ORC Turbine and Generator, And Method Of Making A Turbine
A turbine-generator device for use in electricity generation using heat from industrial processes, renewable energy sources and other sources. The generator may be cooled by introducing into the gap between the rotor and stator liquid that is vaporized or atomized prior to introduction, which liquid is condensed from gases exhausted from the turbine. The turbine has a universal design and so may be relatively easily modified for use in connection with generators having a rated power output in the range of 50 KW to 5 MW. Such modifications are achieved, in part, through use of a modular turbine cartridge built up of discrete rotor and stator plates sized for the desired application with turbine brush seals chosen to accommodate radial rotor movements from the supported generator. The cartridge may be installed and removed from the turbine relatively easily for maintenance or rebuilding. The rotor housing is designed to be relatively easily machined to dimensions that meet desired operating parameters.
This application is a divisional application of U.S. patent application Ser. No. 13/937,978, filed Jul. 9, 2013, entitled “Overhung Turbine and Generator System With Turbine Cartridge,” now allowed, which application claims the benefit of priority of U.S. Provisional Patent Application Ser. No. 61/699,649, filed Sep. 11, 2012, entitled “Axial Overhung Turbine and Generator System For Use In An Organic Rankine Cycle.” All of which are incorporated herein by reference in their entirety.
FIELD OF THE INVENTIONThe present invention generally relates to the field of turbine generator power systems for industrial waste heat recovery and other applications. In particular, the present invention is directed to an overhung turbine coupled to a direct-drive, electrical power generator.
BACKGROUNDConcerns about climate change and rising energy costs, and the desire to minimize expenses in various industrial operations, together lead to an increased focus on capturing waste heat developed in such operations. Organic Rankine Cycle (“ORC”) turbine generator electrical power systems have been used in industrial waste heat recovery. Unfortunately, known systems for capturing waste heat and converting it to electricity are often too large for the space available in certain industrial operations, are less efficient than desired, require more heat to operate efficiently than is available, are too expensive to manufacture for certain applications, or require more maintenance than is desired. In other applications, such as geothermal energy recovery and certain ocean thermal energy projects, abundant heat is available and an efficient ORC system is a satisfactory means for conversion of such heat to electricity. Even in such other applications, however, known ORC systems tend to be too expensive for some such applications, are less efficient than desired and/or require more maintenance than is desired.
SUMMARY OF THE INVENTIONIn one implementation, the present disclosure is directed to a system for converting heat energy into electricity. The system includes a turbine having an inlet, an outlet, a stator and a turbine rotor, wherein said turbine is configured to receive a first volume of working fluid via said inlet and to exhaust said first volume of working fluid via said outlet, wherein said turbine rotor rotates about a rotational axis; and a generator coupled with said turbine, said generator having a stator and a generator rotor , said generator rotor being coupled with said turbine rotor so as to be rotatably driven by said turbine rotor about said rotational axis, said generator including a gap between said generator rotor and said stator for receiving a second volume of said working fluid, said gap having an entrance port and an exit port, wherein said generator is designed so that, in operation, said second volume of working fluid present in said gap cools said generator rotor and said stator.
In another implementation, the present disclosure is directed to a turbine cartridge. The turbine cartridge includes a plurality of rotor plates, each having a centerline, a first contact surface and a second contact surface contacting said first contact surface, said first and second contact surfaces being substantially parallel and each of said first and second contact surfaces being flat in the range 0.00005″ to 0.020″, wherein said plurality of rotor plates are positioned proximate one another so that said centerlines of said rotor plates are mutually coaxial; a plurality of stator plates, each having a centerline, a first contact surface and a second contact surface contacting said first contact surface, said first and second contact surfaces being substantially parallel and each of said first and second contact surfaces being flat in the range 0.00005″ to 0.020″, wherein said plurality of stator plates are positioned proximate one another so that said centerlines of said stator plates are mutually co-axial; and wherein said plurality of rotor plates are positioned in alternating relationship with corresponding respective ones of said plurality of stator plates so as to define a multi-stage rotor assembly with an upstream direction, further wherein at least one of said plurality of rotor plates includes a first plurality of vanes with an axial chord and an adjacent one of said plurality of stator plates includes a second plurality of vanes with an axial chord, wherein said first plurality of vanes is axially spaced from said second plurality of vanes to define a space having an axial dimension that is no more than two axial chords to ¼ of 1% of an axial chord, as measured with respect to the axial chord of the one of said rotor plate and stator plate immediately upstream of said space.
