Quasiturbine> Theory> QT Concept


Is the piston engine concept the best for ever?
Why is it so difficult to substitute it?
The Quasiturbine systematic engine concept analysis gives answers...

Theory - Quasiturbine Concept

Quasiturbine Not a Vane Type

The vane-type pumps are known for their very limited engine torques due to the amplitude of their seal movements, a movement the Quasiturbine brings back to imperceptible. They have also the major geometrical defect of not allowing a high geometric compression ratio, which makes them doubly inapt for combustion engines. The compressible fluid must initially charge in pure lost the residual chamber volume at Top Dead Center before providing the push, which destroys their efficiency. An efficient positive expansion machine must be capable of very high geometrical compression ratio, reducing the charging loss to nearly zero, and this is one of the multiple Quasiturbine objectives. Furthermore, the Quasiturbine has 2 different compress fluid circuits (vane motor have only one), which double the torque, as well as the specific power density.

Origin of the Quasiturbine Idea

The Quasiturbine researcher team has initially established a list of 30 conceptual piston deficiencies www.quasiturbine.com/ETheoryQTVersusPiston.htm and as many Wankel deficiencies www.quasiturbine.com/ETheoryQTVersusWankel.htm. The Quasiturbine general concept www.quasiturbine.com/QTImages/QTBrevet12Fig1Net.jpg 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. The inventors have made a systematic analysis of engine concepts, their value, their weaknesses, and their potential for improvement. All improvement ideas converged when they suggested to make a turbo-shaft turbine having only one turbine in one plane... In order to achieve that, the turbine blades had to attached one to an other in a chain like configuration, where the rotor acts as compressor for a quarter of a turn, and as engine the next quarter of a turn... Furthermore, to be able to shape the pressure pulse at will in order to optimized the thermodynamic and reach photo-detonation, extra degrees of freedom at design needed to be introduced by a set of peripheral carriages. This is the Quasiturbine, which is also a theory about efficient engine!

It is a type of rotary engine invented by the Saint-Hilaire family and first patented in the general configuration www.quasiturbine.com/QTImages/QTBrevet12Fig1Net.jpg in 1996. The engine uses a four-sided articulated rotor supported by carriages that turns within a complex computer calculated oval shape 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 or pump. It is capable of burning fuel using photo-detonation, an optimal combustion mode of the future the piston cannot support...

Prior Art: « La principale raison pour laquelle les concepts du 20 ième siècle ne se sont pas développés résulte du fait qu'ils sont statiques et que les prototypes
correspondants ne tournent pas correctement, ni ne sont fonctionnels. Il aura fallu attendre la venue de puissants ordinateurs personnels à la fins des années 1980, et les travaux de simulation numérique de la famille Saint-Hilaire pour qu'émerge le concept général dynamique de la Quasiturbine www.quasiturbine.com , comprenant une vaste famille de nouvelles machines www.quasiturbine.com/QTImages/QTBrevet12Fig1Net.jpg  incorporant des solutions essentielles au bon fonctionnement et au succès ultérieur. Les Quasiturbines incorporent aussi des profils de confinement « patinoires Saint-Hilaire » plus généraux, qui permettent d'optimiser les usages. Les brevets Quasiturbines citent une vingtaine de brevets principaux antérieurs, malheureusement tous condamnés à l'échec anticipée par les simulations numériques. Comme quoi l'informatique aura aussi aider à la révolution mécanique! Il est consternant de constater qu'après tant d'années, la Quasiturbine reste toujours incomprise... et demeure à tord souvent comparée à de nombreux concepts très différents dans leur comportement, voir sans issu. »

When the distances between the 2 wheels of a carriage is set to zero, the carriages become an articulated jointure (no-carriage limit case). While there is no prior art for the general Quasiturbine concept, a non exhaustive review of the no-carriage limit case (SC model) is given in Quasiturbine patent back to 1902 (more patent references exist in several countries, but the most significant are listed - Numerical simulations have shown that all these implementations have conceptual flaws or defects which make them non-practical running engine as patented). They are applications not throughout studied and understood by their inventors at the time and not comparable to the Quasiturbine in their behavior, abandoned for the good reasons that they do not run properly (try them to see). No past reference states or uncovers difficulties to which Quasiturbine already incorporates solutions, and no one had found nor identified the superior properties of the skating rink family type of confinement profiles...

