Why is the Quasiturbine superior to the piston engines ?
Readers unfamiliar with rotary engines are invited to read also the section :
Why is the Quasiturbine so exceptional ?
Why is the Quasiturbine not a Wankel's type engine ?
The combustion chamber is a parasite volume which has to be pressurized in pure lost
before being able to push efficiently on the piston and make work.
Piston engines work find in to interesting limit cases:
1) Gas - Desirable uniform combustion with undesirable large combustion chamber.
2) Diesel - Undesirable non-uniform combustion with desirable small combustion chamber.
For over 50 years, researchers have been dreaming about the perfect engine,
having uniform combustion, with a small combustion chamber (high compression ratio).
This is what the Quasiturbine does by producing much shorter pressure pulses,
and furthermore accepting photo-detonation, because compression and relaxation slopes are very nearby in time.
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.
During 2 rotations, the 4 strokes piston completes 4 strokes while the Quasiturbine completes 32 !
Continuous intake and exit flow make better use of intake and exhaust manifold,
and allow to reduce the weight and the volume of the engine by a factor 4.
A faster 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 efficiency over the piston engine.
The equivalent of the overlapping of the intake and exhaust valves in the piston
can be adjusted by a variable vane between the two ends of the admission angular range of the Quasiturbine.
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Here is a list of the main conceptual deficiencies which limit the piston engine :
- The 4 engine strokes should not be of equal duration.
- The piston makes positive torque only 17% of the time and drag 83% of the time.
- At mi-stroke, the gas would push more efficiently on a moderated speed piston,
while it is in fact at its maximum speed escaping in front of the gas.
- The gas flow is not unidirectional, but changes direction with the piston direction.
- While the piston descent, the ignition thermal wave front has hard time trying to catch the gas moving it that same direction.
- The valves opens only 20% of the time, interrupting the flows at intake and at exhaust 80% of the time.
- The duration of the piston rest time at top and bottom are without necessity too long.
- Long top dead center confinement time increase the heat transfer to the engine block reducing engine efficiency.
- The non-ability of the piston to produce mechanical energy immediately after the top dead center.
- The proximity of the intake valve and the exhaust valve prevent a good mixture filling of the chamber.
and the open overlap lets go some un-burnt mixture into the exhaust.
- The non-ability of the piston to efficiently intake mixture right after the top dead center.
- The piston does not stand fuel pre-vaporization, but required fuel pulverization detrimental to combustion quality and environment.
- The instantaneous torque impulse is progressive, and would gain to have a plateau.
- The component use factor is low, and those component would gain to be multifunctional.
- The average torque is only 15% of the peak torque, which imposes a construction robustness for the peak 7 times the average.
- The flywheel is a serious handicap to accelerations and to the total engine weight.
- The connecting rod gives an oblique push component to the piston, which then required a lubrication of the piston wall.
- The lubricant is also heat coolant, which require a cumbersome pan, and imposes low engine angle orientations.
- The need of complex set of valves, of came shaft and of interactive synchronization devices.
- The valves inertia being a serious limitation to the engine revolution.
- The heavy piston engines require some residual compressed gas before top dead center to cushion the piston return.
- The internal engine accessories (like the came shaft) use a substantial power.
- The poor homokinetic geometry imposes violent accelerations et stops to the piston.
- Complete gas flow reversal from intake to exhaust.
- Quite important noise level and vibration.
- At low load factor, the intake depressurization of the Otto cycle dissipates power from the engine
(vacuum pump against the atmospheric pressure).
Engine displacement: Definition and clarification
It is generally of public evidence that engine power goes up with displacement,
but because historical definition, this is not quite true, and led to substantial confusion in the world of engine.
For all piston engines, the displacement is the maximum cylinder volume,
but the 4 strokes piston for example, does intake this volume of fuel mixture only once every 2 revolutions.
In order to compare different types of engine, one has to get back to basic where the power of a theoretically good engine
(which piston and Quasiturbine are, but not the Wankel because PV diagram),
is proportional to its fuel-mixture intake capability per revolution, and not its displacement.
