Compressor Rotating Stall Detection via Blade Pass Frequency Energy
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Solution Overview
Problem
Existing methods fail to accurately detect rotating stall in turbine blades of compressors, leading to undetected overloading and potential damage, as they do not account for the specific operational conditions and cannot differentiate between normal operation and stall states effectively.
Innovation Solution
Monitoring the blade pass frequency and associated vibration energy using microphones and vibration-sensitive sensors, with signal processing techniques like Fast Fourier Transform to identify incipient and developed rotating stall by comparing energy levels at specific frequency ranges, allowing for early detection and prevention of compressor breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional monitoring methods are used, then the system is simple, but rotating stall cannot be detected accurately
Solution Approach 1:
The monitoring system segments the frequency spectrum into multiple bands (normal blade pass frequency, higher blade pass frequencies, lower blade pass frequencies) and analyzes vibration energy in each segment separately. This segmentation allows the system to detect specific frequency patterns characteristic of rotating stall without being overwhelmed by the entire frequency spectrum, thereby improving detection accuracy while keeping the analysis manageable.
Solution Approach 2:
The patent introduces a new dimension of analysis by examining vibration energy distribution across different frequency ranges rather than relying on a single frequency metric. By adding the frequency spectrum dimension to the monitoring approach, the system can distinguish rotating stall conditions from normal operation based on the characteristic frequency patterns, enhancing detection precision without requiring overly complex sensor arrays.
2Reliability
If monitoring is not performed, then the system is simple, but compressor failure risk increases
Solution Approach 1:
The monitoring system performs preliminary detection of rotating stall conditions by analyzing vibration energy patterns before actual compressor failure occurs. By identifying the characteristic frequency signatures of rotating stall in advance, the system enables proactive maintenance actions, preventing catastrophic failures while maintaining relatively simple monitoring hardware that can be installed without disrupting existing compressor operations.
Solution Approach 2:
The system continuously monitors vibration energy across different frequency ranges and provides feedback about the operational state of the compressor. When the vibration energy patterns indicate rotating stall, the feedback mechanism can trigger alerts or control responses to prevent failure, thereby improving reliability without requiring complex intervention systems, as the monitoring itself provides sufficient value for maintenance scheduling.
3Reliability
If maintenance is scheduled frequently, then component reliability is improved, but maintenance time and cost increase
Solution Approach 1:
The monitoring system enables preliminary assessment of turbine blade condition by detecting rotating stall events and accumulating damage data. This allows maintenance scheduling to be based on actual condition rather than fixed time intervals, preventing both premature maintenance and missed maintenance opportunities. The system provides sufficient lead time for planning maintenance during optimal windows, reducing overall maintenance time while ensuring blade reliability.
Solution Approach 2:
The monitoring system serves the maintenance function by automatically detecting rotating stall conditions and providing the data needed for maintenance decision-making. Rather than requiring complex manual inspection procedures, the system self-monitors the turbine blade condition and delivers actionable information that enables optimized maintenance scheduling, reducing time loss while maintaining reliability through continuous condition assessment.
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
Enables reliable detection of rotating stall, reducing the risk of compressor failure by providing timely alerts for adjusting back pressure and improving maintenance scheduling through accurate lifetime estimation.
Implementation Method 1
The microphone and sensor pick up acoustically generated pressure waves from the turbine blades by pressure waves propagating through the air
Implementation Method 2
a vibration-sensitive sensor, for example in the form of an accelerometer, which is mounted externally on the compressor casing
Data Source
AI summary
A method and device for determining the occurrence of rotating stall in the turbine blade of a compressor, in which the blade pass frequency of at least one compressor stage and the associated vibration energy are monitored, the normal blade pass frequency being constituted by the operating speed of rotation of the compressor multiplied by the number of turbine blades in the stage, and in which incipient rotating stall in a compressor stage is indicated when, at the normal blade pass frequency of the compressor stage, the vibration energy falls below a predetermined first value at the same time as, at a blade pass frequency above the normal blade pass frequency, the vibration energy rises above a predetermined second value.