A device designed to allow the passage of gaseous and liquid media in one direction and block their return stroke is called a flap valve. He found application in axial fans, where atmospheric air cannot enter the room, and in internal combustion engines, which prevents the return of fuel from the cylinder to the carburetor.
The product for fans consists of a housing in the bearings of which a specific shape of the blade is fixed. Bearings maintain the valve free travel in case of fan operation at low temperatures. A working fan delivers air flow to the blades, which are constantly in the open position. After the cessation of operation, the blades become in their original position, due to which they close the valve section.
There is a special modified flap valve. Tulip - its second name, at the heart of its design is a box-shaped body of four walls. Profiled leaves made of galvanized steel are rigidly fixed on the axes of the body. The type of junction of the wings is the lock.
From simple devices based on one blade, the flap check valve is distinguished by a low response inertia rate and a lower standard flow rate that opens it. It is especially advantageous to use such a product in axial types of fans, where the flow rate is lower in comparison with radial types.
As for internal combustion engines, for vehicle owners the flap valve resolves several issues. Its petals are made from flexible materials. When the piston goes to compress the mixture, due to the pressure difference in the communicating chambers, they, by virtue of their flexibility, are unbent, opening the holes in the valve body through which the fuel mixture flows. The onset of the purge phase when the piston moves down creates a directionality of pressure on the opposite side, which makes the petals pressed against the body, blocking the holes, which prevents the mixture from rolling back. Among the positive qualities of the product, the following can be noted:
- Fuel economy. The translational upward movement of the piston forms a vacuum in the crankcase. Then, air is sucked in through the carburetor, mixed with gasoline, which forms the fuel mixture. The mixture enters until the piston moves up. As soon as it starts to go down, pressure exerts an effect on the flap valve, and the petals block the flow of the mixture back. Around the carburetor will be clean, and the mixture is not released into the atmosphere, losses are minimized.
- Engine power. The petal valve allows you to increase power at low and medium speeds. The secret is that more mixture enters the crankcase and the cylinder, since the portion previously released into the atmosphere is used for its intended purpose.
- Squat of the vehicle. This phenomenon is a direct consequence of the previous property - an increase in power.
- Steady idling. The fact is that the idle mode consists of low engine speeds. Just at these revolutions the effect of the reverse stroke of the mixture is most pronounced. The petal valve with each movement of the piston passes the exact amount of the mixture into the crankcase.
- Easy engine start. The receipt of a stable portion of the mixture in the cylinders makes it possible to start the engine more easily, as they say - “with a dime”.