WO2020223544A1

WO2020223544A1 - Expander and nozzle system for converting energy in a working fluid into work

Info

Publication number: WO2020223544A1
Application number: PCT/US2020/030829
Authority: WO
Inventors: Piero Scapini; Glen L. Bostick
Original assignee: Nooter/Eriksen, Inc.
Priority date: 2019-05-01
Filing date: 2020-04-30
Publication date: 2020-11-05

Abstract

An engine or fluid expander is disclosed having a stator receiving a working fluid from a source via a stator inlet and delivering the working fluid via passages in the stator to a rotor so that the working fluid can rotatably drive the rotor and a load coupled to the rotor. The speed of the rotor can be selected so as to produce the power required to drive a load at desired operating speed by selecting the radius R1 of the point of force application on the rotor to be somewhat larger than the radius of the stator inlet radius R2 such that the expander operates at the desired operating speed with sufficient power to drive the load, with the operating speed of the rotor being in inverse proportion to the ratio of R1/R2.

Description

EXPANDER AND NOZZLE SYSTEM FOR CONVERTING ENERGY IN A WORKING FLUID INTO WORK

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 62/841 ,679, filed on May 1 , 2019, which is incorporated by reference herein in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

[0002] Not Applicable.

BACKGROUND OF THE DISCLOSURE

[0003] The high energy density of certain working fluids, such as supercritical carbon dioxide,“sC02”, presents a challenge to the design of mechanical drives powered by such working fluids. The high energy density of such working fluids means that significant energy can be transported in a comparatively lower flowrate than with other working fluids, such as steam/water.

[0004] The reduced flowrate associated with these high energy density working fluids means that mechanical drives, where mechanical output power is both a function of torque and rotational speed, often must run at speeds that require mechanical gearing to be utilized, which reduces the overall efficiency of the system_^ For example, where electrical production is the goal of such systems and when the targeted power production is less than about 100 MW, the operational speed at which such systems operate using such high energy working fluids is typically well above the normal operational speed of electrically synchronous generators. Such high operational speed is due in part to the lower torque generally achievable when compared to other working fluids at the same operating conditions. Synchronous electrical generator speeds are a function of the number of magnetic poles used and the desired electrical frequency, typically 60 Hz for the US and 50 HZ for much of the rest of the world. In applications (e.g., electrical power production or a mechanical drive for pump) when the drive must operate at speeds above synchronous speeds (power) or desired process speeds, mechanical gearing or electrical modulation is required, both of which introduce inefficiency into the system.

[0005] Torque is linearly related to both force and a moment arm. For high energy density fluids and the subsequent low flow rates that accompany them for a given targeted power, the associated momentum (as well as the kinetic energy) of the working fluid is generally reduced as the fluid is distributed to a working area where an appreciable moment arm can be achieved.

[0006] The difficulties/problems identified above are addressed with the proposed inlet nozzle delivery system of the present disclosure. The term “delivery system”, as used in this disclosure, allows the flow of the working fluid to be distributed in discrete passages within a stator from a common location to the points of application on a rotor such that as the fluid exits from the passages in the stator, the energy density of the working fluid does not diminish at the same level as it would if the entire flow were simply expanded to the remote areas through a bulk fluid expansion. In applications where the working fluid has a high bulk modulus, such as supercritical carbon dioxide, sC02, means that even small expansions of the fluid result in significant loss in availability.

[0007] Furthermore, the subject of this disclosure allows one to design and engineer the individual passages in a stator to deliver, at the passage exit or outlet, a fluid with precise process conditions (e.g., flow rates, velocities, pressures, angle of application) suitable for a defined application.

[0008] In application, the subject of this disclosure allows for the generation of high levels of torque to be created with an economically and geometrically suitable moment arm while operating at reduced rotational speeds (RPMs) when compared to other designs using the same working fluid.

[0009] In power generation applications targeting lower levels of electrical production (e.g., < 1 MWe), the impact of the high energy density associated with some working fluids, such as sC02, and the noted impact on momentum to remote locations, have resulted in the general design of these lower power producers having rotational speeds as high as 75,000 RPM. While the resulting configuration is very small in size, the high rotational speed of such a configuration poses significant engineering challenges (e.g., vibration, friction heating, bearing design, gearing to application, and the like) in designing and operating such systems. Furthermore, fabrication of the resulting diminutive equipment for lower power producers (e.g., < 1 MW) presents many challenges as the parts become difficult to handle/assemble. In addition, components of such a system that can be readily available in larger sizes are often limited when working with such a small scale. Also, the design of such gear speed reducers capable of transmitting significant power (e.g., 250 HP or more) and capable of reducing the speed of a small diameter fluid powered expander to the lower speeds needed to drive a load, for example, a mechanical pump or an electrical generator, present a challenge in gearing design and cost.

SUMMARY OF THE DISCLOSURE

[0010] An expander system, comprising a low momentum loss delivery system (i.e. stator nozzle(s)) for delivering a working fluid and a mechanical drive (i.e. rotor) is described having a stator and a rotor in close proximity to the stator with the rotor rotating about an axis common to both the rotor and to the stator. The stator and the rotor are housed in a sealed enclosure or housing. The stator has an inlet generally coaxially with respect to its central axis for receiving the working fluid from a source and for delivering the working fluid to a plurality of stator outlets located on a common radial periphery of the stator relative to the central axis, but potentially at different axially locations along the shaft when parallel rotors are employed, such that the radius of the stator inlet is substantially smaller than the radii of the stator outlets. The working fluid entering the stator inlet has a predetermined amount of energy. As such, with the working fluid flowing through the stator and discharged from the stator outlets into an annular gap or chamber between the outer periphery of the stator and an inner surface of the rotor, the rotor is rotationally driven relative to the stator by the working fluid in the gap or chamber. For a given power output, the rotor’s rotational speed is lower than if the radius of the common radial periphery of the stator outlets were only somewhat larger than the radius of the stator inlet, where the rotational speed of the rotor is approximately in inverse proportion to the ratio of the radius of the stator inlet relative to the radius of the common radial periphery of the stator outlets. Thus, for a predetermined power output of the expander having a corresponding developed torque, the expander’s developed torque is linear with respect to the ratio of the stator inlet radius/the radius of the common radial periphery of the stator outlets. As such, substantially all of the energy of the working fluid is converted into rotational energy of the rotor at a lower rotational speed. The stator inlet is configured to receive the working fluid source, and it has at least one nozzle therewithin that extends downstream from the inlet and defines an annular flowpath within the stator. The stator further has a plurality of outwardly extending flow passages extending from the stator inlet to the stator outlets. Preferably, there is at least one of such flow passages for each of the stator outlets. The flow passages lead from a downstream portion of the stator inlet flowpath to the stator outlets to deliver the working fluid to the annular gap and thus to the rotor, preferably in a substantially tangential direction to the rotor. The rotor has a plurality of rotor flow paths. The working fluid discharged from the stator outlets into the annular gap flows to the inlets of the rotor flow paths, or to otherwise interact with the rotor flow paths, so as to transfer momentum from the working fluid to the rotor to rotationally drive the rotor relative to the stator.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Fig. 1 is a cross-sectional view of an expander of the present disclosure having a stator and a rotor mounted in generally face-to-face relation within an enclosure, the rotor being rotatable about a central axis, with the stator being supplied with a working fluid via a central inlet and distributing the working fluid to a plurality of stator outlets via fluid passageways extending generally outwardly in the stator, for communication of the working fluid to a plurality of rotor flow paths provided in the rotor so that the fluid rotatably drives the rotor;

