FIELD OF THE INVENTION

The invention relates to pumps and turbines, and more particularly, to integral sealless pumps and turbines.

BACKGROUND OF THE INVENTION

Rotodynamic pumps and turbines are often highly similar in their physical designs, such that the difference between a pump and a turbine can sometimes be mainly a question of use rather than structure. Accordingly, features of the present invention and of the prior art that are discussed herein with reference to a turbine or to a pump should be understood to refer equally to both, except where the context requires otherwise.

In a conventional rotodynamic pump design, fluid flow and pressure are generated by a rotor, also referred to as an “impeller,” that is rotating inside a stationary pump casing. The torque required to drive the rotor is provided by an external motor and transmitted through a rotating shaft to the rotor that rotates within a pump housing. Similarly, in the case of a conventional turbine design, fluid flow and pressure are applied to a rotor, which in the case of a turbine is also referred to as a “runner,” causing the rotor to rotate inside of a stationary turbine casing, and the rotation and torque generated by the rotor are transmitted through a rotating shaft to an external generator.

One of the difficulties of these approaches is that they require the use of dynamic seals to maintain the pressure boundaries at the location where the rotating shaft penetrates the stationary pump or turbine casing. These seals are a source of leakage and other failure modes. In addition, rigid baseplates are required to allow the pump and the motor or turbine and generator to be mounted and aligned with each other, so as to avoid vibration issues. Even with rigid baseplates, nozzle loads on the pump or turbine can cause alignment problems between the motor or generator and the mechanical seals.

These difficulties are avoided by designs that do not include shaft seals. Magnetic coupling drives, for example, do not require dynamic seals on the pump or turbine shaft, because the motor or generator is coupled magnetically through the pump housing to an internal shaft that is supported by product-lubricated bearings located within the housing. However, these designs still require careful alignment of the motor or generator with the rotor housing to couple the motor or generator with the rotor shaft as efficiently as possible. Also, the components used for magnetic coupling add complexity and cost to the design.

Another approach that avoids dynamic shaft seals altogether is to use an integral design, wherein the motor or generator is included within the same housing as the rotor, so that shaft seals are not required. Some of these integral so-called “sealless motor” or “sealless generator” approaches use a radial field motor or generator design, whereby magnets are attached at or near the outer radius of the rotor, which is sealed within a thin-walled “can,” and an electromagnetic stator located outside of the sealed can surrounds the rotor. However, radial field designs necessarily require a significant increase in the diameter and length of the rotor housing. Another approach to integral pump designs is to implement an axial field motor or generator design, whereby a disk or “pancake” permanent magnet, brushless DC motor or generator is included within the rotor housing to provide high power density and create the most compact and lightweight single stage pump or turbine units possible.

However, it can be difficult to cool the motor or generator coils of an integral sealless motor pump or sealless generator turbine. Typically, special flow paths must be provided within the housing to shunt some of the working fluid through grooves in submerged bearings and/or through another appropriate path to extract heat arising from the coils of the motor or generator. The shunted working fluid is heated by convection from the stator wall and carries the heat away from the stator to be expelled along with the un-shunted working fluid.

Unfortunately, as the shunted fluid passes through passages adjacent to the stator wall, through a hollow rotating shaft, through the shaft bearings, and/or through other appropriate channels, a phase change may occur due to the combination of fluid heating and/or a pressure drop due to the transition from discharge to suction pressure. The resulting exposure to fluid in the vapor phase can result in motor/generator overheating and/or bearing failure. Furthermore, the requirement of diverting a certain fraction of the pump output or turbine input into a cooling flow necessarily reduces the efficiency of the pump or turbine.

Another disadvantage of pumps and turbines before the present invention that include a mechanically integral motor or generator is that each pump or turbine design necessarily requires a corresponding, integral motor or generator design. Accordingly, when a new pump or turbine design is introduced a new motor or generator design must also be introduced, even if the torque and electrical requirements of the new motor or generator remain unchanged as compared to an existing design. And if it is necessary to simultaneously produce and/or support a plurality of such pumps or turbines, then separate productions and/or inventories must be maintained for the distinct motor and generator designs.

