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The Quasiturbine or Qurbine engine, also called Kyotomoteur is a type of Rotary engine, invented by the Saint-Hilaire family, with patents (in the most general AC concept with carriages) awarded in 1996 and 2003. The engine uses a four-sided articulated rotor that turns within a stator, creating regions of increasing and decreasing volumes as the rotor turns. The Quasiturbine design can also be used as an air motor, steam engine, gas compressor, hot air engine, or pump. It is capable of burning fuel using photo-detonation, an optimal combustion type.

: "The Quasiturbine researcher team has initially established a list of 30 conceptual piston deficiencies and as many Wankel deficiencies. The Quasiturbine general concept is the result of an effort to improve both engines by suppressing the limiting sinusoidal crankshaft and offering up to 7 degrees of freedom at design." -- Gilles Saint-Hilaire (Oct. 18, 2007)

Official Websites

eMotionReports Quasiturbine White Paper (PDF, 247 KB).

Crom's Quasiturbine Comparison White Paper (Microsoft Word format, 232 KB).


The Quasiturbine (Qurbine) or Kyotoengine is a pressure driven continuous torque deformable spinning wheel a no crankshaft rotary engine having a 4-faced articulated rotor with a free and accessible centre, rotating without vibration or dead time, and producing a strong torque at low RPM under a variety of modes and fuels. The Quasiturbine can be used as air motor, steam engine, Stirling engine, compressor and pump. The Quasiturbine is also an optimization theory for extremely compact and efficient engine concepts.

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 info

How it works

Image:QTWiki180px jp70.jpg

In the Quasiturbine engine, the four strokes of a typical cycle de Beau de Rochas - Otto cycle are arranged sequentially around a near oval, unlike the reciprocating motion of a piston engine. In the basic single rotor Quasiturbine engine, an oval housing surrounds a four-sided articulated rotor which turns and moves within the housing. The sides of the rotor seal against the sides of the housing, and the corners of the rotor seal against the inner periphery, dividing it into four chambers. In contrast to the PowerPedia:Wankel engine where the crankshaft moves the rotary piston face inward and outward, the Quasiturbine rotor face rocks back and forth with reference to the engine radius, but stays at a constant distance from the engine center at all time, producing only pure tangential rotational forces. Because the Quasiturbine has no crankshaft, the internal volume variations do not follow the usual sinusoidal engine movement, which provides very different characteristics from the piston or the Wankel engine.

As the rotor turns, its motion and the shape of the housing cause each side of the housing to get closer and farther from the rotor, compressing and expanding the chambers similarly to the "strokes" in a reciprocating engine. However, whereas a four stroke cycle engine produces one combustion stroke per cylinder for every two revolutions, i.e. one half power stroke per revolution per cylinder, the four chambers of the Quasiturbine rotor generate four combustion "strokes" per rotor revolution this is eight times more than a four-stroke piston engine.


Image:Quasiturbine pieces 300.jpg

Piston engine uses a one-chamber-does-all-strokes principle, where cold process (intake) efficiency is destroyed by the high chamber temperature and hot process efficiency (combustion) is destroyed by low temperature cylinder. A problem the impractical piston split-cycle design attempts to solved, while the Quasiturbine has a cold intake area in a different location form the hot combustion area, for enhence efficiency. While the Quasiturbine offers 7 degrees of freedom at design enabling geometric volume pulse shaping, conventional turbine offers one degree of freedom (Rotation) and piston engines offers only two (Linear piston motion and crankshaft Rotation) both linked by a solid connecting rod offering no flexibility to shape the volume pulse. While the Quasiturbine torque continuity produces a peak torque within 20% its average torque, the 4-stroke piston has a long propulsive dead time resulting in a peak torque 7 times the average torque, which dictate the need for extra piston engine robustness. While piston engine size is typically 15 to 20 times the engine displacement, the Quasiturbine is so compact, it occupies a volume only a little more than its displacement. Consequently, weight reduction and high torque at low rpm offer mobility operational saving during the entire vehicle live time.

