Multistage Compressor Surge Control Using Single Flow Measurement
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Solution Overview
Problem
Calculating the surge limit line for multistage compressors is challenging when only one flow-measuring device is available, making it difficult to determine the operating point's distance to the surge limit line and perform protective regulatory control actions.
Innovation Solution
A method that uses a single flow-measuring device and overall surge recycle valve to accurately calculate the surge limit line for multistage compressors, simplifying the control system configuration by focusing on reliable surge prevention control and eliminating the need for complex individual PID controllers at each stage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple flow measuring devices are installed at each stage for accurate surge detection, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges the surge prevention control for multiple compressor stages into a single unified control system. Instead of implementing separate PID controllers at each stage, the invention uses one overall surge recycle valve and one flow measuring device to control the entire multistage compressor, thereby reducing device complexity while maintaining surge detection accuracy through unified surge limit line calculation
Solution Approach 2:
The single flow measuring device installed at the suction of the first stage serves multiple functions: it measures flow for surge detection, calculates the surge limit line for the entire multistage compressor, and provides control feedback for the overall surge prevention system, eliminating the need for dedicated measuring devices at each stage
2Manufacturing precision
If individual PID controllers are implemented at each compressor stage, then control precision is improved, but device complexity and interaction between control modules increase
Solution Approach 1:
The patent combines multiple individual stage control functions into a single overall surge prevention control system. One unified controller calculates the surge limit line for the entire multistage compressor and controls a single overall surge recycle valve, eliminating the need for multiple interacting PID controllers at each stage while maintaining effective surge protection
Solution Approach 2:
The invention extracts the essential surge prevention function from complex multi-stage individual controls and implements it through a simplified unified control approach, removing unnecessary complexity from intermediate control modules while retaining the core surge detection and protection capabilities
Data Source
AI summary
A method and apparatus for surge prevention control for multistage compressors with at least two stages, at least one flow measuring device, and one overall surge recycle valve is disclosed. Furthermore, a method of accurate calculation of surge limit line for overall multistage compressor using one available flow measuring device is also disclosed. The method of surge prevention calculates multistage compressor's surge limit line as a product of individual stages surge limit lines that differs from those revealed in the prior art. This method allows accurate calculation of the distance of operating point to surge limit line that takes in account surge lines of all stages and allows reliable surge prevention control.