The interaction of multiple fires may lead to a higher flame height and more intense radiation flux than a single fire, which increases the possibility of flame spread and risks to the surroundings. Experiments were conducted using three burners with identical heat release rates (HRRs) and propane as the fuel at various spacings. The results show that flames change from non-merging to merging as the spacing decreases, which result in a complex evolution of flame height and merging point height. To facilitate the analysis, a novel merging criterion based on the dimensionless spacing S/z_c was proposed. For non-merging flames (S/z_c > 0.368), the flame height is almost identical to a single fire; for merging flames (S/z_c ⩽ 0.368), based on the relationship between thermal buoyancy B and thrust P (the pressure difference between the inside and outside of the flame), a quantitative analysis of the flame height, merging point height, and air entrainment was formed, and the calculated merging flame heights show a good agreement with the measured experimental values. Moreover, the multi-point source model was further improved, and radiation fraction of propane was calculated. The data obtained in this study would play an important role in calculating the external radiation of propane fire.

与单次火灾相比，多次火灾的相互作用可能导致更高的火焰高度和更强的辐射通量，从而增加了火焰蔓延的可能性和对周围环境的危险。使用三个具有相同放热率（HRR）的燃烧器和丙烷作为燃料以不同的间距进行了实验。结果表明，随着间距的减小，火焰从不合并变为合并，从而导致火焰高度和合并点高度的复杂演变。为了便于分析，提出了一种基于无量纲间距S / z _c的新型合并准则。对于非合并火焰（S / z _c > 0.368），火焰高度几乎与单个火焰相同。用于合并火焰（S / z _c⩽0.368），基于热浮力B和推力P（火焰内部与外部之间的压力差）之间的关系，对火焰高度，合并点高度和夹带空气进行了定量分析，并计算出合并的火焰高度与测得的实验值显示出良好的一致性。此外，进一步改进了多点源模型，并计算了丙烷的辐射分数。在这项研究中获得的数据将在计算丙烷火的外部辐射中起重要作用。