Not only a Quasiturbine rotary expander can control the pressure, the flow,
and the temperature of an expanding gas, but it can also
recover the pressure energy, and even partially recompress the gas if needed!

Quasiturbine Rotary Expander

The Objective: Expand!

The objective of pneumatic and steam Quasiturbine is to produce mechanical energy, while similar machines can be used with the objective to control the pressure, the flow, and the temperature of an expanding gas while recovering the pressure energy. The dual role of the Quasiturbine turbo-compressor mode applies to large industrial units (including LNG), down to household conditioning heat pumps and geothermal systems.

This chainsaw is shown only as a sample of 1.5 kW QT engine application.
The chainsaw is not available for sale at this time.

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 rapidly recovered in operational cost...

Recovering Pressure Energy

Conventional fossil energies are great, the renewable energies are better, but why not some free energies? The pressure energy of gas pipeline is considerable and it is not harvested in pressure reduction stations; this is a precious mechanical energy that Quasiturbines can recover without any gas combustion and pollution.

Contrary to low temperature thermal waste energy which can be recovered with low efficiency, the low pressure waste energy can be recovered with high efficiency.

The pressure energy in a gaseous line (like in gas pipeline) comes from 2 subtile but important distinct origins: the pressure which initially compresses the gas volume, and the force which is later deployed to maintain constant the pressure in the line (a moving force as the flow is going, regardless of the actual gas expansion, just like if the gas column would be a rigid stick moving forward). To recover the energy of the gas compression, it is better to have some intake cutoff (instead of dissipative restriction at rotary expander intake...) but to recover the energy deployed to maintain the pressure constant in the line, little gas expansion needs to occur, just let the flow go through the rotary expander (with some differential pressure). This has serious applications in particular with gas pipeline energy recovery and underground mining compressed air uses.

Pressure Gas Power

A positive displacement pneumatic motor can be ideally represented (case without truncating the intake) by a piston in an infinitely long cylinder, in which case the power is proportional to the product of the pressure time the flow.

Power (HP) = Pressure (psi) X Flow (cfm) / 229
                                               (As an example: 1 HP = 10 cfm at 22.9 psi)
or (1 m3 / min = 35.3 cfm):
Power (kW) = Pressure (bar) X Flow (m3/min) X 1.70
                                               (As an example: 1 kW = 0.294 m3/min at 2 bar)

If the intake pressure increases, the flow (rpm) increases also, such that generally the engine power increases as the square of the pressure.

Remember that there could be a significant difference between the pressure applied at the motor intake and the actual pressure into the motor chambers. Conventional turbine or piston engines are driven by similar pressure-flow relation (case without truncating the intake).

The Cooling Efficiency Gain

The energy given to reduce the volume of a gas also produces heat, which after thermalization is restituted as cold during expansion. If compression and expansion are done locally without heat transfer, it is a quite good reversible process. However, when done at different locations (like the refrigeration compressor and its remote expansion valve), then the energy balance can be split up to generate simultaneously both heat and cold.

At the expansion valve of a refrigeration circuit using only gaseous state (which was known to be less efficient than liquid-gaseous phase change circuit), the volume of the gas increases and produces cooling, while the moving force of the flow is dissipating high speed kinetic flow energy in that same cool gas, heating it up and so destroying the cooling efficiency. Because the moving force is much less in the case of an incompressible liquid (which has much lower volume and consequently flow) being vaporized through an expansion valve, the efficiency is much higher in phase-change refrigeration circuits. However, in the gaseous state only circuit, if the gas moving force energy is taken out by the Quasiturbine Rotary Expander and used to partially recompress the gas, then both phase-change and no-phase change process become of similar efficiency. This has a beneficial impact on energy and environment, because it does remove the need of unfriendly sophisticated chemical product like Freon and others. This has serious applications in refrigeration, including in co-generation, heat pump and natural gas liquefaction - LNG, where methane can be efficiently used as it own process fluid.

