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).
Compared to contemporary two-stroke engines, which used a conventional design of one piston per cylinder, the advantages of the opposed-piston engine have been recognized as:
The main drawback was that the power from the two opposing pistons have to be geared together. This added weight and complexity when compared to conventional piston engines, which use a single crankshaft as the power output.
The most common layout was two crankshafts, with the crankshafts geared together (in either the same direction or opposing directions). [6] The Koreyvo, Jumo, and Napier Deltic engines used one piston per cylinder to expose an intake port, and the other to expose an exhaust port. Each piston is referred to as either an intake piston or an exhaust piston, depending on its function in this regard. This layout gives superior scavenging, as gas flow through the cylinder is axial rather than radial, and simplifies design of the piston crowns. In the Jumo 205 and its variants, the upper crankshaft serves the exhaust pistons, and the lower crankshaft the intake pistons. In designs using multiple cylinder banks, each big end bearing serves one inlet and one exhaust piston, using a forked connecting rod for the exhaust piston.
One of the first opposed-piston engines was the 1882 Atkinson differential engine, [7] which has a power stroke on every rotation of the crankshaft (compared with every second rotation for the contemporary Otto cycle engine), but it was not a commercial success. [8]
In 1898, an Oechelhäuser two-stroke opposed-piston engine producing 600 hp (447 kW) was installed at the Hoerde ironworks. [9] This design of engine was also produced under licence by manufacturers including Deutsche Kraftgas Gesellschaft in Germany and William Beardmore & Sons in the United Kingdom. [10]
In 1901, the Kansas City Lightning Balanced Gas and Gasoline Engines were gasoline engines producing 4–25 hp (3–19 kW). [11]
An early opposed-piston car engine was produced by the French company Gobron-Brillié around 1900. In April 1904, a Gobron-Brillié car powered by the opposed-piston engine was the first car ever to exceed 150 km/h with a "World's Record Speed" of 152.5 km/h (95 mph). [12] On 17 July 1904, the Gobron-Brillié car became the first to exceed 100 mph (161 km/h) for the flying kilometre. [13] The engine used a single crankshaft at one end of the cylinders and a crosshead for the opposing piston.
Another early opposed piston car engine was in the Scottish Arrol-Johnston car, which appears to have been first installed in their 10 hp buckboard c1900. The engine was described and illustrated in some detail in the account of their 12-15 hp car exhibited at the 1905 Olympia Motor-Show. [14] The engine was a 4-stroke with two cylinders (with opposed pistons in each) with the crankshaft underneath and the pistons connected by lever arms to the two-throw crankshaft.
The first diesel engine with opposed pistons was a prototype built at Kolomna Locomotive Works in Russia. The designer, Raymond A. Koreyvo, patented the engine in France on 6 November 1907 and displayed the engine at international exhibitions, but it did not reach production. The Kolomna design used a typical layout of two crankshafts connected by gearing.
In 1914, the Simpson's Balanced Two-Stroke motorcycle engine was another opposed-piston engine using a single crankshaft beneath the centre of the cylinders with both pistons connected by levers. [15] This engine was a crankcase compression design, with one piston used to uncover the transfer port, and the other to open the exhaust port. The advantage of this design was to avoid the deflector crowns for pistons used by most two-stroke engines at that time.
Doxford Engine Works in the United Kingdom built large opposed-piston engines for marine use, with the first Doxford engine being installed in a ship in 1921. [16] This diesel engine used a single crankshaft at one end of the cylinders and a crosshead for the opposing piston. [17] [18] After World War I, these engines were produced in a number of models, such as the P and J series, with outputs as high as 20,000 hp (14,914 kW). Production of Doxford engines in the UK ceased in 1980. [17] [19] [20]
Later opposed-piston diesel engines include the 1932 Junkers Jumo 205 aircraft engine built in Germany, which had two crankshafts, not using a design similar to the 1900–1922 Gobron-Brillié engines. [21]
The Fairbanks Morse 38 8-1/8 diesel engine, originally designed in Germany in the 1930s, was used in U.S. submarines in the 1940s and 1950s, and in boats from the 1930s-present. [22] It was also used in locomotives from 1944.
