A poppet valve is a type of valve commonly used in engines, hydraulic systems, pneumatic systems, and other mechanical devices to control the flow of fluids or gases. It consists of a disc or plug (referred to as the poppet) that moves up and down or back and forth within a seating surface to open or close the flow passage. Poppet valves are named after the "popping" sound they make when opening or closing rapidly.

Here's how a poppet valve works:

1. Construction:

   • A poppet valve typically consists of a cylindrical or tapered poppet (plug or disc) and a valve seat.
   • The poppet is attached to a stem or shaft that allows it to move vertically or horizontally within the valve body.
   • The valve seat is a machined surface within the valve body against which the poppet seals when closed to prevent fluid or gas from flowing.

2. Operation:

   • When the poppet valve is in the closed position, the poppet rests against the valve seat, creating a seal that prevents fluid or gas from passing through the valve.
   • To open the valve, a force is applied to the poppet to move it away from the valve seat, allowing fluid or gas to flow through the passage.
   • The poppet can be actuated by various means depending on the application:
     • In engines, the poppet valve is often actuated by a camshaft or rocker arm mechanism. The camshaft pushes against the valve stem, causing the poppet to move away from the valve seat to allow air or fuel to enter the combustion chamber.
     • In hydraulic or pneumatic systems, the poppet valve may be actuated by a solenoid, pneumatic cylinder, hydraulic piston, or manual lever.
   • Once the desired flow rate or pressure is reached, the force acting on the poppet is reduced or removed, allowing the poppet to return to its closed position under the influence of a spring or by gravity.

3. Sealing:

   • When the poppet is in the closed position, it forms a tight seal against the valve seat to prevent leakage of fluid or gas.
   • The sealing surface of the poppet and valve seat is often designed to ensure proper sealing even at high pressures or temperatures.

4. Applications:

   • Poppet valves are used in a wide range of applications, including internal combustion engines (both gasoline and diesel), hydraulic systems, pneumatic systems, refrigeration systems, and industrial equipment.
   • They are preferred for their ability to provide positive shutoff, precise control, and reliable operation in various operating conditions.

Overall, poppet valves are essential components in many mechanical systems, providing control over the flow of fluids or gases with reliability and efficiency. Their simple design and versatility make them suitable for a wide range of applications across different industries.