Essentially, the extra cooling power will be equal to the extracted power on the Quasiturbine expander shaft. More pressure power you remove mechanically, less heat power there is in the gas flow to warms it up during relaxation! (See example of calculation below)

Quasiturbine Turbo-Pump
Two Circuits for Expansion or Compression

In the pump mode, a Quasiturbine driven by an external motor has 2 intakes and 2 exits related to 2 quasi-distinct circuits. Each circuit can be used as vacuum or pressure pump, for compressible or non-compressible fluids. The Quasiturbine is a positive displacement pump, and does not make use of aero- or hydro-dynamic flow consideration.

Because each Quasiturbine has 2 quasi-independent circuits, one can be used in expander motor mode, while the other is used as vacuum or pressure pump. In such a set-up, no external motor is needed to drive the Quasiturbine Turbo-pump. There is no need of a central shaft either. Possible absence of check valve is of considerable interest in many applications.

Since the 2 circuits share the moving pivoting blade rotor surface, this mode is mainly suitable to applications where the fluid contamination between the 2 circuits causes no problem, or for uses as vacuum pump. In this mixed mode, the Quasiturbine is at the same time the turbo-engine and the pump and has no shaft in the center, the engine circuit being pressurized at its intake port and the exhaust exit being 90 degrees away. The other pumping cycle intakes by the following port and expels at exit 90 degrees further away. The optimized turbo-pump is derived from the standard Quasiturbine engine with minor manufacturing modifications. The Quasiturbine is a very compact and light device, without power shaft, which allows to pump large volumes with the flexibility of pneumatic propulsion which self adapt to torque variations without damaging the equipment.

Most of the Power Premium Value

Not only energy has a price, but power also! Because utilities will pay a prime value for peak power, storage facility may allow to substantially increase the overall economic of a system (some storage projects do not bother with energy generation, but just buy low cost off peak energy to resell it at a premium during peak periods). Nothing is free, but it could make (economical) sense not to run the system always at optimum efficiency. This is why the engine ability of efficient power modulation is a very valuable one.

Windmill Energy Storage Case:
For example, a windmill could produce a steady power over the day, but thanks to storage, much higher power could be deliver for a short period of time during the peak demand period. This extra power involves equipments and storage facility which demand an extra premium revenu. It could also affect the total efficiency of the system, because it could require not to cut-off as much during such peak, with the advantage to keep supplying the customers. Windmill energy storage is not needed only for low wind period, but to harvest the most energy even when the demand is lower than the power generated, and also to provide supplemental peak power (in excess of the windmill capability) when needed. Because it does not make much sense to store an energy which is needed right away, a simple windmill system could include in addition to the generator, a reversible Quasiturbine compressor - air motor to store exceeding energy only, and to help speedup somewhat the windmill when needed, or to run its generator alone while the windmill is un-clutched (By the way, if you local energy network accepts to store your windmill energy for free, you are lucky, but this will not last for ever...).

Steam Pressure Reduction Station

Conventional valve or pin hole pressure regulator control makes the line pressure energy to be dissipated in heat on the low pressure side of the valve, which overheat the low pressure steam and required some cooling device generally not recovering this energy (often megawatts). Using a Quasiturbine rotary expander removes and converts the line pressure energy into mechanical work, useful for running air compressor, ventilators or generators... An energy and environmental target.

Gas Pipeline Energy Recovery

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). Substantial heat is now given to conventional expansion valve in pure lost, while heat given to the gas at the intake of a rotary expander is essentially all recovered in mechanical energy or electricity.

Because conventional turbines cannot 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. With such a system, any heat added in front of 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 carries 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.

Economics: Take any similar fossil fuel electric generation station, and set the fuel cost to zero, as the pressure energy recovery does not consume any fuel. It is even better than renewable, it is free energy, until the utilities start to charge for it, and make an easy extra income!