The latest (November 2021) version of the Fairbanks-Morse 38 8-1/8 is known as the FM 38D 8-1/8 Diesel and Dual Fuel. This two-stroke opposed-piston engine retains the same extra-heavy-duty design and has a rated in-service lifespan of more than 40 years, but now the optional capability of burning dual fuels (gaseous and liquid fuels, with automatic switchover to full diesel if the gas supply runs out) is available. [23]
The Commer TS3 three-cylinder diesel truck engines, released in 1954, have a single crankshaft beneath the centre of the cylinders with both pistons connected by levers. [24]
Also released in 1954 was the Napier Deltic engine for military boats. It uses three crankshafts, one at each corner, to form the three banks of double-ended cylinders arranged in an equilateral triangle. The Deltic engine was used in British Rail Class 55 and British Rail Class 23 locomotives and to power fast patrol boats and Royal Navy mine sweepers. Beginning in 1962, Gibbs invited Mack Trucks to take part in designing FDNY’s super pumper and its companion tender. DeLaval Turbine was commissioned to design a multistage centrifugal pump with a Napier-Deltic T18-37C diesel to power the pumps. [25]
In 1959, the Leyland L60 19 L (1,159 cu in) six-cylinder diesel engine was introduced. The L60 was produced in the United Kingdom for use in the Chieftain tank. The Soviet T-64 tank, produced from 1963-1987, also used an opposed-piston diesel engine 5TDF.
In 2014, Achates Power published a technical paper citing a 30% fuel economy improvement when its engine was benchmarked against a next-generation diesel engine equipped with advanced technologies. [26]
Volvo filed for a patent in 2017. [27]
The Diesel Air Dair 100 is a two-cylinder 100 hp (75 kW) diesel aircraft engine, designed and produced by Diesel Air Ltd of Olney, Buckinghamshire for use in airships, home-built kitplanes, and light aircraft. [28]
In July 2021, Cummins was awarded an $87M contract by the United States Army to complete the development of the Advanced Combat Engine (ACE), a modular and scalable diesel engine solution that uses opposed-piston technology. [29]
A variation of the opposed-piston design is the free-piston engine, which was first patented in 1934. Free piston engines have no crankshaft, and the pistons are returned after each firing stroke by compression and expansion of air in a separate cylinder. Early applications were for use as an air compressor or as a gas generator for a gas turbine.
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 two-strokeengine is a type of internal combustion engine that completes a power cycle with two strokes of the piston during one power cycle, this power cycle being completed in one revolution of the crankshaft. A four-stroke engine requires four strokes of the piston to complete a power cycle during two crankshaft revolutions. In a two-stroke engine, the end of the combustion stroke and the beginning of the compression stroke happen simultaneously, with the intake and exhaust functions occurring at the same time.
The Napier Nomad is a British diesel aircraft engine designed and built by Napier & Son in 1949. They combined a piston engine with a turbine to recover energy from the exhaust and thereby improve fuel economy. Two versions were tested, the complex Nomad I which used two propellers, each driven by the mechanically independent stages, and the Nomad II, using the turbo-compound principle, coupled the two parts to drive a single propeller. The Nomad II had the lowest specific fuel consumption figures seen up to that time. Despite this the Nomad project was cancelled in 1955 having spent £5.1 million on development, as most interest had passed to turboprop designs.
The Napier Deltic engine is a British opposed-piston valveless, supercharged uniflow scavenged, two-stroke diesel engine used in marine and locomotive applications, designed and produced by D. Napier & Son. Unusually, the cylinders were disposed in a three-bank triangle, with a crankshaft at each corner of the triangle.