In yet another implementation, the present disclosure is directed to a system for conversion of heat energy into electricity. The system includes an electric generator having a proximal end, a distal end, a generator rotor and a stator, said generator rotor being disposed for rotational movement within said stator about a rotational axis, said generator also including a first magnetic radial bearing positioned adjacent said proximal end and a second magnetic radial bearing positioned adjacent said distal end, said first and second magnetic radial bearings surrounding said generator rotor and retaining said generator rotor, during operation, in substantially coaxial alignment with respect to said rotational axis; and a turbine having at least one stator and at least one turbine rotor supported for rotational movement within said at least one stator about said rotational axis, said at least one turbine rotor being coupled with said at least one generator rotor so as to rotationally drive said generator rotor, said at least one turbine rotor being attached to said proximal end of said generator in an overhung configuration such that no radial bearings are included in said turbine for radially supporting said at least one turbine rotor for rotational movement, said at least one turbine rotor having a radially outermost surface and said at least one stator having a radially innermost surface, said turbine further including at least one seat, a first brush seal engaging said radially outermost surface of said at least one rotor, and a second brush seal engaging said at least one seat.
In yet another implementation, the present disclosure is directed to a method of making a turbine for driving a generator, said turbine having a power output sufficient to drive the generator to produce electric power in the range 50 KW to 5 MW. The method includes providing a universal turbine hood having a floor with a first thickness; providing a rotor stage having a radial height, the rotor stage positionable in the turbine hood; and machining material away from the hood to decrease the thickness of the floor and machining material away to decrease the radial height of the rotor stage, said machining performed so as to produce a turbine having a power output sufficient to drive the generator to produce a maximum electric power output at a target value in the range 50 KW to 5 MW.
For the purpose of illustrating the invention, the drawings show aspects of one or more embodiments of the invention. However, it should be understood that the present invention is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein:
The present disclosure is directed to a turbine powered electrical generator for use in an Organic Rankine Cycle (ORC), Kalina cycle, or other similar cycles, industrial operations that generates waste heat, or in connection with other heat sources, e.g., a solar system or an ocean thermal system. High-pressure hot gas from a boiler, which is heated by the heat source, enters the turbine housing and is expanded through the turbine to turn the rotor, which turns the generator shaft to generate electricity, as described more below.
Referring to
ORC system 22 includes a boiler 28 that is connected to a heat source 30, such as waste heat from an industrial process. Boiler 28 provides high-pressure hot vapor via connection 32 to turbine 24. As discussed more below, the hot vapor, aka, the working fluid, is expanded in turbine 24, where its temperature drops, and is then exhausted from the turbine and delivered via fluid connection 34 to condenser 36. In condenser 36, the vapor cooled in turbine 24 is cooled further, typically to a liquid state, and then a first volume of such liquid is delivered via fluid connection 38 to pump 40, where the liquid is returned via connection 42 to boiler 28. This liquid is then reheated in boiler 28 by heat from heat source 30 through a heat exchanger or other structure (none shown) in the boiler and then, repeating the cycle, is returned as high-pressure hot vapor via fluid connection 32 to turbine 24.
Turning now to
The cooling vapor is introduced into gap 70, and as the vapor passes through gap 70 it extracts heat from stator 72 and generator rotor 74, which vapor is then exhausted via fluid connection 34, along with the hot vapor exhausted from turbine 24, for cooling by condenser 36. Optionally, as illustrated in
Referring now to
Turning next to
In some applications, it may be desirable to provide just cooling of stator 72 via cooling jacket 76, and not provide vapor or atomized liquid to gap 70. In other applications, the reverse may be desired.