[0012] Fig. 2 is a vertical cross section taken along line 2 - 2 of Fig. 1 illustrating a front face view of the rotor and the stator illustrating a common circumference or periphery of the stator having a plurality of stator outlets spaced therearound for the discharge of the working fluid into an annular gap between the outer circumference of the stator and the rotor, each of the rotor flow paths of the rotor has an inlet and an outlet, with each of the rotor flow path inlets being in communication with the working fluid in the annular gap;

[0013] Fig. 3 is a view of an alternate embodiment of an expander of the present disclosure having an enclosure where the front and the back of the enclosure are flat having a stator and a rotor therein;

[0014] Fig. 4 is a vertical cross section taken along line 4 - 4 of Fig. 3 similar to Fig. 2, but illustrating another embodiment of the stator and the rotor where the fluid outlets of the stator are each located within a respective“saw tooth” formed in the outer periphery of the stator such that the working fluid discharged from each of the stator outlets is discharged into the annular gap between the stator and the rotor in a generally tangential direction relative to the outer circumference of the stator so as to enter the inlets of the rotor flow paths; [0015] Fig. 5 is a portion of Fig. 4 shown on an enlarged scale;

[0016] Fig. 6 is a cross-sectional view similar to Fig. 1 of an expander of the present disclosure having an enclosure of a different shape than the enclosures shown above, where one half of the enclosure is of a convex semi-elliptical shape and the other half is“bean-shaped”;

[0017] Fig. 7 is a cross-sectional view similar to Fig. 1 of still another expander of the present disclosure, where one half of the enclosure is a convex semi-elliptical shape and the other half is a flat planar shape;

[0018] Fig. 8 is a view of the expander shown in Fig. 7, further illustrating the location of seals (as shown by the dotted circles) for sealing the enclosure, the stator, and the rotor and its drive shaft relative to the enclosure;

[0019] Fig. 9 is an enlarged portion of the expander shown in Fig. 1 illustrating the location of a circumferential seal between the outer portions of the stator and the rotor, and illustrating one of a plurality of the flow passageways leading from the working fluid inlet of the stator to the outer circumference of the stator and for discharging working fluid within a sealed annular gap between the outer circumference or periphery of the stator and an inner circumference of the rotor for supplying working fluid at relatively high pressure to the inlets of the rotor flow paths of the rotor so that the rotor is rotatably driven by the working fluid flowing through the rotor flow paths and discharged into the relatively lower pressure within the enclosure;

[0020] Fig. 9B is an enlarged view taken along line 9B of Fig. 9 illustrating a labyrinth-type seal as well as a spring type seal for sealing between the stationary stator and the rotating rotor;

[0021] Fig. 9C is an enlargement of a portion of the outer stator and rotor illustrating how a rotor flow path, such as a J-bucket or air foil type fluid blade is mounted in the outer portion of the rotor to receive fluid within a seal annular gap between the stator and the rotor in such manner that the fluid will exert a force on the rotor so as to rotate the rotor relative to the stator;

[0022] Fig. 10 is an exploded view of Fig. 9 illustrating the major components of the expander of the embodiment of the expander shown in Fig. 9;

[0023] Figs. 1 1 - 16 are similar perspective views of the stator shown in Fig. 1 having different arrangements, for example and not by way of limitation, of the working fluid inlet and of the working fluid passageways leading from the working fluid inlet to the outer circumference of the stator with the flow passageways being of different cross-sectional shapes and having different fluid outlets, as specified in the notation on each of these drawing figures;

[0024] Figs. 17, 19 and 21 illustrating perspective views, for example and not limitation, of three different arrangements and shapes of fluid passageways within the stator for the flow of working fluid from the working fluid inlet of each stator to its outer circumference, and with Figs. 18, 20 and 22 being side elevational views of Figs. 17, 19 and 21 , respectively;

[0025] Figs. 23 - 26 are perspective views of “J” bucket rotor flow paths of different cross sections and shapes forming nozzles of different types, for example and not by way of limitation;

[0026] Fig. 27 is a schematic diagram of two of the expanders of the present disclosure supplied by working fluid from a common source where each of the expanders drives a respective load, such as an electrical generator or the like;

[0027] Fig. 28 illustrates a portion of the outer circumference of the stator and a portion of the inner circumference of the rotor and the annular gap therebetween with a plurality of air foil type in such gap and constituting at least a part of the rotor flow passages;

[0028] Fig. 29 illustrates another embodiment of the expander of the present disclosure in which there are multiple rotors connected to a common shaft such that fluid flow is presented to each rotor through proper sizing of the stator nozzles/pathways.

[0029] Corresponding reference characters indicate similar parts of the drawings throughout this speciation.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0030] In the design of an expander, such as a rotational engine having a rotor powered by a suitable working fluid, the Instantaneous Power Vector (P) for the engine is equal to the Torque (T) around the center of mass of the rotor crossed with the rotational or angular velocity (w) of the rotor. In scaler terms, the Power (P) generated by a thermodynamic engine is equal to the torque (T) multiplied by the rotational velocity or speed of the rotor (in RPM) x a constant K. In the English system, Power (P) in Horsepower (HP) = Torque (T) in pounds-feet (Ib-ft) x RPM ÷ 5252. In the SI system, Power (P) in Kw = Torque (T) in Nm x (w) in radians/second x K (9549). For a given design power output (P) for an engine or expander, the engineering challenge is to find the right optimization of Torque (T) and rotational velocity (w) not only for performance but also for the cost and service life of the engine.

[0031] If a rotational engine is driving a load, such as an electrical generator, it is desirable for the rotational speed of the engine’s rotor to be equal (or to be within a low multiple or a large fraction) of the synchronous frequency (f) of the electrical generator so to avoid the necessity of providing speed reducing (or speed increasing) gearing for connecting the rotor to the load and for the load so that the load can be operated at its desired synchronous speed or frequency (f). In the United States and in a few other countries, the typical synchronous speed or frequency of an electrical generator is 60 Hz (3,600 rpm), while for many other countries the synchronous frequency is 50 Hz (3,000 rpm). However, the desired rotational speed of an expander of the present disclosure can be designed to match the speed of the expander to the synchronous speed of the load by conserving the fluid energy in the distribution system (e.g., in the stator or expansion) and delivering the fluid to a rotor of sufficient width such that targeted torque maybe achieved more easily.

[0032] However, for radial expander engines, the Force (F) is a function of the radius R1 because as the radius increases, so does the distance from the center of mass of the rotor to the point of application of force on the rotor. The rotor, which creates the Torque, also has a certain width or depth. Thus, for a fixed rotor width, the working area of the rotor (as described in the next paragraph) over which the working fluid can react increases linearly with the radius R1 . More specifically, the working area of a rotor is the total rotor flow path area (or bucket flow area) through which momentum is transferred from the working fluid to the rotor as the working fluid flows from the outlets of the stator through the rotor flow paths of the rotor and is discharged from the rotor.

