Quasiturbine - Efficacité
comparative aux autres moteurs
Discussion on the Minimum Gas Flow at
operational RPM, Load factor, Gas Expansion,
Total engine output
and Residual pressure energy lost
All the following is within the Carnot efficiency rule
This discussion is about geometrical or mechanical pressure energy loss in the
flow or exhaust of the four most common engine concepts: Piston, Turbine, Wankel
and Quasiturbine. It is not about thermal energy lost, but one has to know and
remember that the gas are thermodynamically cool down during the expansion
process, so that the exhaust thermal energy is much less than thermal fuel
combustion energy, the difference being hopefully efficiently converted into
mechanical energy?
Notice that some piston steam engine preheat the piston in compression with some
exhaust steam to increase the efficiency,
which is not needed in the Quasiturbine since the exhaust stroke is the steam compression
stroke,
and is in great proximity as the exhaust stroke become without any delay an expansion stroke.
The energy of the compression and
expansion strokes
Some people tend to believe that engine compression stroke
is an engine energy lost,
which it is not, since this stored compression energy
is largely recovered during the following power stroke.
Notice also that if we consider the three equal "early, mid and late"
piston expansion volume zones,
they all produce under constant pressure the same amount of energy,
since the angular shaft displacement is larger in early and late volume
variations.
However, the torque will be highly modulated, being fare superior in the mid
stroke.
Square torque pulse like in the Quasiturbine produces the same energy with a
more constant torque
and require a relatively less robust machine, since robustness is dictated by
the peak torque.
Adiabatic versus isothermal expansion
When a compressible fluid is compressed, its temperature increases, and
conversely when it expands, it cools itself.
Gas cooling during expansion is not a good thing,
because it reduces the pressure in the expansion machines (positive displacement),
and lowers the gas speed in turbines.
To get the most power out of a machine (not necessarily to get more efficiency),
one likes to add heat to the expanding gas,
and if this is not possible in the process, the expansion is split in several
stages (like 2 and 3 stages steam turbine).
One must understand that the extra power obtained this way is not free,
since heat has to be supplied, but it does give a better output per pound of
engine.
What is nice about internal combustion engine,
is their ability to provide the maximum heat by combustion while the expansion
is actually occurring,
something no other gas compressible engine can do easily! (this excludes
hydraulic engine)
Comme la Quasiturbine pneumatique / vapeur comprend deux circuits, ces circuits
peuvent au choix aussi
être alimentés en série en reliant la sortie de la première chambre à l'entrée
de la seconde.
En plaçant un échangeur sur ce conduit on peut ajouter de la chaleur
et faire en sorte que la détente totale dans le moteur se rapproche d'une
détente isothermal.
Remarquer que dans ce cas, les différentiels de pression interne vont s'auto-répartir
entre les 2 chambres successives.
Dans les turbines conventionnelles, on fait souvent une telle chauffe
intermédiaire
afin d'augmenter la puissance totale de la machine, sans nécessairement
accroître le rendement.
Dans le cas de la Quasiturbine, le raccord en série réduit forcément la
puissance spécifique
mais peut accroître le rendement si la chaleur intermédiaire est sans frais,
comme dans le cas de la chaleur atmosphérique en mode pneumatique.
Le recours au mode série peut présenter de l'intérêt dans le cas de forte
pression
où la détente produit un grand refroidissement, mais présente peu d'intérêt
avec la Quasiturbine aux basses pressions, disons inférieur à 50 lb/po2 (psi).
Si le différentiel de pression est considérable,
les volumes et déplacements impliqués dans la détente initiale sont beaucoup
moindre qu'à la détente finale,
de sorte que la machine en phase initiale doit être de plus petite dimension
(disons pour une détente de 600 à 300 psi) que pour la phase finale (de 300 à 0
psi).
Si l'utilisation d'une machine unique requiert une réduction initiale de
pression,
cette perte initiale de pression dans un détendeur n'est pas convertie en
énergie mécanique,
mais en énergie cinétique puis thermique dans la conduite, ce qui atténue
évidemment le refroidissement adiabatique...
Parce que les volumes et déplacements en phase finale sont plus importants,
le même différentiel de pression à ce niveau produit plus d'énergie que
lorsqu'on le traite à une pression plus élevée.
Autrement dit, pour tirer le maximum d'énergie d'une très haute pression,
il faudrait une cascade de machine commençant par les plus petites, chacune
réduisant un peu la pression et alimentant la suivante...
