Compressor Diffuser Blades With Varying Cross-Section Cavities
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Solution Overview
Problem
Diffusers in centrifugal or mixed compressors of gas turbines face issues with fluid separation and stall due to non-homogeneous fluid suction, leading to detrimental surge phenomena.
Innovation Solution
The diffuser design features a varying cross-section cavity in the transverse direction of the blade, with orifices on the upper and lower surfaces communicating with cavities, ensuring uniform suction flow by increasing the cross-sectional area towards the first flank, preventing fluid detachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If holes are made on the extrados to suck fluid for cooling, then cooling effect is improved, but fluid suction becomes non-homogeneous causing flow separation
Solution Approach 1:
The cavity cross-section is designed with varying local properties - larger at the extrados side and smaller at the intrados side - to create non-uniform suction distribution that compensates for the natural flow patterns, ensuring homogeneous fluid suction across the blade surface while maintaining cooling effectiveness
Solution Approach 2:
The cavity geometry parameters are specifically optimized by varying the cross-sectional area along the blade span, with the cross-section being larger near the extrados and tapering toward the intrados, which controls the suction flow distribution to prevent flow separation while maintaining cooling performance
2Reliability
If uniform suction is achieved through varying cavity cross-section, then flow stability is improved, but device complexity increases
Solution Approach 1:
The blade is designed with an internal cavity system that acts as a distributed porous structure, where the varying cross-section cavities distribute suction uniformly across the blade surface, achieving flow stability without requiring complex external suction devices or multiple discrete holes
Solution Approach 2:
The solution moves the complexity from the two-dimensional blade surface (multiple holes) to the three-dimensional internal cavity structure, where a single varying cross-section cavity can serve multiple orifices, simplifying the overall device while achieving uniform suction distribution
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
This design achieves homogeneous fluid suction on both surfaces, preventing fluid separation and stall, thereby enhancing the operational stability of the compressor.
Implementation Method 1
the cross-section of the cavity varies in the transverse direction of the blade according to a law of increasing variation towards the first flank... the suction of the fluid is homogeneous both on the upper surface of the blade and on its lower surface
Data Source
Figure 1
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AI summary
The invention relates to a diffuser (18) for a mixed flow or centrifugal compressor of a gas turbine, comprising at least one blade (20, 120) having a pressure side (I), a suction side (E), and a first flank (22, 122), said blade being provided with a plurality of apertures (26, 126, 34, 134, 32, 132) in communication with the suction side (E) and/or the pressure side (I) and communicating with at least one recess provided in the blade, said recess (30, 36, 200, 210) extending transversely relative to the blade and in communication with the first flank. The invention is characterised in that the cross-section of the recess (30, 36, 200, 210) varies in the transverse direction of the blade according to a law of increasing variation towards the first flank.