Since all referenced patents were expired (a couple dozens of patents is almost like none in the field of engines), a new and more advanced implementation concept of the Quasiturbine SC model (without carriage) has been developed, with a complex jointure carrying a complete seal set able to meet the blades stress analysis. This implementation SC concept result of a detail numerical simulations in order to define an optimized engine stator profile with a center free rotor, and dynamically guide-free blades, including several central differential solutions. Inventors which have been in the past working on the no-carriage concept variations have fail tenacity, and among them came this comment: "Je ne vous en veut pas, mais je suis en rage contre moi-même de ne pas avoir vu ni compris tout le potentiel de ce concept, d'avoir manqué de persévérance, et ne pas avoir fait progresser cette invention pour amener moi-même là où est la Quasiturbine aujourd'hui..." . This is often the case when engine inventors do not start from basic thermodynamic objectives, but rather focus their researches on a volume modulation machine, leaving to hazard the later interest of the device. A path not followed by the Saint-Hilaire family.

Some like to say that the Quasiturbine (the special simple case without carriage) look like other rotaries, but none seem comfortable to say that other rotaries look like the Quasiturbine! No matter the level of apparent similitude, there are great differences between the Quasiturbine and other rotary concepts, and those who fail to understand it theoretically, could sadly discover it experimentally following considerable worthless effort and investment.

To the exception of the Quasiturbine team, none of the inventors having previously work on this no-carriage idea seem to have strongly believed in it, at least not to the extend of actively promoting it during the last decades. The Quasiturbine  more advanced implementation SC concept and general application disclosures create a new context in which some prior art inventors tend today to re-interpret their works under a light not previously available, crediting their past works with a plus value not known or apparent at the time, and sometime source of un-confirmed historical pretensions which would not have append without the recent Quasiturbine existence and growing popularity... Not being the first inventor could be very frustrating, but should never be humiliating.


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. Contrary to the Wankel engine where the crankshaft moves the rotary piston face inward and outward, the Quasiturbine rotor face rocks back and forth in 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.

Qtv2-SCAnim2.gif (70956 bytes)

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. 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. 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.

Quasiturbine Definition

The Quasiturbine (Qurbine) is a no crankshaft rotary engine having a 4 faces articulated rotor with a free and accessible center, rotating without vibration nor dead time, and producing a strong torque at low RPM under a variety of modes and fuels. The Quasiturbine design can also be used as an air motor, steam engine, gas compressor or pump. The Quasiturbine is also an optimization theory for extremely compact and efficient engine concepts.

More to Understand...

While most rotary engines use the principle of volume variation between a curve and a moving cord, this new engine concept makes use of a "seven degrees of freedom  X, Y, q, ø1, ø2, ø3, ø4" rotor, trapped inside an internal housing contour, and does not require a central shaft or support. This concept is the result of research for an hybrid turbine-piston engine with a fixed center of gravity during rotation (zero vibration). The invention is an assembly of four carriages supporting the pivots of a four-element, variable-shape rotor. This rotor rolls on the inner surface of a profiled stator shaped like a skating rink (just like a roller bearing). During the rotation, the rotor components align alternatively in a lozenge and a square configuration. This device can act as a pump, a compressor, a flow meter, or as an engine (including pressurized fluid mechanical energy converter). It is self-synchronized and uses no valve (only fixed ports in the stator or alternatively, ports on the lateral side covers). Central support of the rotor is not required for most applications. Four cycles are completed in every rotation. The maximum geometrical compression ratio is a function of the maximum diagonal ratio selected at design. As for turbine engines, ignition is only required initially, since combustion is kept continuous between successive cycles by way of an ignition transfer slot or cavity. The continuous combustion produces an enhanced dynamic compression ratio. The device incorporates few parts. It has an excellent torque continuity even at low rpm (Due to its high torque pulsation rate, this device requires less flywheel effect and gearbox ratio for most applications). It is suitable for uses such as aeronautics, where high reliability is required. Having no oil pan, it can be operated in completely submerged or hostile environments. The asymmetry of the strokes and the precocity of the mixture intake and gas expansion (without excess volume during expansion) allow for a better initial mechanical energy conversion. A fast reduction in the combustion chamber of the temperature, the pressure and the confinement time leads to less NOx production, and less heat transfer toward the engine block, all contributing to improve the power density and the efficiency over the piston engine. The Quasiturbine meets the hydrogen engine criteria.