Les machines à vapeur anciennes utilisent jusqu'à 3 machines (ou plus d'étages
dans le cas de turbines),
le Titanic avait des machines à vapeur utilisant 4 étages de détentes...
MDI pour sa part propose une voiture pneumatique à très haute pression utilisant
3 étages à piston.
Rien n'empêche de juxtaposer 3 Quasiturbines de dimensions différentes pour
faire encore mieux !
Dans le cas d'une source de pression qui s'épuise avec le temps comme l'air
comprimé dans des cylindres,
l'inconvénient évident est qu'il faut traîner un ou des étages inutiles lorsque
la pression devient moindre.
Un réservoir haute pression se refroidi progressivement lorsqu'il se déverse
dans un réservoir intermédiaire basse pression,
mais c'est à l'entrée du réservoir basse pression que la détente est violente et
où le refroidissement est le plus considérable.
Cependant, la violente détente amène avec elle de l'énergie cinétique
qui ne se transforme pas alors en travail mécanique, mais en chaleur,
réduisant ainsi l'effet net de refroidissement dans le réservoir basse pression
ou dans la conduite.
Il n'est cependant pas très sage d'utiliser l'énergie de pression du réservoir
haute pression
pour réchauffer partiellement le réservoir intermédiaire basse pression,
d'où l'intérêt d'utiliser des détentes mécaniques multiples avec des
réchauffeurs isobars entre les étages !
L'énergie étant proportionnel à la pression fois le volume, l'énergie est faible
après chaque détente même s'il y a pression,
parce que le volume est contracté et faible, et c'est la chauffe qui redonne du
volume,et donc de l'énergie
Ces détentes multiples sont rentables dans le cas de systèmes de plusieurs
mégawatts
(à pression initiale élevée et soutenue) ayant des facteurs d'utilisation
importants,
mais sont plus difficile à justifier dans le cas de petits véhicules demandant
quelques dizaines de kW seulement,
dont le facteur d'utilisation est d'une demi-heure par jour, et dont la haute
pression des réservoirs n'est pas soutenue !
Tout ceci démontre que plus les pressions sont élevées et que les températures
sont basses,
moins le système de production / récupération est efficace.
REMARQUE SUR L'EFFICACITÉ DES SYSTÈMES
PNEUMATIQUES
Un moteur pneumatique de haute efficacité ne garantie pas que le
système dans son ensemble sera de haute efficacité.
Tous les gaz se réchauffent en se comprimant et se refroidissent lors de la
détente.
L'effet du refroidissement ne doit pas être sous-estimé. Par exemple, une
bombonne type à 200 bar (atm.)
vidée adiabatiquement (sans thermalisation à la température ambiante) donne à la
fin de l'air tellement froid
que son volume est alors le 1/4 de celui de l'air une fois ramené à la
température ambiante (détente isothermale).
Dans ces conditions de température à l'entrée d'un moteur pneumatique, le
rendement est catastrophiquement bas
et le lubrifiant se solidifie, augmentant considérablement la friction interne
du moteur...
Généralement, la réversibilité du cycle compression - détente se détériore avec
l'augmentation de la pression,
d'où l'intérêt d'utiliser pour fin d'efficacité élevée la plus basse pression de
design possible.
La mesure de la température des échappements constitue généralement une bonne
indication de l'efficacité,
puisque le minimum d'énergie perdue dans l'environnement correspond à une
température d'échappement
égale (ni inférieur, ni supérieure) à la température ambiante.
Cette condition peut être atteint par une légère chauffe (solaire) du gaz avant
l'entrée dans le moteur pneumatique.
La Quasiturbine peut faire beaucoup de détente si elle est construite
avec une restriction dominante à l'entrée de la chambre, et non aux
échappements.
Les ouvertures d'échappement doivent alors être plus grands que les ouvertures
d'admission,
de sorte que l'air sort plus facilement qu'il n'entre, et abaisse ainsi de
pression dans le moteur.
Dans ce cas, la Quasiturbine a moins de puissance spécifique, mais parce qu'elle
fait de la détente, elle est plus efficace.
On peut faire plus de détente en réduisant encore l'accès d'admission à la
chambre, et ce sans vanne de synchronisation.
Comme la Quasiturbine tourne à partir de pression aussi basse que 1/10
d'atmosphère (bar) (one psi !),
on comprend pourquoi la Quasiturbine est particulièrement bien adaptée aux
systèmes à la haute efficacité...
