Quasiturbine> Type> Steam Engine


Steam is a source of energy, specially in co-generation and geo-thermal...
Steam power is more and more prominent in industry around the world.
Steam Quasiturbine could not come at a better time.

Quasiturbine Steam Engine

Demonstration at the 2011 Great Oregon Steam-Up

Quasiturbine Uniflow Characteristic

In most reciprocating piston engines, the steam reverses its direction of flow at each stroke (counter-flow). By entering and exhausting the cylinder by the same port, the cylinder valve and walls are cooled by the passing exhaust steam, while the hotter incoming admission steam is wasting some of its energy in restoring the temperature. Some energy is further lost in reversing the motion momentum of the mass of steam within the piston. The aim of the piston uniflow is to remedy this defect by providing an exhaust port at the end of the stroke, making the steam flowing only in one direction, but has the inconvenience of recompressing some residual cylinder steam. Quasiturbine is a uniflow engine, with the further advantage of not recompressing any residual steam, resulting in superior energy efficiency. Recompressing residual steam means some reversibility losses, and the pressure increases makes a substantial restriction to the initial steam flow into the chamber, not to ignore the truncated cycle near bottom dead center - None of this with the Quasiturbine.

Quasiturbine has no vane

Unlike vane pumps, which vane extension is important and against which the pressure acts to generate the rotation, the Quasiturbine contour seals have an imperceptible extension and the rotation does not result from pressure against these seals. The vane geometry does not allow high compression ratio at TDC (top dead center), while Quasiturbine does, and this is why QT is efficient (less pressure charging losses), and this is why there is no vane combustion engine. Quasiturbine publishes « efficiency data » while vane motor manufacturers don't. Premium on « efficient equipment » is rapidely recovered in operational cost...

Mechanical Conversion of Low Heat

From looking at the USA energy flow chart at


The amount of Low temperature heat discarded is quite impressive. This waste energy has a tremendous potential for energy recovery, and the Quasiturbine offers more ways to tackle the challenge through Brayton, Ranking and Stirling cycles!

La pression d'un circuit vapeur est déterminer par le point le plus froid (condensation),
alors que l'éfficacité est donné par la température de la vapeur (les surchauffeurs font une chauffe à pression constante - celle du point froid, souvent la chaudière elle-même). L'efficacité optimum requiert souvent un surchauffeur distinct de la bouilloir, laquelle fixe la pression. Coté efficacité du cycle lui-même, la basse pression de vapeur réduit la demande de puissance de la pompe d'alimentation en phase liquide, ce qui est pratique mais pas critique, parce que du point de vue globale, l'addition d'énergie au système par la pompe est presque totalement récupérée par la turbine...
Mise à part la chaleur latente, l'énergie est essentiellement dans les débits volumiques, et les débits en phase liquide sont typiquement 600 fois moindre qu'en phase vapeur.

Souvent, l'optimum est d'utiliser les thermies basses températures comme préchauffe d'un cycle à plus haute température, au quel cas l'efficacité différentielle du carburant utiliser pour la haute température est bonifiée... La QT favorise un cycle vapeur basse pression aussi pour une raison réglementaire, car les hautes pressions sont dangeureuses et bien exigentes. Dans le cas de la QT, nous préconisons pour le solaire, de supprimer la chaudière, et de chauffer le bloc moteur de la QT lui-même, et d'injecter de la vapeur gardée en phase liquide dans un injecteur pour vapeur éclaire (flash steam). Pratique aussi pour les unités mobiles qui craignent les réservoirs d'eau bouillante.

Quasiturbine Steam

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. Steam Quasiturbine could not be at a better time.

The Quasiturbine steam engine does not produce vibration.

Quasiturbine pneumatic-steam model QT75SC (Without carriage)
Usable with intake sustained pressure as low as 20 to 50 psi!
The Quasiturbine steam engine does not make any vibration.

Approximated first order theoretical steam case with a 33 bars (500 psi) effective differential pressure at 1800 RPM without any gearbox. This simplified linear extrapolation does not guaranty that the steam flow will permit to reach 1800 RPM for the larger units. Preliminary sizing data for Quasiturbine are as follows (no intake cut off):

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 almost linearly to this maximum 1800 RPM. Notice that the Quasiturbine power increases almost linearly with the RPM on a large range.

