Bi-Tri SRV Stator Spacing for Open Rotor Noise Reduction
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Solution Overview
Problem
Open rotor propulsion systems face challenges with acoustic response and modal forcing due to differing airfoil stage counts between the rotor and stator, which can cause damage and noise, particularly in swirl recovery vane (SRV) engines.
Innovation Solution
Implementing non-uniform stator spacing, specifically a bi-tri configuration, to reduce the forcing function and acoustic signature by creating positive and negative resonances that cancel each other out, thereby minimizing structural and noise-related issues.
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 noise and potential damage
Solution Approach 1:
The patent applies asymmetry by transitioning from uniform to non-uniform stator spacing, specifically using bi-tri spacing patterns where stators are arranged in groups of three with different spacing intervals. This asymmetric arrangement disrupts the periodic forcing function that causes modal resonance on the rotor, thereby reducing noise and vibration while maintaining structural feasibility
Solution Approach 2:
The patent implements local quality by applying different spacing patterns to different portions of the stator array. The bi-tri spacing configuration uses two distinct spacing patterns (first spacing and second spacing) in different radial or axial regions, allowing each local region to contribute differently to noise reduction while accommodating engine pylon integration requirements
2Object-affected harmful factors
If non-uniform stator spacing is implemented, then modal forcing on the rotor is reduced, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the stator array into multiple discrete groups (typically groups of three stators) with distinct spacing characteristics. This segmentation allows the complex non-uniform spacing to be broken down into manageable, repeating units that can be manufactured and assembled systematically, reducing the practical complexity despite the non-uniform pattern
3Ease of manufacture
If standard stator spacing is used, then engine integration is straightforward, but acoustic signature and noise levels increase
Solution Approach 1:
The patent uses asymmetry in stator spacing to reduce the acoustic signature by disrupting the coherent noise generation that occurs with uniform spacing. The bi-tri spacing pattern creates irregular wake structures and reduces tonal noise components while still allowing for standardized engine pylon integration through careful placement of the non-uniform pattern
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 bi-tri stator spacing reduces high-cycle fatigue stress, lowers noise levels, and enhances airflow by minimizing resonance reinforcement, providing structural and acoustic benefits while allowing for optimal engine integration with the wing.
Implementation Method 1
The stators are spaced in a bi-tri spacing configuration to reduce a forcing function created by movement of the rotor blades past the stators. The bi-tri spacing of the stators provides a positive resonance with respect to a first portion of the stators and a negative resonance with respect to a second portion of the stators.
Data Source
AI summary
A swirl recovery vane (SRV) open rotor engine include an engine core, a rotor having a plurality of rotor blades mounted to an end of the engine core and a plurality of stators mounted adjacent to the rotor. The stators are spaced in a non-uniform spacing to reduce a forcing function created by movement of the rotor blades past the stators.