In addition to the issues that are discussed above, another general problem that is encountered in the design of both integral and non-integral pumps and turbines is how to scale up the capacity of an existing pump or turbine design to meet the requirements of a new application, which generally requires redesigning the physical shape and size of the rotor, operating the rotor at a higher speed, and/or adding additional rotors.

The total head that is generated by a pump is a function of the rotor diameter and its rotation speed, while the flow delivery for a given rotor diameter and speed is determined by the rotor width. For a given rotor design, the maximum rotor speed is limited by the amount of torque that the motor can develop. The speed of rotation is also limited by both the frequency limitations of the inverter used to drive the motor and the NPSH (Net Positive Suction Head) available at the inlet of the rotor.

Similarly, in the case of a generator turbine, the generator places a “load” on the turbine rotor according the electromagnetic coupling between the rotating magnets and the generator coils, under the control of an inverter or other control electronics associated with the generator, such that the maximum output of the generator depends on the maximum torque that can be delivered to the generator by the rotor, which for a given fluid flow depends on the rotor diameter and width.

One approach to increasing output of a pump or turbine is therefore to increase the size of the rotor and the capacity of the motor or generator. However, the additional size and bulk that result from this approach can be problematic.

The size and bulk of the rotor casing and other components of a pump or turbine can be reduced, when higher fluid pressures or generator outputs are required, by using small diameter rotors operating at high speeds. However, this approach does not work for sealless motor and generator designs, because the rotor is also a component of the motor or generator. In particular, in axial sealless designs smaller diameter rotors provide smaller available disk areas for mounting permanent-magnets or inductive magnets, thereby limiting the torque that can be developed by the motor, or the electrical power that can be produced by the generator. Another limitation is the relative unavailability of sealless motor designs (magnetic rotors and stators) that can deliver a range of pressures and flow rates, and of sealless generator designs that operate efficiently over a range of pressures and flow rates.

Accordingly, for an axial motor sealless pump or turbine, the pump head or turbine output provided by a rotor can only be increased by enlarging the diameter of the rotor. However, this approach increases the bulk of the apparatus, because it requires use of a larger and thicker rotor casing and other structural components to contain the larger components and higher fluid pressures.

Increasing output by expanding the number of rotors can also be problematic for any pump or turbine design. In a non-integral, multi-stage pump or turbine, a single, large motor provides torque to a plurality of rotors through a common shaft, or a single, large generator receives torque from a plurality of rotors through a common shaft. This approach typically requires a large and bulky motor or generator, and further requires that the shaft must be enlarged in diameter and increased in length as the number of rotor stages is increased, so that the combined torque and weight of all of the rotors can be accommodated.

Whether configured in a horizontal or a vertical arrangement, these long shafts with multiple rotor stages require larger bearings and increase the likelihood of bearing failures. In addition, the long shafts of multi-stage pumps can lead to various roto-dynamic issues related to shaft deflections and critical speeds. Because of these issues, and for other reasons, each multi-stage pump design is applicable only to a specified maximum number of stages, and cannot be easily scaled to accommodate requirements for different numbers of stages. Instead, scaling of an existing design typically requires a new pump or turbine design.

Furthermore, the elongated shaft, multi-stage approach requires that all of the rotors rotate at the same speed, which can limit the efficiency and/or NPSH (net positive suction head) performance of the design. In addition, a failure of any one stage in a multi-stage pump will cause an immediate and total failure of the entire pump or turbine.

Of course, one alternative to designing and implementing a multi-stage integral or non-integral pump or turbine is simply to interconnect a plurality of single-stage pumps or turbines in series and/or parallel. In the case of pumps, the output of each pump in series becomes the input of the next pump, which further increases the pressure, while the outputs of pumps configured in parallel are combined to increase output flow. In the case of turbines, the fluid flows through the rotors, either in series or in parallel, and the electrical outputs of the turbine generators are combined in series and/or in parallel to create a higher total output voltage and/or current.

However, this approach of combining a plurality of pumps or turbines into a multi-stage apparatus requires the use of bulky and complex fluid interconnections or manifolds, so that excessive space is consumed. In addition, the reliability of the apparatus is reduced, because the number of hoses and/or other fluid connections, and therefore the opportunities for leaks and/or other failure modes, increases as the number of pumps or turbines is increased.

