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Pneumatic Engine

Pneumatic is used everywhere: It is safe, needs little maintenance, lasts long...
The Quasiturbine is a pure positive expansion machine.
which can be simulated numerically as expansion in an infinitely long tube...

Quasiturbine Pneumatic Engine


Remark on Pneumatic 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-estimated. 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 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 solidifies, increasing considerably the internal engine friction... Generally, the reversibility of the compression - relaxation cycle reduces with an increase in pressure, which favors 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 achieved by a slight heating (solar) of the gas before its entry into the pneumatic motor.

In the case of very high pressure gas tank, not only one wants to harvest the energy actually in the pressurized air tank, but also take advantage of the energy amplification possible from using available external heat. On one side it is not efficient to make a too important pressure drop into one expander because the adiabatic cooling will strongly reduce the pushing pressure, and the exhaust gas will be thrown out at valuable high pressure. On the other side, using a regulator will dissipate pressure energy, but will allows the reduced pressure gas to be thermalized, such as to run the expander with much less adiabatic cooling and less gas pressure energy thrown at exhaust. Both methods are compromises. Multi-stages with heat input is hardware intensive, but the best way to get the most mechanical energy out of a high pressure gas tank with an external available heat source...

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 the Quasiturbine rotates from pressure as low as 1/10 of atmosphere (bar) (one psi !), the Quasiturbine is well adapted to high efficiency system... For very high air tank pressure drop (not necessarily suitable with the prototype), an intake air heating coil in hot water would be necessary to prevent freezing of the oil within the Quasiturbine.

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.


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 - Air engine or air motor.

Since the pneumatic - 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 relaxations... 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!

In the case of a source of pressure which becomes exhausted with time, like a compressed air cylinder, the obvious disadvantage is that it is necessary to keep useless stages as the pressure becomes less. A high pressure tank cools gradually when it flows into an intermediate lower pressure tank, but it is at the entry of the low pressure tank where the relaxation is violent and where cooling is most considerable.

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


Rotary Pressure Regulator
Gas Pipeline Expander

Gas Pipeline Pressure Energy Recovery - Rotary Pressure Expander
What about an "energy recovery rotary pressure regulator" ? An interesting application of the pneumatic Quasiturbine is to recover the pipeline high pressure energy at local distribution stations. Instead of using a conventional pressure regulator (an energy dissipative device), a pneumatic 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. It does act as a dynamic active rotary valve. 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 (better than pre-heating the gas before that same "rotary expander", to avoid any residual condensation as done with conventional regulators). 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. Notice that producing high value mechanical or electrical energy is preferable even if some of the gas has to be burnt to avoid excessive expansion cooling. With such a system, any heat added before the Quasiturbine expands the gas and increases the available volumetric flow with the result that this heat is converted in mechanical energy with a very high efficiency. All experimental demonstration has to be done only by gas experts and under all current rules and regulations. Ignoring gas expansion and considering only the gas pressure flow, a 36 inches diam. gas pipeline at 700 psi carry typically a pressure power in excess of 30 MW - 25 millions of pound-ft/sec - of zero pollution pure mechanical energy almost totally recoverable through Quasiturbines in the heart of cities and industrial parks. This is tens of giant windmills on kW-h basis!. A survey (M. Dehli, GWF Gas-Erdgas 137/4, p.196, 1996) showed that in Germany alone, the potential for utilizing this pressure in 1996 was 200-700 MW, and the gas consumption has increased since then... See the conceptual diagram and a pipeline technical paper.

Enhance efficiency of LNG liquefaction cycle. Adsorption Refrigeration Engineering Thermal Physics. Conventional pressure regulators make all the gas to expand from the constant high pressure side, and the gas pressure-kinetic energy at the needle is converted into undesirable heat, reducing accordingly the amount of cold produced. The Quasiturbine rotary expander allow for individual chamber to expand at a variable reduced pressure during expansion, and such reduces the gas kinetic energy transformation into destructive heat. Furthermore, the Quasiturbine recuperates mechanically the gas differential pressure energy, which can be used to run more compressors and make more cold... A double energy efficiency gains! This offers great enhancement of thermodynamic cooling machine, and specially in high power LNG - Liquid Natural Gas liquefaction stations. Of course, this efficiency enhancement is also available for more modest cooling system and air conditioning equipments.


