on fire 使燃烧， 使兴奋；
He boasted that if he could find the solution to the problem, the result of it would set the world on fire.
他吹嘘果找到这个问题的答案，其成果就会轰动全世界。
on the fire 在火上
With a chicken being toasted on the fire,I can't leave even a minute.
由于鸡在火上烤，所以我甚至一分钟也不能离开。
over the fire 在火上
Pull off your wet clothes and let me dry them over the fire.
快点脱下你的湿衣服，让我在炉火上为你烘干。
