Variable Outlet Guide Vanes for Axi-Centrifugal Compressor Stability
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Solution Overview
Problem
Axi-centrifugal compressors face challenges in maintaining efficiency at varying flow rates due to the mismatch between the maximum flow of the centrifugal and axial compressor portions, leading to instability and the need for bleeding or variable inlet guide vanes, which can negatively impact performance.
Innovation Solution
Incorporating variable guide vanes between the axial and centrifugal portions of the compressor, allowing for adjustable stagger angles to optimize flow and pressure ratios, with actuator systems to control the vanes' positions based on operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the diffuser throat flow area is reduced to achieve high pressure ratio, then the pressure ratio improves, but the maximum flow of the centrifugal portion becomes less than the minimum stable flow of the axial compressor
Solution Approach 1:
The patent introduces variable outlet guide vanes that can dynamically adjust their stagger angle to control the flow rate through the centrifugal portion of the compressor. This dynamic adjustment allows the system to adapt to different operating conditions, enabling the centrifugal portion to handle variable flow rates while maintaining compressor stability and avoiding stall conditions.
2Reliability
If bleeding is used to achieve compressor stability, then stability improves, but performance deteriorates
Solution Approach 1:
Instead of extracting or bleeding excess flow from the system, the patent controls the flow rate by adjusting the outlet guide vane angle to match the centrifugal portion's maximum flow with the axial compressor's minimum stable flow. This eliminates the need for bleeding while maintaining stability and preserving performance.
3Reliability
If variable inlet guide vanes are used to throttle mass flow, then compressor stability improves, but performance deteriorates
Solution Approach 1:
The patent adjusts the outlet guide vane angle in advance to pre-control the flow rate entering the centrifugal portion, matching it to the axial compressor's stable operating range. This preliminary flow control prevents instability before it occurs, eliminating the need for performance-degrading variable inlet guide vanes.
4Productivity
If the axial compressor operates beyond its stall line, then flow rate increases, but stability deteriorates
Solution Approach 1:
The patent implements a control system that monitors compressor operating conditions and adjusts the outlet guide vane angle in response to maintain stability. This feedback mechanism ensures the centrifugal portion's flow capacity matches the axial compressor's output, preventing operation beyond the stall line while maintaining desired flow rates.
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 solution ensures efficient operation across a range of flow rates by matching flow rates between compressor portions, reducing the need for bleeding and improving stability and efficiency, resulting in lower weight and optimized loading between axial and centrifugal components.
Implementation Method 1
Variable outlet guide vanes are disposed between the axial and centrifugal portions
Implementation Method 2
variable guide vanes between the axial and centrifugal portions
Data Source
AI summary
An example compressor includes a casing having a main portion and an outer skirt collectively defining an annular plenum, an outlet guide vane coupled to the main portion, an actuator mounted outside the outer skirt, and a linkage coupled to the actuator and the outlet guide vane through the annular plenum.