Lets see what happen when comparing a 50cc four strokes piston engine with a QT50cc Quasiturbine at the same RPM ?
Both engines have 50 cc maximum chamber volume (displacement). The 4 strokes piston will intake 50cc every 2 revolutions,
while the Quasiturbine intakes 8 chambers x 50cc = 400cc in two revolutions !
The Quasiturbine will intake 8 times more chambers and fuel-mixture, and produce something like 10 times more power !
(Notice that the Wakel intakes only 1 chamber of fuel-mixture per shaft revolution, but 3 per rotor revolution).
Obviously, the power is not proportional to displacement here,
where engines compare on 1 to 1 by displacement, but 1 to 8 by intake fuel-mixture volume and power.
Consequently, to produced the equivalent power of a 4-strokes piston engine,
the Quasiturbine displacement would have to be only 1/8 of it !
Furthermore, on the long run the Quasiturbine maximum RPM will probably exceed
by a factor of 2 to 5 the maximum piston RPM, because there is no valve and no crankshaft.
Since the power goes up quasi-linearly with RPM, superiority will become even more drastic !
All this suggest that car manufacturers should start printing on the car trunk the intake volume per revolution,
instead of the displacement.
Consequently, for the same power and RPM, the Quasiturbine is about 4 times less cumbersome
and 5 times lighter than a piston engine,
and produced at least 20 % more power (excluding the photo-detonation mode which would produce even more power),
at a much higher torque, which is what every experts are looking for...
It will also be 20 time less noisy, which may not be what teenagers are looking for...
Quasiturbine model of series AC (with carriages)
1 - Comparison with the Wankel Engine - See http://quasiturbine.promci.qc.ca/QTpasWankel.html
2 - More effective conversion into mechanical energy: Engines that use crankshaft generate sinusoidal volume impulses during which the piston stay a relatively long time at the top while it decelerates and reverses direction, and stay briefly at mid-course, which is contrary to the logic of a better engine (Compression impulses should be as short as possible, and the stay at mid-courses the longest possible for a better mechanical energy extraction). On the other hand, the Quasiturbine is more effective because it has less accessories engine to operate (no valves, rockers, push rods, cam, oil pump...). In addition, the piston engines suffers from the symmetry of the back and forth piston movement. Ideally, the piston should have a longer displacement for the expansion (extracting most possible mechanical energy), and smaller for the admission, without reduction of volume. The Quasiturbine has this asymmetry by compressing the mixture in a smaller angular zone, and by using a greater angular displacement for the expansion. The admission stroke of the piston presents also a major defect in the sense that it is taking-in little volume initially and most at mid course, which does not leave much time to the mixture to enter the cylinders (The role of turbo are essentially to correct this default); for its part the Quasiturbine admits a significant volume initially and leaves much more time to flow for a better effective filling which can even be extended in the next cycle without flow back (In this case, the turbo would be a real improvement, and not a default correction). At the time of the expansion, this same defect of the piston stroke does prevent the piston to extract mechanical energy at the beginning of the stroke, which the Quasiturbine manages to do. Also, with the Quasiturbine the gearbox can often be removed with an increase in efficiency, to which the reduction of weight can also contributed. An other fundamental improvement over the piston is the intake and expansion characteristics. Contrary to the piston which must releases its residual pressure at the end of the expansion to avoid counter push, the Quasiturbine asymmetry defines a post-expansion confinement zone in which the residual pressure can be maintained without slowing down the rotation, and during which gas treatment can be done, and the residual energy can be extracted, either through a turbine or in building up a compress gas reserve. If the confinement zone is grouped with the exhaust, we then have an exhaust evacuation which must less counter-push than the piston, which improves still further the comparative efficiency of the Quasiturbine (less energy is required to expel the exhaust gases).
