A poppet valve is a type of valve used to control the flow of fluid or gas within a system. It consists of a movable element, called the poppet, which opens and closes an orifice or port to allow or restrict the flow of the fluid or gas. Poppet valves are commonly found in various applications, including internal combustion engines, hydraulic systems, pneumatic systems, and industrial processes.

Here's how a typical poppet valve works:

1. Construction: A poppet valve typically consists of a cylindrical or conical-shaped plug, called the poppet, which is attached to a stem. The poppet fits into a seat or opening within the valve body. The valve body also contains passages or ports through which the fluid or gas flows.

2. Seating: When the valve is closed, the poppet is pushed against the valve seat by a spring or other actuating mechanism. This creates a seal that prevents the fluid or gas from passing through the valve.

3. Opening: When the valve needs to open, an external force is applied to the poppet, typically through the valve stem. This force overcomes the resistance of the spring or actuating mechanism, causing the poppet to move away from the seat, thus opening the valve.

4. Flow Control: The flow of fluid or gas through the valve is controlled by the position of the poppet. When the poppet is fully open, the fluid or gas can flow freely through the valve. Conversely, when the poppet is fully closed, the flow is completely blocked.

5. Closing: When the external force is removed, the spring or actuating mechanism pushes the poppet back into its seated position, closing the valve and stopping the flow of fluid or gas.

Poppet valves offer several advantages, including precise control over flow rates, low leakage rates when closed, and the ability to handle high pressures and temperatures. They are also relatively simple in design and can be configured for various applications by adjusting factors such as materials, sizes, and actuation methods.