Various high molecular weight organic fluids, alone or in combination, may be used as the working fluid in system 20. These fluids include refrigerants such as, for example, R125, R134a, R152a, R245fa, and R236fa. In other applications fluids other than high molecular weight organic fluids may be used, e.g., water and ammonia.
System 22 also includes a power electronics package 86 connected to generator 26. Package 86 converts the variable frequency output power from generator 86 to a frequency and voltage suitable for connection to the grid 87, e.g. 50 Hz and 400 V, 60 Hz and 480 V or other similar values.
Discussing generator 26 in more detail, in one embodiment the generator is a direct-drive, permanent magnetic, generator. Such a construction is advantageous because it avoids the need for a gearbox, which in turn results in a smaller and lighter system 20. Various aspects of the invention described herein may, of course, be effectively implemented using a generator having a gearbox mechanically coupled between turbine rotor 104 of turbine 24 and generator rotor 74 of generator 26, and a suitable wound rotor that does not include permanent magnets, e.g., a doubly wound, induction-fed rotor. In addition, in certain applications direct-drive synchronous generators may be used as generator 26. The rated power output of generator 26 will vary as a function of the intended application. In one embodiment, generator 26 has a rated power output of 5 MW. In another embodiment, generator 26 has a rated power output of 50 KW, and in yet other embodiments, generator 26 has a rated power output somewhere in between these values, e.g., 200 KW, 475 KW, 600 KW, or 1 MW. Rated power outputs for generator 26 other than those listed in the examples above are encompassed by the present invention.
To permit high-speed (e.g., on the order of 20,000-25,000 rpm) operation, and to minimize maintenance, it may be desirable in some embodiments of generator 26 to support generator rotor 74 for rotational movement using magnetic radial bearings 88 (see
In another embodiment of the invention, fluid-film bearings may be used in place of magnetic radial bearings 88 and thrust bearing 89. For purposes of illustration, the schematic depiction of magnetic bearings 88 and 89 in
Optionally, in addition to magnetic bearings 88 and 89, rolling element radial bearings 92, e.g., radial bearings 92a and 92b, may be provided at opposite ends of rotor shaft 93 of generator rotor 74 surrounding the rotor shaft, typically adjacent magnetic bearings 88a and 88b, respectively. Rolling element radial bearings 92 support generator rotor 74 and its shaft 93 in substantially coaxial relation to rotational axis 106 when magnetic bearings 88 and 89 are not energized. More particularly, rolling element radial bearings 92 provide a rest point for generator rotor 74 when magnetic bearings 88 are not activated and provide a safe landing for the generator rotor in the event of a sudden electronic or power failure. It may be desirable in some cases to size rolling element radial bearings 92 to support generator rotor 74 with a relatively loose fit so that during operation when magnetic bearings 88 and 89 are energized, the rotor has limited, if any contact, with rolling element radial bearings 92, even during times of maximum radial deflections of generator rotor 74 due to perturbations in the operation of magnetic bearings 88. When fluid-film bearings are used in place of magnetic radial bearings 88, rolling element radial bearings 92 are typically not required, although in some applications it may be desirable to include such radial bearings.
In one embodiment, rolling element radial bearings 92 are sized to permit rotor shaft 93 to deviate radially from perfect coaxial alignment with rotational axis 106 an amount that is 1.01 to 5 times as great as the maximum radial deviation of shaft 93 from rotational axis 106 that may occur when magnetic radial bearings 88 are fully activated, including during times of major radial deflection that may occur due to perturbations of the magnetic radial bearings , e.g., from a fluid dynamic instability or a failed control system or a power failure (without backup). In another embodiment, this deviation permitted by radial bearings 92 is about 2 to 3 times as great as the radial deviation of shaft 93 from rotational axis 106 that occurs when magnetic bearings 88 are activated, again including during major perturbations that occur over time. Rolling element radial bearings 92 are often referred to as “bumper bearings” or “backup bearings” in the art.
