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The static compression ratio,, of an internal combustion engine or external combustion engine is a value that represents the ratio of the volume of its combustion chamber from its largest capacity to its smallest capacity. It is a fundamental specification for many common combustion engines.
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. In a pump, the function is reversed and force is transferred from the crankshaft to the piston for the purpose of compressing or ejecting the fluid in the cylinder. In some engines, the piston also acts as a valve by covering and uncovering ports in the cylinder.
A petrol engine is an internal combustion engine with spark-ignition, designed to run on petrol (gasoline) and similar volatile fuels.
A four-stroke engine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either direction. The four separate strokes are termed:
- Intake: Also known as induction or suction. This stroke of the piston begins at top dead center (T.D.C.) and ends at bottom dead center (B.D.C.). In this stroke the intake valve must be in the open position while the piston pulls an air-fuel mixture into the cylinder by producing vacuum pressure into the cylinder through its downward motion. The piston is moving down as air is being sucked in by the downward motion against the piston.
- Compression: This stroke begins at B.D.C, or just at the end of the suction stroke, and ends at T.D.C. In this stroke the piston compresses the air-fuel mixture in preparation for ignition during the power stroke (below). Both the intake and exhaust valves are closed during this stage.
- Combustion: Also known as power or ignition. This is the start of the second revolution of the four stroke cycle. At this point the crankshaft has completed a full 360 degree revolution. While the piston is at T.D.C. the compressed air-fuel mixture is ignited by a spark plug or by heat generated by high compression, forcefully returning the piston to B.D.C. This stroke produces mechanical work from the engine to turn the crankshaft.
- Exhaust: Also known as outlet. During the exhaust stroke, the piston, once again, returns from B.D.C. to T.D.C. while the exhaust valve is open. This action expels the spent air-fuel mixture through the exhaust valve.
In an internal combustion engine, the cylinder head sits above the cylinders on top of the cylinder block. It closes in the top of the cylinder, forming the combustion chamber. This joint is sealed by a head gasket. In most engines, the head also provides space for the passages that feed air and fuel to the cylinder, and that allow the exhaust to escape. The head can also be a place to mount the valves, spark plugs, and fuel injectors.
An opposed-piston engine is a reciprocating internal combustion engine in which each cylinder has a piston at both ends, and no cylinder head.
Volumetric efficiency (VE) in internal combustion engine engineering is defined as the ratio of the mass density of the air-fuel mixture drawn into the cylinder at atmospheric pressure to the mass density of the same volume of air in the intake manifold. The term is also used in other engineering contexts, such as hydraulic pumps and electronic components.
The firing order is the sequence of power delivery of each cylinder in a multi-cylinder reciprocating engine.
On a two-stroke engine, an expansion chamber or tuned pipe is a tuned exhaust system used to enhance its power output by improving its volumetric efficiency.
In a piston engine, the valve timing is the precise timing of the opening and closing of the valves. In an internal combustion engine those are usually poppet valves and in a steam engine they are usually slide valves or piston valves.
Cylinder head porting refers to the process of modifying the intake and exhaust ports of an internal combustion engine to improve the quality and quantity of the air flow. Cylinder heads, as manufactured, are usually suboptimal due to design and manufacturing constraints. Porting the heads provides the finely detailed attention required to bring the engine to the highest level of efficiency. More than any other single factor, the porting process is responsible for the high power output of modern engines.
The split-cycle engine is a type of internal combustion engine.
In automotive usage, scavenging is the process of pushing exhausted gas-charge out of the cylinder and drawing in a fresh draught of air or fuel/air mixture for the next cycle.
The uniflow type of steam engine uses steam that flows in one direction only in each half of the cylinder. Thermal efficiency is increased in the compound and multiple expansion types of steam engine by separating expansion into steps in separate cylinders; in the uniflow design, thermal efficiency is achieved by having a temperature gradient along the cylinder. Steam always enters at the hot ends of the cylinder and exhausts through ports at the cooler centre. By this means, the relative heating and cooling of the cylinder walls is reduced.
Piston valves are one form of valve used to control the flow of steam within a steam engine or locomotive. They control the admission of steam into the cylinders and its subsequent exhausting, enabling a locomotive to move under its own power. The valve consists of two piston heads on a common spindle moving inside a steam chest, which is essentially a mini-cylinder located either above or below the main cylinders of the locomotive.
A two-stroke diesel engine is a Diesel engine that works in two strokes. It was invented by Hugo Güldner in 1899. Charles F. Kettering and colleagues, working at the General Motors Research Corporation and GM's subsidiary Winton Engine Corporation during the 1930s, advanced the art and science of two-stroke diesel technology to yield engines with much higher power-to-weight ratios and output range than contemporary four-stroke diesels. The first mobile application of two-stroke diesel power was with the diesel streamliners of the mid-1930s and continued development work resulted in improved two-stroke diesels for locomotive and marine applications in the late 1930s. This work laid the foundation for the dieselisation of railroads in the 1940s and 1950s.
The split-single, is a variant on the two-stroke engine with two cylinders sharing a single combustion chamber.
The Derbi GPR 125 is a street motorcycle sold by Derbi - Nacional Motor since 2005. The original GPR125 was powered by a single-cylinder two-stroke engine with a steel lined cast iron cylinder manufactured by Yamaha, but this bike has now been superseded by an all-new DOHC four-stroke four-valve model.
An internal combustion engine (ICE) is a heat engine where the combustion of a fuel occurs with an oxidizer in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine. The force is applied typically to pistons, turbine blades, rotor or a nozzle. This force moves the component over a distance, transforming chemical energy into useful mechanical energy.
