Swirl Recovery Vane Stator Spacing for Modal Force Reduction
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Solution Overview
Problem
Open rotor engines face challenges with acoustic response and modal forcing due to differing airfoil stage counts between the rotor and stator, leading to potential damage and noise issues.
Innovation Solution
Implementing non-uniform and bi-tri stator spacing configurations to reduce the forcing function and acoustic signature, utilizing a combination of positive and negative resonances to cancel out modal forces and optimize airflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform stator spacing is used, then the structure is simple and easy to manufacture, but modal forcing on the rotor increases causing high-cycle fatigue stress and noise
Solution Approach 1:
The patent applies asymmetry by transitioning from uniform stator spacing to non-uniform spacing patterns, specifically bi-tri spacing where stators are arranged in groups of three with different spacings. This asymmetric configuration disrupts the periodic forcing function that causes modal resonance and high-cycle fatigue on rotor blades, while maintaining manufacturing feasibility through standardized stator components arranged in different spatial patterns.
Solution Approach 2:
The patent implements local quality by creating different spacing characteristics in different regions of the stator array. The bi-tri spacing pattern divides stators into distinct groups with different inter-stator distances, allowing each local region to contribute differently to the overall flow conditioning while collectively reducing the cumulative modal forcing on the rotor through destructive interference of pressure waves.
2Object-generated harmful factors
If differing airfoil stage counts between rotor and stator are used, then noise levels are reduced, but modal forcing on the rotor from downstream stator increases
Solution Approach 1:
The patent combines asymmetric stator spacing with differing airfoil stage counts between rotor and stator. The non-uniform spacing pattern creates destructive interference of pressure waves that reduces both noise radiation and modal forcing simultaneously, overcoming the limitation of uniform spacing where noise reduction through stage count differences would increase periodic forcing on the rotor.
Solution Approach 2:
The patent utilizes periodic action by arranging stators in repeating bi-tri spacing patterns around the annulus. This periodic non-uniform spacing creates controlled pressure wave interference that reduces noise while the specific phase relationships in the bi-tri pattern prevent strong modal forcing, allowing both noise reduction and force reduction to coexist.
3Object-generated harmful factors
If non-uniform stator spacing is implemented, then forcing function and acoustic signature are reduced, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the stator array into discrete groups (typically groups of three stators) with characteristic spacings within each group and between groups. This segmented bi-tri spacing pattern simplifies the design process compared to fully arbitrary non-uniform spacing, as each segment follows a standardized pattern that can be manufactured and installed systematically while still achieving the desired reduction in acoustic signature and forcing function.
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
Reduces high-cycle fatigue stress, lowers noise levels, and enhances airflow by minimizing resonance reinforcement, thereby improving engine performance and reducing noise both inside and outside the cabin.
Implementation Method 1
The stators are spaced in a non-uniform spacing to reduce a forcing function created by movement of the rotor blades past the stators
Implementation Method 2
utilizing a combination of positive and negative resonances to cancel out modal forces
Implementation Method 3
The stators are spaced in a non-uniform spacing to reduce an acoustic signature of the engine
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A swirl recovery vane, SRV, open rotor engine (20) includes an engine core (200), a rotor (38) having a plurality of rotor blades (70) mounted to an end of the engine core (200) and a plurality of stators (100) mounted adjacent to the rotor (38). The stators (100) are spaced in a nonuniform spacing to reduce a forcing function created by movement of the rotor blades (78) past the stators (100).