[0033] The amount of working fluid that is supplied to a rotary engine or expander that is required to operate the engine to drive its load at its desired speed and target power is determined by the source of the working fluid and its condition (that is, the energy or enthalpy contained in the working fluid) that is supplied to the inlet of the expander, and a sink (nominally, the outlet of the expander). These factors determine the thermodynamic conditions for the expander. If the radius R1 is increased, and if the mass flow of the working fluid flowing through the engine remains the same, the operating speed of the engine will be decreased while producing the same target power necessary to drive the load rotor flow path. This is critical for the engine to develop its desired torque T. This is a large part of the challenge when working with a high energy density fluid like C02. More specifically, with the larger radius R1 that is needed to achieve the required torque T, if a working fluid, such as C02, is expanded uncontrollably into a larger area of the expander within its housing, there can consequently be a decrease in the C02 enthalpy. That enthalpy decrease means that less work can be achieved for a given mass flow of the working fluid. The term“enthalpy” is defined to mean a property of a thermodynamic system that is equal to the system's internal energy plus the product of its pressure and volume. In a system enclosed so as to prevent mass transfer, for processes at constant pressure, the heat absorbed or released equals the change in enthalpy.

[0034] The stator/nozzle of the expander of the present disclosure delivers the working fluid to the rotor inlets in such manner as to result in a lower operational speed (w) of the rotor and to develop the desired torque T at this lower operational speed. In the rotational engine of the present disclosure, the number of rotor flow paths or buckets on the rotor is such so as to achieve and maintain desired velocities of the working fluid discharged from the rotor buckets. However, a larger radius R1 of the rotor may result in an undesirable increase in a potentially standing reservoir of fluid in an annular gap between an inner circumference of the rotor and an outer circumference of the stator where the inlets to the rotor flow paths are located. More specifically, for a fixed spacing or gap between the stator and rotor and for a fixed width of the rotor, the volume of the annular gap increases with the length of radius R1 because, as will be recognized, the length of the working area is effectively the circumference of the inlets or entrances to the rotor flow paths of the rotor. Any stagnant or low velocity working fluid within this annular gap creates undesirable drag forces on the rotor and may dissipate the high velocity fluid being discharged from the stator outlet nozzles. This drag and/or dissipation retards the goal of the stator, which is, in general, to accelerate the flow of the working fluid to the rotor, but in such manner as to minimize pressure losses of the working fluid so that the kinetic energy of the working fluid is transferred into the rotor. Thus, minimization of the annular gap is desired. The stator has an inlet for the working fluid and a series of stator flow passages through which the working fluid flows. In practical terms, the thickness of the annular gap is the spacing between the outer circumference of the stator and the inner circumference of the rotor. If the stator inlet radius R2 is only somewhat smaller than the rotor radius R1 (as shown in Fig. 2) , the rotor will be driven at a high rotational speed, typically much higher than the desired speed of its load. Alternatively stated, the radius R1 is preferably somewhat larger than radius R2 such that there is adequate structure in the rotor to support the stator flow passages 1 1 and the outlets 13. The term “the radius R1 is preferably somewhat larger than radius R2” will be understood to mean that radius R1 is about 20% on the low end larger than radius R1 . It also should be recognized that a larger radius R1 creates a larger potential for leakage of the working fluid from within the working area between the stator and the rotor both radially inwardly and transversely outwardly of the annular gap between the stator and the rotor such that effectiveness of seals is important. For example, if the radius R2 is equal to 1 .0 inch (2.54 cm.), if the radius R1 is only slightly larger than R2 such that the rotational speed of the rotor shaft is 75,000 RPM, and if the desired operating speed of rotor shaft 33 is 3,600 RPM, then the radius R1 will be 20.83 inches (52.9 cm.).

[0035] Succinctly stated, and as shown in the drawings of this disclosure along with reference characters shown in the drawings that will be described in greater detail hereinafter, a low momentum loss expander system 1 of the present disclosure is for use with a working fluid flowing from a source S, where the working fluid has an amount of energy or enthalpy therein, and where the expander system produces a target power sufficient to drive a load. The expander system comprises a stator 5 and a rotor 7 with the rotor configured to rotate relative to the stator about an axis A - A common to both the rotor and to the stator. The stator has a stator inlet 9 generally coaxial with respect to the axis for receiving the working fluid from the source and for delivering the working fluid to the rotor by way of a plurality of passages 1 1 in the stator. The stator passages are configured to be in fluid flow connection with the stator inlet and to extend from the stator inlet to a plurality of stator outlets 13 located radially outwardly of the stator inlet on an outer circumference 15 of the stator concentric with the axis. The rotor has an inner circumference 27 concentric with the axis that is located radially outwardly of the circumference of the stator outlets with an annular gap 25 between these circumferences. The rotor has a plurality of substantially similar rotor flow paths 31 .

[0036] Each of the rotor flow paths is further configured so that the working fluid can act upon each rotor flow path at a point of application that can be at any location along the rotor flow path with a force that rotatably drives the rotor about the axis. The points of force application form a generally circular locus of such points concentric with the axis having a radius R1 with respect to the axis. The stator inlet has a respective radius R2 with respect to the axis such that the radius R2 is smaller than the radius R1 and configured so that the working fluid entering the stator inlet can flow through the stator passages and can be discharged from stator outlets into the annular gap so that the working fluid can act upon the rotor flow paths and rotatably drive the rotor relative to the stator. When the radius R1 is substantially larger than radius R2, the expander of the present disclosure can generate the target power and can operate at a substantially lower speed than if the radius R1 is only somewhat larger than radius R2, whereby the operating speed of the expander having such substantially larger radius R1 is approximately in inverse proportion to the ratio of R1/R2. Hereinafter, the expander 1 will be described in greater detail in relation to the drawings.

[0037] It will also be understood that the expander of the present disclosure, and more specifically its stator and rotor work to overcome the above-mentioned design issues and results in an expander that operates at a desired rotational speed, and develops the power required to operate a load at or closer to its intended speed, while maximizing the change in enthalpy of the working fluid.

[0038] Further, the mechanical drive expander of the present disclosure is a low loss delivery system that makes use of a low momentum loss delivery system, which distributes a working fluid via multiple passages of potentially varying cross sections, thus gaining the benefit of having a high energy density of the bulk working fluid being conserved and/or having the fluid momentum adjusted.

[0039] Still further, the expander of the present disclosure comprises a rotary outflow expander in which a rotor assembly is fed a working fluid via a delivery system having a plurality of enclosed passages within a stator that is generally concentric with the rotor. Those passages direct the incoming working fluid from a generally common central inlet to a remote geometry of stator fluid outlets radially distal from the common central stator inlet location. The stator fluid outlets have a larger overall diameter or cross sectional area than the common central stator inlet location. With such configuration the point of application has larger total cross section than common area. The working fluid transfer maintains, as much as possible, the overall energy of the working fluid while adjusting the momentum of the bulk fluid in a manner that is advantageous for the downstream user of the working fluid (e.g., an expander). This allows the working fluid to generate a desired power output of the expander at a lower operating speed of the rotor. In turn, this reduces the demand on a gear speed reducer to drive a load, such as an electrical generator, to produce output power (e.g., electrical power) at a lower operational speed. In the case of an electrical generator, the generator is driven at a speed so as to produce electricity at the normal frequencies of a conventional power grid, such as at about 1800 or 3600 Hz by a lower loaded gear when compared to other conventional expander designs.

