I had hardly opened the door when he rushed in

问题描述:

I had hardly opened the door when he rushed in
had 在这里有什么作用?

had opened 是过去完成时,had没有实际意义,配合动词的过去分词来表示时态.
过去完成时 表示过去的过去,从句用过去时,主句用过去完成时表示时间的先后.