The piston engine has been primordial to the planet recent
Why was it so difficult to replace it by a better concept?
Could it be because scientists are more interested by atoms and cosmos?
Theory - Quasiturbine versus Piston
What are the Conventional Engine Deficiencies? The piston being the most
common engine reference, the Quasiturbine researcher team has initially
established a list of 30 conceptual piston deficiencies
open for improvement (see below). The
Quasiturbine innovative concept is the result of an effort to improve the piston
engine, and indirectly other engines as well, not excluding the Wankel. To
achieve major engine improvements, the Quasiturbine concept suppresses the use
of the limiting sinusoidal crankshaft and offers up to 7 degrees of
freedom at design.
Engine comparison can be made on different basis, as good one another.
It is generally of public evidence that engine power goes up with displacement,
but because of historical definition, this is not quite true, and led to
substantial confusion in the world of engines.
For all piston engines, the displacement is the total of the maximum cylinder volume,
but for example, the 4-stroke piston 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 basics
where the power of a theoretically good engine
(which piston and Quasiturbine are, but not the Wankel because
of the PV diagram),
is proportional to its fuel-mixture intake capability per revolution, and not
As an example, the Quasiturbine may compare 1 to 1 by chamber displacement, but
1 to 8 by total intake fuel-mixture volume and power, because the chambers are used 8
times more often by revolution.
Engine displacement versus the Total engine volume
4 strokes engine type
15 to 25
10 to 15
1.5 to 5
The Quasiturbine is a positive
with a total displacement almost equal to the engine volume
(Imagine one day, a 3 liters car engine into a
3 liters volume!)
Piston engine deserves respect and should not be arbitrary and globally
condemns. However it has deficiencies that no one seems to be willing to list ? Here is
our list of the main conceptual
piston engine deficiencies :
- A one-chamber-does-all-strokes is not good (opposed to split cycle) - Hot process (combustion) destroys
efficiency of cold process (intake), an cold process (intake) destroys efficiency of hot
process (combustion). Rotary engines have cold area in distinct location of the hot
area leading to improve thermodynamic efficiency.
- 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 moderate 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. Complete reversal of the flows from intake to exhaust.
- While the piston descents, the ignition thermal wave front has hard time
trying to catch the gas moving in that same direction.
- The valves open 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
- 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 prevents 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 intakes mixture right after the
top dead center.
- The piston does not stand fuel pre-vaporization, but requires fuel
pulverization detrimental to combustion quality and environment.
- The instantaneous torque impulse is progressive, and would gain to have a
- The components use factor is low, and those components 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
- The connecting rod gives an oblique push component to the piston, which then
requires a lubrication of the piston wall.
- The lubricant is also heat coolant, which requires a cumbersome pan, and imposes
low engine angle orientations.
- The need of complex set of valves, of camshaft and of interactive synchronization
- The valves inertia being a serious limitation to the engine revolution.
- The seal wears most at rest near TDC and BDC, when they stop surfing
(rotary seals never rest).
- The heavy piston engines require some residual compressed gas before top dead
center to cushion the piston return.
- The piston tumble and swirl flows effects are largely compensated
by gas rolling effects in-between the rotary 2 near surfaces in
- Limited combustion flame front velocity soon limits the piston rpm
when scaling up to large displacement, while the Quasiturbine splits
each piston chamber in 8 smaller chambers allowing shorter cycle
duration corresponding to higher rpm for large engine.
- The internal engine accessories (like the camshaft) use a substantial power.
- The poor homo-kinetic geometry imposes violent accelerations et stops to the piston.
- 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).
- Multi-piston crankshaft twists under load while the cam do not,
failing to keep optimum operation timing on forward pistons.
- Too slow chamber movement near top dead center to support
- Square piston (stroke equal to diameter) as the Wankel
produce near TDC in the combustion chamber a modest converging
draft toward the cup, while the QT converging draft is much more important,
and favor better ignition.