While beneficial for the reasons discussed above, rolling element radial bearings 92 also present a challenge because the radial clearance of such bearings is much higher than the desired clearances for the conventional seals (not shown in detail) of turbine 24. Typical rolling element radial bearings 92 have a radial clearance on the order of 0.005 to 0.015 inch. By contrast, desired radial clearances for the seals of turbine 24 are typically on the order of 0.000-0.001 inch. As generator 26 is assembled, shipped and stored, or during a loss of levitation of generator rotor 74 during operation due to failure of magnetic bearings 88, the generator rotor will drop to rolling element radial bearings 92. A consequence of such “play” in generator rotor 74 is that portion of shaft 93 proximate rolling element radial bearings 92, along with seals in turbine 24, can be damaged over time. Indeed, in certain applications, as few as 1-10 “bumper” events can cause sufficient damage to components of turbine-generator assembly 20 that disassembly and repair/replacement of such components is required.
A solution to this problem is to add a radial brush seal 94 (
Referring now to FIGS. 2 and 4-10, turbine 24 will be described in more detail. In the embodiment illustrated in
Turbine 24 includes a turbine rotor 104 that rotates about rotational axis 106 and a stator 108 that is fixed with respect to housing 98. As discussed more below, in one example of turbine 24 featuring a modular design, turbine rotor 104 includes a plurality of individual bladed plates 110 and stator 108 includes a plurality of individual plates 112 positioned in alternating, inter-digitated relationship with the rotor plates, as best seen in
As best illustrated in
Referring now to
With continuing reference to
With particular reference to
Referring to
Stator plates 112, and spacer segments 117 if provided, may, for example, be secured together in alternating, inter-digitated relationship so as to form a unitary cartridge 198. The latter may be releasably secured in cavity 114 (
By providing separate rotor plates 110 and stator plates 112, and by making such plates relatively flat as discussed above, these plates may be assembled as a cartridge 198 (see
In some applications, it will be desirable to more substantially isolate generator 26 from turbine 24. To achieve this objective, as best illustrated in
The embodiment of turbine 24 shown in
Consistent with the objective of providing a turbine 24 that can be readily modified to meeting desired operating parameters, housing 98 is designed to facilitate such modification. One aspect of such design of housing 98 involves providing floor 204 with a thickness sufficient to accommodate turbine rotor 104 and stator 106 having varying radial heights. Δr, as measured between said rotational axis and an outermost portion of said at least one turbine rotor, said axial turbine including a hood having a floor with a first thickness, wherein said first thickness is selected to permit said floor to be machined on the inside to a thickness sufficient to accommodate said at least one turbine rotor with a radial dimension that varies between Δr and 1.4 Δr. Further, housing 98 is provided with a configuration that permits easy access to floor 204 by conventional machine tools, e.g., a 5-axis CNC milling machine or a CNC lathe, that can be used to machine the floor so as to create a cavity 114 sized to receive turbine rotor 104 and stator 106 with the desired radial heights.
Another aspect of providing a modifiable housing 98 is to include a backplate 250 having a thickness that may be adjusted so as to selectively vary width l4, i.e., the distance l4 between backplate 250 and housing wall 252, and to selectively vary width l1, i.e., the exit width. In this regard, width l4 may be varied so that it ranges from one half to four times the width of diffuser exit l1. Backplate 250 may be an integral portion of housing 98 in some embodiments and a separate element in others, as illustrated in
Housing performance depends on several factors, but alignment of the entry flow at the housing inlet 100 and housing base dimensions are important as taught in the literature. A very good flow entry provides for diffuser exhaust flowing up the housing backplate 250, as configured in
Turbine 24 is depicted in
Turning next to
Depending on the desired balancing of thrust in turbine-generator system 20, it may be desirable to configure rotors 104 of a multi-stage radial turbine in a back-to-back arrangement, as illustrated in
Although not specifically illustrated, turbine-generator system 20 may also be implemented using a mixed-flow turbine. The latter is very similar in design to radial turbine generators 324 and 424, and so is not separately illustrated.