Remark on Steam Efficiency

An high efficiency steam motor does not guaranty the high efficiency of the entire steam system. The cooling steam effect during relaxation must not be under-estimated. For high pressure drop (not allowed with the prototypes), intermediary heating is a must to keep up the pressure and avoid condensation. No steam circuit is easy to design and operate.

The Quasiturbine can further make internal gas expansion if the dominant restriction is made to be at the intake, such that the flow is not sufficient to keep the internal pressure at the level of the pressure intake line. This internal expansion can then be done without any synchronization valve. Efficiency increases as the involved gas pressure is lower.

Since water requires an important quantity of latent vaporization heat (which is not generally recovered in the condenser or in the atmosphere open circuit), operation with saturated steam will always give low efficiency (5 - 10 %) (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 linked 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.

From the steam engine point of view, 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 (engine efficiency, not necessarily the system efficiency) at all pressures, all load levels and all RPM, and can produce substantial power with sustained intake pressure as low as 20 to 50 psi 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, reduces substantially the risk, improves the safety level, and reduces the law constraints and the qualifications needed from the employees.

For optimum performance, the feed line must be well balanced between the two intake ports, which must be done by ending the line passed the 2 T by an accumulator (buffer) tank, on which the pressure gage can be located.

The Feed Pump is not a net energy lost

Historically, to avoid feed pumps, the steam boiler was over-designed to hold sufficient water for a full operating cycle. This is still of interest for the solar steam systems (or geothermal), ou il est avantageux d'avoir une citerne d'eau pressurisé en marge du circuit vapeur suffisante pour l'alimentation la journée entière (remplissage la nuit), justement pour ne pas avoir à injecter les condensats contre la pression de vapeur. Une seconde citerne peut accumuler les condensats à la sortie de la turbine à pression atmosphérique, et le transvasage peut se faire la nuit sans soleil... Ici, la pulsation quotidienne est obligatoire de toute façon.

Coté puissance spécifique, la pulsation du cycle à haute fréquence impose l'arrêt du circuit vapeur et la chûte de pression de la chaudière (et son refroidissement en pure perte), un inconvénient majeur qui fait baisser à la fois la puissance moyenne et l'efficacité thermique. Voilà pourquoi on revient à la pompe de remplisage en phase liquide et continue! Many think that the feed pump in a steam (Rankin cycle) is a system waste of energy, while in fact, most of the feed pump energy is recovered by the turbine. It is like the compression energy in a piston engine which is almost all recovered at relaxation, or the energy of the compressor turbine in a Brayton cycle (jet engine), recovered in the hot turbine.

Adiabatic versus Isothermal

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, including steam engine. Like for the pneumatic, the steam Quasiturbine includes two circuits, these circuits can be fed in parallel, or in series by connecting the exit of the first chamber to the entry of second. By placing an exchanger on this conduit one can add heat and doing so, the total relaxation in the engine approaches an isothermal relaxation. Notice that in this case, the pressure differential between the two circuits will be automatically equalized.

In the conventional turbines, such an intermediate heating is often done in order to increase the total power of the machine, without necessarily increasing the efficiency. In other words, to extract the maximum energy from a very high pressure, it would be necessary to use a cascade of machines starting with the smallest, each one reducing the pressure a little and feeding the following one through a heat exchanger... The old steam engines used up to 3 machines (or more stages in the case of turbines), the Titanic had steam engines using 4 stages of relaxation... The MDI air car for its part suggests to use a very high pressure 3 stages piston engine. Nothing prevents from juxtaposing 3 Quasiturbines of different dimensions to do still better!

Cascade Expansions?

Because the Quasiturbine has 2 independent circuits which can be used in serial, many could suggest that a single Quasiturbine can acts as a dual equal-size stages expander with an intermediary heat exchanger (with reduced specific power, unless the intake pressure is raised). This is not likely to be the case, because the serial interconnection of the chambers makes the exhaust volume of the first stage to move into the exact same volume of the intake chamber of the second stage without making any net additional torque or work (at constant pressure, or even if an intermediary heat exchanger increases the temperature and the pressure during the transfer). Because the exhaust and the intake chambers stay at the same pressure during the transfer, that pressure would not be a constraining back pressure to the first stage. The final result would be equivalent to give heat to the exhaust without getting any work out, and would give a neutral role to the second stage. Characteristics would be similar to the one circuit only steam mode.