A Family of Devices

Because the Quasiturbine is defined by a set of 7 geometric parameters (see the patents) which can be individually set to be positive, negative or null, an infinity of Quasiturbine configurations can be achieved. One of the most simple Quasiturbine geometry has no carriage (Model QT-SC) as follows:

This illustrates some details of a Quasiturbine without carriage (Model QT-SC).

Other more complex geometries involve carriages (Model QT-AC) as shown below.

Quasiturbine3D-3l.gif (31631 bytes)
QT-AC (With carriages) is intended for detonation mode,
where high surface-to-volume ratio
is a factor attenuating the violence of detonation.

Furthermore, the eccentricity is also an important geometric factor which dictates the shape of the stator as a more or less complex oval, to a very distorted shape still acceptable... The plurality of Quasiturbine designs produces different pressure and torque characteristics, often very different from the piston and the Wankel engine, which allows for operation mode not possible with the piston.

Each Quasiturbine device is at the crossroad of the 3 modern engines: Inspired by the turbine, it perfects the piston, and improves on the Wankel.

Improved Characteristics

The Quasiturbine theory optimizes the use of time by eliminating dead times, reallocating time among the different engine strokes and replacing the progressive torque impulses with impulse plateaus. This theory concurrently takes advantage of space by adopting multi-functional and homo-kinetic engine components which are indispensable at all times during rotation, and demands continuous flow at the engine's intake and exhaust. This theory optimizes 14 engine parameters at once and suggests pressure profiles allowing the detonation.

The Quasiturbine is a continuous flow engine at intake and exhaust. An engine's piston completes 4 strokes in two rotations, the Quasiturbine completes 32 ! Compressor, pump or turbo-pump made possible without any check valve or obstruction.

Continuous combustion, high torque, low RPM, zero vibration, potentially oil free, fast acceleration, 20 times less noise, less pollution, and high power density (by a factor of 4) in volume and weight. Compatible with hydrogen and some Quasiturbine design accepting detonation mode.

Quasiturbine SC - Without Carriage

The SC model has not internal parts - because the center is accessible, all engine components have a face accessible externally, including through the center. This property is quite precious in application related to thermal heat exchanges with the engine block.

When the eccentricity (here 0,578 for the model QT-SC, without carriage) is chosen such as to produce a straight side on the top and on the bottom, the Saint-Hilaire skating rink confinement profile is quite obvious:

Quasiturbine rotor confinement "Saint-Hilaire skating rink profile"
This configuration displaces its entire volume every revolution,
Eccentricity can be still higher, but for current devices,
a less eccentric Quasiturbine is easier to built,
and well able to exceed piston engine performance.

Why does it Turn ?

This diagram show the force vector in a Quasiturbine when one or two opposed chambers are pressurized either by fuel combustion, or by external pressure fluids. Because the pressure vectors are off center, the Quasiturbine rotor experiences a net rotational force. It is that simple !

Click here for a 2000 pixels high resolution image 

This diagram compares piston engine with steam and fuel combustion Quasiturbine.

Quasiturbine AC - With Carriages

More complex Quasiturbine designs can follow from the defining set of equations. Contrary to the piston or the Quasiturbine QT-SC (without carriage), which have volume characteristics near sinusoidal, the more complex Quasiturbine designs can shape the volume pulse almost at will by varying the parameter sets.