[0040] The fluid discharged from each of the individual passages in the stator can be sub-sonic, sonic, or supersonic. Flow conditions within the delivery system are adjusted by decreasing, increasing, or both decreasing/increasing the cross-sectional area of the individual flow paths as well as the total number of flow paths. The cross-sectional area adjustments can be smooth and continuous, or can be achieved in step changes. The cross-sectional area of the stator passages, while generally curvilinear, can also be circular, elliptical, or of any polygonal cross section (e.g., 3 sides, 4 sides, ... n sides).

[0041] Furthermore, the number of stator inlets to the delivery system need not be equal to the number of stator outlets from the delivery system. That is, the delivery system can combine inlet passages in the stator to have a reduced number of outlets or can create multiple outlets for a given inlet by creating multiple branches from the single inlet all within the delivery system.

[0042] The system of this disclosure comprises a delivery pipeline or other common inlet that supplies operating fluid to the stator where the incoming working fluid has a predetermined potential energy level or enthalpy. The working fluid is provided to a stator inlet of the distribution system, which can have an inlet cone or spike downstream from a common working fluid inlet such that the inlet and the cone form an annular inlet of decreasing annular cross section (a converging nozzle) that is in communication with a fluid delivery system comprising fluid passages within the stator leading from the annular inlet to stator outlets at the distal end of the passages. Each of these passages may be optionally provided with an integral inlet nozzle and with an integral outlet nozzle. The passages can include branches and/or junctions. The integral outlet nozzles are preferably oriented to discharge the working fluid into a gap or space between the outer periphery of the stator and an inner surface of the rotor in general tangential direction relative to the outer periphery of the stator. However, in accord with the broader aspects of this disclosure, the outlet nozzles can be directed in any desired orientation to best suit application. While any number of working fluids may be used in accord with this disclosure, one preferred working fluid is carbon dioxide (C02), and more specifically supercritical carbon dioxide (sC02).

[0043] The stator is preferably a stationary disc having a plurality of the above-said fluid passages therein including outlet ports leading to a respective rotor flow path associated with a rotor where the rotor flow paths can be conventional curved fluid blades of general“airfoil” shape or can be in the form of “J” buckets, as will be hereinafter described. The rotor and the stator are enclosed in a pressure retaining enclosure or housing. The rotor along with its rotor flow paths are attached to a shaft for transferring rotational mechanical energy generated by the transfer of momentum of the working fluid flowing through the rotor flow paths in the rotor. The shaft is journalled in bearings carried by the enclosure, and seals are provided for sealing the shaft to the enclosure. View ports can be provided in the enclosure allowing for visual examination of select areas of interior of the enclosure and the components therein, without having to open or otherwise disassemble the components in the enclosure. Warmup ports and startup port(s) can also be desirably included in the enclosure.

[0044] Turning now to a more detailed description of the expander system of the present disclosure, as shown in in the drawings, a low momentum loss expander system of the present disclosure is generally indicated in its entirety at 1 for delivering a working fluid to a mechanical drive, expander or engine 3. Expander 3 has, a stator 5 and a rotor 7 in close face-to-face proximity to one another. The rotor rotates about a central centerline or rotational axis A - A common to both the rotor and to the stator. The stator 5 has an inlet, generally indicated at 9, which is generally coaxial with respect to the axis A - A. Inlet 9 receives pressurized working fluid from a source S, as best shown in Fig. 27, and delivers the working fluid to a plurality of stator flow passages 1 1 that communicate to a plurality of stator outlets 13 (as best shown in Figs. 5 and 1 1 - 16. Outlets 13 are located on a common outer radial periphery or outer circumference 15 of stator 5 relative to the axis A - A. As discussed earlier, R3 is the radius from the axis A - A to the stator outlets 13. Figure 2 shows the radius R2 , of the stator inlet 9 is substantially smaller than the radius R3 . Also as mentioned earlier, the distance from the center of mass of the rotating rotor 7 to the point of force application on the rotor 7 by the fluid discharged from the stator outlets 13, is labeled“R1” as shown in Fig. 2. More precisely and as noted above, the moment arm for the rotor 7 that generates the required torque T is dependent on the radial distance R1 from the center of mass of the rotating rotor 7 (from axis A - A) to the point of force application on the rotor 7 by the fluid discharged from the stator outlets 13. There is a generally an annular gap 25 between the outer circumference 15 of the stator 5 and the inner circumference 27 of the rotor 7. As previously described, radius R1 is somewhat radially outward of the outer circumference of the stator 5 and is located on the locus of the point of force application by the working fluid on the rotor flow paths. For example, the width of this gap 25 is desirably as small as practicable and, for example and not by way of limitation, can range between about 0.003 inch (about 0.07 mm.) and about 0.25 inch (5 about mm.) or more, depending on the length of radius R1 .

[0045] The working fluid entering the stator inlet 9 has a predetermined amount of potential energy (or enthalpy) such that with the working fluid flowing through the stator and being discharged from the stator outlets 13 into the gap 14 between the stator outer circumference 15 and the rotor 7 inner circumference rotationally drives the rotor 7 at a lower rotational speed than if the radius R1 is only somewhat larger than the radius R2 of the stator inlet 9. It will be recalled that the radius R1 is stated to be the locus of the points of force application on the rotor flow paths of the rotor, and the radius R2 is the radius of the stator inlet. The rotational speed of the rotor is approximately in inverse proportion to the ratio of the radius R1 relative to the radius R2 (i.e., R1/R2). For example, if the radius R1 is about twice radius R2, the rotational speed of rotor 7 is about half the speed for the same power production if the radius R1 and R2 were substantially equal. Accordingly, for a predetermined power output, the expander 3 has a corresponding developed torque T such that the developed torque of the expander is linear with respect to the R1/R2 ratio. As a result of such configuration, substantially all of the potential energy of the working fluid is converted into rotational energy of the rotor at a lower rotational speed than if R1 is only slightly larger than R2. In accord with this disclosure, the rotor 7 and thus radius R1 can be of any desired radius necessary to generate the target torque required to drive the load coupled to the output shaft of the expander at a desired operating speed. R2, can be about 1/2 inch (1 .24 cm.)) and rotor R1 can be as large as about 44 inches (1 1 1 .8 cm.) and rotational speeds can vary, in general, between 400 rpm and 60,000 rpm.