It has been suggested that a sealless disk motor pump might include more than one motor within a common housing. However, the fluid interconnections and motor/generator cooling requirements of a sealless disk motor design tend to limit this approach to only two stages at most.

For example, with reference toFIG. 1, one approach that has been proposed includes two centrifugal pump stages within a single sealless motor design100, whereby each stage is driven by its own motor102, and whereby the two stages are positioned back-to-back, such that the two motors102are included within a common central space within the casing112, so that they can be cooled by a common process flow path104. In the example shown inFIG. 1, the two rotors106face in opposite directions, and each includes permanent magnets110attached to a rear side thereof.

In some versions of this approach, the motors102are controlled by separate variable frequency drives (“VFD's”)114and each of the rotors106rotates about a separate, fixed shaft108. In other versions, the motors share a common controller and/or shaft. By placing the two motors102within the same volume, the cooling path104in this approach is only slightly more complex than the cooling path in a single stage integral motor design, and the loss of efficiency due to diverting flow into the cooling path is minimized. However, this approach is, by its nature, limited to only two stages, and there is no obvious approach for expanding the design beyond the two-stage limit.

What is needed, therefore, is an integral, “sealless” pump or sealless turbine design that is compact and modular, such that more than two of the pump or turbine modules, preferably up to an arbitrarily large number, can be combined in series without bulky fluid interconnections therebetween. It is further preferable in embodiments that little or no process fluid be diverted away from the primary flow path for cooling the motor or generator within each module, that the rotors in the modules rotate separately, and/or that the motors/generators in the modules be separately controllable. It is still further desirable that the motor or generator that is integral to the pump or turbine module should itself also be modular, so that the same motor or generator design can be incorporated into different pump or turbine designs.

SUMMARY OF THE INVENTION

The present invention is a “sealless” motor pump or sealless generator turbine that is configured as a highly compact module having a “concentric” flow design. The disclosed modular design enables more than two of the pump or turbine modules, preferably up to an arbitrarily large number, to be combined in series without bulky fluid interconnections therebetween, and with the rotor in each module rotating separately on its own shaft or other supports. In embodiments, little or no process fluid is diverted away from the primary flow path for cooling the motor or generator within each module. In various embodiments, the rotors in the module motors or generators are separately controllable. And in embodiments, the motor or generator that is integral to the pump or turbine modules is itself modular, so that the same motor or generator design can be incorporated into different pump or turbine designs.

According to the present invention, the coil housing, i.e. stator housing, of the motor or generator is concentrically surrounded by the outer housing of the module, i.e. the module housing, thereby creating an annular space therebetween surrounding the motor or generator coils and centered on a primary axis of the motor or generator. Working fluid enters the module axially through a proximal inlet that is located substantially along the primary axis, and is discharged axially from the module through a distal outlet that is also located substantially along the primary axis. Within the module, the working fluid flows symmetrically past the stator housing that surrounds the motor or generator coils through either a plurality of substantially identical flow passages arranged symmetrically about the circumference of the stator housing, or through a single, annular flow passage that surrounds the stator housing. This symmetric distribution of the flow passage(s) in the region surrounding the motor or generator coils provides a compact design wherein the module housing is only moderately larger in diameter than the stator housing of the motor or generator.

In various embodiments suitable for use with relatively cool working fluids, the flow passages or single annular flow passage is/are in direct thermal contact with the housing of the motor or generator coils, thereby directly cooling the motor or generator coils. In some of these embodiments, more than 80% of the working fluid is brought into thermal contact with the motor or generator coil housing, and at least 20% of the motor or generator coil housing is in thermal contact with the working fluid. In various embodiments, more than 90% of the working fluid is brought into thermal contact with the motor or generator coil housing, and at least 50% of the motor or generator coil housing surface is in thermal contact with the working fluid.

In multi-passage embodiments suitable for use with hot working fluids, thermal insulation is provided between each of the plurality of substantially identical flow passages and the housing of the motor or generator coils. In some of these embodiments, a cooling fluid is circulated around the motor or generator coil housing in an annular space, such that the cooling fluid is in direct contact with the housing of the motor or generator coils, thereby cooling the motor or generator coils and protecting them from any residual heating by the hot working fluid.