Thermo-Pneumatic Nitrogen

Liquid nitrogen is somewhat a secondary product of oxygen distillation process, and is consequently relatively affordable. Energy can be produced by a thermo-pneumatic open cycle, making use of a nitrogen evaporator (which can be the Quasiturbine itself, which then acts as a "flash steam generator"), followed or not by an over heater (or overheating the Quasiturbine itself).

The world of new ecological energy often considers sources 2 orders of magnitude under that offered by petroleum. Assuming that an ambient temperature heat source is always available for free, a gallon of liquid nitrogen contains only 10 to 15 times less mechanical energy than a gallon of gasoline used at 10% efficiency in today's vehicles, and it creates zero pollution! This high performance cycle is especially simple to built, non-polluting, and appears highly suitable for mobile units. It also conforms with pure thermal sources, like solar energy thermal conversion stations (solar hot water systems?) very well . This concept also allows the design of a working cycle in which the quantity of heat given to the liquid nitrogen is such that the exhaust temperature after expansion is equal to the ambient temperature!


Innovative Concepts

The pneumatic Quasiturbine engine does not produce vibration. As an example, a chainsaw with a pneumatic engine (running from pressure air bottle regulated to less than 100 psi) allows for a non combustible "all condition" running unit for the fireman and national safety teams. It does run in heavy smoke and under water as well. Exhaust can even be inhaled by the fireman ! A must for all civil defense organization ...

Because the Quasiturbine center is free and available, a jet boat propeller can be inserted inside, and because the Quasiturbine has no oil pan, it could be submerged to provide direct underwater boat or recreational pneumatic propulsion.

A small submarine innovative pneumatic Quasiturbine concept could have a cabin free of any propulsion component, where the air tank is droppable below, the propulsion Quasiturbine is at the rear, and the air exhaust of the Quasiturbine goes into the cabin to be inhaled by the crew.

Powerful hand air tools like mining drills can be developed...

The return of pneumatic vehicles (air car) will benefit from the Quasiturbine engine.

Pneumatic is well suitable for safety reason like for subway propulsion...

Fuel cells cooled by liquid nitrogen could be teamed with a pneumatic nitrogen Quasiturbine for a remarkable total output...

Low Pressure Modulated Power Station
Solar radiation varies greatly during the day while most engine keep their optimum efficiency at design power only. Because the Quasiturbine (steam or pneumatic) keeps it high efficiency on a large power range, it is well suitable for modulated (from source or demand) power production like solar, windmill, ocean wave station... where the pressure is generally low, and efficiency critical!

A 10 second vehicle Power Booster. Originally, hybrid was intended for efficiency increase, not for performance increase. More and more vehicles use 2 engines not for fuel savings, but to increase acceleration performance: As a 10 seconds Power Booster, benefiting a government grant! In this regards, the Quasiturbine QT600SC pneumatic with an onboard air tank and compressor could eventually provide hundreds of additional HP for 10 seconds, and make an unbeatable acceleration Quasiturbine Hybrid vehicle... the market seem to ask for? Many others applications require high power bursts, like in smooth landing parachuting (with fast line-winding in less than 10 seconds).


More Technical

Quasiturbine pneumatic

Quasiturbine - Comparative efficiency with other engines

Quasiturbine Pneumatic and Fuel cell : A perfect Match (using liquid nitrogen)!

A Thermo-Pneumatic Quasiturbine Locomotive (with addendum on subway)

A project intended to make a Quasiturbine liquid nitrogen motorcycle

Quasiturbine Air Car (compressed air vehicle)

CRYOCAR from the Washington State University

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