Compact, modular, integral pump or turbine with coaxial fluid flow

Abstract

A coaxial pump or turbine module directs working fluid past a rotor and through a flow path symmetrically distributed within an annulus formed between an outer module housing and an inner motor or generator coil housing. The inner housing can be cooled by working fluid in the flow path, or by a cooling fluid flowing between passages of the flow path. The flow path can extend over substantially a full length and rear surface of the inner housing. The rotor can be fixed to a rotating shaft, or rotate about a fixed shaft, which can be threaded into the motor and / or module housing. A plurality of the modules can be combined into a multi-stage apparatus, with rotor speeds independently controlled by corresponding variable frequency drives. The motor or generator can include radial or axial permanent magnets and / or induction coils. Embodiments include guide vanes and / or diffusers.

Description

RELATED APPLICATIONS[0001]This application is a continuation in part of U.S. application Ser. No. 15 / 793,457, filed Oct. 25, 2017, which is herein incorporated by reference in its entirety for all purposes.FIELD OF THE INVENTION[0002]The invention relates to pumps and turbines, and more particularly, to integral sealless pumps and turbines.BACKGROUND OF THE INVENTION[0003]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.[0004]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...

AI Technical Summary

Benefits of technology

The present invention provides an improved design for pumps and turbines that allows for individual control of each stage, resulting in fail-safe redundancy and continuous operation even if one stage fails. The design also eliminates the need for multiple sensors and instrumentation on each stage. The coil housing of the motor or generator is surrounded by the housing of the module, creating an annular space therebetween surrounding the motor or generator coils. The working fluid flows symmetrically past the motor or generator coils through either a plurality of substantially identical flow passages arranged symmetrically about the circumference of the motor or generator coils, or through a single, annular flow passage that surrounds the motor or generator coils. 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 motor or generator housing.

Problems solved by technology

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.

Even with rigid baseplates, nozzle loads on the pump or turbine can cause alignment problems between the motor or generator and the mechanical seals.

Also, the components used for magnetic coupling add complexity and cost to the design.

However, radial designs necessarily require a significant increase in the diameter of the rotor housing.

However, it can be difficult to cool the motor or generator coils of a sealless motor pump or sealless generator turbine.

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 problem that is faced by designers of 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.

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.

However, the additional size and bulk that result from this approach can be problematic.

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 the 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 sealless generator designs that operate efficiently over a range of pressures and flow rates.

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.

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 rotordynamic 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 number of stages, and cannot be easily scaled to accommodate requirements for different numbers of stages.

Furthermore, the elongated shaft, multi-stage approach requires that all of the rotors rotate at the same speed, which can limit the efficiency 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.

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.

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.

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.

Images