[0046] As noted, the stator inlet 9 is configured to receive the working fluid from source S (as shown in Fig. 27) of pressurized working fluid. As shown, an inlet nozzle 17, and preferably but not necessarily a converging inlet nozzle, extends downstream from inlet 9 within the stator 5. The inlet nozzle 17, as shown in Figs. 1 , 3, 5, and 7 - 10, is a converging nozzle, but within the broader aspects of this disclosure, it can also be a diverging nozzle or a converging-diverging nozzle. The outer wall 18 of nozzle 17 (i.e., the inner cylindrical wall of inlet 9) is of a substantially constant diameter. The converging inlet nozzle 17 is formed by a conical spike or cone 19 extending along the centerline A - A with the apex of the conical spike pointed toward the incoming working fluid from inlet 9 so that the outer surface of the conical spike and the inner cylindrical surface 18 of the inlet form a converging annular flowpath therebetween. The included or conical angle of cone 19 is preferably about 20°, but it can vary considerably. For example, the conical angle can range between about 10° and about 35° or more, depending on the flow characteristics of the working fluid. Also, the cone 19 can have flow straightening fins, channels, or contours for straightening the flow of the working fluid in the annular inlet or to impart a rotational velocity to the working fluid as it is fed to the stator passages 1 1 .

[0047] As shown in Fig. 9, a hub 21 is provided at the downstream end of the converging inlet nozzle 17 having a plurality of passage inlets 23 each leading to a respective stator flow passage 1 1 . As best shown in Figs. 1 1 - 16, hub 21 has a plurality of passage inlets 9 therein. Preferably (but not necessarily), there is at least one such inlet 9 for each of the flow passages 1 1 in stator 5. Each passage inlet 23 is, preferably, in the form of an inlet nozzle 23 in hub 21 leading to a respective one or more of the stator flow passages 1 1 . The stator flow passages 1 1 extend from its respective inlet passage nozzle 23 in hub 21 to its respective stator outlet 13 on the outer periphery or circumference 15 of the stator 5. The inlet passage nozzles 23 can either have a smooth transition in the upstream face of hub 21 or they can be cut with individual sections for each inlet passage nozzle. As shown in Figs. 1 , 2, 4, 5, 9 and 10, the stator outlets 13 deliver the working fluid to the rotor via the space or gap 25 between the outer periphery 15 of the stator and an inner surface 27 of rotor 7. Each of the stator flow passages 1 1 preferably, but not necessarily, has a generally circular, curvilinear, or polygonal cross section, and can have either a smooth or roughened inner surface. The face of hub 21 along with the passage inlet nozzles 23 therein can be contoured or straight-faced and they can be tilted into the flow of incoming the working fluid in inlet nozzle 17, tilted away from the flow, or normal (perpendicular) to the direction of flow of the incoming working fluid. The sum of the cross-sectional areas of the passage inlet nozzles 23 is preferably, but not necessarily, as large as possible so that substantially no step or lip exists at the inlet nozzles 23. Different end views of hub 21 , as taken along line 1 1 A - 1 1 A of Fig 9 and as shown in Fig. 1 1 A— 16A, illustrate different arrangements of passage inlet nozzles 23 in hub 21 . It will be noted in Figs. 1 1 A - 16A that the arrangements of the passage inlet nozzles 23 in hub 21 resemble the appearance of a“revolver” cylinder of a revolver-type hand gun.

[0048] As shown, the inlet nozzles 23 in the end face of hub 21 are preferably, but not necessarily, in the same plane perpendicular to axis A - A. The inlet nozzles 23 can be of different sizes (diameters) and shapes with contours worked into the hub 21 or in inlet cone or spike 19 so as to define a common inlet and/or the sloped portion on the interior of the converging inlet nozzle 17 that minimizes any pressure drop as the working fluid enters the passage inlet nozzles 23 and so as to facilitate fluid delivery to stator passages 1 1 . The number of passage inlet nozzles 23 in the end face of hub 21 and the number of passages 1 1 in stator 5 is preferably at least two, and more preferably would include as many as possible given the size of the passage inlet nozzles 23 in the end face of the hub so as to maximize the inlet areas of the passage inlet nozzles in hub 21. While the cross section of the passages 1 1 is preferably identical at any point along their length, the cross section or configuration of each passage 1 1 may be constant or may vary along its length.

[0049] Still further, it will be appreciated that while the stator passages 1 1 are preferably generally parallel to one another within stator 5, each passage can follow any desired flow path within the stator 5. Preferably, passages 1 1 have similar frictional pressure drops so as to not unduly restrict the flow of the working fluid from inlet 9 to outlets 13. The passages can, however, be heavily contoured with bends and the passages can be bent in a single or multiple planes, as generally shown in Figs. 17 - 22. In a preferred layout of the passages 1 1 in stator 5, the passages can include a degree of rotation (as shown in Figs. 17, 19 and 21 ) to form a spiral, helical, or helical-like configuration enabling the passages to convert the bulk translational motion of the flow of the working fluid upstream of the inlet 23 (which are, at their downstream ends, generally parallel to axis A - A) to form a rotational flow at the discharge of the working fluid from the stator outlets 13 into gap 25. While each of the passages 1 1 is shown to have a single inlet and a single outlet, it will be understood that each passage can have multiple outlets 13, or the flow from two or more of the passages 1 1 can be combined to discharge from a single outlet 13. Still further, the passages 1 1 can be configured to combine or to converge such that the number of outlets can be fewer than the number of inlets, and collection chambers (not shown) can be provided within each passage from which flow of the working fluid can be directed to the final discharge outlets 13. Still further, in accord with this disclosure, the passages 1 1 can take on a helical or helical-like spiral within stator 5 so that the stator outlets 13 discharge the working fluid into gap 25 in a generally tangential manner. While the hydraulic diameter of passages 1 1 may be of any desired dimension, it generally will range between about 0.1 mm. to about 100 mm., depending on the power output of the drive expander 3.

[0050] Various arrangements for the inlets 1 1 in the upstream end face of hub 21 are illustrated in Figs. 1 1 A - 16A. Preferably, but not necessarily, such flow from the stator outlets 13 into gap 25 and thus to rotor 7 is in a substantially tangential direction by means of outlet nozzles 29 formed in stator outlets 13, where the angle of the fluid discharged from outlets 13 is generally tangential, yet can include angles up to about 30°. The rotor 7 has a plurality of rotor flow paths, as generally indicated at 31 , for having the working fluid in gap 25 transfer momentum to the rotor via the rotor flow paths so as to rotationally drive the rotor 7 about axis A - A relative to the stator 5. The outlet nozzles 29 can be of any desired shape and size so as to best generate the desired rotor torque or the desired rotor speed while reducing frictional losses of the working fluid flowing through the stator passages 1 1 . The rotor flow paths 31 will be described in greater detail hereinafter in relation to Figs. 23 - 26.

[0051] As shown in Fig. 1 , rotor 7 is mounted on a shaft 33 such that the shaft rotates with the rotor so as to perform useful work, such as to drive a load (e.g., an electrical generator G, as shown in Fig. 27). The rotor 7, the shaft 33, and the stator 5 are coaxially mounted on axis A - A within a sealed housing 35 through which the stator fluid inlet 9 and shaft 33 sealably extend. Of course, shaft 33 may be directly coupled to a load or to a geared speed reducer or increaser (not shown) that may be used to drive the load in such manner that a load, such as an electrical generator, can be driven at a desired rotational speed. The housing 35 has housing parts 35a, 35b that are sealably secured together to form the housing. As shown in Figs. 1 , 9 and 10, housing 35 has a generally elliptical shape for efficiently retaining internally pressurized working fluid therein, but other housing shapes, such as are shown in Figs. 3 and 6 - 8 may be used. Of course, other shaped housings, such as spherical or part-spherical can be utilized.