Vapeur versus pneumatique - Effet de la
condensation
Le moteur pneumatique n'a pas de changement de phase en cours de détente,
de sorte qu'au moment de l'échappement il doit évacuer un volume important de
gaz,
alors que le changement de phase de la vapeur en condensât en cours de la
détente
réduit considérablement le volume à évacuer (tout comme le refroidissement
adiabatique dans les moteurs à combustions)
et aide à l'accroissement de la
performance moteur.
Pour bénéficier pleinement de cette effet,
il est avantageux de procéder à une coupure ou à
un étranglement de l'alimentation vapeur à mi-course
pour s'assurer une véritable détente et condensation dans la chambre avant
l'ouverture à l'échappement.
Zero Load factor high-revolution
efficiency - Minimum Gas Flow at operational RPM
Some people tend to believe that a free running engine (from which we do not
take power) require a very small fuel consumption used only to compensate for
friction or internal energy dissipation. Let first explain why this is not true,
and why a Minimum Gas Flow (or
consumption) at operational RPM is needed and vary from one an engine concept to
an other.
Rotating any of the four engine concepts with an external power source will
generate a gas flow (not obstructed) at engine intake and exhaust, confirming
that engines are in fact pumping devices operated in reverse mode. This flow
will increase with the RPM and will also depend of the engine concept. Assuming
four engines concepts of equivalent power but having different operational RPM,
one will notice that the highest flow will be produced by the conventional
turbine, because its is aerodynamically working at very high RPM. Next down will
be the Wankel, then the piston and the Quasiturbine on the same level (At the
same RPM, the Quasiturbine will pump 4 times more than the piston, but since its
operational RPM is four time less, they compare exactly). If we want to self-run
those 4 engines concepts at operational RPM, the reversibility principle will
required that we provide an equivalent reverse Minimum Gas Flow at operational
RPM in order to maintain the "free running"
(without taking out any engine power - zero
Load factor). Making this Minimum
Gas Flow at operational RPM from
pneumatic, steam or internal combustion is
energy consuming, and seriously limit the low-power (zero
Load factor) high-revolution engine
efficiency, because this minimum flow energy is in pure waste. The conventional
turbine is the engine which requires the highest gas flux (and consequently the highest
consumption) just to maintain its free operational RPM (without producing any
net energy), explaining why they are so fuel inefficient when not producing
their full power. It must be understood
that in order to actually deliver power, the flow must be increased from this Minimum
Gas Flow at operational RPM. Mechanically, the Quasiturbine flow case is the
easiest to understand, because it is obvious that to maintain the revolution,
the Minimum Gas Flow at operational RPM must have the same velocity as the
tangential blades turning around the Saint-Hilaire confinement profile. This
discussion explains why for efficiency reason, an engine should never be
selected more powerful than required. Idling (zero Load factor) a powerful
engine always consumes more than idling a less powerful one. It does also
explain why it is advantageous at low power to cancel down combustion on some of
the pistons in order to increase efficiency.
Photo-détonation et Diesel versus cycle
Otto
À faible facteur de charge, la dépressurisation à l'admission du cycle Otto
dissipe de la puissance moteur puisque le papillon est presque fermé et que le
piston descendant agit en pompe à vide colmatée contre la pression atmosphérique,
vide qui est subséquemment partiellement détruit par la
vaporisation du carburant durant la compression. En raison de cet effet,
le moteur en cycle Otto résiste à toute augmentation RPM de vitesse (bien
connu comme frein moteur en compression) et cette résistance intrinsèque à
l'augmentation de vitesse est combattue par une consommation constante et
importante de carburant. Le mode photo-détonation n'utilise pas de papillon et
accepte sans contrainte toute l'air disponible à pression atmosphérique (comme
le Diesel d'ailleurs, où l'énergie de pressurisation est alors restituée à
la détente). Pour cette raison, le rendement à faible facteur de charge du
moteur à photo-détonation est le double de celui du cycle Otto conventionnel,
et considérant que le facteur de charge d'une auto se situe en moyenne autour
de 10 à 15%, cela n'est pas peu dire (économie encore plus grande dans les
embouteillages...). Voir: http://www.vok.lth.se/CE/research/HCCI/i_HCCI_uk.html
Compression ratio and parasite volume -
Effects on engine efficiency
Pneumatic and steam engines get their
pressure from an external source,
and it is obvious that any residual chamber (charging volume) within the TDC top
dead center position
will have to be pressurized in pure lost before the pressure can make work on
the piston itself.
