What Is an Exhaust Valve?

                                                Exhaust Valve:

An exhaust valve is found in the cylinder head of an internal combustion engine. When the fuel and air mixture has been ignited in the cylinder, the spent gasses are sent out of the engine through the exhaust valve. In the typical internal combustion engine, the exhaust valve is larger than the intake valve. This is due to the fact that it is more difficult to clear the cylinder of exhaust gasses than it is to introduce fuel and air into the combustion chamber   

Valves Used In Internal Combustion Engine:

1. Poppet valve

A poppet valve (also called mushroom valve) is a valve typically used to control the timing and quantity of gas or vapour flow into an engineJames Watt was using poppet valves to control the flow of steam into the cylinders of his beam engines in the 1770s. A sectional illustration of Watt's beam engine of 1774 using the device is found in Thurston 1878:98, and Lardner (1840) provides an illustrated description of Watt's use of the poppet valve.

When used in high-pressure applications, for example, as admission valves on steam engines, the same pressure that helps seal poppet valves also contributes significantly to the force required to open them. This has led to the development of the balanced poppet or double beat valve, in which two valve plugs ride on a common stem, with the pressure on one plug largely balancing the pressure on the other. In these valves, the force needed to open the valve is determined by the pressure and the difference between the areas of the two valve openings. Sickels patented a valve gear for double-beat poppet valves in 1842. Criticism was reported in the journal Science in 1889 of equilibrium poppet valves (called by the article the 'double or balanced or American puppet valve') in use for paddle steamer engines, that by its nature it must leak 15 percent.