[0052] Shaft 33 is rotatable relative to the housing and is journalled relative to the housing in a suitable bearing 37. The working fluid, after performing work on the rotor flow paths 31 of rotor 7 is discharged from the rotor into the relatively lower pressure within housing 35. The housing has one or more fluid outlets 39a, 39b, which return the working fluid to the source S at a lower pressure for being reheated or otherwise recharged. A rotor isolation (or shear limiting) plate 41 is mounted within enclosure 35 in close proximity to the rotor 7 for substantially isolating the rotating rotor from the fluid within the enclosure to as to minimize windage losses of the rotor rotating within the fluid contained within the enclosure. As best shown in Figs. 9 and 10, a thermal insulation layer 43 is provided on the outside face of stator 5. The thermal insulation layer extends axially on the outside of inlet 17 so as to thermally insulate the inlet 17 upstream of hub 21 thereby to insure that thermal energy is retained in the working fluid prior to its being admitted into stator passages 1 1 . It will be appreciated that the lower pressure and thus lower temperature working fluid within housing 35 may tend to cool the incoming working fluid in inlet 17.

[0053] As shown in Figs. 17 - 22, each of the stator flow passages 1 1 has a proximal end 45, which is its inlet passage nozzle 23 located at the inlet end face of hub 21 joining the annular flowpath 17 of the stator inlet 9 and a distal end 47 constituting the stator outlet 13. As noted, the stator outlet 13 is preferably in the form of an outlet nozzle 29 so as to discharge the working fluid from the flow passages with as much momentum as possible into gap or space 25 between the stator and the rotor.

[0054] As best shown in Figs. 9 and 10, the stator 5 is shown to have an outer portion 49 extending radially outwardly beyond the common radial periphery or circumference 15 of the stator in face-to-face relation with an outer portion 51 of rotor 7. The stator has an inner portion 53 extending radially inwardly from the common radial periphery 15. Inner stator portion 53 is preferably in face-to-face relation with an inner portion 55 of the rotor. Spaced radially inwardly from circumference 15, an inner seal 57 is provided between the inner stator portion 53 and the inner portion 55 of the rotor. Spaced radially outwardly from circumference 15, an outer seal 59 is provided between the outer stator portion 51 and the outer rotor portion 51 . Seals 57 and 59 define the above-noted sealed annular chamber or space 25 enclosing the stator outlets 13 and the inlets to the rotor flow paths 31 (as will be described hereinafter) such that upon the working fluid being discharged from the stator outlets 13 into the annular chamber 25, the working fluid is in communication with the inlets to the rotor flow paths. The seals 57, 59 can be a labyrinth seal, as best shown in Fig. 9B, so as to substantially seal the stator outlets 13 relative to the rotor and to permit rotation of the rotor relative to the stator while maintaining these seals. Alternatively, seals 51 , 53 can be spring biased seals or seals of any other suitable design for a sliding seal between the rotor and the stator. As shown by the dotted circles in Fig. 8, seals are provided for sealing the inlet 9, and shaft 33 relative to housing 35. It will be appreciated that additional seals can be provided on the inside of the rotor that is common to the shaft 33 and that perforations (not shown) can be provided in the rotor so that pressure differentials across the portion of the rotor that is in contact with shaft are minimized thus allowing for thickness of these components to be reduced.

[0055] As best shown in Figs. 2, 5, and 23 - 26, each of the rotor flow paths 31 is, preferably, so-called J-bucket 61 rotor flow path that is curved along its length from its inlet 63 to its outlet 65 and decreases in cross-sectional area (that is, it converges) along its length so as to accelerate the working fluid flowing therethrough and to thus transfer the momentum of the working fluid flowing through the rotor flow paths so as to rotatably drive rotor 7 relative to stator 5. The rotor flow path inlets and outlets can be converging nozzles, diverging nozzles, or converging/diverging nozzles as the flow of the working fluid moves through the rotor flow paths from the high pressure region in gap 25 to the lower pressure region outside of the rotor 7 within housing 35. The nozzle delivery system for supplying the working fluid to gap 25 imparts a degree of impulse to the rotor. Also, by providing a relatively large number of rotor flow paths 31 in rotor 7, substantial disruptions in the working fluid in gap 25 are minimized. This minimizes any flow hindrance and lessens any impacts of the flow of the working fluid to the rotor and does not degrade performance of the expander 3. Alternatively, the rotor flow paths can be conventional air-foil blades (not shown) in a manner well known to those skilled in the art so as to rotatably drive the rotor. It will be appreciated that additive manufacturing techniques, such as 3-D printing, may be used to fabricate rotor 7 with the above described J-bucket or air foil rotor flow paths formed on the rotor.

[0056] The inlet 63 of each J-Bucket tube is configured and positioned relative to annular gap 25 to receive working fluid from within the gap as it is discharged from stator outlets 13. As shown in Fig. 9 and more particularly in Fig. 9C, the outer portion 51 of rotor 7 has a plurality of slots, as indicated at 60. Each of these slots is configured to receive a respective J-Bucket tube (which is shown in cross section in Fig. 9C) with its inlet 63 positioned within its respective slot 60 to receive fluid from gap 25. It will be appreciated that the inlet 63 faces“out of the paper”, as shown in Figs. 9 and 9C, and while the inlet 63 may project into annular gap 25, it is preferred that the inlet be out of the slot and be within its slot 60 so as to reduce associated pressure drops within the gap. The fluid pressure within the gap forces fluid into the inlet 63 and through the rotor flow paths in such manner as to rotatably drive the rotor. As the fluid enters the inlet 63 of the J-bucket, it is accelerated through the J-Bucket tube and is discharged through outlet 65 into the housing 35 in a direction preferably tangent to the outer circumference of rotor 7, as shown in Figs. 2, 4, and 5. This imparts a force on the rotor that rotates the rotor in counter-clockwise direction, as shown by the arrow labeled CCW in Fig. 2. In Figs. 2, 4 and 5, the J- bucket outlets 65 are shown to be on the outside of rotor 7 and to project into the interior of housing 35. However, it will be understood that the outlets 65 need not be on the outside of the rotor, but rather the outlet can be flush or even somewhat recessed in the exterior of the rotor. As shown in Figs. 9 and 9C, the radial height of gap 25 is illustrated on a greatly exaggerated scale for purposes of illustration. It will be understood that the radial height of the gap desirable should be as small as practicable, preferably a small fraction of an inch or a few millimeters.

[0057] Various configurations for the stator inlet 9 and inlet nozzle 17 are illustrated and described in Figs. 1 1 - 16. As shown, the arrangement of the passages 1 1 in the stator 5 can take on various arrangements and shapes. Each of these views has a cross sectional view of the annular inlet 19 portion of the inlet flowpath taken along the cross sectional line 1 1 A— 1 1 A of Fig. 9 at the upstream face of hub 21 showing the upstream or proximal ends of passages 1 1 in the stator. These cross section views are indicated at 12A, 13A, ..., 16A, and depict different arrangements for the inlets of passages 1 1 in the stator.