QT Uniflow Characteristic - In piston, the flow reverses
its direction at each stroke (counter-flow) to exhaust which cools the head and
extra energy is needed to restore the temperature (piston uniflow provides an
exhaust port at the end of the stroke, but has the inconvenience of
recompressing residual gas, meaning reversibility losses, and the pressure increases makes a substantial restriction
to the initial flow into the chamber, not to ignore the truncated cycle
near bottom dead center). Quasiturbine is a uniflow engine, with none of these
Without being pretentious, the fact is that the Quasiturbine corrects or
improves each of these deficiencies.
Side by Side
Like the piston engine, the Quasiturbine is a volume
modulator of high intensity, and acts as a positive displacement engine. Here is a diagram showing the Piston and the Quasiturbine side by side.
Click here for a 2000 pixels high resolution
Quasiturbine may compare 1 to 1 by displacement,
but 1 to 8 by total intake fuel-mixture volume and power,
because the chambers are used 8 times more often by revolution.
Better torque continuity and acceleration (exceeds even the 2-stroke
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).
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
Continuous combustion with lower temperature: As
the Quasiturbine strokes 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
(Model AC) is more
effective, and prevents hot point. From the thermal point of view, the
Quasiturbine does not contain any internal parts requiring coolant fluid (like
Better overlaps: 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
Quasiturbine Rotor Dynamic
The eccentric crankshaft machines reach their maximum
and minimum mechanical extension in synchronization with the pressure
strokes, while in the Quasiturbine, the rotor reaches it maximum and
minimum extension at half-stroke, producing a smooth kinetic transition
near Top and Bottom pressure Dead Center. Le piston atteint ses positions
extrêmes en coïncidence avec le début et la fin des cycles de pression, et
comme lui, le vilebrequin du Wankel impose aussi cette synchronisation,
qui favorise un cognement du rotor sur le stator près des points haut et
bas. Dans la Quasiturbine, les positions extrêmes du rotor correspondent à
l’élongation en losange, alors que les cycles de pressions débutent et
terminent en configuration carrée, ce qui crée une situation
particulièrement heureuse pour la continuité du mouvement de rotation et
le balancement des efforts internes sur le rotor lors du passage (sans
cognement) en configuration carrée, ce qui accentue la compatibilité avec
Une fois la déformation du rotor lancée depuis une élongation losange sur
un axe vers une élongation sur un autre axe, le système des 4 pales
présente une inertie qui assure la continuité (sans cognement) de la
déformation lors du passage à la configuration carrée, là où sont les
principales et violentes perturbations de pression. Notons que cette
inertie de la déformation est freinée par l’action des joints de contour
sur les parois internes du stator dans la région éloignée du centre, mais
que l’effet de rappelle dynamique dû à la pression interne dans les
chambres vient aider ce freinage, voir même le dominer à certain régime.
Here is a table comparing engines (order of magnitude only) on the basis of same combustion chamber
volume and same rpm.
Quasiturbine model of series AC (with carriages)
Same chamber displacement, same rpm.
High power density engine: The Wankel is already known as a
high power density engine. At comparable power, the Quasiturbine presents an additional
reduction of volume. 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.
Same dynamic power range than piston engines: Just a
word 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).
Same range of nominal power: Like the piston 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 piston engines or Wankel. On the
other hand, 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
More effective conversion into mechanical energy: Engines that use crankshaft generate sinusoidal volume impulses during which
the piston stays a relatively long time at the top while it decelerates and reverses
direction, and stays 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 engine accessories to operate (no
valve, rocker, push rod, cam, oil pump...).
In addition, the piston engine suffers
from the symmetry of the back and forth piston movement. Ideally, the piston should have
a longer displacement for the expansion (extracting the 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 is 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 contribute. An
other fundamental improvement over the piston is the intake and expansion
characteristics. Contrary to the piston which must release 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.
Engine Exhaust Heat Recovery:
By placing a hot Quasiturbine into or around an engine exhaust pipe, and
injecting pressurized hot water (steam keep in the liquid state for better heat
transfer), some heat can be recovered into mechanical energy. Stirling and short
steam circuit Quasiturbine could do similarly!