Associated Heat Recovery

Pressure energy recovery allows also to recover some low temperature heat as well. On consumer site, substantial amount of wasted low temperature heat can be used to preheat the natural gas just before expansion into the Quasiturbine, increasing the gas volume with direct energy output enhancement, without any additional gas consumption. Heat does not have to come from gas combustion, it could be from industrial processes, geothermal or solar. This technique could apply to all sorts of compressed gas, including high pressure hydrogen storage coupled with engine or fuel cell heat source.

Any source of pressurized gas (pipeline, hydrogen tank, propane, air...) offers heat energy recovery amplification: It is the basis of the open Brayton cycle. Close Brayton cycle also offers this possibility through more heat exchanger at the cold end of the cycle... As an example, fuel cell produces a substantial amount of heat which can be recover through the preheat of the high pressure hydrogen from the feeding tank before flowing through a rotary expander (some cooling) and getting consumed into the fuel cell...

ORC (Organic Rankine Cycle)

Engine suitable for ORC (Organic Rankine Cycle) in Solar, Geothermal and Waste Heat Recovery.

Refrigeration / Heat pump

Why can a Quasiturbine rotary expander double the efficiency of a gaseous phase-only refrigeration system? Because it does remove some line pressure energy (? 50%) which is transformed in heat in conventional regulator and reduces the amount of cold produced. Furthermore the line pressure energy removed is directly usable (? 50%) to recompress partially some of the thermalized gas back toward the main compressor intake. Excess energy is likely to be also available form the rotary expander that could drive for example an auxiliary compressor or an electric generator.

EXAMPLE OF CALCULATION
Essentially, the extra cooling power will be equal to the extracted power on the Quasiturbine expander shaft. More pressure power you remove mechanically, less heat power there is in the gas flow to warms it up during relaxation! As an example, the QT600SC expands 600 cc per chamber and 8 chambers per revolution. At 500 rpm, this is 2,4 cubic meters per minute at intake, for up to 12 kW of output shaft power under 60 psi differential. Every second, the Quasiturbine expander removes (12 kW-sec) 12000 joules of thermal energy out of (2,4/60) 40 liters of 60 psi intake gas (at the expander exit, this volume is about 5 x 40 = 200 liters, if expanded to the atmospheric pressure). This is a removal of 300 joules of heat per liter (or 300 watts out of a 1 liter/sec flow) at intake (60 psi); or 60 joules of heat per liter (or 60 watts out of a 1 liter/sec flow) at exhaust (atmospheric pressure). The cooling temperature gain depends of the gas specific heat capacity. The exhaust gas cooling efficiency is consequently enhanced (and could be even somewhat more, by using intake valve cut-off cycle) compared to the use of a simple valve or pin hole, even if the Quasiturbine expander shaft output power is simply dissipated and lost. However, this shaft power can be re-used, possibly to recompress part of the gas, for a double efficiency gain!

What is the physic of this phenomena? The pressure energy in a gaseous line (like in gas pipeline) comes from 2 subtle but important distinct origins: the pressure which initially compresses the gas volume, and the force which is later deployed to maintain constant the pressure in the line (a moving force as the flow is going, regardless of the actual gas expansion, just like if the gas column would be a rigid stick moving forward). When a gas from a constant pressure line is let to expand, it does it from the fix-constant line pressure which provides pressure energy to accelerate the expanding gas at a constant sustained speed through the pin hole, which kinetic energy provided by the pressure is transformed in heat reducing as much the cold produced.

The benefit of chopping the flow? Let considerer the same average gas flow is now chopped into consecutive equal volumes. Each volume will start expansion with a pressure equal to the feedline, but rapidly the pressure will fall and the pressure energy given into kinetic energy through the pin hole regulator will be less (no more sustained), providing more cooling power. After one chamber has expanded, let open the next one, and later the following, etc. This will provide more cooling power, but because the pressure energy is not dissipated, the successive chambers will be located more and more ahead in the pressure line. Translating the chambers no. 3 at the pin hole location would required to remove the flow pressure energy (pressure time the moving chamber distance), or otherwise it will destruct the cold by dissipating into the gas.

