Subsea Compressor Surge Prevention via Chord Angle Design
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Solution Overview
Problem
Conventional turbo compressors require complex and costly anti-surge control systems, which are difficult to implement effectively in subsea multiphase applications due to inadequate fast-acting valves and flow rate measurements, limiting their remote control and performance.
Innovation Solution
A subsea fluid pressure increasing machine with a contra-rotating design featuring impeller blades with chord angles less than or equal to their stall angles, and multiple orifices extending from the high pressure side to the low pressure side, eliminating the need for anti-surge control systems by preventing compressor surge through enhanced stall angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional turbo compressors use anti-surge control systems to maintain stable performance, then mechanical integrity is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent removes the anti-surge control system entirely from the compressor design. Instead of adding complex control valves, flow rate measurements, and remote control systems, the invention extracts this unnecessary complexity by designing impeller blades with chord angles inherently less than or equal to the stall angle, making the compressor surge-free by design rather than by control system intervention.
Solution Approach 2:
The compressor serves itself by maintaining stable operation through its own geometric design parameters. The impeller blade chord angle is designed to be less than or equal to the stall angle, creating a self-regulating system that inherently prevents surge conditions without requiring external control systems, sensors, or actuators.
2Reliability
If anti-surge control systems use fast acting valves and flow rate measurements to maintain stability, then mechanical integrity is improved, but ease of operation and remote control capability worsen
Solution Approach 1:
The patent removes fast-acting valves and flow rate measurement systems from the compressor design. These components are extracted because they complicate remote control operations and are inadequate for subsea multiphase applications. The surge prevention function is achieved purely through the impeller blade geometric design.
Solution Approach 2:
The compressor maintains mechanical integrity through self-service design rather than active control. The impeller blade chord angle geometry inherently prevents surge conditions, eliminating the need for remote-controlled valves and sensors that would otherwise be required to monitor and maintain stability.
3Power
If conventional compressors operate with narrow operating envelopes to achieve high pressure increase and efficiency, then power output is improved, but adaptability to different operating conditions worsens
Solution Approach 1:
The patent changes the critical geometric parameter of the impeller blades - specifically designing the chord angle to be less than or equal to the stall angle. This parameter change fundamentally alters the compressor's operating characteristics, enabling surge-free operation across a wide range of flow rates while maintaining high pressure increase and efficiency, thus expanding the operating envelope without sacrificing power output.
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
The solution enables surge-free operation without anti-surge control systems, achieving higher nominal flow rates and maintaining mechanical integrity, particularly suitable for remote and multiphase subsea applications, by delaying boundary layer separation and increasing stall angles.
Implementation Method 1
multiple orifices that extend through the impeller blade from a high pressure side of the impeller blade to a slot that extends to a low pressure side of the impeller blade
Implementation Method 2
each impeller blade... has multiple orifices... that effectively increases the stall angle of the impeller blade
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A compressor includes impellers each having its chord angle less than its stall angle. The impellers can be used in a contra-rotating impeller arrangement without static diffusers. The contra-rotating impeller arrangement provides for much larger nominal flow rates than conventional single rotating impeller arrangements with the same chord angles. Accordingly, a surge free design is provided without excessively compromising the nominal flow rate. Techniques for enhancing stall characteristics of the impellers are also described.