For efficiency reason, one like those engines to have a very high geometric
compression ratio 100:1 or higher.
Even if less obvious, the situation is alike with the IC internal combustion
engine,
because from the pressure point of view, the TDC combustion chamber is a
parasite volume,
which has to be pressurized in pure lost before producing any work on the piston
itself.
To be more efficient, the combustion chamber must be the smallest possible,
which means the highest possible compression ratio.
To a certain extend, the Diesel engine does that, but looses the advantage of
the uniform combustion.
However, there are other obstacles to increase the compression ratio.
In relation to mechanical limitation, the stress is proportional to the product
( Pressure X Time ),
such that if the compression pulse can be made shorter,
much higher compression ratio can be achieved without increasing the stress and
fatigue on the engine.
This is exactly what the Quasiturbine does by having a pressure pulse at the tip
which is 15 to 30 times shorter!
In relation to self-firing or photo-detonation, piston can not permit higher
compression ratio
because such a timing is not controllable, and can not be postponed until the
piston fall down.
The Quasiturbine fast raising and falling pressure pulse guaranty that the
photo-detonation occurs at the right time.
In relation to fuel pollutant generation, piston does confined the gas for too
long, and allows the chemistry of NOx to be completed.
The Quasiturbine short confinement time does not allow NOx to be
generated.
The short Quasiturbine pressure pulse reduces the
confinement time, but also the gas thermal exchange with the engine block,
and consequently leaves more heat into the expanding gas, which increasing the
thermodynamic efficiency.
The Quasiturbine IC end result goes toward an
engine in photo-detonation mode,
having a compression ratio of 30:1 or higher, using low octane gas, producing no
NOx,
benefiting from fast radiation photo-detonation combustion process
(Knocking - Leaving extra combustion time to eliminate all un-burnt hydrocarbon),
with the advantage of uniform combustion
without any synchronized intake or firing sparkplug,
being more efficient,
and furthermore multi-fuel capable, more compact,
lighter, high torque at low RPM, 20 times less noisy, zero
vibration...
Pushing gas versus expanding gas
Conventional
turbines and all positive expansion machines (including the Wankel) do have a
similar exhaust residual mechanical energy lost dilemma particularly sensitive
in fluid flow engine mode when using an "external compressed fluid (air,
steam...) reservoir", a dilemma which does not exist with incompressible
(hydraulic) fluids flow. It does take energy to compress gas, but positive
expansion machines do take only energy from the pressure action, careless how
much energy is actually stored internally in the pressurized pushing gas in the expansion
chamber, which is later exhausted. Let explain differently : If a piston is
released after it has compressed air, compression work is very efficiently given
back in energy, and the final differential expansion pressure is zero like at
the starting point (which is not the case when using external gas pressure
reservoir). This means that using gas (steam) from a compressed reservoir,
optimum expansion efficiency required to inject only a certain quantity of
loading pressured air (steam) at Top Dead Center, such that the final exhaust
expansion pressure differential will be small (which do not means a null exhaust
flow). Doing so, the gas in the expansion chamber will push with a reduced
average pressure, and the total engine output will not be the highest (since
pressure decreases as 1/x, the average pressure will be much less than half of
the maximum). Similarly, conventional turbine convert tank pressure and
expansion energy all at once, and trying to take out too much power from a
conventional turbine will lead to blades stall and very inefficient regime. By
maintaining the high pressure injection for a long time period (the expansion is
then replace by a more constant pressure push), the total engine output power will
increase substantially and so will the final exhaust pressure with substantial
decrease in engine efficiency. Theoretically, mechanical efficiency (not
thermal) at constant and continuous maximum injection pressure of compressible
gas fall quite rapidly with the exhaust pressure differential, from 80% at 4
atmospheres to 60 % at 120 psi, and to 30 % at 500 psi (not to be confused with
thermal cycle or internal combustion efficiency). Said otherwise, to maintain
near
100% mechanical efficiency (extracting reservoir pressure energy and the total
enclosed expansion energy with a zero exhaust final pressure, and ignoring
thermal), the total
Quasiturbine (or most positive expansion machine) power would have to be reduce
to 1/3 of its maximum power at 7 bars (120 psi), or to 1/8 (which only double
the engine size) at 33 bars (500 psi). Active or passive flow control (power
control) using
restrictions ( and intake cavities) can be designed to limit the
injection pressure duration when needed (The Quasiturbine restriction being
sufficient), and make sure that gas expansion
effectively occurs for a better efficiency in all engine. Internal combustion engines work
from a limited combustion gas volume which actually expands and produces a
similar substantial residual exhaust pressure mechanical energy (and thermal) lost (efficiency
also decreases as the load or the internal piston pressure increases).
