In mechanical engineering, the cylinders of reciprocating engines are often classified by whether they are single- or double-acting, depending on how the working fluid acts on the piston.
In mechanical engineering, the cylinders of reciprocating engines are often classified by whether they are single- or double-acting, depending on how the working fluid acts on the piston.
A single-acting cylinder in a reciprocating engine is a cylinder in which the working fluid acts on one side of the piston only. A single-acting cylinder relies on the load, springs, other cylinders, or the momentum of a flywheel, to push the piston back in the other direction. Single-acting cylinders are found in most kinds of reciprocating engine. They are almost universal in internal combustion engines (e.g. petrol and diesel engines) and are also used in many external combustion engines such as Stirling engines and some steam engines. They are also found in pumps and hydraulic rams.
A double-acting cylinder is a cylinder in which the working fluid acts alternately on both sides of the piston. In order to connect the piston in a double-acting cylinder to an external mechanism, such as a crank shaft, a hole must be provided in one end of the cylinder for the piston rod, and this is fitted with a gland or "stuffing box" to prevent escape of the working fluid. Double-acting cylinders are common in steam engines but unusual in other engine types. Many hydraulic and pneumatic cylinders use them where it is needed to produce a force in both directions. A double-acting hydraulic cylinder has a port at each end, supplied with hydraulic fluid for both the retraction and extension of the piston. A double-acting cylinder is used where an external force is not available to retract the piston or it can be used where high force is required in both directions of travel.
Steam engines normally use double-acting cylinders. However, early steam engines, such as atmospheric engines and some beam engines, were single-acting. These often transmitted their force through the beam by means of chains and an "arch head", as only a tension in one direction was needed.
Where these were used for pumping mine shafts and only had to act against a load in one direction, single-acting designs remained in use for many years. The main impetus towards double-acting cylinders came when James Watt was trying to develop a rotative beam engine, that could be used to drive machinery via an output shaft. [1] Compared to a single-cylinder engine, a double-acting cylinder gave a smoother power output. The high-pressure engine, [lower-roman 1] as developed by Richard Trevithick, used double-acting pistons and became the model for most steam engines afterwards.
Some of the later steam engines, the high-speed steam engines, used single-acting pistons of a new design. The crosshead became part of the piston, [lower-roman 2] and there was no longer any piston rod. This was for similar reasons to the internal combustion engine, as avoiding the piston rod and its seals allowed a more effective crankcase lubrication system.
Small models and toys often use single-acting cylinders for the above reason but also to reduce manufacturing costs.
In contrast to steam engines, nearly all internal combustion engines have used single-acting cylinders.
Their pistons are usually trunk pistons, where the gudgeon pin joint of the connecting rod is within the piston itself. This avoids the crosshead, piston rod and its sealing gland, but it also makes a single-acting piston almost essential. This, in turn, has the advantage of allowing easy access to the bottom of the piston for lubricating oil, which also has an important cooling function. This avoids local overheating of the piston and rings.
Small petrol two-stroke engines, such as for motorcycles, use crankcase compression rather than a separate supercharger or scavenge blower. This uses both sides of the piston as working faces, the lower side of the piston acting as a piston compressor to compress the inlet charge ready for the next stroke. The piston is still considered as single-acting, as only one of these faces produces power.
Some early gas engines, such as Lenoir's original engines, from around 1860, were double-acting and followed steam engines in their design.
Internal combustion engines soon switched to single-acting cylinders. This was for two reasons: as for the high-speed steam engine, the high force on each piston and its connecting rod was so great that it placed large demands upon the bearings. A single-acting piston, where the direction of the forces was consistently compressive along the connecting rod, allowed for tighter bearing clearances. [2] Secondly the need for large valve areas to provide good gas flow, whilst requiring a small volume for the combustion chamber so as to provide good compression, monopolised the space available in the cylinder head. Lenoir's steam engine-derived cylinder was inadequate for the petrol engine and so a new design, based around poppet valves and a single-acting trunk piston appeared instead.
Extremely large gas engines were also built as blowing engines for blast furnaces, with one or two extremely large cylinders and powered by the burning of furnace gas. These, particularly those built by Körting, used double-acting cylinders. Gas engines require little or no compression of their charge, in comparison to petrol or compression-ignition engines, and so the double-acting cylinder designs were still adequate, despite their narrow, convoluted passageways.