The sinusoidal volume variations of the piston make a bad intake pump when just passed the TDC, whereas the early relaxation of the QT aspires much earlier, and much more strongly. Added with the transients of flow in piston, the effects is more that cumulative, since the early establishment of the flow amplifies more than linearly the flows intaken at every subsequent moment. Taking also into account the effect of the continuous flow at intake, there is improvement from 2 to 3 times compare to the piston when at high RPM. This is why the inventors of Quasiturbine affirm ...that the turbo do nothing but to correct bad intake piston characteristics! Of course, turbo on a QT will produce a much more significant effect than with a piston. With relaxation, mechanical conversion is earlier and later with Quasiturbine, specially with model AC (with carriages). Spreading out better the push of gases! This intake improvement is particularly crucial for the planes in altitude, where the atmospheric pressure is reduced and moderates the ingestion of mixture.
Quasiturbine model of series AC (with carriages)
3 - Better torque continuity and acceleration (exceeds even the 2 strokes engines): The crankshaft and the flywheel are the main obstacle to engine acceleration, and since the flywheel are unable to store energy at low rpm, the engine torque at idle is highly handicapped by the engine dead times. The piston of a 4 stroke engine works in power mode about 120 degrees / 720 degrees (2 turns), and thus constitutes a drag 80% of time, period during which the flywheel assumes a relative torque continuity. The Quasiturbine has jointed torque impulses, and presents a profile of almost flat torque characteristics, without the assistance of a flywheel (Quasiturbine torque continuity would compare to a 16 or more pistons conventional engine). Besides this profiles reflects the property of continuous combustion of the Quasiturbine (need for lighting only to starting). This torque continuity, added to the fact that the Quasiturbine does not require any flywheel, allows spectacular accelerations, largely higher than the 2-stroke engine even.
4 - Continuous combustion with lower temperature: Due to an earlier expansion than in the piston engines, initial energy is immediately transformed into mechanical energy, without awaiting the middle of the stroke as in the piston engines. This initial expansion cools immediately the combustion gas which have then less time to transfer their heat to the engine block (with a limitation effect on the NOx). As the Quasiturbine stroke are jointed (what is not the case with the Wankel), the lighting is necessary only in launching, since the flame transfers itself from one chamber to the following. The thermalisation of the Quasiturbine by contacts with rollers is more effective, and prevents any hot point. From the thermal point of view, the Quasiturbine does not contain any internal parts requiring coolant fluid (like oil). The intake and exhaust ports being at different ends of the combustion chamber, it is possible to do a better filling of the chamber by having a simultaneous open overlapping of the two ports, without risking that a portion of the intake gas goes into the exhaust, as it is the case with the piston engine.
5 - Less pollution and fuels options: The Quasiturbine can be fed (if adapted) by a whole fuel range going from methanol to the Diesel oils, including the kerosene, natural gas and possibly hydrogen. The Quasiturbine shows characteristics superior than the engine 2 times, with a quality of the exhausts better than the 4 stroke engine. In all engine, the NOx results from three factors: high pressures, high temperatures, and prolonged times of confinement. As the Quasiturbine expansion starts quicker than in the other engines, the initial temperatures and pressures are less, as well as the time of confinement in the extreme conditions. It thus results less time for the NOx formation, and less transfer of heat to the engine block (for a better effectiveness). Additionally, using high technology material (ceramic) for the seals would allows the Quasiturbine to run with no need of lubrication, nor maintenance. Furthermore, the assumption that fully pre-vaporized gasoline is desirable is not true for piston (the optimum liquid-vapour ratio is around 65%) owing to considerations of the fact that piston produces torque mainly at mid stroke and it is consequently wise do spread the combustion in time such that the pressure peak occurs near maximum piston torque capability, and having intaked gasoline droplets help spread the combustion time. Piston mass injection (droplet density and inertia are greater that vapour and affected by valve flow perturbation) and exhaust valve cooling (rapid combustion is hotter) are two other vaporization piston limitations. However, fully pre-vaporized gasoline does improve combustion quality and is desirable from the environment point of view even if the piston engines do not stand it well... (conventional gas turbines prefer gaseous state or very rapid liquid fuel vaporization). The Quasiturbine engine has no valve, and continuous intake flow permit optimum mass injection. Furthermore, being able to produce early torque pass the top dead center, the Quasiturbine does favour the fully vaporized gasoline in Otto cycle, for better combustion quality and environment.