However, experimentation with inter-stages check-valves, intermediary tank, Venturi pressure phase shift... and super-heater could make it a worth avenue to explore. The Quasiturbine can further make internal gas expansion if the dominant restriction is made to be at the intake, such that the flow is not sufficient to keep the internal pressure at the level of the pressure intake line. This internal expansion can then be done without any synchronization valve (cut-off intake). Efficiency increases as the involved gas pressure is lower. The present possibilities have not yet been tested.

High Temperature Steam

Utilities are the place to find high temperature steam, and the Quasiturbine is a very interesting option for such an energy station.

Use of superheated steam could be done in one of the Quasiturbine circuits, while the other circuit could be used to circulate cooling air (Quasiturbine turbo-pump mode), permitting to extend the Quasiturbine operation without reaching the material temperature limit.

Co-generation Saturated Steam

The Quasiturbine is an unmatched alternative to saturated steam turbine with modulated power output.


Like for co-generation, the Quasiturbine Steam is unique for such a low level thermal source.

Nuclear Steam

Nuclear reactor have very sensitive core and are used to give thermal energy at almost constant temperature. Temperature level in nuclear power plant are much less than in coal or heavy fuel station. For this reason, nuclear steam cannot expand as much before reaching condensation point, and their turbine are not as efficient. With the Quasiturbine however, full expansion would be possible to the condensation point, and this would improve the efficiency. Furthermore, the Quasiturbine can drive a generator without gearbox, one of the costly element of conventional turbine...

Flash Steam Quasiturbine

In conventional boiler, the heat is capture in large quantity by the latent liquid evaporation prior overheating, and none is capture later at relaxation time. By contrast, in flash steam system much less heat is initially capture while overheating the flow in the liquid phase, but some additional heat is being capture at the flashing time from the engine bloc. In both cases, for equivalent power and temperature condition, similar liquid and heat flows could be involved. To get the most heat transfer in flash steam system, high pressure maintains a water liquid state into the feed line and prevent evaporation prior to expansion until it get into the QT, which could be at a somewhat lower temperature as the heat recovery system may provide heat gradients. When the steam is released into the QT and expansion takes place, the pressure of the overheated water is largely reduced and its over-heat is provided to the latent evaporation, while complementary heat energy is being captured from the hot engine bloc.

Consider a water feed line pressure of 1000 psia at the saturation temperature of 544 F. If the water is entering at 100 F, then the liquid temperature rise would be 544 -100 = 444 degrees F, and about 444 btu per pound of water energy could be extracted from the source (In one hours time 2545 / 444 = 5.7 lbs of water per hour per HP. If expansion was to atmospheric pressure, the specific volume would be would be about 26.8 cu ft per pound, or 26.8 x 7.7 = 206 cu ft per hour per HP). During the process, the hot engine bloc would provide additional heat to the expansion. By contrast, allowing the water to boil and evaporate at 1000 psia would capture 3 times more heat (meaning 1/3 of the flow for the same capture) hg = 1198 btu per pound (Then 2545 / 1198 = 2.1 lbs water per hour per HP, and expanded to atmospheric pressure, the volume would be 26.8x2.1 = 56 cu ft water per hour per HP), with an efficiency of the saturated case of about 33%. Flash steam efficiency may not be the best, but practicability of the system may be much more suitable in mobile applications by allowing the Quasiturbine to run cooler, without any dangerous pressurized steam reservoir.

Small Quasiturbine Steam Engines

I - Conventional steam engine - An engine in the boiler!
Because it is an efficient, compact and zero vibration engine, the Quasiturbine can be located inside the boiler in a very compact and portable way:

II - Hot water injection engine (in-situ evaporation) Flash steam Quasiturbine
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 becomes 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 boiler. This option also presents the advantage of requiring a much smaller boiler, pipes of small dimensions, miniature control valves, and permits 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).

Because pressure steam only exist for a short time and only within the chamber (no steam boiler), this alternative is one of the safest in term of blowing-up, and as potential to avoid most pressure product legislations and rules, which is today a serious steam project handicap (no qualified steam expert needed for operation!).

