Subsea Compressor Driven by Submerged Permanent Magnet Motor
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Solution Overview
Problem
Current subsea compressor systems are costly, complex, and inefficient due to sensitive electrical components, limited speed, and high complexity, with existing technologies not tolerating sour service and experiencing windage losses from liquid lubrication, leading to size and performance limitations.
Innovation Solution
A compressor system utilizing a permanent magnet motor with a common shaft or coupling to a compressor unit, supported by plain lubricated bearings within a hermetically sealed housing filled with a barrier liquid for cooling and lubrication, which also acts as a barrier against process fluids, featuring a circulation and cooling arrangement to manage liquid flow and pressure, and potentially incorporating a balancing piston for axial force balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If standard induction motors with large diameter rotors are used submerged in liquid, then the motor can be cooled and lubricated by the liquid, but windage losses increase and rotational speed is limited
Solution Approach 1:
The patent changes the motor type from standard induction motor to permanent magnet motor, which allows for a smaller rotor diameter and larger clearance between stator and rotor. This parameter change reduces windage losses significantly while still allowing the motor to operate submerged in liquid for cooling and lubrication.
Solution Approach 2:
The patent replaces the standard induction motor mechanism with a permanent magnet motor mechanism. The permanent magnet motor generates magnetic fields more efficiently, allowing for compact rotor design with reduced diameter, which directly reduces windage losses and enables higher rotational speeds while maintaining liquid cooling capability.
2Reliability
If hermetically sealed compressor/motor with active magnetic bearings is used, then the system is protected from sour service, but complexity and cost increase
Solution Approach 1:
The patent extracts the sensitive electrical windings and connections from the process gas environment by submerging the motor in liquid and using plain liquid lubricated bearings. This removes the components that are vulnerable to sour service, eliminating the need for active magnetic bearings and complex control systems while maintaining protection against corrosive environments.
Solution Approach 2:
The patent uses plain liquid lubricated bearings instead of expensive active magnetic bearings. The liquid barrier provides sufficient protection against sour service without requiring complex sealed systems, resulting in a simpler, more cost-effective solution that is easier to maintain.
3Speed
If two contra rotating electric motors are used to generate relative speed, then the required speed for gas compression is achieved, but device complexity and size increase
Solution Approach 1:
Instead of using two contra-rotating motors to generate relative speed, the patent inverts the approach by using a single motor that directly drives the compressor at the required speed. The permanent magnet motor's ability to operate at high speeds submerged in liquid eliminates the need for contra-rotating mechanisms, simplifying the system while achieving the same compression function.
Solution Approach 2:
The patent merges the motor and compressor into a single integrated unit with a common shaft, eliminating the need for separate contra-rotating motors and their associated complexity. The permanent magnet motor directly couples to the compressor, creating a compact, simple system that achieves the required rotational speed for gas compression.
4Speed
If induction motor with step-up gearing is used, then compressor speed is increased, but device complexity and loss of time increase
Solution Approach 1:
The patent extracts the step-up gearing mechanism entirely by using a permanent magnet motor that can directly generate the required high rotational speeds. This eliminates the need for complex gear trains, reducing device complexity and removing the time losses associated with mechanical gear engagement and maintenance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for higher operational speeds, reduced windage losses, and increased efficiency while maintaining a compact design, enabling operation in sour service environments with improved performance and reduced complexity compared to existing systems.
Implementation Method 1
A compressor system is disclosed utilizing a permanent magnet motor
Implementation Method 2
The motor and bearings are submerged in a liquid within the housing, which liquid would act as a cooling, lubricating and barrier liquid
Implementation Method 3
The motor unit and bearings are submerged in a liquid within the housing, which liquid would act as a cooling, lubricating and barrier liquid
Implementation Method 4
The motor and bearings are submerged in a liquid within the housing, which liquid would act as a cooling, lubricating and barrier liquid
Implementation Method 5
The barrier liquid is enclosed within the housing, and in one embodiment with mechanical seals as barriers towards the gas compression section of the unit
Data Source
AI summary
A compressor system includes a compressor unit having a first rotor and a permanent magnet motor unit having a second rotor connected to the first rotor. The first and second rotors are rotatably supported on at least first, second and third bearings, and the compressor system further includes a housing having a first chamber in which the motor unit is located, a second chamber in which the compressor unit is located and a third chamber in which at least the first bearing is located. The first and third chambers are fluidly sealed from the second chamber and contain a cooling, lubricating and barrier liquid within which the motor unit and the first bearing are submerged, and during operation of the compressor system the fluid is circulated between the first and third chambers.