Short Impeller Geometry for Surge-Free Subsea Fluid Compression
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Solution Overview
Problem
Conventional turbo compressors face limitations in achieving high head due to low specific loads and phase separation, which restricts the number of impeller stages on a single shaft, necessitating complex control systems and narrow operating envelopes.
Innovation Solution
A subsea fluid pressure increasing machine with impellers having chord angles less than or equal to stall angles, incorporating features like gaps and slots to reduce pressure peaks and specific loading, allowing for a contra-rotating design without anti-surge control systems, enhancing stall angles and enabling higher nominal flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi-phase impellers use low specific blade load to reduce phase separation, then phase separation is reduced, 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 (close to 90 degrees) and reduced blade chord lengths. This parameter change allows the impeller to achieve high nominal flow rates while maintaining low specific blade loads, thereby reducing phase separation without limiting maximum head capacity. The blade angle and chord length are optimized to balance these competing requirements.
Solution Approach 2:
The patent transitions from conventional low cord angle blade designs to high cord angle blade designs, fundamentally changing the orientation of the blades relative to the rotation axis. This dimensional change in blade geometry enables the impeller to achieve both high flow rates and high head capability simultaneously, resolving the contradiction between phase separation reduction and maximum head capacity.
2Stress or pressure
If impeller blade chord length is maintained to not increase specific impeller blade load, then specific blade load is controlled, but axial length of the impeller increases
Solution Approach 1:
The patent reduces the blade chord length parameter while compensating by increasing the cord angle. This parameter change allows the impeller to maintain acceptable specific blade loads while significantly reducing the axial length of the impeller blades, thereby resolving the contradiction between load control and length reduction.
3Reliability
If conventional turbo compressors use complex control systems to ensure operation within acceptable boundaries, then operational reliability is improved, but device complexity increases
Solution Approach 1:
The patent designs the impeller with inherent surge-free characteristics through high cord angle blades and optimized geometry. The impeller self-regulates its operation within acceptable boundaries without requiring external control systems, achieving operational reliability through design rather than active control, thereby eliminating complex control system complexity.
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 design achieves surge-free operation without anti-surge control systems, enabling larger nominal flow rates and increased head capacity by reducing impeller axial length and specific blade load, suitable for subsea and multiphase applications.
Implementation Method 1
an elongated member rotatable about a longitudinal axis... a plurality of impellers... exerted on a fluid in a direction primarily parallel to the longitudinal axis when the member is rotated in the rotation direction
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.