This is
not however a concern with incompressible fluid like water or oil in stable
phase (viscosity may be ?),
since it is not possible to store significant
internal pressure energy in such a liquid.
Never the less for similar
applications, the Quasiturbine has the highest efficiency compared to any other
engine.
Always remember that all engine efficiency fall with increasing exhaust pressure
and temperature (output power).
Efficiency improvement by Asymmetric
compression ratio ! Atkinson cycle :The Atkinson cycle engine is a type of Internal-combustion engine invented by James Atkinson in 1882. The Atkinson cycle is designed to provide efficiency at the expense of power. The Atkinson cycle allows the intake, compression, power, and exhaust strokes of the Four-stroke cycle to occur in a single turn of the crankshaft. Owing to the linkage, the expansion ratio is greater than the compression ratio, leading to greater efficiency than with engines using the alternative Otto cycle. The Atkinson cycle may also refer to a four stroke engine in which the intake valve is held open longer than normal to allow a reverse flow into the intake manifold. This reduces the effective compression ratio and when combined with an increased stroke and/or reduced combustion chamber volume allows the expansion ratio to exceed the compression ratio while retaining a normal compression pressure. This is desirable for good fuel economy because the compression ratio in a spark ignition engine is limited by the octane rating of the fuel used, while a high expansion ratio delivers a longer power stroke and reduces the heat wasted in the exhaust. This makes for a more efficient engine. Four stroke engines of this type with forced induction (supercharging) are known as Miller cycle engines. Miller cycle :In engineering, the Miller cycle is a combustion process used in a type of four-stroke internal combustion engine. The Miller cycle was patented by Ralph Miller, an American engineer, in the 1940s. This type of engine was first used in ships and stationary power-generating plant, but has recently (late 1990s) been adapted by Mazda for use in their Millenia large sedan. The traditional Otto cycle used four "strokes", of which two can be considered "high power" – the compression and power strokes. Much of the power lost in an engine is due to the energy needed to compress the charge during the compression stroke, so systems to reduce this can lead to greater efficiency. In the Miller cycle the intake valve is left open longer than it normally would be. This is the "fifth" cycle that the Miller cycle introduces. As the piston moves back up in what is normally the compression stroke, the charge is being pushed back out the normally closed valve. Typically this would lead to losing some of the needed charge, but in the Miller cycle the piston in fact is over-fed with charge from a supercharger, so blowing a bit back out is entirely planned. The supercharger typically will need to be of the positive displacement kind (due its ability to produce boost at relatively low RPM) otherwise low-rpm torque will suffer. The key is that the valve only closes, and compression stroke actually starts, only when the piston has pushed out this "extra" charge, say 20 to 30% of the overall motion of the piston. In other words the compression stroke is only 70 to 80% as long as the physical motion of the piston. The piston gets all the compression for 70% of the work. The Miller cycle "works" as long as the supercharger can compress the charge for less energy than the piston. In general this is not the case, at higher amounts of compression the piston is much better at it. The key, however, is that at low amounts of compression the supercharger is more efficient than the piston. Thus the Miller cycle uses the supercharger for the portion of the compression where it is best, and the piston for the portion where it is best. All in all this leads to a reduction in the power needed to run the engine by 10 to 15%. To this end successful production versions of this cycle have typically used variable valve timing to "switch on & off" the Miller cycle when efficiency does not meet expectation. In a typical Spark Ignition Engine however the Miller cycle yields another benefit. Compression of air by the supercharger and cooled by an intercooler will yield a lower intake charge temperature than that obtained by a higher compression. This allows ignition timing to be altered to beyond what is normally allowed before the onset of detonation, thus increasing the overall efficiency still further. A similar delayed valve closing is used in some modern versions of Atkinson cycle engines, but without the supercharging. |
Steam considerations
For a thermal energy efficiency superior to 50% ! (theoretical)
Since water requires an important quantity of latent vaporization heat
(which is not generally recover in the condenser or in the atmosphere open
circuit),
operation with saturated steam will always gives low efficiency (5 %) (unless
with a cogeneration application),
because of the important volume of water which needs to be evaporated to
maintain the pressure.
