The Quasiturbine engine is a type of rotary combustion engine, invented by the Saint-Hilaire family and first patented in 1996. The engine uses a four-sided articulated rotor 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, hot air engine, or pump. It is capable of burning fuel using photo-detonation, an optimal combustion type.
Definition : The Quasiturbine (Qurbine) is a no crankshaft rotary engine having a 4 faces articulated rotor with a free and accessible centre, rotating without vibration nor dead time,
and producing a strong torque at low RPM under a variety of modes and fuels. The Quasiturbine is also an optimization theory for extremely compact and efficient engine concepts.
How it works
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 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.
Advantages
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 valves 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 vibrations. 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.
By opposition to dozens of new engine designs, the most important at this time about the Quasiturbine is not the actual machine, but the fact that it does unknot a new field of development and offers means to achieve what no other engine design has suggested or is able to, and specially for photo-detonation where piston engine has failed for over 40 years...
Disadvantages
The design of the Quasiturbine engine is typically built of aluminum and cast iron which expand and contract by different degrees when exposed to heat leading to some incidence of leakage. A similar problem was encountered in early Wankel engines but engineering development has brought these problems under control for both engines.
History
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. Small pneumatic and steam units are available for research, academic training and industrial demonstration. Similar combustion prototypes are also intended for demonstration. In November 2004, a Quasiturbine engine was demonstrated on a go-kart.
Potential applications
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 or snowmobiles. Variations on the basic Quasiturbine design also have applications as air compressors and as superchargers.
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 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.
Photo-detonation
Photo-detonation is the optimum combustion mode, like a laser volumetric combustion, a mode the sinusoidal piston or Wankel pressure pulse shape cannot withstand. Diesel combustion is driven by thermal ignition; gasoline piston engine is driven by thermal combustion wave; knocking detonation is driven by a supersonic shock wave; while photo-detonation is a volumetric combustion driven by intense radiation in the combustion chamber. 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 that the piston or Wankel volume pulse, and with rapid linear rising and falling ramps. This kind of volume pulse is photo-detonation 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 become less as the power produced by the engine increases. Photo-detonation engines do not need intake vacuum as they intake all the air available, and mainly for this reason, 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; may be more environment friendly as it will require low octane additive-free gasoline or diesel fuel; may be multi-fuel compatible, including direct hydrogen combustion; and may offer reduction in the overall propulsion system weight, size, maintenance and cost. For these reasons it could be better or competitive with hybrid car technology.
Hybrid alternative
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 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.
However, it has not been proven that the Quasiturbine engine would be able to use the hoped for photo-detonation. And although a working prototype has now been constructed, there are no results indicating fuel consumption per unit power. Furthermore, a vehicle powered by a Quasiturbine, photo-detonating engine will not provide one of the most important benefits of hybrid technology, regenerative braking, without additional equipment. Because the engine is still in the prototype phase, it may be decades before it is ready to be a competitive technology for vehicles
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