Quasiturbine Pneumatic Engine
(For the steam engine, see http://quasiturbine.promci.qc.ca/QTVapeur.html )
Since the Quasiturbine is a pure expansion engine
(which the Wankel is not, neither most of other rotary engines),
it is well suitable as compressed fluid engine - Air engine or air motor.
From the basic 200cc per revolution engine bloc,
a compressed air prototype has been built making use of 2 parallel expansion circuits
of 200cc per revolution each, for a total of about 14 cubic feet intake per minute at 1000 RPM.
The pneumatic engine does not show any vibration on the shaft.
As an example, a chainsaw with a pneumatic engine (running from pressure air bottle regulated to 300 psi)
allows for a non combustible "all condition" running unit for the fireman and national safety teams.
It does run in heavy smoke or under water as well. Exhaust can even be respirated by the fireman !
A must for all civil defence organization ...
(See the old 1998 pneumatic chainsaw video on the website entry page)
REMARK ON PNEUMATIC SYSTEM EFFICIENCY
An high efficiency pneumatic motor does not guaranty the high efficiency of the entire pneumatic system.
All gas heat up during compression and cool down during relaxation.
The cooling effect must not be under-estimate. As an example, a typical 200 bar (atm.) cylinder
empty adiabatically (without thermalization to ambient temperature) gives at the end an air so cold
that its volume is then a 1/4 of that of the air once back to the ambient temperature (isothermal relaxation).
In those temperature conditions at the entrance of a pneumatic motor, the efficiency is catastrophically low
and the lubricant solidified, increasing considerably the internal engine friction...
Generally, the reversibility of the compression - relaxation cycle reduces with an increase in pressure,
which favours for high efficiency consideration the use of the lowest design pressure possible.
The measurement of the exhaust temperature gives generally a good indication of the efficiency,
since the minimum of energy lost into the environment correspond to
an exhaust temperature equal (neither inferior, nor superior) to the ambient temperature.
This condition can be achieve by a slight heating (solar) of the gas before its entry into the pneumatic motor.
Quasiturbine makes much more relaxation if it is use
with a dominant restriction at the entries of the chambers, and not at the exhausts.
The openings of exhaust must then be larger than them openings of intakes,
so that the air leaves more easily than it does enter, and thus lowers of pressure in the engine.
In this case, Quasiturbine has less specific power, but because it makes more relaxation, it is more effective.
One can make more relaxation by still reducing access to the intake, without synchronization valve,
or by reducing somewhat the torque taken out of the machine.
Since the Quasiturbine rotates from pressure as low as 1/10 of atmosphere (bar) (one psi !),
one understand why the Quasiturbine is so well adapted to high efficiency system...
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).
Like pneumatic / vapour Quasiturbine includes two circuits, these circuits can
be as desired fed in series by connecting the exit of the first room to the entry of the second.
While placing an exchanger on this conduit one can add heat in an attempt
to make that the total relaxation in the engine approaches an isothermal relaxation.
In this case, the differentials of internal pressure is distributed between the 2 successive chambers.
In the conventional turbines, one often makes such an intermediary heating
in order to increase the total power output of the machine, without necessarily increasing the efficiency.
In the case of Quasiturbine, the connection in series reduces inevitably the specific power
but can increase the output if intermediate heat is available free,
as in the case of atmospheric heat in pneumatic mode.
The recourse to the series mode can be of interest in the case of strong pressure
where the relaxation produces a strong cooling, but presents little interest
with Quasiturbine with the low pressures, let us say lower than 50 lb/po2 (psi).
If the differential of pressure is considerable,
the volumes and displacements involved in the initial relaxation are much less than with the final relaxation,
so that the machine in initial phase must be of smaller dimension
(let us say for a relaxation from 600 to 300 psi) that for the final phase (of 300 to 0 psi).
If the use of a single machine requires an initial pressure reduction,
this initial loss of pressure in a regulator is not converted into mechanical energy,
but in thermal cooling and kinetic energy, the last one attenuates obviously adiabatic cooling...
