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The Quasiturbine or Qurbine engine is a proposed pistonless rotary engine using a four-sided rhomboid rotor whose sides are hinged at the vertices.

Patents for the Quasiturbine (in the most general AC concept with carriages) [1] [2] are held by the Saint-Hilaire family of Quebec. As well as an internal combustion engine, the Quasiturbine has been proposed as a possible pump design, and demonstrated as a pneumatic engine using stored compressed air and as a steam engine [3].

Three designs have been proposed:

  • Two-port with carriages, suitable for use as an internal combustion engine.
  • Four-port without carriages, suitable for use as a pneumatic or hydraulic engine, steam engine or pump.
  • Two-port without carriages, a conceptual design which is hoped to combine some of the advantages of the existing two- and four-port prototypes.

The main problems with this design are

  • it has far more moving parts than the Wankel engine
  • it has never been shown to work as an internal combustion engine
  • for all other possible uses there are many other designs that are more reliable and function more efficiently


Two-port with carriages

The earliest Quasiturbine design used a three-wheeled carriage (French chariot, hence avec chariots or AC for with carriages) to support each vertex of the rotor. The wheels of these four carriages, making twelve wheels in total, ran around the periphery of the engine chamber.

A prototype of an internal combustion engine to this design was constructed, and enthusiastically reviewed in European Automotive Design magazine September, 1999. The prototype was turned by an external engine for 40 hours.

However, ignition with fuel was never achieved. If it was attempted no results were ever released, and development work on this design was suspended.


  • Cylinder ports in place of valves reduce the number of moving parts, in common with the Wankel engine and some two stroke engines.
  • The carriages keep the seals almost perpendicular to the cylinder walls, in contrast to the Wankel engine where the angle varies plus and minus 60°.
  • The rotor can be designed so its centre of gravity remains stationary or nearly so, minimising vibration.
  • Sixteen strokes per revolution of the rotor, as opposed to twelve for a single-rotor Wankel engine and two for a revolution of the crankshaft of a single-cylinder single-acting piston engine.


The two-port design with carriages was proposed to make possible a new and superior mode of combustion, termed photo-detonation by the Quasiturbine inventors. This resembles detonation, as used in the Bourke engine, akin to knocking and pinging undesirable in common internal combustion engines. As of 2005, no research has been published supporting this claim. A related idea that flame transfer would be possible through special ports is similarly unsupported.

Four-port without carriages


The second Quasiturbine design is greatly simplified to eliminate the carriages (French sans chariots or SC). At the same time, the ports were duplicated on the opposite side of the housing, thus converting the operation from four strokes per cycle to two and doubling the number of cycles per rotor revolution. This mechanism has been demonstrated running as a pneumatic engine using stored compressed air, and also as a steam engine. This is also the design proposed for use as a pump, and particularly as a supercharger.

This design uses redesigned blades, longer than those for a similar sized housing of the first type owing to the absence of the carriages, and lacking the distinctive crown contour. Only the basic rotor geometry is common with the earlier design.

A pneumatic engine of this design was demonstrated powering a go-kart in November 2004, and another powering a small car in September 2005, both vehicles using stored compressed air to power the engine. As of 2005 a pneumatic chain saw driven by an air hose from a conventional external compressor is under development.

With a suitably redesigned housing to allow for thermal expansion, the same rotor design has been demonstrated as a steam engine.

Another potential variation of this design uses the two sets of ports independently, one as an engine and the other as a pump, thus potentially integrating the functions of a pump and its driving motor in one shaftless unit. One restriction of this usage is that the two fluids must be similar; It would not be possible for example to drive an integrated air pump with hydraulic fluid, as the rotor design is significantly different. As of 2005 no prototype of this variation has been demonstrated.


  • Fewer moving parts than most engines (including of course the Quasiturbine design with carriages).
    • Absence of valve gear required by many other forms of steam and pneumatic engines.
  • Little vibration.
  • High power-to-weight ratio.
  • Possibility of integrated turbo-pump and turbo-expander configurations.


Two-port without carriages

This third design combines aspects of the first two. As of 2005 this design is conceptual only. It has not been built, but is used for purposes of illustration. If built it would not support photo-detonation.

Many other designs are possible within the patented Quasiturbine model, with or without carriages and with differing numbers of ports. As of 2005, which design will be used for further work on the internal combustion version has not been announced.


The Quasiturbine was conceived by a group of 4 researchers, led by Dr. Gilles Saint-Hilaire, a thermonuclear physicist, and consisting of members of his immediate family. The original objective was to make a turbo-shaft turbine engine where the compressor portion and the power portion would be in the same plane. In order to achieve this, they had to disconnect the blades from the main shaft, and chain them around in such a way that a single rotor acts as a compressor for a quarter turn, and as an engine the following quarter of a turn.

The general concept of the Quasiturbine was first patented in 1996. Small pneumatic and steam units are available from the patent holders for sale or hire for research, academic training and industrial demonstration, as is a book (largely in French) describing the concepts and development of the design. Lacking any forced lubrication system, these engines function only for short periods, a few hours at most, before requiring maintenance.

The patent holders have announced that they intend to make similar internal combustion prototypes available for demonstration.

See also

  • Pistonless rotary engine, which discusses general advantages of rotary engines and comparisons between Quasiturbine, Wankel and orbital (Sarich) engines.


  1. ^ US Patent Quasiturbine AC (With Carriages) Dec. 1996
  2. ^ US Patent Quasiturbine SC (Without Carriage) Feb. 2003
  3. ^ Quasiturbine Low RPM High Torque Pressure Driven Turbine for Top Efficiency Power Modulation. Peers reviewed paper - Published in The Proceeding of Turbo Expo 2007 of the IGTI (International Gas Turbine Institute) and ASME (American Society of Mechanical Engineers). Abstract and info
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Quasiturbine". A list of authors is available in Wikipedia.
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