[0058] Figs. 17 - 22 depict different arrangements and shapes of the passages 1 1 in stator 5, and further illustrate different arrangements of the passage outlets 13 on the periphery or circumference 15 of the stator. It will be understood in Figs. 17 - 22 that only the passages 1 1 are shown, and the structure of the stator has been removed for purposes of clarity so that the passages can be seen. It will be further appreciated that, as noted above, the passages or flowpaths can be arranged in a helical or spiral manner with respect to axis A - A within stator 5, and that such arrangements and shapes of the passages or flowpaths can be fabricated using 3-D metal printing techniques. [0059] As shown in Figs. 4 and 5, the outer periphery 15 of stator 5, instead of being a smooth circular surface, can have a series of “teeth”, as indicated at 67, having a generally radial wall 69 and an inclined wall 71 with a circumferential wall 73 therebetween with the outlets 13 being provided on radial walls 69 of these“teeth” such that the working fluid is discharged from stator outlet nozzles 29 into gap 25 in a generally tangential manner allowing for a more uniform distribution of the working fluid into the gap. This results in the pressure of the working fluid in the gap being more uniform and eliminating or minimizing pressure drops between the outlet nozzles.

[0060] Referring to Fig. 27, two or more of the expanders 1 of the present disclosure can be supplied working fluid from a commons source S. Of course, source S may supply a single expander 1 . The two expanders may be similar to the expanders 3 shown and described above. Control valves 75 are used to control the flow of working fluid to the expanders. Of course, working fluid exiting the expanders is returned to source S and is reheated or otherwise recharged so that it may be supplied to the inlets 9 of the expander.

[0061] Referring now to Fig. 28, an alternate rotor flow path 31 is shown to be a series of spaced air foil type rotor blades, as generally indicated at 77, which extend from the inner surface 27 of the rotor 7 into gap 25, but stop short of the outer surface of the stator. Each blade 77 has a leading edge 79, a trailing edge 81 with a convex, curved pressure side 83 between the leading and trailing edges against which fluid from within gap 25 reacts to apply a force on the blade, which, in turn, rotates the rotor. Such blades 77 are positioned within slot 60 of the outer rotor portion 51 with the pressure side of the blade oriented toward the incoming pressure of the fluid within gap 25. In this manner the fluid will exert a force on the blades 77 in the well-known manner for similar air foil blades. Of course, after the fluid has transferred its energy to the blades to rotatably drive the rotor, the fluid is discharged from the rotor into housing 35. It will be understood that the forces exerted on the blades have a resultant point of application of the force of the fluid on the blade, which may, for example, be at the aerodynamic center of the blade or at some other location along the blade such that the distal end of the radius R1 will typically lie somewhere along the radial length of the blades 77. The structure and operation of such air foil-type blades are well known to those skilled in the art and thus these blades are not described in detail in this disclosure.

[0062] Still further, while the expander 1 has been above-described as having a single rotor 7, those skilled in the art will understand that multiple rotors can be mounted on shaft 33 and located within the same pressure housing 35. Thus, the rotor 7 can be singular (single stage expansion), or, the expander 1 of the present disclosure can be a series of nested rotor discs (multistage expansion) with intervening stators between the rotor stages. As shown in Fig. 29, a plurality of nested rotors 7a, 7b, 7c is mounted on shaft 33 with a stator 5a or 5b positioned between each of the rotors where the stators supply working fluid from inlet 9 to each of the rotors via stator passages 1 1 through proper sizing and positioning of the stator flow passages 1 1 and the stator outlets 13 with their respective rotor flow paths 31 so that stators discharge working fluid into the annular gap 25 between a respective rotor and stator such that the working fluid can acts upon the rotor flow paths 31 to exert a force on the rotor so as to rotatably drive the and shaft 33. In this manner, the power output of the expander can be markedly increases with only moderate increases in the size of housing 35.

[0063] The stator 5 and rotor 7 of the present invention can be formed by a variety of manufacturing processes well known to those skilled in the art. However, because of the complex and curved forms that the stator flow passages 1 1 can take in the stator, the stator can be formed by 3D additive printing, preferably 3D additive metal printing. It will be appreciated that when the stator 5 is 3D printed, complex shapes for the nozzle inlet 17, cone 19, hub 21 with the passage inlet nozzles 23 formed therein, outlet nozzles 29, the outer stator circumference 15, and other details of the stator can be simultaneously formed with the stator. Rotor 7 can be likewise formed by 3D additive printing and the rotor flow paths 31 , whether such flow paths be J-bucket flow paths 61 or airfoil-type flow paths 77, can be formed simultaneously with the rotor by means of 3D additive printing such that the rotor flow paths are integral with the rotor.

[0064] The method of this disclosure involves selecting the ratio between the radius R1 and R2 such that multiplying this ratio times the rotational speed of the rotor if the radius R1 is somewhat larger than radius R2, a desired operating rotational speed of shaft 33 will be achieved. As stated above, if the radius R2 is equal to 1.0 inch (2.54 cm.), if the radius R1 is only slightly larger than R2 such that the rotational speed of the rotor shaft is 75,000 RPM, and if the desired operating speed of rotor shaft 33 is 3,600 RPM, then the radius R1 will be 20.83 inches (52.9 cm.).

[0065] The description herein is merely exemplary in nature and, thus, variations that do not depart from the gist of that which is described are intended to be within the scope of the teachings. Moreover, although the foregoing descriptions and the associated drawings describe example embodiments in the context of certain example combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions can be provided by alternative embodiments without departing from the scope of the disclosure. Such variations and alternative combinations of elements and/or functions are not to be regarded as a departure from the spirit and scope of the teachings.

Claims

1 . A low momentum loss expander system for use with a working fluid flowing from a source for producing a target power sufficient to drive a load, said working fluid having an amount of potential energy therein, said system comprising:

a. a stator and a rotor with said rotor configured to rotate relative to said stator about an axis common to both said rotor and to said stator;

b. said stator having a stator inlet generally coaxial with respect to said axis for receiving said working fluid from the source and for delivering said working fluid to said rotor by way of a plurality of passages in the stator;

c. said stator passages being configured to be in fluid flow connection with said stator inlet and to extend from said stator inlet to a plurality of stator outlets located radially outwardly of said stator inlet on an outer circumference of said stator and concentric with said axis; d. said rotor having an inner circumference concentric with said axis and located radially outwardly of said outer circumference of said stator outlets with an annular gap between said circumferences; e. said rotor having a plurality of substantially similar rotor flow paths, each rotor flow path having an inlet configured to receive said working fluid from said annular gap and configured to have an outlet for discharging said working fluid from said rotor;

f. each said rotor flow paths being further configured so that said working fluid can act upon each said rotor flow path at a point of application of a force that rotatably drives said rotor about said axis, said points of force application of said rotor flow paths forming a generally circular locus of such points concentric with said axis having a radius R1 with respect to said axis; and

g. said stator inlet having a respective radius R2 with respect to said axis such that the radius R2 is smaller than the radius R1 and is configured so that said working fluid entering said stator inlet can flow through said stator passages and can be discharged from stator outlets into said annular gap so that the working fluid can act upon said rotor flow paths to rotatably drive the rotor relative to the stator, wherein with radius R1 being substantially larger than radius R2 the expander can generate said target power and can operate at a substantially lower speed than if the radius R1 is only somewhat larger than radius R2.