By placing rotor 104 in a reverse orientation so that the low-pressure, cooled working fluid is discharged from the last rotor stage of turbine 24 proximate generator 26, heat transfer to the generator is minimized, thereby prolonging generator life. The low-pressure exhaust of turbine 24, as a consequence of its reverse orientation, draws the second volume of working fluid out of gap 70 in generator 26 via ports 254 and into the discharge stream of turbine 24 while balancing thrust forces sufficiently so that the generator thrust bearing 89 can handle the remaining axial load of turbine 24. Such a design is efficient, compact and thermally efficient.
Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions and additions may be made to that which is specifically disclosed herein without departing from the spirit and scope of the present invention.
Claims
1. A system for converting heat energy into electricity, comprising:
- a turbine having an inlet, an outlet, a stator and a turbine rotor, wherein said turbine is configured to receive a first volume of working fluid via said inlet and to exhaust said first volume of working fluid via said outlet, wherein said turbine rotor rotates about a rotational axis; and
- a generator coupled with said turbine, said generator having a stator and a generator rotor, said generator rotor being coupled with said turbine rotor so as to be rotatably driven by said turbine rotor about said rotational axis, said generator including a gap between said generator rotor and said stator for receiving a second volume of said working fluid, said gap having an entrance port and an exit port, wherein said generator is designed so that, in operation, said second volume of working fluid present in said gap cools said generator rotor and said stator.
2. A system according to claim 1, further including a vaporizer for receiving said second volume of said working fluid and vaporizing said second volume before introduction into said entrance port of said gap.
3. A system according to claim 1, further including an atomizer for receiving said second volume of said working fluid and atomizing said second volume before introduction into said entrance port of said gap.
4. A system according to claim 1, wherein said turbine includes a hood with a backplate and said exit port includes a plurality of orifices positioned in said backplate.
5. A system according to claim 1, wherein said turbine has a through flow rate and said second volume of said working fluid travels through said gap with a flow rate, further wherein said second volume of said working fluid is introduced into said gap to have a flow rate of no more than 50% of said through flow rate.
6. A system according to claim 1, further including a condenser and a pump, wherein said condenser is fluidly coupled with said outlet of said axial turbine to receive and condense said first volume of working fluid into said second volume of working fluid and to exhaust said second volume of working fluid into said pump, wherein said pump is coupled with said entrance port so as to deliver said second volume of working fluid to said gap in said generator.
7. A turbine cartridge, comprising:
- a plurality of rotor plates, each having a centerline, a first contact surface and a second contact surface contacting said first contact surface, said first and second contact surfaces being substantially parallel and each of said first and second contact surfaces being flat in the range 0.00005″ to 0.020″, wherein said plurality of rotor plates are positioned proximate one another so that said centerlines of said rotor plates are mutually coaxial;
- a plurality of stator plates, each having a centerline, a first contact surface and a second contact surface contacting said first contact surface, said first and second contact surfaces being substantially parallel and each of said first and second contact surfaces being flat in the range 0.00005″ to 0.020″, wherein said plurality of stator plates are positioned proximate one another so that said centerlines of said stator plates are mutually co-axial; and
- wherein said plurality of rotor plates are positioned in alternating relationship with corresponding respective ones of said plurality of stator plates so as to define a multi-stage rotor assembly with an upstream direction, further wherein at least one of said plurality of rotor plates includes a first plurality of vanes with an axial chord and an adjacent one of said plurality of stator plates includes a second plurality of vanes with an axial chord, wherein said first plurality of vanes is axially spaced from said second plurality of vanes to define a space having an axial dimension that is no more than two axial chords to ¼ of 1% of an axial chord, as measured with respect to the axial chord of the one of said rotor plate and stator plate immediately upstream of said space.
8. A turbine cartridge according to claim 7, wherein said space has an axial dimension that ranges from ⅓ to 1 of said axial chord of the one of said rotor plate and stator plate immediately upstream of said space.
9. A turbine cartridge according to claim 7, wherein said plurality of rotor plates are secured with respect to one another and said plurality of stator plates are secured with respect to one another and positioned relative to said plurality of rotor plates so as to form a unitary cartridge system.
