Compressor Rotating Stall Detection via Acoustic Energy Filtering
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Solution Overview
Problem
Current methods for detecting rotating stall in compressors, particularly in the diffuser region, are inadequate as they either focus solely on impeller rotating stall or fail to effectively differentiate between stall-related and non-stall related acoustic energy, leading to potential premature failure of compressor systems.
Innovation Solution
A system utilizing analog or digital circuits with high pass and low pass filters to analyze acoustic energy in specific frequency bands (10-300 Hz and 300-600 Hz) to detect rotating stall, with a method to subtract energy from the secondary frequency band to avoid unwanted VGD closure and enhance stall detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If acoustic energy monitoring is used to detect rotating stall, then stall detection capability is improved, but false positives from non-stall acoustic energy increase
Solution Approach 1:
The acoustic spectrum is segmented into multiple frequency bands (e.g., 50-200 Hz, 200-400 Hz, 400-600 Hz) rather than monitoring the entire spectrum as a single band. This allows the system to analyze the distribution of acoustic energy across different frequencies, identifying the characteristic pattern of rotating stall (increased energy in lower bands) while filtering out non-stall noise (energy distributed differently across bands).
Solution Approach 2:
The monitoring system applies different evaluation criteria to different frequency bands. Instead of treating all acoustic energy equally, the system weights or prioritizes specific frequency ranges where rotating stall generates characteristic signals, while de-emphasizing bands where non-stall phenomena dominate. This local differentiation improves detection accuracy by focusing on stall-specific acoustic signatures.
2Measurement precision
If multiple frequency bands are monitored, then stall detection accuracy is improved, but system complexity increases
Solution Approach 1:
The electronic package uses a single multi-functional signal processing unit that can analyze multiple frequency bands simultaneously. Rather than requiring separate monitoring systems for each frequency band, the invention employs one versatile device capable of spectral analysis across the entire acoustic range, reducing hardware complexity while maintaining multi-band monitoring capabilities.
Solution Approach 2:
The invention replaces complex mechanical or electronic filtering systems with digital signal processing techniques. By using digital algorithms to analyze acoustic spectra, the system achieves multi-band monitoring without the need for multiple physical filters or complex analog circuitry, thereby simplifying the electronic package while improving detection accuracy.
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 provides a robust and simplified electronic package for detecting rotating stall in the diffuser, reducing false positives and preventing premature VGD closure, thus improving compressor reliability and operational stability.
Implementation Method 1
measuring a value representative of acoustical energy associated with rotating stall in a radial diffuser of a compressor
Implementation Method 2
filtering the measured value with a first filter to obtain a first filtered value corresponding to a first stall frequency range
Implementation Method 3
a low pass filter is used to attenuate frequencies above a break frequency of about 300 Hz
Implementation Method 4
rectifying the first filtered value with a first rectifier to obtain a first rectified value
Data Source
AI summary
A system and method is provided for detecting and controlling rotating stall in the diffuser region of a compressor. A pressure transducer is placed in the gas flow path downstream of the impeller, preferably in the compressor discharge passage or the diffuser, to measure the sound or acoustic pressure phenomenon. Next, the signal from the pressure transducer is processed either using analog or digital techniques to determine the presence of rotating stall. Rotating stall is detected by comparing the detected energy amount, which detected energy amount is based on the measured acoustic pressure, with a predetermined threshold amount corresponding to the presence of rotating stall. Finally, an appropriate corrective action is taken to change the operation of the compressor in response to the detection of rotating stall.