The Jumo 205 aircraft engine was the most famous of a series of aircraft diesel engines produced by Junkers. The Jumo 204 first entered service in 1932. Later engines of this type comprised the experimental Jumo 206 and Jumo 208, with the Jumo 207 produced in some quantity for the Junkers Ju 86P and -R high-altitude reconnaissance aircraft, and the 46-meter wingspan, six-engined Blohm & Voss BV 222 Wiking flying boat. All three of these variants differed in stroke and bore and supercharging arrangements. In all, more than 900 of these engines were produced, in the 1930s and through most of World War II.
A V18 engine is an eighteen-cylinder piston engine where two banks of nine cylinders are arranged in a V configuration around a common crankshaft.
The Jumo 204 was an opposed-piston, inline, liquid-cooled 6-cylinder aircraft Diesel engine produced by the German manufacturer Junkers. It entered service in 1932. Later engines in the series, the Jumo 205, Jumo 206, Jumo 207 and Jumo 208, differed in stroke, bore, and supercharging arrangements.
In a piston engine, the crankcase is the housing that surrounds the crankshaft. In most modern engines, the crankcase is integrated into the engine block.
The Bourke engine was an attempt by Russell Bourke, in the 1920s, to improve the two-stroke internal combustion engine. Despite finishing his design and building several working engines, the onset of World War II, lack of test results, and the poor health of his wife compounded to prevent his engine from ever coming successfully to market. The main claimed virtues of the design are that it has only two moving parts, is lightweight, has two power pulses per revolution, and does not need oil mixed into the fuel.
Scavenging is the process of replacing the exhaust gas in a cylinder of an internal combustion engine with the fresh air/fuel mixture for the next cycle. If scavenging is incomplete, the remaining exhaust gases can cause improper combustion for the next cycle, leading to reduced power output.
A two-stroke diesel engine is a diesel engine that uses compression ignition in a two-stroke combustion cycle. It was invented by Hugo Güldner in 1899.
In internal combustion engines, a split-single design is a type of two-stroke where two cylinders share a single combustion chamber.
The Commer TS3 was a diesel engine fitted in Commer trucks built by the Rootes Group in the 1950s and 1960s. It was the first diesel engine used by the company.
The Fairbanks-Morse 38 8-1/8 is a diesel engine of the two-stroke, opposed-piston type. It was developed in the 1930s, and is similar in arrangement to a contemporary series of German Bombers aircraft diesels. The engine was used extensively in US diesel electric submarines of the 1940s and 1950s, as backup power on most US nuclear submarines, as well as in other marine applications, stationary power generation, and briefly, locomotives. A slightly modified version, the 38ND 8-1/8, continues in service on Los Angeles-, Seawolf-, and Ohio-class nuclear submarines of the US Navy. The 38 8-1/8 has been in continuous production since its development in 1938, and is currently manufactured by a descendant of Fairbanks-Morse, FMDefense, in Beloit, Wisconsin.
Achates Power is an American developer of opposed-piston, two-stroke, compression ignition engines for use in commercial and passenger vehicles. Based in San Diego, California, the company was founded in 2004 by James U Lemke.
Gobron-Brillié was an early French automobile manufactured from 1898 to 1930. The original company, Societé des Moteurs Gobron-Brillié, was founded by the French engineer, Eugène Brillié, and industrialist, Gustave Gobron, at 13, quai de Boulogne, Boulogne-sur-Seine, near Paris, in 1898.
The Michel engine was an unusual form of opposed-piston engine. It was unique in that its cylinders, instead of being open-ended cylinders containing two pistons, were instead joined in a Y-shape and had three pistons working within them.
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.
The Diesel Air Dair 100 is an opposed-piston diesel aircraft engine, designed and produced by Diesel Air Ltd of Olney, Buckinghamshire for use in airships, home-built kitplanes and light aircraft. The prototype was built in the 1990s and exhibited it at PFA airshows. Although Diesel Air engines have been fitted to an AT-10 airship and to a Luscombe 8A monoplane, production numbers have been very limited.
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