Quasiturbine engines are simpler, and contain no gears and far fewer moving parts. For instance, because intake and exhaust are openings cut into the walls of the rotor housing, there are no valve or valve trains. This simplicity and small size allows for a savings in construction costs. Because its center of mass is immobile during rotation, the Quasiturbine tends to have very little or no vibration. Due to the absence of dead time between strokes, the Quasiturbine can be driven by compressed air or steam without synchronized valve, and also with liquid as hydraulic motor or pump. Other claimed advantages include high torque at low rpm, combustion of hydrogen and compatibility with photo-detonation mode in Quasiturbine with carriages, where high surface-to-volume ratio is an attenuating factor of the violence of the detonation.


The Quasiturbine was conceived by a group of 4 researchers lead by Dr. Gilles Saint-Hilaire, a thermonuclear physicist. 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. Demonstrations have been done on an Air Gokart in 2004, on « APUQ Air Car » in 2005, on the University of Connecticut « Brash Steam Car » Video in 2010, and other products (Chainsaw and generator). Small pneumatic and steam units are available in 600 cc and 5 liters displacement sizes for research, academic training and industrial demonstration. Similar combustion prototypes are also intended for demonstration.


US Patent Quasiturbine AC (With Carriages) Dec. 1996

US Patent Quasiturbine SC (Without Carriage) Feb. 2003

Potential applications

Image:QT75SCSteamNet jp70.jpg

The Quasiturbine's high power-to-weight ratio makes it exceptionally suitable for aircraft engine and its no-vibration attributes make it suitable for use in, for example: chainsaws, powered parachutes, snowmobiles, jet skis and other watercraft, aircraft,etc. Variations on the basic Quasiturbine design also have applications as air compressors and as turbochargers. Rotary expander applications include gas pipeline pressure recovery, low thermal heat recovery, heat pumps, pneumatic air energy storage and recovery... It is well suitable to recover the pressure energy of hydrogen storage while recovering the low heat energy generated by fuel cells. As a compact, low vibration and low noise engine, the Quasiturbine is most suitable for onboard hybrid vehicle generator.

As a positive displacement steam engine, the Quasiturbine volume modulator is particularly suitable for Brayton and Rankin low temperature heat recovery cycle, not to exclude engine exhaust heat recovery. This includes steam electricity production from solar heat, biomass, geothermal, and even nuclear thermal concepts A White Paper: Engine Exhaust Heat Recovery with Quasiturbines Offering Essential Efficiency Characteristics. Distributed electricity generation can further involve the Quasiturbine in pneumatic energy storage and recovery (ex.: windmills). While natural gas pipeline national distribution is done at up to 100 bars (1500 psi), final customers use the gas at less than 1 bar. The Quasiturbine is most suitable for gas pipeline pressure energy recovery at pressure reduction stations, where it can regulate the gas flow. This is an important free source of mechanical and electrical energy (when compared for example to windmills), both at the utility and consumer locations, that Quasiturbines can recover without any gas combustion or pollution Using the Quasiturbine to Regulate Natural Gas Pipeline Pressure and Flow-rate. In refrigeration systems, replacing the pin-hole expansion valve by a Quasiturbine rotary expander allows recovering of pressure energy, while enhancing efficiency by removing gas kinetic energy otherwise dissipated on the cold side.

Wankel comparison

The Quasiturbine is superficially similar to the Wankel engine, but is quite distinct from it. The Wankel engine has a single rigid triangular rotor synchronized by gears with the housing, and driven by a crankshaft rotating at three times the rotor speed, which moves the rotor faces radially inward and outward. The Wankel attempt to realize the four strokes with a three-sided rotor, limits overlapping port optimization, and because of the crankshaft, the Wankel has near sinusoidal volume pulse characteristics like the piston. The Quasiturbine has a four-sided articulated rotor, rotating on a circular supporting track with a shaft rotating at the same speed as the rotor. It has no synchronization gears and no crankshaft, which allows carriage types to shape "almost at will" the pressure pulse characteristics for specific needs, including achieving photo-detonation.