6 - Less noisy: For comparable power, the Quasiturbine is much quieter than the piston engine, since it splits each expansion in 4 per turn (or 8 by 2 turns for the 4 stroke engines), and evacuates the gases more gradually and on a greater angular displacement (in opposition to the piston which evacuates gases especially at med course).
7 - Low revolution - Reduction of gearbox ratio: The gear boxes are evils necessary (expensive, complicated, delicate, and energy consuming). The RPM required by the human activity are generally lower that the performance optimum speed of the engines (e.g.: an automobile wheel generally does not rotate to more than 800 or 1000 RPM, which is 4 to 5 times less than the engine RPM). As the Quasiturbine turns 4 to 5 times less quickly than the other engines (including the Wankel), the gear boxes can often be removed (amongst other things in the field of transport) with an increase in efficiency.
8 - Zero Vibration: The foundation of the Dr. Raynaud syndrome in Chicago is dedicated to the preoccupant problem of vibrations. The vibrating portable tools (of which the chainsaws) gave name to the " disease of the logger " which goes
from insensitivity of the hands and the arms, until the back bone pain, and capillary vessels and blood bursting. The professional truck drivers generally suffer from the syndromes of vibrations. The Quasiturbine is a perfectly balanced engine which turns without vibration, and generates less noise. This the motive for our priority project of a therapeutic chainsaw with zero vibration to fully emphasize the characteristics of Quasiturbine.
9 - High density engine: The Wankel is already known as a high density engine. At comparable power, the Quasiturbine presents an additional reduction of volume of about 30%, and more in relation to weight (also withdrawing the gears). Integrated into a use, the density factor is even more impressive (no flywheel, less gear box ratio, optional central shaft...). Because of its quasi-constant torque, the use factor of the intake and exhaust pipes is 100% (still better than the Wankel), implying tubes of smaller dimension, etc.
10 - Not sensitive to the detonation: The the piston stroke does not allow a rapid increase in the volume of the expansion chamber in the vicinity of the T.D.C., and consequently badly supports the photo-detonation. The Quasiturbine reacts better to the photo-detonation thanks to an earlier expansion process (which means the end of additives to increase the rate of octane of gazoline). Moreover, the fact that the blow occurs at the time of the robust square configuration of the blades, and that there is no load transfer on a central shaft, the Quasiturbine is candidate with the photo-detonation driving mode. Instabilities in the combustion of hydrogen should not affect the Quasiturbine appreciably neither.
11 - Robust and reliable construction: The Quasiturbine does not present the critical sealing problem of the Wankel. The Wankel must make use of 3 joints at the tops of a triangle (Apex), which meet the driving profile with a variable angle around the normal (-60 degrees with +60 degrees). As the joints of the Quasiturbine are assembled on a swivel carrier, they are perfectly normal (perpendiculars) to the perimeter profile in all time. The rotary engines are generally active between a robust external profile and a central shaft assembled mounted on good bearings, able to take the load on the shaft created by the pressure during combustion. For its part, the Quasiturbine requires only one robust external profile, on which is also applied the load created by the pressure during combustion; the central shaft is optional and is only needed to the transfer the torque when necessary. Moreover, contrary to the Wankel, the Quasiturbine does not require any synchronization gears (fragile, complicated, expensive to build, and prone to lubrication and wear!), nor a lighting synchronization system (particularly if one makes use of the continuous combustion option). In addition, the average torque of a 4 strokes piston engine do not exceed 15% of the maximum instantaneous torque (which dictates the required engine strength), while for the Quasiturbine the average torque is equal at 90% of the maximum torque, thus illustrating the substantial internal stress reduction and the unique homo-kinetic quality of the Quasiturbine.
12 - Submersible, because no crankcase or lubricant coolant: Lighting (piezo electric) is necessary only in launching, since the transfer of flame is done from one chamber to the following. Consequently, the Quasiturbine engine can be immersed without fearing an electric lighting breakdown, nor a water infiltration in the crankcase (the Quasiturbine does not have one). The Quasiturbine is thus an ideal engine for use in hostile environment (for example, in boat propulsion, the blades of the propeller could be directly welded to the rotor, and the whole engine immersed, which also as the advantage of lowering the centre of gravity). The use of high technology (ceramic) seals makes it possible to conceive a Quasiturbine without any lubrication, and without maintenance.
