A swing-piston engine is a type of
internal combustion engine
An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combus ...
in which the pistons move in a circular motion inside a ring-shaped "cylinder", moving closer and further from each other to provide compression and expansion. Generally two sets of pistons are used, geared to move in a fixed relationship as they rotate around the cylinder. In some versions the pistons oscillate around a fixed center, as opposed to rotating around the entire engine. The design has also been referred to as a oscillating piston engine, vibratory engine when the pistons oscillate instead of rotate, or toroidal engine based on the shape of the "cylinder".
Many swing-piston engines have been proposed, but none have been successful. Two attempts in about 2010 are the prototype American-made MYT engine and prototype Russian ORE for use in the
Yo-Mobile
The Yo-mobil ( rus, ё-мобиль, p=ˈjɵ mɐˈbʲilʲ) was a planned Series hybrid, series type hybrid electric vehicle, hybrid electric car that was going to be produced by the Russian ''Yo-auto''. The company was a joint venture betwee ...
hybrid car. Both claimed high
fuel efficiency
Fuel efficiency is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical potential energy contained in a carrier (fuel) into kinetic energy or work. Overall fuel efficiency may vary per device, wh ...
and high power-to-weight ratio, but there have been no successful demonstrations of claimed efficiency or that the engines are durable enough for practical use.
Steam engines
Swing-piston engines were initially introduced during the 1820s as alternate
steam engine
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 trans ...
designs, prior to the widespread introduction of the
steam turbine
A steam turbine is a machine that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft. Its modern manifestation was invented by Charles Parsons in 1884. Fabrication of a modern steam turbin ...
. In these examples the "piston" is typically not cylindrical as in a modern internal combustion design, and is generally rectangular in cross-section as seen from the top, rotating in a flat disk "cylinder". From the side they are either flat plates or pie-wedge shaped. The term "swing-piston" is not entirely accurate in these cases, but the operating cycle is identical and is properly considered here.
The first known example was introduced by Elijah Galloway in 1829 for ship propulsion. It featured a single vane rotating through 270 degrees. It appears this version was never built, although a model still exists in the
Science Museum
A science museum is a museum devoted primarily to science. Older science museums tended to concentrate on static displays of objects related to natural history, paleontology, geology, industry and industrial machinery, etc. Modern trends in mu ...
. Galloway also designed a wide variety of pure rotary engines using vanes as well.
A more serious attempt was the "Cambrian System" of John Jones in 1841. This design used two or three flat plates that were geared to move closer or further apart as the cycle continued. When the plates were at their closest point, steam was admitted between them using a valve, pushing them apart as the cycle continued. When the plates reached their maximum distance, an internal passage was uncovered that allowed the partially expanded steam to flow across the center of the device into the area on the other side of the vanes, which were now at their minimum distance. In this fashion the design was effectively a
compound engine
A compound engine is an engine that has more than one stage for recovering energy from the same working fluid, with the exhaust from the first stage passing through the second stage, and in some cases then on to another subsequent stage or even st ...
.
Many variations followed, and a number of these saw limited use in the field. Notable among them was
John Ericsson
John Ericsson (born Johan Ericsson; July 31, 1803 – March 8, 1889) was a Swedish-American inventor. He was active in England and the United States.
Ericsson collaborated on the design of the railroad steam locomotive ''Novelty'', which com ...
's design of 1843, which powered the
USS ''Princeton'', the United States' first screw-powered steamship.
Charles Parsons examined the concept and appears to have produced two swing-piston engine designs before moving on to the steam turbine. The Roots brothers designed a swing-piston engine of a unique type, although they are better known for their
supercharger design.
Internal combustion
![US2301667-Figure1](https://upload.wikimedia.org/wikipedia/commons/d/d8/US2301667-Figure1.png)
It is unclear whether or not any internal combustion swing-piston engine has ever reached production, but the closest attempt appears to be the German
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
-era design by . His design had six pistons in total, three each attached to two disks. The disks were geared to each other to form six chambers between the pistons, such that at any one time one set of three chambers were "close together" while the other set of three was "wide apart", varying between those two extremes as the disks rotated. The timing was arranged such that the chambers reached their "close together" point over the spark plug, and their "wide apart" point over the intake and exhaust ports. This action is similar to the
Wankel engine
The Wankel engine (, ) is a type of internal combustion engine using an Eccentric (mechanism), eccentric rotary combustion engine, rotary design to convert pressure into rotating motion. It was invented by German engineer Felix Wankel, and desi ...