The Wankel engine divides the perimeter into three sections while the Quasiturbine divides it into four, for a 30% less elongated combustion chamber. The Wankel geometry further imposes a top dead center residual volume which limits its compression ratio and prevents compliance with the Pressure-Volume diagram. The Wankel has three 30 degree dead times per rotor rotation, while the Quasiturbine has none which allows continuous combustion by flame transfer, and allows it to be driven by compressed air or steam without synchronized valves (also by liquid as a hydraulic motor or pump). During rotation, the Wankel apex seals intercept the housing contour at variable angles up to from -60 to +60 degrees, while the Quasiturbine contour seals are almost perpendicular to the housing at all time. While the Wankel engine requires dual (or more) out-of-phase rotors for vibration compensation, the Quasiturbine is suitable as a single rotor engine, because its center of mass is immobile during rotation. While the Wankel shaft rotates continuously, the rotor does not, as it stops its rotation (even reverses) near top dead center, an important rotor angular velocity modulation generating strong internal stresses not present in the Quasiturbine.

The Quasiturbine circumvent 4 major Wankel deficiencies Quasiturbine versus Wankel:

The excessive exhaust-intake overlap, Wankel trying to make 4-stroke with a 3 side rotor, while the Quasiturbine is making 4 stroke with a 4 side rotor with no overlap.

The Wankel chamber geometry does not close properly at TDC (unable to gather the gas in one location, leaving it spreaded around the chamber). This is a similar (or worse) situation as that of a flat surface piston with a flat cylinder head (where the gas is not gathered in one location - Such a piston geometry is showing a similar problem as the Wankel). The Quasiturbine chamber closes at TDC in gathering most of the gas in one location, like the modern piston does.

The Wankel chamber minimum volume is not constant as it is reduced during rotation, which prevents the applicability of the P-V efficiency diagram.

The Quasiturbine has no internal mechanical synchronization gear.


Image:Qt-Flash-Final 250.gif

Detonation is a phenomenon that occurs when an air/fuel mixture is compressed well past the point of thermal-self-ignition. This is commonly called knocking in piston engines and is generally not desired in conventional sinusoidal volume pulse type engines. Detonation is a very efficient combustion mode, a mode that has this far not been successfully exploited in piston or Wankel engine designs. Diesel combustion (without detonation) is driven by thermal ignition of a fuel pulverized into very hot air gasoline piston engine combustion is driven by a relatively slow, controlled, thermal combustion wave through an homogeneous mixture "knocking" detonation also happens in an homogeneous mixture, driven by a supersonic shock wave, or ultimately by radiation as photo-detonation. See PhotoDetonation versus HCCI.

Supersonic shock wave detonation is accidentally seen in gasoline engines, because the vaporization of micro-droplets is only partially completed at the time of maximum compression. To actually achieve photo-detonation, a fast and narrow pressure pulse like that achieved in the Quasiturbine is necessary to rapidly skip straight through the sequence of events (thermo-ignition and shock waves), and rapidly access that mode. Little information or research is available regarding this phenomenon because engineers first need to control the less demanding shock wave detonation. Photo-detonation (designation specific to fuel mixture) is today mainly a curiosity among scientists, but the special pulse characteristics of the Quasiturbine will help bring this phenomenon into actual application.

Because the Quasiturbine has no crankshaft and can have carriages, the pressure pulse can be shaped like the minuscule cursive letter " i ", with a high pressure tip 15 to 30 times shorter than the piston or Wankel volume pulse, and with rapid linear rising and falling ramps. This kind of pressure pulse is self-synchronizing and reduces the immense stresses by shortening the high pressure duration.

