Axial Compressor Recirculation Passage for Surge Limit Extension
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Solution Overview
Problem
Axial compressors in gas turbines face instability and energy loss issues during low flow rate operations, with existing self-circulating casing treatments extending the surging limit but causing unnecessary energy loss in rated operations.
Innovation Solution
An axial compressor design featuring a recirculation passage with a suction port positioned rearward of stator blade leading edges and an ejection port forward of rotor blade centers, along with a flow control device to adjust recirculation air flow rate, enhancing air flow rate and reducing energy loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If self-circulating casing treatment is used to extend the surging limit in low flow rate operation, then the operation region is extended, but unnecessary energy loss occurs in rated operation
Solution Approach 1:
The recirculation passage is designed with adjustable flow control means that can vary the recirculation air flow rate based on operating conditions. During low flow rate operation, the passage remains open to extend the surging limit, while during rated operation, the flow control means reduces or closes the passage to minimize energy loss, making the system adaptive to different operational states
Solution Approach 2:
The invention changes the flow rate parameter of recirculation air based on operating conditions. By controlling the recirculation air flow rate to be higher during low flow rate operation and lower or zero during rated operation, the system optimizes performance across different operational regimes, resolving the contradiction between extending surging limit and reducing energy loss
2Reliability
If the ejection port is positioned forward of the rotor blade row, then the structure is simpler, but the surging limit cannot be extended as effectively
Solution Approach 1:
The ejection port is positioned not only forward of the rotor blade row but also at a location that opposes the rotor blade tips in the radial dimension. This multi-dimensional positioning (axial forward position combined with radial alignment with blade tips) enhances the effectiveness of extending the surging limit while maintaining reasonable structural complexity
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 design extends the surging limit during non-rated operations while minimizing energy loss in rated operations by optimizing air flow and reducing vortex generation.
Implementation Method 1
a recirculation passage (70) provided in the casing and having a suction port (72) provided on a downstream side of the fluid passage and an ejection port (74) provided on an upstream side of the fluid passage
Implementation Method 2
the suction port is located rearward of leading edges (47B) of bases (47A) of the stator blades, and the ejection port is located at a position forward of centers (45X) of tips (45A) of the rotor blades
Data Source
AI summary
An axial compressor includes: a rotary shaft rotatably supported in a cylindrical casing such that an annular fluid passage is defined therebetween; a rotor blade row including rotor blades provided on an outer circumferential surface of the rotary shaft; a stator blade row including stator blades provided on an inner circumferential surface of the casing at a position adjacent to and behind the rotor blade row; and a recirculation passage provided in the casing and having a suction port and an ejection port on downstream and upstream sides of the fluid passage, respectively. The suction port is located rearward of leading edges of bases of the stator blades, and the ejection port is located at a position forward of centers of tips of the rotor blades and at least partially opposing the tips of the rotor blades.