, the primary difference being that the Wankel creates compression and expansion via the shape of the engine and rotor, rather than the relative motion of the pistons.
Lutz's engine was being designed as an experimental
gas generator
A gas generator is a device for generating gas. A gas generator may create gas by a chemical reaction or from a solid or liquid source, when storing a pressurized gas is undesirable or impractical.
The term often refers to a device that uses a ...
for a new type of
aircraft engine
An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Most aircraft engines are either piston engines or gas turbines, although a few have been rocket powered and in recent years many ...
, one that replaced a traditional
centrifugal
Centrifugal (a key concept in rotating systems) may refer to:
*Centrifugal casting (industrial), Centrifugal casting (silversmithing), and Spin casting (centrifugal rubber mold casting), forms of centrifigual casting
*Centrifugal clutch
*Centrifug ...
or
axial compressor
An axial compressor is a gas compressor that can continuously pressurize gases. It is a rotating, airfoil-based compressor in which the gas or working fluid principally flows parallel to the axis of rotation, or axially. This differs from other ...
with his swing-piston design. Ultimately the exhaust would be used to drive a turbine, that power being used to drive a
propeller
A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...
to produce a
turboprop
A turboprop is a turbine engine that drives an aircraft propeller.
A turboprop consists of an intake, reduction gearbox, compressor, combustor, turbine, and a propelling nozzle. Air enters the intake and is compressed by the compressor. Fuel ...
. For this role the exhaust gas was too hot to be used directly in a turbine, given the materials available at the time, so the engine had a second "exhaust port" that vented cold pressurized air, which was then mixed into the hot exhaust. For direct power use, as opposed to driving a turbine, this "third area" of the engine could simply be left open to the air to avoid losing power by unnecessary compression.
The initial test engines had some minor problems, notably with sealing, but these were worked through and the engines were under test during 1944. One particularly good feature of swing-piston engines is that they can be bolted back to back along a common crank shaft to make a larger engine, and with each additional stage the running becomes smoother and the only part that needs to be made larger is the crankshaft. A similar arrangement with a
radial engine
The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is ca ...
is generally more difficult to arrange, especially cooling, and ones with
inline engine arrangements soon become so long that keeping the crankshaft from vibrating becomes a serious problem (see
Chrysler IV-2220
The Chrysler XIV-2220 (XI-2220 from 1944) was an experimental 2,500 hp, 2,220 cubic inch (36.4 liter) liquid-cooled inverted- V-16 aircraft engine designed by Chrysler starting in 1940. Although several aircraft designs had considered usi ...
for example).
Each "cylinder" from Lutz's design was 0.70 m in diameter and only about 30 cm in depth, providing 445 hp from 140 kg, an excellent
power-to-weight ratio
Power-to-weight ratio (PWR, also called specific power, or power-to-mass ratio) is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measuremen ...
compared even to jet engines of the era. A five-block version was proposed for his turboprop concept, providing 3,450 hp from an engine about 2 m long. While the power-to-weight ratio was good, the ''density'' of the engine was simply superb.
The overall turboprop looked much more like a jet engine than a piston one. The swing-piston gas generator was located in the middle of a long nacelle, with a five-stage axial compressor in front and a three-stage turbine behind. The compressor was used both to act as a
supercharger
In an internal combustion engine, a supercharger compresses the intake gas, forcing more air into the engine in order to produce more power for a given displacement.
The current categorisation is that a supercharger is a form of forced induct ...
for the piston engine, as well as provide cold air to cool the turbine. The actual power to the propeller, combining both the pistons and the turbines, was 4,930 hp at 10,000 m altitude, far greater than any German wartime project.
Why all this complexity to produce a new version of an engine, the turboprop, whose primary advantage was simplicity? The main problem with conventional jet engines is that the combustion takes place in an open chamber, which is considerably less efficient than the closed chamber of a piston engine, where it has constant volume (or close to it). The
Otto cycle
An Otto cycle is an idealized thermodynamic cycle that describes the functioning of a typical spark ignition piston engine. It is the thermodynamic cycle most commonly found in automobile engines.