In other embodiments where hot working fluid flows through a single, annular flow passage, thermal insulation is provided between the annular flow passage and the housing of the motor or generator coils, and in some of these embodiments a separate cooling fluid is circulated through a cooling annulus or cooling passages provided beneath the thermal insulation.

In embodiments, the concentric design of the present invention is implemented as a highly compact module that can be used alone or in series with a plurality of identical modules to form a multi-stage pump or turbine in which each stage includes both a rotor and an associated motor or generator. This modular design allows combination of the modules into an arbitrary number of stages without adding additional complexity or complications to the design, operation, and maintenance of the apparatus. In particular, because the rotor in each module is supported by a dedicated shaft or other supports, high stage counts do not raise any issues regarding shaft size, shaft deflection, roto-dynamics, bearing loads, motor alignment, or alignment between stages.

In some embodiments, the rotor of each module is fixed to a rotating shaft. In other embodiments, the shaft of each module is fixed, and the rotor rotates about the shaft, e.g. on bearings. For example, the shaft for each module can be inserted through the rotor hub and threaded into the module housing, which facilitates easy assembly and maintenance without special tools.

Certain embodiments include modules having an inverted rotor/stator configuration, whereby the rotor and the stator can both rotate independently from each other in opposite directions. Some embodiments include stators and/or diffusers that rotate individually. In some of these embodiments, the diffusers are implemented in a manner similar to the disclosure of patent application U.S. Ser. No. 15/101,460, which is included herein by reference in its entirety for all purposes.

In still other embodiments, the disclosed module does not include a shaft. Instead, a wear ring clearance on the front of the rotor acts as the primary radial and axial bearing. Torque is thereby transmitted directly from or to the electromagnet stator coils of the motor to the rotor, or electromagnetic energy is transferred directly from the rotor to the generator, without the use of a rotating shaft.

In some embodiments, the disclosed pump or turbine module includes a radial motor or generator design, whereby a plurality of permanent magnets are attached at or near the periphery of the rotor, and the rotor is surrounded by an electromagnet stator. In other embodiments, the disclosed module includes an axial, “disk” or “pancake” motor or generator, whereby a plurality of permanent magnets are attached to a rear side of the rotor, and are caused to pass close to electromagnetic coils of an axially adjacent stator as the rotor is rotated. Some embodiments that include permanent magnet motors or generators further include variable speed drives that enable the synchronous operating speeds of the modules to rise above 3600 rpm.

Other embodiments include induction motors or generators that utilize non-permanent magnets, such as “squirrel cage” rotor coils in which currents are induced by the stator electromagnets during pump or turbine operation.

In embodiments, the motor or generator coils are sealed from the working fluid using static sealing methods, which eliminates any need for dynamic mechanical seals, and avoids the problems of alignment, leakage, and/or maintenance that would otherwise arise therefrom.

Various embodiments having centrifugal designs include radial flow rotors. Some of these embodiments include rotors with specific speeds up to 2,000 US units, 4000 US units, or even 5000 US units. Other embodiments include stages with radial flux motor or generator designs and higher specific speed mixed flow rotor designs.

In embodiments, the rotors are axially and radially located by product-lubricated bearings provided in each modular stage, which allows the bearings in each stage to be designed to handle the loads from that stage only. This approach completely eliminates the risk of overloading bearings due to combined stage loading in a multistage arrangement, and provides a design that is more compact because there is no need to use oversized bearings. Using the working fluid as a lubricant for the bearings in embodiments also eliminates the need for an external oil lubrication system and greatly simplifies the overall pump design. In embodiments, combined radial and one-way thrust bearings are used in place of separate axial and radial bearings.

In various embodiments, the motors or generators in a multi-stage apparatus are separately controllable. Embodiments include a plurality of variable frequency drives (VFD's), and in some of these embodiments the motor or generator in each stage is independently controlled by a dedicated VFD. One of the key benefits in some of these embodiments is that the first stage can run at lower speeds than the rest of the apparatus, so as to accommodate low net positive suction head (“NPSH”) and off-peak conditions. In some applications, varying the speed of only the final stage provides a useful approach precisely controlling the output pressure and/or flow.