Efficiency at low power

The modern high-power piston engine in automobiles is generally used with only a 15% average load factor. The efficiency of a 200 kW gas piston engine falls dramatically when used at 20 kW because of high vacuum depressurization needed in the intake manifold, which vacuum becomes less as the power produced by the engine increases. Photo-detonation engines do not need an intake vacuum, as they take in all the air available, and mainly for this reason and higher compression ratio, efficiency stays high even at low engine power.

The development of a photo-detonation engine may provide a means to avoid that low-power-efficiency penalty it may be more environmentally friendly as it will require low octane additive-free gasoline or diesel fuel it may be multi-fuel compatible, including direct hydrogen combustion and it may offer reduction in the overall propulsion system weight, size, maintenance and cost. For these reasons it could be better than or competitive with hybrid car technology.

Hybrid alternative

Detonation and hybrid are two different means to harvest the low efficiency of reduced power piston engine, and both are compatible with efficient electrical (in-wheel) power train. Detonation engine is however a more direct and efficient way, and because the «on board fuel» is already a form of energy storage, the detonation engine avoids to re-stock this energy electrically into batteries. The chemical energy stored in the fuel is degraded when chemically re-stored into batteries.

It is the purpose of the hybrid car concept to avoid the low efficiency of the Otto cycle engine at reduced power. There is a 50% fuel saving potential, of which only about half could be harvested the hybrid way. But getting extra efficiency this way requires additional power components and energy storage, with associated counter-productive increases in weight, space, maintenance, cost and environmental recycling process. The development of a photo-detonation engine like the Quasiturbine would provide more direct means to achieve the same or better. Furthermore, a 30 % engine heat recovery efficiency (not easy to achieve, but feasible) would out-perform most of today's hybrid concepts. One way is to heat a steam Quasiturbine engine block by placing it in or around the exhaust pipe (corrosive condensation will not affect the inside) and flashing hot pressurized steam fluid directly into the chambers. This way, the Quasiturbine acts simultaneously as the boiler and the expander, and suppresses the danger associated with steam reservoir.

Distributed Power Generation

The future of energy strategies involves resources, efficiency, distribution and mobility. No thermal distributed power generation will become reality until the market offers small detonation capable engines as efficient and clean as large utility stations. Because of (synthetic) fuel mobility, specific energy and power advantages, efficient internal combustion engines will then have little substitute in the mobility market (couple with intelligent electrical power train).

Related Sites

YouTube Quasiturbine Video Channel - Video

Vidéo YouTube français - La Quasiturbine: le moteur de l'avenir

Vidéo Google français - La Quasiturbine sur Radio-Canada Découverte

How Quasiturbine Engines Work (How Stuff Works)

Quasiturbine entry on INIS at IAEA.

PhotoDétonation versus HCCI

University of Connecticut « Brash Steam Car » Video

In the News

The Quasiturbine: Promising To Revolutionize Engines - promises to revolutionize the internal combustion engine. It is said to make engines more efficient, quieter and much lighter for the same torque and horsepower abilities. It also promises to make for better compressors and pneumatic motors (refrigeration, heat pumps, stirling engines, steam turbines). (TreeHugger June 22, 2006)

The Quasiturbine Gilles Saint-Hilaire on Next Generation Rotary-Engines (pdf) - Interview with Tim Ventura, April 24 2006, American Antigravity

Quasiturbine tech promises engine paradigm shift (Gizmag Nov. 27, 2004)

FutureWatch: From the Piston to the Wankel to the Quasiturbine (Future Energies Oct. 20, 2000)


See Talk:PowerPedia:Quasiturbine


Download - On Oct. 15, 2007, Congress:Founder:Sterling D. Allan conducted a live interview with Gilles Saint-Hilaire of Quasiturbine, as part of the Free Energy Now radio series.

- 'What are the Piston engine deficiencies?'

: QT team identified 30 piston deficiencies

: One chamber for hot and cold strokes

: Otto compression limitations and vacuum

: Poor for environment and energy

- 'How can the piston be improved?'