The Otto cycle is a description of what happ ...
or
Diesel cycle
The Diesel cycle is a combustion process of a reciprocating internal combustion engine. In it, fuel is ignited by heat generated during the compression of air in the combustion chamber, into which fuel is then injected. This is in contrast to ign ...
used in piston engines has a much lower
specific fuel consumption than the
Brayton cycle
The Brayton cycle is a thermodynamic cycle that describes the operation of certain heat engines that have air or some other gas as their working fluid. The original Brayton engines used a piston compressor and piston expander, but modern gas tur ...
of a traditional gas turbine engines at low speed. Lutz's design was intended to power very long-range
bomber
A bomber is a military combat aircraft designed to attack ground and naval targets by dropping air-to-ground weaponry (such as bombs), launching aerial torpedo, torpedoes, or deploying air-launched cruise missiles. The first use of bombs dropped ...
s and
patrol aircraft
A maritime patrol aircraft (MPA), also known as a patrol aircraft, maritime reconnaissance aircraft, or by the older American term patrol bomber, is a fixed-wing aircraft designed to operate for long durations over water in maritime patrol rol ...
, where fuel economy was more important than simplicity and performance.
Lutz later patented the design under "Rotary compressor and other engines", United States patent 2,301,667.
Other examples
Lutz's design is not the only way to produce such an engine:
BMW experimented with a traditional engine with
poppet valve
A poppet valve (also called mushroom valve) is a valve typically used to control the timing and quantity of gas or vapor flow into an engine.
It consists of a hole or open-ended chamber, usually round or oval in cross-section, and a plug, usual ...
s on the combustion chambers, which had been used a number of times previously in experiments. Another approach entirely is to recover some of the heat of the exhaust in a
heat exchanger
A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contac ...
and use that instead of fuel to heat the compressed air, a concept used by
General Motors
The General Motors Company (GM) is an American Multinational corporation, multinational Automotive industry, automotive manufacturing company headquartered in Detroit, Michigan, United States. It is the largest automaker in the United States and ...
in a series of automobile turbines. Generally, however, improvements in the basic piston engine in "low-power" roles have kept any of these advanced designs out of the marketplace.
In the 1990s, a number of inventors re-introduced the concept as if it were new. Examples include Angel Labs' "Massive Yet Tiny" engine, the Rotoblock, the Roundengine, the Trochilic Engine and designs by Tschudi and Hoose. In 2009, Russian billionaire industrialist
Mikhail Prokhorov
Mikhail Dmitrievich Prokhorov ( rus, Михаил Дмитриевич Прохоров, p=mʲɪxɐˈil ˈdmʲitrʲɪjɪvʲɪtɕ ˈproxərəf; born 3 May 1965) is a Russian-Israeli oligarch, politician, and former owner of the Brooklyn Nets. I ...
announced his plans to enter an automotive business with a series of a lightweight
hybrid vehicle
A hybrid vehicle is one that uses two or more distinct types of power, such as submarines that use diesel when surfaced and batteries when submerged. Other means to store energy include pressurized fluid in hydraulic hybrids.
The basic princip ...
s using this design as their
prime mover
Prime mover may refer to:
Philosophy
*Unmoved mover, a concept in Aristotle's writings
Engineering
* Prime mover (engine), motor, a machine that converts various other forms of energy (chemical, electrical, fluid pressure/flow, etc) into energy o ...
. Another recent introduction aimed at the hybrid market is the "Hüttlin Kugelmotor", which combines the swing-piston concept with a modified
swashplate
A swashplate, also known as slant disk, was invented by Anthony Michell in 1917. It is a mechanical engineering device used to translate the motion of a rotating shaft into reciprocating motion, or vice versa. The working principle is similar to c ...
to produce a spherical design that directly powers an internal
electrical generator
In electricity generation, a generator is a device that converts motive power (mechanical energy) or fuel-based power (chemical energy) into electric power for use in an external circuit. Sources of mechanical energy include steam turbines, gas ...
.
Other names
The Tschudi engine is also known as a "cat-and-mouse engine" or a "scissor engine".
See also
*
Free-piston engine
A free-piston engine is a linear, 'crankless' internal combustion engine, in which the piston motion is not controlled by a crankshaft but determined by the interaction of forces from the combustion chamber gases, a rebound device (e.g., a piston i ...
*
Opposed piston 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 f ...
*
Oscillating cylinder steam engine
An oscillating cylinder steam engine (also known as a wobbler in the US) is a simple steam-engine design (proposed by William Murdoch at the end of 18th century) that requires no valve gear. Instead the cylinder rocks, or oscillates, as the cra ...
References
Notes
Bibliography
*
External links
Youtube.comToroidal engine from Franky Devaere
{{Piston engine configurations
Piston engine configurations
Proposed engines