Providing individual VFD drives for each stage can also serve as a fail-safe redundancy, whereby if one stage fails, the rest will continue to operate and the apparatus will continue to function. The continued function after failure of a pump or turbine stage may be with reduced head and flow, or the speed of the remaining stages can be increased to compensate for the lost head and flow of the failed stage. This approach creates a failure scenario wherein the pump or turbine continues to operate, possibly at reduced head and flow, until an operator, after becoming aware of the stage failure, has time to safely shut down the system. In contrast, the failure of one stage in a traditional pump or turbine would result in failure of the entire apparatus, with a complete loss of performance and a sudden, uncontrolled shutdown of the system. Using a sensor-less motor along with an appropriate VFD also reduces the instrumentation required on each stage in various embodiments.

In various embodiments, the motor or generator that is included in each module is modular in design, whereby a given motor or generator design can be incorporated into a plurality of different pump or turbine designs. In particular, the plurality of permanent magnets or other magnetic devices that are included in the motor or generator included in a detachable, modular magnet structure that can be axially and rotationally constrained to be cooperative with the rotor of the pump or turbine. Axial and rotational constraint of the magnet structure can be by any means known in the art that is able to constrain the magnet structure both axially and rotationally in relation to the rotor. Embodiments include a snap ring that axially constrains the magnet structure and one or more pins that rotationally fix the magnet structure to the rotor. Other embodiments include threaded attachment of the magnet structure to the rotor or attachment by screws or bolts, whereby the magnet structure is constrained both axially and rotationally. Some of these embodiments further include an electrical port that can form a sealed conduit between the motor or generator housing and the pump or turbine housing so as to provide a path for electrical leads and/or control lines to extend between the stator and the environment external to the pump or turbine.

In embodiments, the magnet structure and/or the stator portion of the motor or turbine that contains the stator coils is/are modular and fully sealed, thereby requiring only mechanical attachment to the housing of the pump or turbine in proximity to each other. In various embodiments, sealed modular magnet structures and/or sealed modular stator assemblies of the present invention can be implemented in different combinations, rendering it unnecessary to configure new instantiations of the magnet structure and/or stator assembly each time a new pump or turbine module is designed.

A first general aspect of the present invention is a sealless pump or turbine module having an integral motor or generator. The module includes an inlet located at a proximal end of the module, the inlet being on a central axis of the module, an outlet located at a distal end of the module, the outlet being on the central axis of the module, a module housing surrounding the module, a rotor suspended within the module housing, and a motor within the module housing configured to drive a rotation of the rotor, or a generator within the module housing configured to be driven by rotation of the rotor.

The motor or generator includes a stator within a sealed stator housing, the stator comprising at least one electromagnet directed toward the rotor, said stator housing being removably axially, radially, and rotationally fixable to the module housing, an electrical port formed in the stator housing and configured to form a seal with the module housing when the stator housing is fixed to the module housing, the electrical port providing a sealed passage through which electrical conductors can be directed for interconnection between the at least one electromagnet and apparatus that is external to the module housing, a plurality of magnetic devices assembled in a magnet structure that is removably constrained to be axially fixed and rotationally cooperative with the rotor, the magnetic devices being configured by the magnet structure to pass in proximity to the at least one electromagnet as the rotor rotates, and a flow path symmetrically distributed about the stator housing,

In addition, the module is configured to direct a flow of working fluid from the inlet through the flow path to the outlet such that the working fluid is symmetrically distributed about the stator housing as it flows past the stator within the flow path.

In embodiments, the flow path is an annular flow path surrounding the stator housing.

In any of the above embodiments, the flow path can include a plurality of flow passages arranged symmetrically about the stator housing.

In any of the above embodiments, the rotor can be suspended by a rotatable shaft, and the rotor can be fixed to the shaft, or the rotor can be suspended by a fixed shaft, and the rotor can be configured to rotate about the shaft.

