Wankel Diesel engine

Last updated

Wankel Diesel engine describes the idea of using the Diesel principle in a Wankel rotary engine. Several attempts to build such an engine have been made by different engineers and manufacturers in the 1960s and 1970s. Due to technical problems and the general disadvantages of the Wankel design, the Wankel Diesel engine never left the prototype stage, and designing a Wankel Diesel engine capable of running under its own power is thus considered unfeasible.

Contents

Design concept

Characteristics of the Diesel engine
Source: [1]
Rolls-Royce 2-R6 prototype, shaped like the 8-digit. RR-R-6.jpg
Rolls-Royce 2-R6 prototype, shaped like the 8-digit.
Rolls-Royce R1C prototype. Two Stage Rotary RR R1C.jpg
Rolls-Royce R1C prototype.

A Wankel Diesel engine shares its basic design, a triangular-like rotor in an oval, epitrochoid-shaped housing, with a regular Wankel engine. The key difference is that it shares all of its operational characteristics with a Diesel engine. In addition to this, supercharging is required: A regular Diesel engine achieves compression ignition by a high compression ratio, which cannot be done in a Wankel engine due to the shape of the Wankel combustion chamber; supercharging ″artificially″ increases the compression ratio to ensure that compression ignition takes place. [2] Several different approaches of designing a supercharger for a Wankel Diesel engine exist. Wankel designed an external supercharger, [3] whereas Rolls-Royce added a secondary supercharging rotor of a bigger size, making the engine a two-stage rotary, which gave the housing an "8"-like appearance. [4]

Reasons for designing a Wankel Diesel engine

Compared with a Diesel engine, a regular petrol engine has a lower thermal efficiency. However, in the 1960s, the petrol engine advantages of lower mass, fewer vibrations and less noise emissions, all of which are important for passenger cars, were still prevailing. Low mass and smooth engine operation are also characteristics of the Wankel engine – combining Wankel design with Diesel characteristics would result in an efficient engine with low mass and few vibrations. Making a Wankel engine that can burn Diesel engine fuel, but which does not use the Diesel principle, can be useful if Diesel engine fuel is less expensive than petrol. [5] In a 1974 study conducted for the EPA, it was attempted to determine whether or not a Wankel Diesel engine has a better exhaust behaviour than a regular Otto cycle petrol engine. [6]

Causes of infeasibility

The main cause of Wankel Diesel engine infeasibility is the shape of the combustion chamber, located in the rotary piston. It is elongated and convex, thus not allowing a high enough compression ratio (without too much heat loss), [7] even in combination with a (solely crankshaft or exhaust gas driven) supercharger. This means that the engine is only functional if it is fed externally compressed air, as it requires more work to operate than it can produce. Also, designing a proper combustion chamber, correctly angled towards the injection nozzle to allow proper mixture formation, proved to be quite difficult; [8] the EPA study proves that the Wankel Diesel engine's exhaust contains disproportionally high levels of carbon monoxide (CO) and hydrocarbons (HC), indicating incomplete combustion. [6]

Prototype development

Diesel-Ring

The Diesel-Ring was a joint venture of the German Diesel engine manufacturers Daimler-Benz, MAN, Krupp and KHD. Development was ceased in 1969, because the shape of the Wankel engine combustion chamber was considered ineligible for the Diesel principle. [8] [7] The Diesel-Ring, attempts were made to modify the geometry of the epitrochoid and rotor in such a way that a higher compression ratio could be achieved. This was done without increasing the K-number and thus disproportionately increasing the overall volume of the engine. These attempts met with little success, as they resulted in vibrations of the apex seal due to excessive movement in the groove. [9]

Rolls-Royce

Rolls-Royce began developing a lightweight military Wankel Diesel engine for the MoD in 1964. [4] Fritz Feller was the leading engineer of the project. [10] Soon, it became obvious that a regular Wankel engine would not be suitable for the high compression ratio needed for compression ignition, which led to the idea of using another rotary piston as a supercharger. Early tests were conducted with a modified NSU Wankel engine that was fed pre-heated compressed air to achieve compression ignition. This test engine displaced 0.25 litre and ran for 94 hours before it broke; the fuel consumption ranged from 0.84 lb/hp·h to 1.4 lb/hp·h (511 g/kW·h to 852 g/kW·h). [11] The sealing material proved to be insufficient, leading to high sealing loss; new materials had to be engineered. Furthermore, designing a good combustion chamber, allowing good mixture of air and fuel, turned out to be considerably difficult and thus required a lot of development work. [12] To avoid the problem of having a complicated combustion chamber in the rotor, a precombustion chamber was considered an option, but it was later abandoned, because making a housing with a proper precombustion chamber seemed unfeasible. [13]

