main valve piston

例句：

1. 1. The mainvalve is responsible for controlling the flow ofoil to the engine.
   主阀负责控制油流向发动机的流动。
2. 2. Themain stem is the mainpart of the plant that supportsthe leaves and flowers.
   主茎是植物的主要部分，支撑着叶子和花朵。
3. 3. The main stem piston is usedin pumps to move fluids throughthe system.
   主阀活塞用于泵中移动流体通过系统。