Compressor Diffuser Fin Curved Trailing Edge
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Solution Overview
Problem
Axial diffusers in radial or mixed compressors of gas turbine engines are prone to circumferential cracks due to vibratory stresses, exacerbated by the small radius of solder and manufacturing dispersions, which complicates industrial control and increases the risk of damage.
Innovation Solution
The diffuser design features a shorter distance between the leading and trailing edges of fins at mid-height, a smaller radius of curvature near the shrouds, an evolving section with low walls, and extra thickness on the shrouds to redistribute stress and enhance mechanical strength, while maintaining aerodynamic functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the diffuser uses traditional fin structure with small solder radius, then the aerodynamic performance is maintained, but circumferential cracks form due to vibratory stresses
Solution Approach 1:
The trailing edge of the fin is designed with non-uniform thickness distribution, featuring a thicker section at the trailing edge compared to the root. This local thickening creates a larger solder radius area that distributes vibratory stresses more effectively, preventing crack initiation and propagation while maintaining the overall aerodynamic profile of the fin
Solution Approach 2:
The invention modifies the geometric parameters of the fin trailing edge by increasing the solder radius through thickness distribution optimization. This parameter change transforms the stress concentration geometry into a stress-distributing geometry, fundamentally changing how vibratory loads are handled at the solder joint without altering the fin's aerodynamic function
2Reliability
If the solder radius is increased to reduce stress concentration, then crack resistance improves, but manufacturing precision control becomes difficult due to manual operation
Solution Approach 1:
The fin is pre-formed with a specific thickness distribution profile before the soldering process. This preliminary geometric preparation ensures that when solder is applied, the larger solder radius is achieved automatically through the pre-designed thicker trailing edge section, reducing dependence on manual soldering skill and improving consistency across production batches
Solution Approach 2:
The trailing edge of the fin incorporates a curved, rounded profile rather than a sharp edge or uniform thickness. This curvature creates a naturally larger solder radius that is more tolerant to manufacturing variations, as the rounded geometry provides a buffer zone that maintains stress distribution benefits even with slight dimensional tolerances
3Reliability
If the fin structure is modified to increase solder radius, then vibratory stress tolerance improves, but the aerodynamic efficiency may be affected
Solution Approach 1:
The thickness modification is localized specifically to the trailing edge region where solder joints are formed, while the majority of the fin surface area maintains its original aerodynamic profile. This localized approach ensures that aerodynamic flow over the fin surface is minimally disturbed, preserving energy efficiency while providing structural reinforcement where needed
Solution Approach 2:
The thickness increase is applied partially only to the trailing edge region rather than uniformly across the entire fin. This partial action provides sufficient structural reinforcement at the critical stress location without excessively altering the overall fin geometry, thereby maintaining aerodynamic performance while achieving the necessary stress tolerance
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 reduces the risk of cracks by shifting the critical stress zone upstream and reducing static and dynamic stresses, making the diffuser more tolerant to vibratory loads and manufacturing variations.
Implementation Method 1
The trailing edge 12 of each fin 10 is curved so that a distance d1 between the leading edge 11 and the trailing edge 12 of the fin 10 at mid-height h/2 of fin 10 is 5% to 15% shorter than a distance d2 between the leading edge 11 and the trailing edge 12 of the fin 10 at the level of the inner shroud 20
Implementation Method 2
By solder radius 8 is meant here the fillet formed by the solder paste 9 deposited between the fin 10' and the slot formed in the shroud 20' after the paste 9 has flowed by capillarity, under the effect of the heat
Data Source
Figure 1
Figure 2~3
Figure 4a~4b
AI summary
The invention relates to a diffuser (5) of a radial or hybrid compressor (2) comprising an internal shroud (20), an external shroud (30) and a series of vanes (10), the trailing edge (12) of each vane (10) being curved in such a way that a distance (di) between the leading edge (11) and the trailing edge (12) of the vane (10) at the mid-height point (h/2) of the vane (10) is 5% to 15% shorter than a distance (d2) between the leading edge (11) and the trailing edge (12) of the vane (10) at the level of the internal shroud (20), the trailing edge (12) also having an evolving cross section comprising a first part forming a low wall (14) in the vicinity of the external shroud (20) and having a height (H) equal to at most 10% of the height (h) of the vane (10), a curved second part and a third part forming a low wall (14) substantially identical to the first part.