The first prototype, made of an NSU KKM 502 Wankel engine, was called R1 and featured a two-stage design with two rotors and an 8-shaped housing. It had a compression chamber volume of 1.126 litre and borrowed its 0.5 litre combustion chamber displacement from the KKM 502. [14] In total, eight different evolutions of the R1 were made, named in alphabetical order, (R1A, R1B, R1C,...). [15] The fifth evolution, which as called R1E, had an increased 1.265 litre compression chamber, but it retained the 0.5 litre combustion chamber. Its power output was about 40 kW; [16] fuel consumption was approximately 220 g/kW·h. [17] The R2 had a 3-rotor design did not get beyond the draft stage; R3 was the first version of a powerplant with a greater displacement, capable of developing more power. [18] The first prototypes having the planned engine size, were called the R4 and R5. In the R5, the first rotor stage was only used for compressing the intake air, the exhaust gas was not used to power it. Instead, the exhaust gas was sent through an external exhaust gas turbine. [19]

In early 1970, [20] the prototype 2-R6 was completed. [21] It is also a two-stage rotary engine, with the smaller combustion rotor on top of the bigger compression rotor. The rotors are connected with a gear ratio of 1 : 1 and rotate in the same direction. Unlike the R5 prototype, the 2-R6 uses the exhaust gas energy with its compression rotor instead of an external exhaust gas turbine. Torque is not taken off the combustion rotor, but the compression rotor instead. The engine has a displacement of 396 in3 (6.5 litre) and was supposed to have a power output of 350 hp (261 kW), [17] but having a mass of only 929 lb (421 kg). At the time, this would have been 50% of the mass of a comparable piston Diesel engine with the same power output. [4] Further plans included a more powerful 700 hp (522 kW) version of the engine in addition to the regular 350 hp variant. [17] [21] However, despite using special alloys, the engine mass was 1150 lb (522 kg) [22] and the power output of 180 hp (134 kW) barely exceeded 50% of the projected 350 hp. All runs on the test bed required using externally produced compressed air, the engine never ran under its own power. [19] It is said that due to financial problems, the Wankel Diesel engine project was cancelled in 1974. It was conjectured that the Yom Kippur War made the British Military lose the interest in a compact tank powerplant, resulting in governmental subsidies being cut. [21] It is much more likely though that designing a working Wankel Diesel engine is simply not possible. [23]

Felix Wankel

Wankel designed a Wankel Diesel engine with two clover-shaped housings and a compressor in between. Unlike in a regular Wankel engine, the rotary pistons are not shaped like a Reuleaux triangle, but like a bulgy quadrate. The compressor rotor has the shape of an ellipse. Despite the unusual design, this engine was functional under test conditions on a test bed. A second prototype with just one rotor for testing purposes was made. It had a displacement of 0.7 litre and passed a 20-hour test run where it produced a peak torque of 60 N·m. [3]

Bibliography

Related Research Articles

<span class="mw-page-title-main">Diesel engine</span> Type of internal combustion engine

The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is called a compression-ignition engine. This contrasts with engines using spark plug-ignition of the air-fuel mixture, such as a petrol engine or a gas engine.

<span class="mw-page-title-main">Reciprocating engine</span> Engine utilising one or more reciprocating pistons

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.

<span class="mw-page-title-main">Wankel engine</span> Combustion engine using an eccentric rotary design

The Wankel engine is a type of internal combustion engine using an eccentric rotary design to convert pressure into rotating motion. The concept was proven by German engineer Felix Wankel, followed by a commercially feasible engine designed by German engineer Hanns-Dieter Paschke. The Wankel engine's rotor, which creates the turning motion, is similar in shape to a Reuleaux triangle, with the sides having less curvature. The rotor spins inside a figure-eight-like epitrochoidal housing around a fixed-toothed gearing. The midpoint of the rotor moves in a circle around the output shaft, rotating the shaft via a cam.