Even if the Quasiturbine can accept saturated steam,
it is not suitable from the energy efficiency stand point, that this steam stays
saturated during all the cycle.
In fact, in all expansion thermal machine (the Quasiturbine being one of the
most efficient),
increase in thermal efficiency is always links to steam overheating (without
having to increase the pressure),
since then one gets the same pressure effect with less molecules,
wherein making a substantial reduction in the quantity of water needed to be
vaporized
(... and saving of the corresponding latent heat energy, while some more
calories are lost in the exhaust).
With an important overheating, the efficiency of the thermal steam engines can
reach and even exceed 50% ...
(The overheating may occur in the steam pipes, or in the Quasiturbine itself).
In practice, a tuned conventional system can have an efficiency exceeding 20%,
with direct drive and instant reverse.
http://quasiturbine.promci.qc.ca/FQTVapeur.html
Why does the piston steam engine save steam by cutting intake before the end
of the stroke?
Because of the sinusoidal crankshaft movement, the piston produces most
mechanical energy
in the central third of its expansion stroke, little at beginning and little at
the end.
It would be nice to cut steam in the first stroke, but it does need to be filled
so that the second third can push,
but the last third is 1/3 of the volume and produces little energy, so it does
make sense to cut the intake and save steam.
Why is it not the same with the Quasiturbine?
Because the Quasiturbine is not sinusoidal, and transform pressure into
mechanical energy
much earlier and much later as well in the stroke, so that cutting intake will
reduce power and make insignificant savings.
This last comment also applies to pneumatic engines.
... Plus besoin de vapeur à très haute
pression pour être efficace!
Les turbines à vapeur conventionnelles exigent de très fortes
pressions
afin de générer de hautes vitesses d'écoulement permettant aux turbines d'être
efficaces.
Il n'en est pas ainsi avec la Quasiturbine qui est très efficace
à toutes les pressions, toutes les niveaux de charge et tous les RPM,
et qui peut produire de substantielles puissances à partir de
pressions d'entrées soutenues aussi basse que 20 à 50 lb/po2 et à
seulement 1800 RPM.
Dans les deux cas cependant, la surchauffe de la vapeur accroît l'efficacité
du cycle thermique,
et des pressions d'opération plus basse peuvent conduire à des
équipements plus volumineux pour la même puissance ...
La Quasiturbine réduit grandement les coûts de fabrication et d'opération des
centrales,
améliore de beaucoup le niveau de risque et de sécurité,
et réduit les exigences réglementaires et la qualification requise des employés.
Stirling engine efficiency considerations
Stirling engine uses a close chamber (cylinder and piston) with a fix amount of
compressible fluid (no intake or exhaust).
This confined gas is alternatively moved from the hot to the cold end of the
cylinder
(generally by using a displacer object free to move within the chamber and
taking the place of the gas),
producing an alternative expansion-contraction pressure variation which does
drive a piston on a relatively short course.
This engine convert a constant heat flux from the hot to cold end of the
cylinder into mechanical work
with a superior potential efficiency since it does not exhaust any residual
thermal or mechanical energy,
but it is very limited in total power output density in weight and volume.
However, it can be combine with hydraulic engines to produce impressive power
where power density is no matter.
Since the gas is moved sequentially rather that alternately from the zones
of different temperature,
the Quasiturbine Stirling is exempted from the need of a regenerator,
which increases its efficiency and power output through an increase in RPM
because preheat and precool increases the chamber charging pressure before
the TDC which is mechanically counter productive.
The Quasiturbine Stirling engine moves the gas around very efficiently,
with higher compression ratio, and allow for more power density.
Since there is no exhaust, they are very quite engines, and the Quasiturbine
Stirling is further vibration free. See:
http://quasiturbine.promci.qc.ca/FQTStirling.html
Exhaust energy recovery (regeneration)
- 2 Quasiturbine ports!
As shown, the engine efficiency falls as exhaust energy in pressure, speed and
temperature increases.
Conversely, one can almost decide at design of the efficiency by fixing the
exhaust initial exit pressure.
Near the BDC bottom dead center of the piston or the Quasiturbine blade, there
is a short angular range
during which back pressure will not significantly affect the
engine operation, where exhaust speed can be recuperated into a turbo,
and pressure energy can be "regenerated" into a secondary pneumatic
Quasiturbine.
