Axial Compressor Recirculation for Stall Prevention
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Solution Overview
Problem
Axial compressors face challenges in maintaining stability under varying operating conditions, particularly at high pressure ratios and low ambient temperatures, with a risk of compressor stall and reduced mass flow, which complicates achieving high pressure with a low number of stages.
Innovation Solution
Implementing a return mechanism that recycles a portion of the compressed fluid's mass flow from the outlet of the last compressor stage back to the inlet of intermediate stages, using blow-in nozzles or channels to increase mass flow in the last stages, thereby reducing the risk of stall and stabilizing operational safety across all stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the number of compressor stages is increased to achieve high pressure, then the pressure ratio is improved, but the design effort and device complexity increase greatly
Solution Approach 1:
The patent merges the functions of multiple compressor stages by implementing a single-stage axial compressor with a return path that recycles compressed gas from the discharge back to the suction side. This combination allows the system to achieve pressure ratios that would normally require multiple stages while maintaining a simpler design with fewer components.
Solution Approach 2:
The return path acts as an intermediary mechanism that takes compressed gas from the discharge side and redirects it to the suction side, creating a recirculation loop. This intermediary path enables the single-stage compressor to effectively achieve multi-stage pressure multiplication without adding intermediate compression stages.
2Device complexity
If the number of compressor stages is reduced to simplify design, then the device complexity is improved, but the ability to generate large pressure differential is worsened
Solution Approach 1:
The return path serves as an intermediary that allows the single-stage compressor to achieve effective multi-stage compression by recirculating a portion of the compressed gas back through the compression stage, thereby multiplying the pressure differential without adding physical compression stages.
Solution Approach 2:
The system changes the operational parameters by implementing a recirculation ratio that controls the amount of gas returned to the suction side. By adjusting this parameter, the compressor can achieve varying effective pressure ratios while maintaining a simple single-stage design.
3Stress or pressure
If the compressor is designed for high pressure ratio operation, then the pressure output is improved, but the stability range under varying operating conditions is worsened
Solution Approach 1:
The return path creates a feedback mechanism where a portion of the discharged compressed gas is continuously recirculated back to the suction side. This feedback loop stabilizes the compressor operation by ensuring sufficient mass flow through the compression stage, preventing stall conditions, and maintaining stable operation across a wider range of operating conditions.
Solution Approach 2:
The recirculation of compressed gas provides a cushioning effect by maintaining a minimum mass flow through the compressor stages even at low inlet flow conditions. This prior cushioning prevents the compressor from entering unstable operating regions and stall conditions before they can develop.
4Productivity
If the mass flow is reduced to operate with fewer stages, then the productivity is improved in terms of simpler operation, but the risk of compressor stall is worsened
Solution Approach 1:
The return path implements a feedback mechanism that recirculates a controlled portion of the compressed gas back to the suction side, ensuring that sufficient mass flow is maintained through the compression stage. This feedback control prevents mass flow reduction to levels that would cause stall, thereby maintaining reliability while allowing simple single-stage operation.
Solution Approach 2:
The recirculated gas provides a cushioning effect that maintains minimum mass flow through the compressor, preventing stall conditions before they can occur. This cushioning allows the compressor to operate safely at lower inlet mass flows than would be possible without the recirculation path.
Data Source
AI summary
An axial compressor of a fluid-flow machine includes a flow path disposed between a rotor shaft and a relatively stationary housing wall. The flow path extends in an axial direction of the rotor shaft concentrically with the rotor shaft and the housing wall. A plurality of compressor stages are axially arranged in sequence along the flow path in the axial direction. Each of the compressor stages includes a rotor blades row and a guide vane row disposed after the rotor blades row in the axial direction. The flow path and the compressor stages operating therein are penetrable by a mass flow of a fluid to be compressed in a flow direction during operation of the compressor. A return is configured to return a part of the mass flow from a compressor discharge.