2. A system as set forth in Claim 1 wherein said stator inlet is configured to receive said working fluid from said source, an inlet nozzle extending downstream within said stator inlet, said stator passages extending outwardly within said stator, there being at least one of said stator flow passages for each of said stator outlets, each of said stator flow passages having a stator flow passage inlet extending from said inlet nozzle to a respective stator outlet so as to deliver said working fluid to said annular gap.

3. A system as set forth in Claim 2 wherein said rotor is mounted on a shaft such that said shaft rotates with said rotor so as to perform useful work.

4. A system as set forth in Claim 3 wherein said rotor and said stator are mounted within sealed housing through which said working fluid inlet sealably extends to said stator inlet and through which said shaft sealably extends, said housing being configured such that the working fluid after performing work on said blades us discharged from said rotor into said housing, said housing having one or more fluid outlets configured to return said working fluid to said source.

5. A system as set forth in Claim 3 further having a rotor isolation plate mounted in close proximity to said rotor, said isolation plate being configured to isolate said rotating rotor from said fluid within said housing to as to reduce windage losses of said rotor rotating within the fluid contained within said housing.

6. A system as set forth in Claim 2 wherein said rotor flow paths are air foil-type blades.

7. A system as set forth in Claim 2 wherein said rotor flow paths are converging J-buckets.

8. A system as set forth in Claim 2 wherein the cross sectional shape of said inlet nozzle is generally circular.

9. A system as set forth in Claim 2 wherein said inlet nozzle is a converging nozzle.

10. A system as set forth in Claim 9 wherein said stator has a cone extending downstream within said inlet nozzle forming said converging nozzle.

1 1. A system as set forth in Claim 10 wherein said converging nozzle has a hub at its downstream end, and wherein said stator flow passage inlets are formed in said hub.

12. A system as set forth in Claim 2 wherein each of said stator passages has a proximal end in fluid communication with said inlet nozzle and a distal end in fluid communication with said gap, and wherein the distal end of each of said stator passages forms one of said stator outlets which is configured to discharge said working fluid into said gap to be in fluid communication with rotor flow paths.

13. A system as set forth in Claim 2 wherein said stator has an outer stator portion extending radially outwardly beyond said outer circumference with said outer stator portion being in face-to-face relation with an outer portion of said rotor, and wherein said stator has an inner portion extending radially inwardly of said outer circumference in face-to- face relation with an inner portion of said rotor, an inner seal between said inner stator portion and said inner rotor portion and an outer seal between said outer stator portion and said outer rotor portion thereby sealing said annular gap such that upon said working fluid being discharged from said stator outlets into said annular gap said working fluid is in fluid communication with said rotor flow paths.

14. A system as set forth in Claim 13 wherein each of said rotor flow paths are mounted within said outer rotor portion in such manner as to be acted upon by fluid in said annular gap and to exert a force on the rotor that is capable of rotationally driving said rotor.

15. A system as set forth in Claim 14 wherein each of said rotor flow paths is a J-bucket having an inlet and an outlet and is curved along its length from its inlet to its outlet so as to change the momentum of the working fluid flowing through said rotor flowpaths.

16. A system as set forth in Claim 15 wherein said J-bucket inlet is positioned and configured with respect to said annular gap such that fluid in said annular opening will flow through each said J-bucket and be discharged from the rotor via said J-bucket outlets.

17. A system as set forth in Claim 1 6 wherein each of said J- bucket rotor flow paths converges along its length from its inlet to its outlet so as to accelerate said working fluid as the latter flows therethrough.

18. A system as set forth in Claim 6 wherein each of said air foil rotor flow paths has a leading edge and a trailing edge with a curved, concave face therebetween, said concave face being configured such that when said working fluid is present in said gap the working fluid exerts a force on said air foil blade that rotationally drives the rotor relative to the stator.

19. A system as set forth in Claim 2 wherein said stator with said stator flow passages therein is configured to be formed by 3D additive printing.

20. A system as set forth in Claim 19 wherein said rotor is configured to be formed along with said stator by 3D additive printing.

21 . A system as set forth in Claim 1 wherein there are a plurality of said rotors mounted on a common shaft, and wherein there are a plurality of said stators for supplying working fluid to said rotors for rotatably driving said rotors.

22. A method of altering the operational speed of an expander system configured to be powered by a working fluid having potential energy sufficient to drive a load connected to said expander system at a desired operating speed, said expander system having a stator and a rotor with said rotor configured to rotate relative to said stator about an axis common to both said rotor and to said stator, said stator having a stator inlet generally coaxial with respect to said axis for receiving said working fluid and for delivering said working fluid to said rotor by way of a plurality of passages in the stator, said stator passages being configured to be in fluid flow connection with said stator inlet and to extend from said stator inlet to a plurality of stator outlets located radially outwardly of said stator inlet on an outer circumference of said stator and concentric with said axis, said rotor having an inner circumference concentric with said axis and located radially outwardly of said outer circumference of said stator outlets with an annular gap between said circumferences, said rotor having a plurality of substantially similar rotor flow paths configured so that said working fluid can act upon each said rotor flow path at a point of application of a force that rotatably drives said rotor about said axis, said points of force application of said rotor flow paths forming a generally circular locus of such points concentric with said axis having a radius R1 with respect to said axis, and said stator inlet having a respective radius R2 with respect to said axis, when radius R1 is only somewhat larger than radius R2 the operating speed of the expander is substantially faster than a desired operating speed, said method comprising providing a stator and rotor wherein radius R1 is configured to be substantially larger than radius R2 such that said expander operates at said desired operating speed to drive the load.

23. The method as set forth in Claim 22 wherein the operating speed of the expander is in inverse proportion to the ratio of R1/R2.

24. A method of operating an expander system to be powered by a working fluid having potential energy, which expander system has:

a stator and a rotor with said rotor configured to rotate relative to said stator about an axis common to both said rotor and to said stator, said stator having a stator inlet generally coaxial with respect to said axis for receiving said working fluid and for delivering said working fluid to said rotor by way of a plurality of passages in the stator;

said stator passages being configured to be in fluid flow connection with said stator inlet and to extend from said stator inlet to a plurality of stator outlets located radially outwardly of said stator inlet on an outer circumference of said stator and concentric with said axis, said rotor having an inner circumference concentric with said axis and located radially outwardly of said outer circumference of said stator outlets with an annular gap between said circumferences;

said rotor having a plurality of substantially similar rotor flow paths configured so that said working fluid can act upon each said rotor flow path at a point of application of a force that rotatably drives said rotor about said axis, said points of force application of said rotor flow paths forming a generally circular locus of such points concentric with said axis having a radius R1 with respect to said axis, and said stator inlet having a respective radius R2 with respect to said axis, with the radius R1 substantially larger than radius R2; the process comprising the steps of:

directing the working fluid to flow through the stator inlet; directing fluid flow from the stator inlet into and through the stator passages and though the stator outlets; and

directing the fluid from the stator outlets to the rotor flow paths to rotate the rotor relative to the stator about the common axis;

25. The method as set forth in Claim 24 further comprising the step of operating the expander at a speed of the rotor relative to the stator which speed is in inverse proportion to the ratio of R1/R2.