Compressor Surge Control via Variable Safety Margin
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Solution Overview
Problem
Existing methods for controlling compressor operation to avoid surge, stall, and flutter in aircraft fans or compressors are inefficient, particularly when dealing with multiple variable geometries and inlet flow distortions, as they often result in a fixed safety margin that compromises thrust and efficiency.
Innovation Solution
A method that dynamically adjusts the safety margin for compressor operation based on inlet guide vane angle, non-dimensional speed, vehicle Mach number, and inlet geometry, using a control parameter with margin-adjusted limiting values stored in a look-up table, allowing real-time monitoring and adjustment to prevent stall, surge, or flutter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed safety margin is established to accommodate all threats under different flight conditions, then compressor surge prevention is improved, but thrust and efficiency are worsened
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed safety margin to a variable safety margin that adapts to different operating conditions. The control system dynamically adjusts the safety margin based on real-time parameters including inlet guide vane angle, corrected speed, and flight conditions, allowing the compressor to operate closer to stability limits when conditions permit while maintaining adequate margins when threats are present
Solution Approach 2:
The patent implements parameter changes by modifying the safety margin parameter based on multiple operating variables. The system retrieves margin-adjusted limiting values from lookup tables that are functions of inlet guide vane angle, non-dimensional speed, vehicle Mach number, and inlet geometry, thereby optimizing the balance between surge prevention and performance
2Stability of the object's composition
If the working line is positioned far from the stability line to prevent surge, then compressor stability is improved, but operating flexibility and efficiency are worsened
Solution Approach 1:
The system dynamically adjusts the working line's distance from the stability line based on real-time operating conditions. By retrieving margin-adjusted limiting values that vary with inlet guide vane angle, speed, and flight conditions, the control system allows the working line to approach closer to stability limits when conditions are favorable while maintaining larger margins when threats are present
Solution Approach 2:
The patent employs feedback by continuously monitoring operating parameters and comparing actual values against margin-adjusted limiting values. The control system uses this feedback to determine when it is safe to operate closer to stability limits, thereby optimizing the balance between stability and flexibility based on real-time conditions
Data Source
AI summary
A compressor or fan is controlled to avoid stall, surge or flutter. The control system includes a look-up table from which is retrieved a margin-adjusted limiting value of a control parameter of the compressor, using inputs representing inlet guide vane angle (IGV), non-dimensional speed of the compressor (N/R√T), vehicle Mach number (Mn) and inlet geometry (IG). A variable stall, surge or flutter safety margin about a nominal limiting value of a control parameter is pre-established to reflect threats to the working, stall, flutter and surge lines, for example as a result of measurement inaccuracies, and from this the margin-adjusted limiting value is derived. An actual value of the control parameter is determined in real time, and the actual value is compared with the margin-adjusted limiting value. An output signal indicating stall, surge or flutter risk is generated if the actual value falls within the stall, surge or flutter safety margin.