intrain

例句：

1. 1. The car has an intrain to help with the engine's performance.
   这辆车有一个内循环来帮助发动机的性能。
2. 2. The engineer found a small crack in the intrain of the pipe.
   工程师发现管道的内循环中有一个微小的裂缝。
3. 3. The intrain of the room is designed to be energy efficient.
   房间的内循环设计成节能的。