Quasiturbine3D-A2.gif (154372 bytes)
QT-AC (With carriages) is intended for detonation mode,
where high surface-to-volume ratio
is a factor attenuating the violence of detonation.

Quasiturbine3D-1s.gif (21619 bytes)

The parameters for the design below allow to shape the volume pressure pulse to have a tip 15 to 30 times shorter than the piston, which provide enhanced torque characteristics for pneumatic and steam Quasiturbine. But more important, this design is most suitable for detonation combustion engine mode, a superior mode the piston has failed to support for over 40 years !

QTDiag1VignetTrans.gif (9572 bytes)
Quasiturbine2D Petit.gif (2642 bytes)                                        Anim3dVignette.GIF (3776 bytes)

Furthermore, in detonation mode, the high surface-to-volume ratio of this design
is an attenuation factor of the violence of the detonation.

Pneumatic - Steam

All of the Quasiturbine family designs can be used in pneumatic and steam mode.

Quasiturbine Uniflow Characteristic

In most reciprocating piston engines, the steam reverses its direction of flow at each stroke (counter-flow). By entering and exhausting the cylinder by the same port, the cylinder valve and walls are cooled by the passing exhaust steam, while the hotter incoming admission steam is wasting some of its energy in restoring the temperature. Some energy is further lost in reversing the motion momentum of the mass of steam within the piston. The aim of the piston uniflow is to remedy this defect by providing an exhaust port at the end of the stroke, making the steam flowing only in one direction, but has the inconvenience of recompressing some residual cylinder steam. Quasiturbine is a uniflow engine, with the further advantage of not recompressing any residual steam, resulting in superior energy efficiency.  Recompressing residual steam means some reversibility losses, and the pressure increases makes a substantial restriction to the initial steam flow into the chamber, not to ignore the truncated cycle near bottom dead center - None of this with the Quasiturbine.


The Quasiturbine model SC is particularly suitable for the Stirling mode (A pure thermal engine without intake and exhaust).

Detonation Engine

Chemists know that the best way to burn fuel is with intense laser radiation. The photo-detonation (Auto Ignition) occurs at slightly higher pressure than the thermal ignition designated in the US as "Homogeneous-Charge Compression-Ignition" HCCI combustion, in Europe as "Controlled Auto Ignition" CAI combustion, and in Japan as "Active Thermo-Atmosphere" ATA combustion...

The efficiency at low load factor of the detonation engine is more than twice that of the conventional Beau de Rocha (Otto) cycle, and considering that the load factor of a car is in average about 10 to 15%, this is not a small difference... Even if the subject passionates the researchers, the thermic and photonic ignition control in the piston is still an unsolved problem, and possibly a dead-end ... that the Quasiturbine does overcome!

In combustion mode, the Quasiturbine QT-AC (With carriages)
is suitable for detonation mode,
where high surface-to-volume ratio is a factor attenuating the violence of detonation.

A White Paper

Quantum Parallel: The Saint-Hilaire "Quasiturbine"
As The Basis For A Simultaneous Paradigm Shift in Vehicle Propulsion Systems

Amidst myriad, and many times unsupportable, claims of technological breakthroughs capable -- fuel cells being at the top of this contention -- of inducing vehicular design and engineering paradigm shifts, we have concluded that the Saint-Hilaire "Quasiturbine" may very well provide impetus to retire the piston engine.  It has served humanity for nearly two centuries, and has earned its rest. eMOTION! REPORTS.com is providing a comprehensive white paper that will perhaps allow you to reach the same conclusion...

Historical Photos - Quasiturbine AC

Quasiturbine QT50AC - Basic drawings and photos of prototype.

Quasiturbine QT50AC : Calculated torque, power and consumption.

More Technical

Why is Quasiturbine exceptional?
Encyclopedic summary
Quasiturbine differences with the Wankel
Quasiturbine differences with the piston engine