10. A turbine cartridge according to claim 9, wherein said unitary cartridge system is designed to be releasably coupled to a turbine housing.
11. A system for conversion of heat energy into electricity, the system comprising:
- an electric generator having a proximal end, a distal end, a generator rotor and a stator, said generator rotor being disposed for rotational movement within said stator about a rotational axis, said generator also including a first magnetic radial bearing positioned adjacent said proximal end and a second magnetic radial bearing positioned adjacent said distal end, said first and second magnetic radial bearings surrounding said generator rotor and retaining said generator rotor, during operation, in substantially coaxial alignment with respect to said rotational axis; and
- a turbine having at least one stator and at least one turbine rotor supported for rotational movement within said at least one stator about said rotational axis, said at least one turbine rotor being coupled with said at least one generator rotor so as to rotationally drive said generator rotor, said at least one turbine rotor being attached to said proximal end of said generator in an overhung configuration such that no radial bearings are included in said turbine for radially supporting said at least one turbine rotor for rotational movement, said at least one turbine rotor having a radially outermost surface and said at least one stator having a radially innermost surface, said turbine further including at least one seat, a first brush seal engaging said radially outermost surface of said at least one rotor, and a second brush seal engaging said at least one seat.
12. A system according to claim 11, wherein said generator rotor is free to move a first radial distance out of coaxial alignment with said rotational axis when said first and second magnetic radial bearings are not activated to radially support said generator rotor, further wherein said first brush seal and said second brush seal have a radial length and rigidity selected to support said turbine rotor so that said turbine rotor, and in turn said generator rotor coupled to said turbine rotor, do not deviate more than a second radial distance out of co-axial alignment with said rotational axis, said second radial distance being less than 0.8 times said first radial distance.
13. A system according to claim 12, wherein said first brush seal is spaced 0.0000″ to 0.010″ from said radially outermost surface and said second brush seal is spaced 0.0000″ to 0.010″ from said seat.
14. A system according to claim 12, wherein said second radial distance is 0.3 to 0.6 times said first radial distance.
15. A method of making a turbine for driving a generator, said turbine having a power output sufficient to drive the generator to produce electric power in the range 50 KW to 5 MW, the method comprising:
- providing a universal turbine hood having a floor with a first thickness;
- providing a rotor stage having a radial height, the rotor stage positionable in the turbine hood; and
- machining material away from the hood to decrease the thickness of the floor and machining material away to decrease the radial height of the rotor stage, said machining performed so as to produce a turbine having a power output sufficient to drive the generator to produce a maximum electric power output at a target value in the range 50 KW to 5 MW.
16. A method according to claim 15, wherein said providing a universal turbine hood step includes providing a turbine hood that includes a backplate, and further including the step of selecting the backplate to have a configuration that permits attainment of said power output sufficient to drive the generator to produce said maximum electric power output at the target value.
17. A method according to claim 15, wherein said providing a universal turbine hood step includes providing a nose piece proximate said floor of said turbine hood, said nose piece having a configuration selected to permit attainment of said power output sufficient to drive the generator to produce said maximum electric power output at the target value.
18. A method according to claim 15, wherein the universal turbine hood includes a backplate opposite the floor and a diffuser exit passage between the backplate and the floor, the diffuser exit passage having a width l1, the universal turbine hood further including a hood wall that is axially spaced a distance l4 from the backplate, further including the step of forming the backplate so the distance l4 ranges from one half to four times the width l1.
19. A method according to claim 16, wherein the backplate used in said providing step is separate from, and releasably attachable to, the turbine hood.
20. A system according to claim 19, wherein said backplate covers an opening in said turbine hood, and said machining material away from said hood is performed using a machining tool sized to fit through said opening so as to remove material from said floor of said hood.
Type: Application
Filed: Jul 13, 2015
Publication Date: Nov 12, 2015
Inventors: Kevin Fairman (Lunenburg, MA), Francis A. Di Bella (Boston, MA), David Japikse (Woolwich, ME), Frederick E. Becker (Reading, MA), Alexander Gofer (Hanover, NH)
Application Number: 14/797,639