Search results
Results from the WOW.Com Content Network
Either valve opens before the piston head reaches top dead centre or bottom dead centre. The amount in crankshaft degrees by which the valves open before top dead centre or bottom dead centre is reached is known as valve lead. The amount in crankshaft by which the valves close after top dead centre or bottom dead centre is reached is known as ...
Most piston valves are of the "inside admission" type, where fresh steam is introduced from the boiler via the space between the two piston heads of the valve, and exhaust steam leaves via the space between a piston head and the end of the steam chest.
The valves are typically operated by a camshaft rotating at half the speed of the crankshaft. It has a series of cams along its length, each designed to open a valve during the appropriate part of an intake or exhaust stroke. A tappet between valve and cam is a contact surface on which the cam slides to open the valve. Many engines use one or ...
In sidevalve engines the head is a simple plate of metal containing the spark plugs and possibly heat dissipation fins. In more modern overhead valve and overhead camshaft engines, the head is a more complicated metal block that also contains the inlet and exhaust passages, and often coolant passages, Valvetrain components, and fuel injectors.
A piston is a component of reciprocating engines. It is located in a cylinder and is made gas-tight by piston rings. Its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. In two-stroke engines the piston also acts as a valve by covering and uncovering ports in the cylinder ...
The common valvetrain configurations for piston engines, in order from oldest to newest, are: Flathead engine: The camshaft and the valves are located in the engine block below the combustion chamber. Overhead valve engine: The camshaft remains in the block, however the valves are located in the cylinder head above the combustion chamber.
The valve is hollow and filled with sodium, which melts at a relatively low temperature and, in its liquid state, convects heat away from the hot valve head to the stem where it may be conducted to the cylinder head. Common in second world war piston engines, now only found in high performance engines. [10]
The models that had the complex 'junk head' installed a non-return purging valve on it; as liquids cannot be compressed, the presence of oil in the head space would result in problems. At top dead centre (TDC), the single-sleeve valve rotates in relation to the piston. This prevents boundary lubrication problems, as piston ring ridge wear at ...