Because volumes and displacements in final phase are more important,
the same differential of pressure on this level produces more energy at a higher pressure.
In other words, to extract the maximum energy from a very high pressure,
one would need a cascade of machine starting with smallest, each one reducing the pressure a little and feeding the following one...
The old steam engines use 3 such stages (or more stages in the case of turbines),
Titanic had steam engines using 4 stages of relaxations...
MDI for its part proposes a pneumatic car with very high pressure using 3 stages with piston.
Nothing prevents from juxtaposing 3 Quasiturbines of different sizes to do still better!
In the case of a source of pressure which becomes exhausted with time like compressed air in cylinders,
the obvious disadvantage is that early stages would become useless as the pressure becomes less.
A high pressure tank cooled gradually when pour in an intermediate low pressure tank,
but it is at the entry of the low tank pressure that the relaxation is violent and where cooling is most considerable.
However, relaxation kinetic energy forces does not transform itself into mechanical work, but into heat,
thus reducing the net effect of cooling in the low tank pressure or in the regulator.
It is however not very wise to use the energy of pressure of high pressure tank
to heat the intermediate partially low pressure tank,
from where the interest to use multiple mechanical relaxations with heaters isobars between the stages!
Energy being proportional to the pressure time the volume, energy is weak after each relaxation even if there is pressure,
because volume is contracted and weak, and it is the heating which gives again the volume, and thus of energy
These multiple relaxations are profitable in the case of systems of several megawatts
(with high and constant initial pressure) having important operating time ratios,
but are more difficult to justify in the case of small vehicles asking for a few tens of kW only,
where the operating time ratio is half an hour per day, and of which high pressure of the tanks is not constant!
All this shows that higher the pressures are, and lower the temperatures are,
less the system of production / recovery is effective.
See Quasiturbine Hydraulic Motor at:
Quasiturbine - Comparative efficiency with other engines
Quasiturbine pneumatic-steam model QT50SC (Without carriage)
Usable with intake sustained pressure as low as 20 to 50 psi!
Quasiturbine pneumatic-steam model QT50AC (With carriages)
Assuming a pressure differential of 500 lb/sq.in., this graph gives for each rpm :
the engine torque, the power and the geometric intake flow.
Those result can be scaled linearly for other pressure differentials.
Usable with intake sustained pressure as low as 20 to 50 psi!
In practice, divide the torque and power by 2 to account for the form factor would provide more realistic results.
THERMO-PNEUMATIC NITROGEN CONCEPT
Liquid nitrogen is somewhat a reject of the oxygen distillation process, and is consequently relatively affordable.
To avoid energy consumption in the high temperature latent heat (like the water evaporation for example),
and better invest this energy in an extreme overheating, which increases the thermodynamic efficiency of the cycle,
we propose a thermo-pneumatic open cycle, making use of a nitrogen evaporateur
which can be the Quasiturbine itself (which then act as a "flash steam generator").
See http://quasiturbine.promci.qc.ca/QTVapeur.html )
followed or not by an overheater (or overheating the Quasiturbine itself).
The world of new ecological energy often consider sources 2 orders of magnitude under the petroleum.
Assuming that an ambient temperature heat source is always available for free,
a gallon of liquid nitrogen contains only 10 to15 times less mechanical energy than a gallon of gasoline, and it is zero pollution !
[Specific energy greater than 110 W-h/kg-LN2 (90 W-h/l-LN2 or 400 kJ/kg-LN2)
without relying on isothermal expanders (which double the energy output).
Gasoline mechanical energy is around 1 third (18% in transportation) of 9600 W-h/liter.
Best lead batteries have ~30 W-h/liter-lead]
(liquid nitrogen is pure mechanical energy, while gasoline is 1/3 mechanical, 2/3 thermal).
This high performance cycle is specially simple to built, non polluant, and appear well suitable for mobile units.
It does also fit very well the pure thermal sources, like the solar energy thermal conversion stations.
