Saturated Steam Quasiturbine Engine
An alternative to saturated steam turbine

See also the Quasiturbine Thermal Stirling Rotary Engine (Sterling) at:
http://quasiturbine.promci.qc.ca/QTStirling.html

* * * * * 
International Association for the Advancement of Steam Power 
http://www.iaasp.org/news.htm
November 2001 - www.quasiturbine.com - Web site of the Month

Steam power is staging what may prove to be the biggest grass-roots comeback 
in the history of the industrial revolution! 
From micro-horsepower to Giga-Watts, from microchips to motorcycles,
and from wheel chairs to missions to mars, STEAM POWER IS BECOMING PROMINENT 
IN VIRTUALLY EVERY INDUSTRY IN EVERY COUNTRY OF THE WORLD. 
Web site of the Month: The Quasiturbine New Engine - Here is a site you have to see! 
* * * * * 

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.

... No more need for very high pressure steam to be efficient!
The conventional steam
turbines require very high pressure 
in order to generate the high flow speed permitting the turbine to be efficient
.
This is not the case with the
Quasiturbine which is very efficient 
at all pressures
, all load levels and all RPM,
and can produce substantial power 
with sustained intake pressure as low as
20 à 50 lb/po2 and at only 1800 RPM.

In those two cases however
, the super-heated steam increases the efficiency of the steam cycle,
and the lower pressure operation may lead to larger equipments for the same power
...
The
Quasiturbine greatly reduces the station construction and operation cost,
improves substantially the risk and safety level
and
reduces the law constraints and the qualification needed from the employees.

Steam versus pneumatic - Effect of the condensation
The pneumatic motor has no phase change during relaxation,
such that at the time of exhaust it must evacuate a large volume of gas,
while the phase change of the steam into condensate during the relaxation
reduces considerably the volume to exhaust
(similarly to the adiabatic cooling in an internal combustion engine)
and help to increase the engine performance.
To benefit of this effect, it is advantageous to make
a cut-off or a strangle of steam intake at mid-course,
to make certain that a relaxation and condensation occur in the chamber before the exhaust opening.

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 also:
Quasiturbine - Comparative efficiency with other engines
http://quasiturbine.promci.qc.ca/QTEfficaciteComparative.html

The Quasiturbine steam engine does not show any vibration on the shaft.

 
Quasiturbine pneumatic-steam model QT50SC (Without carriage) 
Usable with intake sustained pressure as low as 20 to 50 psi!

  QTCaractCalcul.gif (6945 bytes)
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.

Using this graph to scale up hypothetical large steam units at 33 bars (500 psi) differential 
and at a reduced speed of 1800 RPM would gives without any gearbox
(no experimental data yet available) :
(This high power regime is not particularly efficient, even if it can be maintained in continuous operation)

Shaft Power Rotor diameter Rotor thickness
50 kW (70 HP)

0,4 MW (530 HP)

3 MW (4 000 HP)

25 MW (33 000 HP)

200 MW (260 000 HP)

13 cm (5 inches)

25 cm (10 inches)

 53 cm (21 inches)

1 m (3,5 feet)

2 m (7 feet)

5 cm (2 inches)

10 cm (4 inches)

20 cm (8 inches)

41 cm (16 inches)

82 cm (32 inches)

Notice that in 4 strokes internal combustion mode, the Quasiturbine power is about 1/8 of the one indicated
increasing with the maximum RPM.
In practice, divide the torque and power by 2 to account for the form factor would provide more realistic results.

 

I - Conventional steam engine (including saturated steam)
Since the Quasiturbine is a pure expansion engine
(which the Wankel is not, neither most of other rotary engines),
it is well suitable as steam engine.
Since the Quasiturbine is an hydrostatic turbine (instead of aerodynamic),
it is also well suited for co-generation project with saturated steam.

From the basic 200cc per revolution engine bloc,
a steam engine 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 concept originality comes also from the fact that the Quasiturbine can be located inside the boiler !

 

II - Hot water injection engine (in-situ evaporation)
Because the Quasiturbine accepts saturated steam,
a positive way to bypass the intake steam flow limitations is
to use the Quasiturbine itself as evaporator.
In this case, the remote boiler become a simple hot water tank without evaporator,
and the pressurized hot water taken in a close loop at the base of the tank is brought to the engine intake,
where droplets of water and oil are directly injected in the expansion chamber,
and consequently evaporated inside the Quasiturbine itself.
In this case, the latent heat of vaporization is also given to the engine by the close pressurized hot water loop
via a pipe coil enclosing the Quasiturbine.
The exhaust steam goes to a conventional condenser and returns to the boiller.
This option also presents the advantage of requiring a much smaller boiler,
pipes of small dimensions, miniature control valves,
and permit potentially to reach higher rotational speed.

In the case of thermal solar systems, if the internal liquid reserve is large enough for all the sunshine period,
this operation mode needs only one unique fill up at night !

III - Cold water injection engine ?
This mode would definitively be unimaginable with conventional turbine, 
since they react to the speed of steam flow, which must be pre-conditioned.
In fact, if a burner heats the Quasiturbine engine bloc directly, there is no need of a boiler any more
(The Quasiturbine acting simultaneously as the boiler, the over heater and the evaporator),
and one can then inject cold water (which will be preheated in the injector)
at a pressure superior to the internal maximum working pressure.
Ideal mode for thermal solar concentrator heating directly the Quasiturbine engine bloc !
(This mode is equivalent of using the Quasiturbine engine bloc as a "flash steam generator")
(Notice that a remote heat source could use an un-evaporating fluid like oil or liquid sodium to transfer heat to the engine bloc).


STEAM DRAIN ENERGY RECOVERY

Since the large industrial vapour boiler cannot be modulated quickly in power,
these boiler generally produce a "vapour surplus" to satisfy the fluctuations demand
which can reach 5 to 10% of the total capacity.
When the vapour demand does not require this supplement, it is generally purged in pure lost.
However, the use of one or several Quasiturbine steam at the point of purging
allows to recover a part of the energy of the vapour
and to produce intermittently compressed air or electricity...

STEAM PRESSURE REDUCTION STATION
In addition, a Quasiturbine placed on a vapour line can act like a volumetric governor
according to the power that one extracted there, and better still,
it can also act like a steam pressure reduction station
for the various stages of industrial processes.

PUMPING STEAM-WATER CONDENSATE
Quasiturbine used in turbo-pump mode
is particularly well adapted to pump vapour condensate
from pressured vapour injection in only one of the Quasiturbine turbo-pump circuit.

See the section :
Why is the Quasiturbine revolutionizing the use of steam and solar energy ?
http://quasiturbine.promci.qc.ca/QTvapeurPourquoiE.html 

The Steam-Powered Quasiturbine in  
Direct-Drive Railway
Locomotive Propulsion
http://quasiturbine.promci.qc.ca/QTLocoVapeurValentineH.htm 

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Quasiturbine Vapeur Inc.
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