In embodiments where the rotor is suspended by a fixed shaft, and the rotor is configured to rotate about the shaft, the rotor can be supported on the fixed shaft by a pair of bearings, one of which maintains an axial position of the rotor while the other of which provides radial support of the rotor, or the rotor can be supported axially and radially on the fixed shaft by a single, one-way thrust bearing. In any of these embodiments the rotor can be supported on the fixed shaft by at least one bearing that is lubricated by the process fluid. In any of these embodiments, the fixed shaft can be fixed to at least one of the stator housing and the module housing by threaded attachment.

In any of the above embodiments, the magnetic devices can be permanent magnets, or squirrel cage coils.

In any of the above embodiments, the flow path can extend over at least 50% of a surface of the stator housing, and at least 90% of the working fluid that flows through the module from the inlet to the outlet is caused to flow through in direct thermal contact with the stator housing.

In any of the above embodiments, the module can be configured to require all of the working fluid flowing from the inlet to the outlet to flow through the flow path.

Any of the above embodiments can further include thermal insulation interposed between the flow path and the stator housing, and a cooling fluid path formed between the thermal insulation and the stator housing, the cooling fluid path being in thermal communication with the stator housing and configured to enable an exchange of heat between the stator housing and a cooling fluid flowing through the cooling fluid path.

In any of the above embodiments, the stator can be configured to rotate independently of the rotor and in a direction that is opposite to a rotation of direction of the rotor.

Any of the above embodiments can further include a diffuser that is cooperative with the rotor but is driven by a separate diffuser motor and is thereby able to rotate independently of the rotor.

In any of the above embodiments, the electromagnet of the stator can be directed toward a radial periphery of the rotor, and the magnetic devices can be fixed near the radial periphery of the rotor, or the electromagnet of the stator can be directed toward a side of the rotor, and the magnetic devices can be fixed to the side of the rotor or to a disk that is coaxial with and proximal to the side of the rotor.

And in any of the above embodiments, the magnet structure can be sealed, thereby excluding the working fluid from reaching the magnetic devices.

A second general aspect of the present invention is a multi-stage apparatus comprising a plurality of interconnected modules. Each of the modules includes an inlet located at a proximal end of the module, the inlet being on a central axis of the module; an outlet located at a distal end of the module, the outlet being on the central axis of the module; a module housing surrounding the module; a rotor suspended within the module housing.

Each of the modules further includes a motor within the module housing configured to drive a rotation of the rotor, or a generator within the module housing configured to be driven by rotation of the rotor. The motor or generator includes a stator within a sealed stator housing, the stator comprising at least one electromagnet directed toward the rotor, said stator housing being removably fixable axially, radially, and rotationally to the module housing; an electrical port formed in the stator housing and configured to form a seal with the module housing when the stator housing is fixed to the module housing, the electrical port providing a sealed passage through which electrical conductors can be directed for interconnection between the at least one electromagnet and apparatus that is external to the module housing; a plurality of magnetic devices assembled in a magnet structure that is removably constrained to be axially fixed and rotationally cooperative with the rotor, the magnetic devices being configured by the magnet structure to pass in proximity to the at least one electromagnet as the rotor rotates; and a flow path symmetrically distributed about the stator housing.

In addition, each of the modules is configured to direct a flow of working fluid from the inlet through the flow path to the outlet such that the working fluid is symmetrically distributed about the stator housing as it flows past the stator within the flow path.

In embodiments of this general aspect, at least two of the motors or generators of the modules can be independently controlled so as to cause the corresponding rotors to rotate at different rates. And in some of these embodiments the two, independently controlled motors or generators are controlled by separate variable frequency drives.

In any of the above embodiments of this general aspect, the modules can be configured such that the apparatus as a whole is able to continue functioning as a pump or as a turbine despite failure of at least one of the modules included in the apparatus.

Any of the above embodiments of this general aspect can further include control electronics that provide shared support to at least two of the modules.

In any of the above embodiments of this general aspect, the plurality of interconnected modules can include at least three interconnected modules.

And in any of the above embodiments of this general aspect, the magnet structure in each of the modules can be sealed, thereby excluding the working fluid from reaching the magnetic devices.

The features and advantages described herein are not all-inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and not to limit the scope of the inventive subject matter.

