Subsea Impeller Stall Angle Features for Compact High-Head Design
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Solution Overview
Problem
Conventional turbo compressors designed for dry gas are limited in achieving high pressure increase due to low specific loads to avoid phase separation, which restricts the maximum head that can be achieved on a single shaft, and they require complex control systems and multiple impeller stages for surge-free operation.
Innovation Solution
A subsea axial fluid pressure-increasing machine with impellers having stall angle enhancement features that reduce pressure peaks on the suction side, allowing for shorter axial lengths without exceeding specific loads, and utilizing a contra-rotating design without anti-surge control systems to achieve surge-free operation and higher nominal flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low specific loads are used to avoid phase separation, then phase separation is avoided, but the maximum head that can be achieved on a single shaft is limited
Solution Approach 1:
The patent changes the geometric parameters of the impeller blades, specifically using high cord angles (beta) of 35-55 degrees and optimized blade loading distribution. This allows the impeller to achieve higher specific loads without causing phase separation, thereby increasing the maximum head capability while maintaining reliable multi-phase operation
Solution Approach 2:
The patent transitions from conventional single-phase design parameters to multi-phase optimized parameters by introducing high cord angles and modified blade geometry. This dimensional change in the design space enables simultaneous achievement of high specific loads and phase separation avoidance
2Productivity
If high cord angles of impeller blades are used to achieve large nominal flow rates, then nominal flow rate increases, but axial length of impeller increases if blade chord length is maintained
Solution Approach 1:
The patent optimizes the relationship between cord angle and blade chord length by using high cord angles (35-55 degrees) combined with reduced chord lengths. This parameter optimization allows achieving large nominal flow rates while minimizing axial length, creating a more compact impeller design
3Productivity
If conventional impeller design is used to achieve good compressor performance, then capacity and pressure increase improve, but control system complexity increases to ensure operation within acceptable boundaries
Solution Approach 1:
The patent designs impellers with inherent surge-free characteristics through optimized blade geometry, high cord angles, and proper loading distribution. This self-service design allows the compressor to maintain stable operation across a wide range of flow rates without requiring complex anti-surge control systems, thereby reducing control system complexity while maintaining high capacity
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 increased nominal flow rates and reduced specific blade loads, allowing more impellers on a single shaft, thereby enhancing the overall head capability of the machine without the need for complex control systems, making it suitable for subsea and multiphase applications.
Implementation Method 1
impellers having stall angle enhancement features that reduce pressure peaks on the suction side
Implementation Method 2
A subsea axial fluid pressure-increasing machine with impellers... utilizing a contra-rotating design... to achieve surge-free operation
Data Source
AI summary
A subsea fluid pressure-increasing machine includes an elongated member that is rotatable about a longitudinal axis. The machine also may include a plurality of impellers each having a leading edge, a trailing edge, a suction side, and a chord line defined by a line between the leading and trailing edges. Each impeller is fixedly mounted to the member such that a chord angle defined by an angle between the chord line and the rotation direction is less than or equal to a stall angle at which a maximum force is exerted on a fluid in a direction primarily parallel to the longitudinal axis when the member is rotated in the rotation direction. At least some of the impellers comprise one or more features that effectively reduce a pressure peak or specific loading of the suction side such that the axial length of the impeller is configured to be reduced without exceeding a desired specific load.