Double-acting cylinders have been infrequently used for internal combustion engines since, although Burmeister & Wain made 2-stroke cycle double-acting (2-SCDA) diesels for marine propulsion before 1930. The first, of 7,000 hp, was fitted in the British MV Amerika (United Baltic Co.) in 1929. [3] [4] The two B&W SCDA engines fitted to the MV Stirling Castle in 1937 produced 24,000 hp each.
In 1935 the US submarine USS Pompano was ordered as part of the Perch class [lower-roman 3] Six boats were built, with three different diesel engine designs from different makers. Pompano was fitted with H.O.R. (Hooven-Owens-Rentschler) 8-cylinder double-acting engines that were a licence-built version of the MAN auxiliary engines of the cruiser Leipzig. [5] Owing to the limited space available within the submarines, either opposed-piston, or, in this case, double-acting engines were favoured for being more compact. Pompano's engines were a complete failure and were wrecked during trials before even leaving the Mare Island Navy Yard. Pompano was laid up for eight months until 1938 while the engines were replaced. [5] Even then the engines were regarded as unsatisfactory and were replaced by Fairbanks-Morse engines in 1942. [5] While Pompano was still being built, the Salmon-class submarines were ordered. Three of these were built by Electric Boat, with a 9-cylinder development of the H.O.R. engine. [6] Although not as great a failure as Pompano's engines, this version was still troublesome and the boats were later re-engined with the same single-acting General Motors 16-248 V16 engines as their sister boats. [6] Other Electric Boat-constructed submarines of the Sargo and Seadragon classes, as well as the first few of the Gato class, were also built with these 9-cylinder H.O.R. engines, but later re-engined. [7]
A hydraulic cylinder is a mechanical actuator that is powered by a pressurised liquid, typically oil. It has many applications, notably in construction equipment (engineering vehicles), manufacturing machinery, and civil engineering.
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders 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 reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common features of all types. The main types are: the internal combustion engine, used extensively in motor vehicles; the steam engine, the mainstay of the Industrial Revolution; and the Stirling engine for niche applications. Internal combustion engines are further classified in two ways: either a spark-ignition (SI) engine, where the spark plug initiates the combustion; or a compression-ignition (CI) engine, where the air within the cylinder is compressed, thus heating it, so that the heated air ignites fuel that is injected then or earlier.
A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be transformed, by a connecting rod and crank, into rotational force for work. The term "steam engine" is generally applied only to reciprocating engines as just described, not to the steam turbine. Steam engines are external combustion engines, where the working fluid is separated from the combustion products. The ideal thermodynamic cycle used to analyze this process is called the Rankine cycle. In general usage, the term steam engine can refer to either complete steam plants, such as railway steam locomotives and portable engines, or may refer to the piston or turbine machinery alone, as in the beam engine and stationary steam engine.
A Stirling engine is a heat engine that is operated by the cyclic compression and expansion of air or other gas between different temperatures, resulting in a net conversion of heat energy to mechanical work.
In mechanical engineering, a crosshead is a mechanical joint used as part of the slider-crank linkages of long reciprocating engines and reciprocating compressors to eliminate sideways force on the piston. Also, the crosshead enables the connecting rod to freely move outside the cylinder. Because of the very small bore-to-stroke ratio on such engines, the connecting rod would hit the cylinder walls and block the engine from rotating if the piston was attached directly to the connecting rod like on trunk engines. Therefore, the longitudinal dimension of the crosshead must be matched to the stroke of the engine.
An opposed-piston engine is a piston engine in which each cylinder has a piston at both ends, and no cylinder head. Petrol and diesel opposed-piston engines have been used mostly in large-scale applications such as ships, military tanks, and factories. Current manufacturers of opposed-piston engines include Cummins, Achates Power and Fairbanks-Morse Defense (FMDefense).
USS Pompano (SS-181), a United States Porpoise-class submarine, was the second ship of the United States Navy to be named for the pompano.
In a piston engine, a piston rod joins a piston to the crosshead and thus to the connecting rod that drives the crankshaft or the driving wheels.
