一些竞争效应，CNF在扑灭坦克火灾方面比CAF稍微更有效。