13 - Electric integration: The Quasiturbine allows for the first time a real monolithic integration of the electric generator with fuel engines (very in demand for the hybrid applications, and without vibrations). Since the center of the Quasiturbine is free, the motionless electrical components can be located on the central core and the peripheral stator. Only the intermediate area is in rotation. Reciprocally, if the electrical components are part of a motor, the Quasiturbine becomes an integrated electric motor-driven pump, or a Bi-energy power group.
14 - Compatible with hydrogen: The high inflammability of hydrogen imposes on " hydrogen " engine (over 15% hydrogen) a stratified admission chamber distinct from the combustion chamber (which disqualifies the piston engines). The Wankel engine succes for direct hydrogen combustion comes for its intake and combustion stratification, which results mainly from early intake (like Quasiturbine) and its excessive volume during expansion (with an efficiency lost). The Quasiturbine engine offers the same hydrogen advantage without the lost of efficiency. The Quasiturbine meets the fundamental criteria's imposed by the "hydrogen" engine of the future (cold intake area, stratified intake, reduced confinement time, low sensitivity to detonation, less polluant, robust and energy efficiency), and even surpasses the Wankel in this respect, since the intakes are separated by 3 strokes instead of two. Frequent instabilities in the combustion of hydrogen should not appreciably affect the Quasiturbine as it is not sensitive to detonation.
15 - Same dynamic power range than piston engines: Just a word here, to recall that the conventional gas turbines are conceived for a precise aerodynamic flow, and do not offer a wide power range with reasonable efficiency. For its part, the Quasiturbine does not use aerodynamic flow characteristic on the blades, and keeps its excellent efficiency on a wide power range. It is the same when the Quasiturbine is propelled by steam, compressed air, or by fluid flow (Plastic Quasiturbine for hydro-electric centrals, etc).
16 - Same range of nominal power: As the pistons engines, the Quasiturbines can be made tiny or huge. Due to concept simplicity and the absence of gears, the small units should be still more tiny than pistons engines or Wankel. On the other and, nothing limits the construction of huge Quasiturbines like for ship power, fix power plan stations, or large Quasiturbines for thermal power plan or nuclear, using steam or hydraulic.
17 - Compressor and pump: The Quasiturbine is also efficient in compressor or pump mode. In this case, it has the unique properties of not offering obstruction, neither require any check valve, a delicate and energetic consuming component found in most compressor.
18 - Better continuity of flow: The flows in the chamber of a piston implies a total and complete inversion of the direction between intake and the exhaust, whereas in the rotary engines, a part only of flow is reversed with each one of these 2 stages. The flow within the intake generally implies volumes much lower than within the exhaust. Initially during intake, a part of gas moves in opposit direction of the rotor to fill the back of the chamber, but already at mid stroke the flow is within the rotor direction. Initially with the exhaust, the gas does not leave the chamber because it is pushed by the walls, but rather because it is under strong pressure and spontaneously moves towards the area of low pressure to the opening of the exhaust ports, preferably in front of the chamber, and it is precisely there that the exhaust port is at this moment of the cycle. Later, when the high pressure is dissipated, the residual gas trails in the back chamber precisely where the exhaust port is... a flow conditions thus appreciably better in the engines rotary and never worse than in the piston engines, which reverses the flow of the total mass of incidental gas (the rotary makes only partial inversion). This, added to the absence of valve increases advantageously the operating time ratio of the inlet and of the exhaust manifolds. The hydraulic case is more symmetrical with regard to the intake and the exhaust, and imposes obviously lower speeds than the cases of compressible fluids, but there is still a better flow continuity in the rotary motor and pumps.
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Quasiturbine Agence Inc., Promotional Agent for the Quasiturbine Continuous Combustion Rotary Engine or Compressor
Casier 2804, 3535 Ave Papineau, Montréal Québec H2K 4J9 CANADA (514) 527-8484 Fax (514) 527-9530