Hydrolock is an abnormal condition of any device which is designed to compress a gas by mechanically restraining it; most commonly the reciprocating internal combustion engine, the case this article refers to unless otherwise noted. Hydrolock occurs when a volume of liquid greater than the volume of the cylinder at its minimum enters the cylinder. Since liquids are nearly incompressible the piston cannot complete its travel; either the engine must stop rotating or a mechanical failure must occur.
Variable compression ratio (VCR) is a technology to adjust the compression ratio of an internal combustion engine while the engine is in operation. This is done to increase fuel efficiency while under varying loads. Variable compression engines allow the volume above the piston at top dead centre to be changed. Higher loads require lower ratios to increase power, while lower loads need higher ratios to increase efficiency, i.e. to lower fuel consumption. For automotive use this needs to be done as the engine is running in response to the load and driving demands. The 2019 Infiniti QX50 is the first commercially available vehicle that uses a variable compression ratio engine.
The hot-bulb engine, also known as a semi-diesel, is a type of internal combustion engine in which fuel ignites by coming in contact with a red-hot metal surface inside a bulb, followed by the introduction of air (oxygen) compressed into the hot-bulb chamber by the rising piston. There is some ignition when the fuel is introduced, but it quickly uses up the available oxygen in the bulb. Vigorous ignition takes place only when sufficient oxygen is supplied to the hot-bulb chamber on the compression stroke of the engine.
The term six-stroke engine has been applied to a number of alternative internal combustion engine designs that attempt to improve on traditional two-stroke and four-stroke engines. Claimed advantages may include increased fuel efficiency, reduced mechanical complexity, and/or reduced emissions. These engines can be divided into two groups based on the number of pistons that contribute to the six strokes.
A steam diesel hybrid locomotive is a railway locomotive with a piston engine which could run on either steam from a boiler or diesel fuel. Examples were built in the United Kingdom, Soviet Union and Italy but the relatively high cost of fuel oil, or failure to resolve problems caused by technical complexity, meant that the designs were not pursued.
The firm of Hooven, Owens, Rentschler, and Company manufactured steam and diesel engines in Hamilton, Ohio. Because the firm was frequently known by its initials, H.O.R., the Hooven is sometimes incorrectly rendered as Hoover, and the Owens may be mistaken for Owen.
The uniflow type of steam engine uses steam that flows in one direction only in each half of the cylinder. Thermal efficiency is increased 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.
Internal combustion engines date back to between the 10th and 13th centuries, when the first rocket engines were invented in China. Following the first commercial steam engine in 1698, various efforts were made during the 18th century to develop equivalent internal combustion engines. In 1791, the English inventor John Barber patented a gas turbine. In 1794, Thomas Mead patented a gas engine. Also in 1794, Robert Street patented an internal-combustion engine, which was also the first to use liquid fuel (petroleum) and built an engine around that time. In 1798, John Stevens designed the first American internal combustion engine. In 1807, French engineers Nicéphore and Claude Niépce ran a prototype internal combustion engine, using controlled dust explosions, the Pyréolophore. This engine powered a boat on the river in France. The same year, the Swiss engineer François Isaac de Rivaz built and patented a hydrogen and oxygen-powered internal-combustion engine. Fitted to a crude four-wheeled wagon, François Isaac de Rivaz first drove it 100 metres in 1813, thus making history as the first car-like vehicle known to have been powered by an internal-combustion engine.
Internal combustion engines come in a wide variety of types, but have certain family resemblances, and thus share many common types of components.
Körting Hannover AG is a long-standing industrial engineering company in Hanover.
A booster pump is a machine which increases the pressure of a fluid. It may be used with liquids or gases, and the construction details vary depending on the fluid. A gas booster is similar to a gas compressor, but generally a simpler mechanism which often has only a single stage of compression, and is used to increase pressure of a gas already above ambient pressure. Two-stage boosters are also made. Boosters may be used for increasing gas pressure, transferring high pressure gas, charging gas cylinders and scavenging.
An internal combustion engine is a heat engine in which 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 typically applied to pistons, turbine blades, a rotor, or a nozzle. This force moves the component over a distance, transforming chemical energy into kinetic energy which is used to propel, move or power whatever the engine is attached to.