drop valve

例句：

1. 1. The drop valve is used to control the flow of oil in a hydraulic system.
   减压阀用于控制液压系统中的油流量。
2. 2.The engineers had to replace the old drop valve with a new one.
   工程师们不得不用一个新的减压阀来替换旧的。
3. 3.The drop valve was designed to prevent overheating in the engine.
   减压阀的设计目的是为了防止发动机过热。