地面常重力（1g）条件下,丙烷/空气预混火焰向上传播的富燃极限为9.2%C_3H_8,而向下传播时的富燃极限仅为6.3%C_3H_8,二者之间存在明显差距。利用微重力条件下的实验,对燃料浓度从6.5%到8.6%（微重力实验中测定的可燃极限）范围内的丙烷/空气预混火焰特性进行了研究。实验发现,重力对近极限丙烷/空气火焰的传播有显著影响,影响程度随着当量比的增加而增大。微重力下丙烷/空气的富燃极限为8.6%C_3H_8（φ=2.24）,明显高于1g条件下向下传播火焰的可燃极限,略低于向上传播火焰的可燃极限。随“,”Flammability limits for flames propagating in rich propane/air mixtures under normal gravity conditions appeared to be 6.3%C_3H_8 for downward propagation and 9.2%C_3H_8 for upward propagation,and the concentration gap between the two limits was extremely