The role of the rotary expander? The rotary expander chopped the flow in successive expanding chambers. But because it does extract the mechanical power associated with the chamber movement, the chambers can all expand at a fix location without the pressure energy, which is gone into mechanical motion. This mechanical motion could be just dissipated outside, but it is a very valuable source of power to compress partially the thermalized gas back toward the main compressor intake, providing a double efficiency benefit (heated compressed gas could move out on a thermally insulated line¸ not to reduce the cooling effect).

Because many have never been exposed to this problematic, it is a largely non-understood principle. Furthermore the Quasiturbine has two separate circuits, one could be the expander one, the other the partial compressor one. Both action accomplished in one device without external or internal shaft at all! (the amount of energy taken from the rotary expander can be controlled by controlling the pressure provided by the partial compressing circuit at an external location where the main compressor is located).

The technique is important for the environment. With a Quasiturbine rotary expander, the efficiency of a gaseous only (like dry air) system reaches almost the efficiency of a phase change liquid-gaseous system, and sophisticated phase change chemical products, often environmentally unfriendly, are not needed anymore! The dual role of the Quasiturbine turbo-compressor mode, applies to large industrial units (including LNG), down to household conditioning heat pumps and geothermal systems.

Please visit:
quasiturbine.promci.qc.ca/ETypeHeatPump.htm
From an Hot Air Engine Reversible
« Quasiturbine Stirling and Short Steam Circuit »

Natural Gas Liquefaction

Using the natural gas itself as an efficient cooling fluid is of considerable interest. Quasiturbine rotary expander allows higher efficiency such as to make it feasible. The Quasiturbine rotary expander allows for individual chambers to expand at a variable reduced pressure during expansion, and therefore reduces the transformation of the gas' kinetic energy into destructive heat. Furthermore, the Quasiturbine mechanically recuperates the gas' differential pressure energy, which can be used to run more compressors and make more refrigeration... for double the energy efficiency gain! A single Quasiturbine in turbo-pump (turbo-compressor) mode could have one circuit used as rotary expander while the other is used to compress back some of the expanded gas. This offers a great enhancement to the thermodynamic cooling machine, especially in high power LNG - Liquid Natural Gas liquefaction stations. Of course, this efficiency enhancement is also available for more modest cooling systems and air conditioning equipment. With Quasiturbine rotary expander, the efficiency of a gaseous only (like dry air) system reaches almost the efficiency of a phase change liquid-gaseous system, and sophisticated phase change chemical products often environmentally unwelcome are not anymore needed.

Mining Applications

Underground mining uses extensively compressed air and consequently expands large compressed air volume. The Quasiturbine is a very compact and light device, without power shaft, which allows to pump large volumes with the flexibility of pneumatic propulsion which self adapts to torque variations without damaging the equipment. Absence of check valve is of considerable interest in many applications. In the underground mines and on explosive construction worksites, it could be used to pump water from compressed air. In pump mode, the Quasiturbine gives a nearly linear flow with the rpm on quite a large range, which makes it a precise flow valve or dosimeter for the chemical industries, or eventually as a powerful rocket fuel injector and mixer driven by the combustion gas itself...

Toward Hydraulic...

Ultimately, a rotary expander used with incompressible fluid like water or oil becomes an hydraulic motor. A Quasiturbine rotary expander can digest gas with a considerable amount of condensate and lubricating oil, but the hydraulic Quasiturbine is designed differently, and both unit should not be substituted one for another.

Flow Metering

Because the Quasiturbine is a positive displacement engine, it does offer a quite precise way to measure the flow in relation to its rpm.

Powerful Mixer

The Quasiturbine central area can be used as a powerful liquid or gaseous state mixer. Centrifuge force tend to move the liquid in the extended diamond corner, but this liquid is propelled inward toward the Quasiturbine center as the configuration changes and the corner is moving near the shorter oval diagonal.

More Technical

Intake Cut Off Valve

Quasiturbine Theory Concept

Quasiturbine Turbo-Pumps

Using the Quasiturbine to Regulate
Natural Gas Pipeline Pressure and Flow-rate
(published in Energy Pulse)