Residual heat can eventually be recuperated though a Quasiturbine Stirling
engine.
Because the exhaust of the Quasiturbine occurs on a substantial angular area,
by making one early exhaust port and one late exhaust port, efficient
regeneration can be done
by a secondary Quasiturbine feed by the early exhaust port, while the late
exhaust port exit to atmosphere...
This kind of exhauts recovery sequence is not possible with the piston machine,
and allows higher efficiency while maintaining exceptional specific power
density.
Optimum efficiency: Load factor versus
RPM
This discussion gives some engine considerations useful for efficiently
integrate an engine into a given application.
There is not one simple solution and every thing is matter of compromises.
Generally speaking :
- Select the smallest engine power suitable for the need.
- Lower the internal engine pressure will be, better the efficiency (be careful
about this statement ?).
- Lower the RPM will be, better the efficiency (be careful
about this statement ?).
- To be efficient, the Minimum Flux suggest to take the maximum power from low
RPM, but then the higher internal pressure will lower the efficiency. To optimized the efficiency, increase
simultaneously the Load Factor and the RPM,
such that the total relative lost (minimum flux + exhaust pressure) / (net
engine output) is keep minimal.
- About conventional turbines, use them only at nominal design RPM, load and
power.
- From the integration point of view, the Quasiturbine looks somewhat like a
super-efficient very
high torque low RPM piston engine...
La turbine conventionnelle est le
moteur qui requiert le plus haut flux de gaz (et donc la plus haute consommation)
juste pour maintenir sa vitesse fonctionnelle libre (sans produire aucune
énergie net), ce qui explique pourquoi elles sont si énergivore lorsqu'elles
ne développent pas leur pleine puissance.
La
Quasiturbine - Un meilleure rendement énergétique
En
ce qui a trait à l’efficacité intrinsèque des moteurs à combustion interne
en général, l’énergie du carburant se perd principalement à 5 niveaux :
dans la consommation interne des
accessoires du moteur (comme les arbres de cames), dans la combustion
incomplète, dans le flux de chaleur au bloc moteur, dans la pression (vitesse)
et la chaleur résiduelle des gaz d’échappement, et dans un rendement
thermodynamique limité dû aux contraintes de température et de pollution. La
Quasiturbine améliore chacune de ces considérations en n’ayant aucun
accessoire moteur interne à entraîner, en permettant une combustion thermique
et photonique plus complète, en limitant le flux de chaleur au bloc moteur par
un confinement plus bref, en refroidissant mieux les gaz d’échappement par détente
adiabatique, en tolérant une plus haute température de combustion par
l’absence de soupapes, et en réduisant la production de polluants par une
compression trop brève pour permettre la chimie des NOx de se réaliser.
La géométrie rotative permet de plus une réduction substantielle de la
surface balayée par les joints, et donc de la friction. De plus, la
continuité des écoulements à l’entrée et à la sortie de la
Quasiturbine permet d’augmenter le facteur d’utilisation des tubulures par
un facteur de 6 à 10.
De nos jours, le rendement ou l’efficacité
des moteurs a une portée qui déborde largement le strict aspect kW (BTU),
parce qu'il ne peut pas être dissocié de son contexte d’opération et de son
usage.
La Quasiturbine
atteint un
rendement énergétique intrinsèque plus élevé entre autre
par une réduction
substantielle des accessoires moteurs énergivores.
Le rendement élevé de la Quasiturbine est
aussi relié à chacun des éléments suivants :
La
Quasiturbine améliore chacun de ces éléments à plusieurs égards,
principalement parce qu’elle :
Avec un haut couple moteur à basse révolution, la Quasiturbine n’a pas toujours besoin de boîtes de vitesses à rapports fixes ou multiples pour la plupart des usages, ce qui accroît directement le rendement par une économie au niveau de la consommation.
The relation between the hybrid
vehicle concept and the Quasiturbine photo-detonation engine. |
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Quasiturbine Agence Inc., Agence
promotionnelle pour Quasiturbine Rotative Motorisée par Combustion Continue ou
Compresseur
Casier 2804, 3535 Ave Papineau, Montréal Québec H2K 4J9 CANADA (514) 527-8484 Fax (514)
527-9530
http://quasiturbine.promci.qc.ca
quasiturbine@promci.qc.ca