IV - Quasiturbine Stirling and Short Steam Circuit
This is also a way to make an interesting compact portable engine as described on the Stirling page www.quasiturbine.com/ETypeStirling.htm

V - Quasiturbine Brayton Short Air Circuit
Flashing steam into a Hot Quasiturbine is a Ranking cycle (phase change requiring a liquid pressure pump), but injecting cold compressed air into a Hot Quasiturbine and letting it expands is like < flashing AIR >, and this is a short circuit Brayton QT cycle. Similarly to the Ranking which need a liquid pressure pump for intake, this Brayton cycle would need an external cold air (QT ?) compressor (Notice that the energy given to the compressor is not lost, but recovered as pushing pressure during the flashing process).

Rotary Pressure Regulator

What about an "energy recovery rotary pressure regulator" ? An interesting application of the steam Quasiturbine is to recover the high pressure energy at pressure reduction stations. Instead of using a conventional cooling station, a steam Quasiturbine will rotate under the pressure differential and the flow will be controlled by the rpm, i.e. the torque applied on the Quasiturbine shaft. This way, the Quasiturbine can transform the pressure differential into useful mechanical work to run pump, compressor, ventilator, electricity generator or locally convert the energy in high grade heat. Because conventional turbines can not be widely modulated in rpm and load, they are not suitable for gas flow and pressure control, while the Quasiturbine is essentially a closed valve at zero rpm, and has high efficiency at all torque and all flow rpm. All experimental demonstration has to be done only by steam experts and under all current rules and regulations.

Other Steam Applications

Apart from conventional uses as for electric production, marine or locomotive propulsion, here some interesting steam applications:

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! Same technology could apply to:
Industrial exhaust gases heat recovery
industrial furnace heat recovery
Industrial process heat recovery
Chimney or stack heat recovery
Waste heat recovery
Solar heat recovery
Geothermal heat recovery
Thermal nuclear heat

Solar thermal plant:
Because the Quasiturbine is efficient at different output level, it is most suitable for modulated power output as solar thermal plant. Direct solar heating of the Quasiturbine steam is also a major feature for solar concentrator plant... Be aware that the technical literature contains a lot of statement referring to system feed pump or piston compression cycle, as a lost of energy: this is not true, piston compression cycle energy is mostly recovered during relaxation, as the feed pump energy increases the system output accordingly...

The intermediary reflector can be suppressed
by moving the power pack inward, and heating the QT on the peripheral.

Steam pressure reduction station:
A Quasiturbine placed on a steam line can act like a volumetric governor according to the power that one extracted from it, and doing so, it acts like a station of reduction of steam pressure for the various stages of the industrial processes, without having to cool the steam, remove the heat, or lose a lot of energy...

Pumping steam-water condensate:
A Quasiturbine used in turbo-pump mode is particularly adapted to pump the condensed steam (condensate) from pressure steam injection in only one of the 2 circuits of Quasiturbine turbo-pump.

Steam Purge energy recovery:
As the boiler of the industrial steam networks cannot be modulated quickly in power, these boilers often produce a "steam supplement" to satisfy the fluctuations of demand which can reach 5 to 10% of the total capacity. When the demand does not require this supplement, it is generally purged in total lost. However, the use of one or several Quasiturbines Steam at the point of purging could allow to recover a part of the energy to produce by intermittency compressed air or electricity...

Steam Engine Lubrication

Periodic oil spray needs to be injected into all engine intakes steam flow. Standard product recommendations start at steam pressures of 150 to 200 psig (366 to 388 F). The grade of recommended steam cylinder oil for these conditions is ISO 460 which contains 4% tallow oil. This is the grade of oil that the “ride-on” locomotive community uses. It is generally available in 55 gallon drums, but Sulphur Springs Steam Models sales@sssmodels.com provides it in quart cans. Chevron USA has a relatively new steam cylinder oil on the market that is lighter in viscosity than ISO 460 by about half (1103 SUS vs. 2335 SUS @ 100 F). Other steam oil may do as well. It does not require much oil, and large steam units generally use a separator in the condenser, and recycle this oil.

More Technical

Quasiturbine steam

A White Paper
Engine Exhaust Heat Recovery with Quasiturbines
Offering Essential Efficiency Characteristics

Why is the Quasiturbine revolutionizing the use of steam and solar energy?

Quasiturbine Stirling and Short steam circuit

The Steam-Powered Quasiturbine in Direct-Drive Railway Locomotive Propulsion

Quasiturbine - Comparative efficiency with other engines

International Association for the Advancement of Steam Power

The Quasiturbine is listed with INIS © International Atomic Energy Agency