Less pollution and more fuel options: In all engines, 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. Additionally, using high
technology material (ceramic) for the seals would allow the Quasiturbine to run
with no need of lubrication, nor maintenance. Piston mass injection (droplet density and inertia are greater that vapor 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
permits optimum mass injection. Furthermore, being able to produce early torque pass the top dead center,
the Quasiturbine does support the fully vaporized gasoline in Beau de Rocha (Otto) cycle, for
better combustion quality and environment.
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 mid
Zero Vibration: The foundation of the Dr. Raynaud
syndrome in Chicago is dedicated to the preoccupant problem of vibration. 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 vibration. The Quasiturbine is a perfectly balanced engine which turns
without vibration, and generates less noise. This is the motive for our priority project of a
therapeutic chainsaw with zero vibration to fully emphasize the characteristics of
Free Green House Gas Internal Combustion Engine: Hydrocarbons contain
only Carbon and Hydrogen which are separated by heat, and recombine with air's
oxygen to make water and CO2. People are complaining of bad combustion when
engine is making black carbon particles though the exhaust, but this may be good
new for GHG? In fact, a way to have a GHG pollution free combustion engine (with
somewhat less total power) is to burn only the hydrogen from the hydrocarbon
fuel, and recover the <burnt> Carbon (...not dropping it in fine particles in
the environment). This is in some way what fuelcell (reformer) are attempting to
do, by <burning> only the hydrogen. Modern diesel engine captures carbon
particle in after treatment filers - where burning it does not bring any energy,
worse is producing pure CO2! So, not burning the carbon from the hydrocarbon
fuel would be a way equivalent or better than the CO2 sequestration. The carbon
in the fossil fuel would then only play the role of a hydrogen storage chemical
bound, a simple way to go around hydrogen storage.
Multi-fuel and Multi-mode
The Quasiturbine can be fed (if adapted) by a whole fuel range going from
methanol to Diesel oils, including the kerosene, natural gas and possibly
hydrogen. The Quasiturbine shows characteristics superior than the 2-stroke
engine, with a quality of the exhausts better than the 4-stroke engine.
Not sensitive to detonation: 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 detonation. The
Quasiturbine reacts better to detonation thanks to an earlier expansion process
(which means the end of additives to increase the octane rate of gasoline). Moreover,
since the detonation occurs at the time of the robust square configuration of the
blades, and because there is no load transfer on a central shaft, the Quasiturbine is
a candidate for the detonation driving mode.
Compatible with hydrogen: The high inflammability of
hydrogen imposes on hydrogen engines (over 15% hydrogen) a stratified
admission chamber distinct from the combustion chamber (which disqualifies
somewhat the piston
engines). The Wankel engine success for direct hydrogen combustion comes from 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 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.
Robust and reliable construction: The Quasiturbine
does not present the critical sealing problem of the Wankel where the 3 seals at
the top of a triangle (Apex) meet the housing profile with a variable angle
around the perpendicular (-60 degrees with +60 degrees). As the seals of the
Quasiturbine are assembled on a swivel carrier, they are perfectly normal
(perpendiculars) to the perimeter profile at all time. The rotary engines are
generally acting between a robust external housing and a central shaft assembly 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 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-stroke piston engine does 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.
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 has the
advantage of lowering the center of gravity). The use of high technology (ceramic) seals
makes it possible to conceive a Quasiturbine without any lubrication, and without
Electric integration: The Quasiturbine allows for
the first time a real monolithic integration of the electric generator with fuel engines
(highly in demand for the hybrid applications, and without vibration). 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.
Differences in Short
Hard to summarize, but 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
During 2 rotations, the 4-stroke piston completes 4-stroke while the Quasiturbine completes 32!
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.
Intake and exhaust ports being at opposite of the chamber, overlapping intake is
more efficient in the Quasiturbine. Continuous intake and exit flows make better use of intake and exhaust
manifold, and allow to reduce the weight and the volume of the engine by a
of Comparison: Diesel Piston versus Quasiturbine
Quasiturbine difference with the
Quasiturbine for vehicles
Why is the Quasiturbine