<span class="mw-page-title-main">Pulsejet</span> Engine where combustion is pulsed instead of continuous

A pulsejet engine is a type of jet engine in which combustion occurs in pulses. A pulsejet engine can be made with few or no moving parts, and is capable of running statically. The best known example is the Argus As 109-014 used to propel Nazi Germany's V-1 flying bomb.

<span class="mw-page-title-main">Aircraft engine</span> Engine designed for use in powered aircraft

An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Aircraft using power components are referred to as powered flight. Most aircraft engines are either piston engines or gas turbines, although a few have been rocket powered and in recent years many small UAVs have used electric motors.

<span class="mw-page-title-main">Mazda Wankel engine</span> Reciprocating internal combustion engine

The Mazda Wankel engines are a family of Wankel rotary combustion car engines produced by Mazda.

<span class="mw-page-title-main">Mercedes-Benz C111</span> Motor vehicle

The Mercedes-Benz C111 was a series of experimental automobiles produced by Daimler-Benz in the 1960s and 1970s. The company was experimenting with new engine technologies, including Wankel engines, diesel engines, and turbochargers, and used the basic C111 platform as a testbed. Other experimental features included multi-link rear suspension, gull-wing doors and a luxurious interior with leather trim and air conditioning.

Homogeneous Charge Compression Ignition (HCCI) is a form of internal combustion in which well-mixed fuel and oxidizer are compressed to the point of auto-ignition. As in other forms of combustion, this exothermic reaction produces heat that can be transformed into work in a heat engine.

The Mercedes-Benz M 950 is a prototype Wankel rotary engine made by Daimler-Benz. It was first described in Wolf-Dieter Bensinger's 1969 essay Der heutige Entwicklungsstand des Wankelmotors, published in January of 1970. The engine was developed by Daimler-Benz's Wankel engine department, headed by Bensinger. About 100 units were built, of which some 3- and 4-rotor units were installed in the Mercedes-Benz C 111 experimental sports car, from 1969 until 1970, as a mid-engine. Although scheduled for commercial introduction in 1970 as a 2-rotor engine, the M 950 had not reached the series production stage by 1972. Daimler-Benz then developed a successor to the M 950, the M 951, but Daimler-Benz's Wankel engine development was abandoned in 1976.

A swing-piston engine is a type of internal combustion engine 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".

<span class="mw-page-title-main">Turbo-diesel</span> Diesel engine with a turbocharger

The term turbo-diesel, also written as turbodiesel and turbo diesel, refers to any diesel engine equipped with a turbocharger. As with other engine types, turbocharging a diesel engine can significantly increase its efficiency and power output, especially when used in combination with an intercooler.

<span class="mw-page-title-main">Suzuki RE5</span> Japanese Wankel engine motorcycle

The Suzuki RE5 is a motorcycle with a liquid-cooled single-rotor Wankel engine, manufactured by Suzuki from 1974 to 1976. Apart from its unusual engine, the RE5 is mostly a conventional roadster, albeit with some peculiar styling details thanks to Italian industrial designer Giorgetto Giugiaro.

<span class="mw-page-title-main">Model engine</span>

A model engine is a small internal combustion engine typically used to power a radio-controlled aircraft, radio-controlled car, radio-controlled boat, free flight, control line aircraft, or ground-running tether car model.

<span class="mw-page-title-main">Supercharger</span> Air compressor for an internal combustion engine

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.

<span class="mw-page-title-main">X-engine</span> US engine manufacturer

The X-engine is a type of pistonless rotary engine manufactured by LiquidPiston of Bloomfield, Connecticut.

The MidWest AE series are lightweight, liquid-cooled, single- and twin-rotor Wankel engines, with dual ignition, designed for light aircraft. They were produced by Mid-West Engines Ltd. at Staverton Airport, Gloucestershire, UK.

Skyactiv is a brand name for a series of automobile technologies developed by Mazda that increase fuel efficiency and engine output. The initial announcement of the Skyactiv technologies included new engines, transmissions, body, and chassis, which appeared in Mazda products from 2011 onwards.

<span class="mw-page-title-main">Internal combustion engine</span> Engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber

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.

David W. Garside is an inventor and former project engineer at BSA's Umberslade Hall research facility. He is notable for having developed an air-cooled twin-rotor Wankel motorcycle engine which powered the Norton Classic road bike. Although the Classic was not the first production rotary-engined bike, it was significantly lighter, smoother, more powerful and better-handling than the contemporary Suzuki RE5.

