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

[0038]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, one-way thrust bearings are used in place of separate axial and radial bearings.

[0039]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

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

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