: Otto thermal improvement, weight, vibration

: By a machine concept with more degrees of freedom

: Efficiency -> Detonation

- 'How does the QT technology work (overview)?'

: Deformable rotor, 4 blades chained

: 7 degrees of freedom at design

- 'What are the differences compared to the Wankel?'

: QT 4 stroke with 4 side rotor is among the Wankel differences

: No eccentric crankshaft -> no radial piston like movement

: Perfectly balanced rotor

: No overlap of exhaust and intake stroke

: No synchronisation gear

: Quasi continuous flow at intake and exhaust

- 'Are you considering other methods?'

: From a general engine survey. QT optimizes...

: Benefit for Environment and Energy

- 'Applications?'

: General engine replacement

: Pipeline pressure energy recovery

: Windmill air pressure energy storage and recovery

: Rotary expander and pump for freezer and air conditioner

: Air engine for mining

: Low pressure Steam

: Distribution Power Generation

: Mobility and transportation

: Advance Stirling, thermal solar and nuclear

- 'Where is QT in the process of implementing commercially?'

: Look at solar, windmill, fuelcell, hybrid... similar road

: Piston has not been overnight, Wankel 1926 to 1957 + 10y

: Early priority air, steam, expander -> combustion

- 'What kind of data have you accumulated?'

: Like new technology, it is slow process

: Look data collection for windmill, fuelcells, hybrids

: priority to pneumatic and steam, step useful for combustion market

- 'Independently tested?'

: This is a must at commercial stage reliable spec. sheet

: Theory is the reference - Present machine confirms the theory

: Priority to mechanical tune up phase

: Robusness and application environment data

- 'What price point to start out at in terms of cents/kw-h?'

: Zero fuel cost in Pipeline pressure energy recovery!

: Modern manufacturing can handle complexity at low cost

: This engine is simple and has everything to be the less costly engine ever made

: Engine is only part of energy system

: Efficiency enhencement in car -> free engine on live time

- 'How much might this price change in the next 5 years?'

: Custom made for now

: Mass production (abroad temptation?)

: Plastic and ceramic toward cost down

- 'How does the QT technology compares to others like it out there?'

: No technology can do it all

: QT is for high torque, low rpm, power modulation, efficiency

- 'What are its strengths?'

: Compact, vibration free, multi-mode, low cost

: Clean and efficient

- 'Weaknesses?'

: Standard innovation credibility gap?

: User affection for known reliable conventional engines?

: Too few demo applications running yet? Need some time...

- 'How might someone invest in the company?'

: As of 2007, QT did not accept investor money, but could soon...

: QT has a long list of people asking to invest

: Projects seem to be pupping up rapidely...


Talk:PowerPedia:Quasiturbine - English - Français


Skeptics say:

"It has more moving parts than the Wankel engine."

: Gilles / Quasiturbine responds: "The Quasiturbine does not need the complex Wankel synchronization gears. Anyhow, modern digital manufacturing has proven that complexity is no objection to success."

"It has never been shown to work as an internal combustion engine."

: Gilles / Quasiturbine responds: "Not all can be done at once when dealing with an emerging technology. Considering the wide field of Quasiturbine applications, the inventors are moving toward commercialisation one step at the time, giving early priority to steam, air motor and rotary expander modes, before tackling the combustion products in the marketplace."

"For all other possible uses there are many other designs that are more reliable and function more efficiently."

: Gilles / Quasiturbine responds: "A non-substantiated opinion."


Agency Head Office

Quasiturbine Agence (Promotional Agent)

Casier 2804, 3535 Ave Papineau,

Montréal Québec H2K 4J9 CANADA

(514) 527-8484 Fax (514) 527-9530


USA Agent

Quasiturbine Agency (Promotional Agent)

Suite 173 - 1316 NE Carlaby Way

Hillsboro Oregon 97124 USA


See also


PowerPedia:Wankel engine

- PowerPedia

- Main Page