This concept also allow to conceive a working cycle in which the heat quantity given to the liquid nitrogen
is such that the exhaust temperature after expansion is equal to the ambient temperature !
(See also the CRYOCAR zero pollution using liquid nitrogen, form the University of Washington state:
As the output efficiency grows quickly with overheat, we propose to use in addition a small burner with propane for example, to overheat gas nitrogen (and consequently the Quasiturbine itself), so that temperatures of exhausts after adiabatic cooling become about 100 degrees Celsius or more. This mode allows several advantages:
Could give output of 50% increases or more.
Although the exhausts of nitrogen is without moisture for the first stage of exchanger of the evaporator,
the condensation of moisture poses problem in the subsequent stages if mixed with the ambient air, problem what the use of a burner removes completely.
Notice that the energy of the burner is later in the exhausts nitrogen heats, and that this energy is recovered by the vaporization of liquid nitrogen, the net contribution is thus transitory and small in steady state.
The burner is in any case necessary in the vehicles of Nordic area to warm the cockpit!
The heat of vaporization and reheating of liquid nitrogen will be recovered later
by replacing the evaporator by a Quasiturbine-Stirling mounted on the same shaft.
Note one the efficiency
As for the vapour, the effectiveness of the cycle is function of the ability overheat the gas.
Cooling in a pressurized gas bottle is initially considerable,
which reduces much the pressure of the bottle, but worse the cold gas increases density and consumes himself then too quickly.
If the ambient conditions can provide free heat, it is much better, but overheating generally imposes a burner (hybrid).
An effective fitting thus requires an exchanger (to heat with ambient temperature) on the outlet side of the bottle,
followed of a superheater of the gas (propane or other) right before the entry into the engine (Quasiturbine).
The privileged set-up would be a burner below, just under the superheater,
on which the bottle could even be to profit from one residual reheating,
and finally the exchanger (to heat at the ambient temperature) capping the whole...
The exhaust gas of the engine deprived of moisture gain to be injected near relaxation to avoid the frost.
The reversibility of a pneumatic system storage worsens with increasing chosen pressure,
unless the heat is also stored in the tank at the time of compression (storage for short duration and low 10 bar - 150 psi).
At the time of use, the liquid nitrogen has a thermodynamic advantage
on compressed gases coming from a bottles at very high pressure.
Indeed in relaxing, the very high pressures produce an intense cold
which reduces the volume of gases gradually and thus reduces the mechanical energy extracted.
Within the bottles, the energy is strictly that of the adiabatic pressure drop
(ignoring the potential energy generated by the coldness of the gas, which is recovered due to an external heat contribution!),
whereas a contribution of sometimes free heat (ambient air or water)
allows to extract from the bottle (relaxation isothermal) more energy than it in contains,
but not more than the total thermal bottle + the contribution.
However, to produce the power necessary for the propulsion of a vehicle
with reasonable Quasiturbine size (QT75SC), a differential of pressure from 50 to 100 psi is enough.
Then why having a differential of 5000 or 3000 psi
which require a multi stages relaxation?
(complicated by the fact that the pressure of the bottles reduces with time),
whereas the vaporization of liquid nitrogen precisely makes it possible to create exactly
the modest pressure differential required,
and to proceed to preheats in the same way...
The lower are the pressures, the better is the effectiveness!
Quasiturbine Pneumatic and Fuel cell :
A perfect Match (using liquid nitrogen) ! http://quasiturbine.promci.qc.ca/QTPileCombustible.html
A Thermo-Pneumatic Quasiturbine Locomotive
(with addendum on subway operation)
A demonstration liquid nitrogen motorcycle
Concours Force Avenir http://quasiturbine.promci.qc.ca/QTRimous0203.html
Why is the Quasiturbine revolutionizing the use of steam and solar energy ?
Air Car (compressed air vehicle)
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Quasiturbine Pneumatique Inc.
Casier 2804, 3535 Ave Papineau, Montréal Québec H2K 4J9 CANADA (514) 527-8484 Fax (514) 527-9530