Wolf-Dieter Bensinger was a German engineer and university professor who contributed significantly to the development of the Wankel rotary engine.

References

  1. ↑ Stefan Pischinger, Ulrich Seiffert (2016). Vieweg Handbuch Kraftfahrzeugtechnik. 8th edition, Springer, Wiesbaden. p. 348. ISBN   978-3-658-09528-4.
  2. ↑ Wolf-Dieter Bensinger: Rotationskolben-Verbrennungsmotoren, Springer, Berlin/Heidelberg/New York 1973, ISBN   978-3-642-52174-4. p. 86
  3. 1 2 Jan P. Norbye: The View Down the Road, Popular Science, March 1973, p. 62
  4. 1 2 3 David Scott: NOW! A Diesel Wankel from Rolls-Royce, Popular Science, February 1971, p. 80
  5. ↑ John B. Hege: The Wankel Rotary Engine: A History, McFarland, 2017, ISBN   978-0-7864-8658-8, p. 100
  6. 1 2 M. L. Monaghan, C. C. J. French, R. G. Freese: A STUDY OF THE DIESEL AS A LIGHT-DUTY POWER PLANT , EPA-460/3-74-011, July 1974, Section 1–15
  7. 1 2 Wolf-Dieter Bensinger: Rotationskolben-Verbrennungsmotoren, Springer, Berlin/Heidelberg/New York 1973, ISBN   978-3-642-52174-4. p. 145
  8. 1 2 Ulrich Christoph Knapp, Gunter Bayerl: Wankel auf dem Prüfstand, Waxmann, ISBN   978-3-8309-6637-1, p. 120
  9. ↑ German Pat. No. 1,158,317 Nov. 28, 1963 Klöckner-Humboldt-Deutz and German Pat. No. 404522 and Pat. No. 1,164,746
  10. ↑ John B. Hege: The Wankel Rotary Engine: A History, McFarland, 2017, ISBN   978-0-7864-8658-8, p. 101
  11. ↑ Fritz Feller: The 2-stage rotary engine – A new concept in diesel power, Proceedings of the Institution of Mechanical Engineers, 1970–71, Vol. 185 13/71, p. 143
  12. ↑ John B. Hege: The Wankel Rotary Engine: A History, McFarland, 2017, ISBN   978-0-7864-8658-8, p. 102
  13. ↑ Road Test, Band 9, Quinn Publications, 1973, p. 10
  14. ↑ Fritz Feller: The 2-stage rotary engine – A new concept in diesel power, Proceedings of the Institution of Mechanical Engineers, 1970–71, Vol. 185 13/71, p. 150
  15. ↑ Fritz Feller: The 2-stage rotary engine – A new concept in diesel power, Proceedings of the Institution of Mechanical Engineers, 1970–71, Vol. 185 13/71, p. 151
  16. ↑ Wolf-Dieter Bensinger: Rotationskolben-Verbrennungsmotoren, Springer, Berlin/Heidelberg/New York 1973, ISBN   978-3-642-52174-4. p. 147
  17. 1 2 3 Wolf-Dieter Bensinger: Rotationskolben-Verbrennungsmotoren, Springer, Berlin/Heidelberg/New York 1973, ISBN   978-3-642-52174-4. p. 148
  18. ↑ Fritz Feller: The 2-stage rotary engine – A new concept in diesel power, Proceedings of the Institution of Mechanical Engineers, 1970–71, Vol. 185 13/71, p. 153
  19. 1 2 Road Test, Band 9, Quinn Publications, 1973, p. 11
  20. ↑ Fritz Feller: The 2-stage rotary engine – A new concept in diesel power, Proceedings of the Institution of Mechanical Engineers, 1970–71, Vol. 185 13/71, p. 156
  21. 1 2 3 John B. Hege: The Wankel Rotary Engine: A History, McFarland, 2017, ISBN   978-0-7864-8658-8, pp. 103
  22. ↑ Road Test, Band 9, Quinn Publications, 1973, p. 92
  23. ↑ Ulrich Christoph Knapp, Gunter Bayerl: Wankel auf dem Prüfstand, Waxmann, ISBN   978-3-8309-6637-1, pp. 121
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.