Stator Shroud Thickness Ratios for Airfoil Frequency Tuning
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Solution Overview
Problem
Gas turbine engine components, such as stator vanes, experience undesired natural frequencies due to flow forces, leading to fatigue and structural distress, which current designs struggle to mitigate without compromising aerodynamic performance.
Innovation Solution
The design incorporates a vane stage assembly with modified inner and outer shrouds, featuring specific thickness ratios between forward, middle, and radial portions, allowing for tuning of airfoil natural frequencies without altering the airfoil geometry, thereby optimizing structural robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the airfoil shape is configured to define a desired natural frequency, then structural reliability is improved, but device complexity increases due to additional shroud design parameters
Solution Approach 1:
The patent applies parameter changes by modifying the shroud thickness ratios (forward radial thickness to forward axial width thickness between 0.64-1.11, and forward radial thickness to middle thickness between 1.40-2.93) to tune the natural frequency of the airfoil-shroud system. This allows adjustment of structural dynamics without changing the airfoil geometry itself, thereby improving reliability while managing complexity through controlled parameter variation in the shroud design.
2Object-affected harmful factors
If the shroud thickness ratios are modified to tune natural frequency, then structural distress is minimized, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies precise parameter ranges for shroud thickness ratios (forward radial thickness to forward axial width thickness: 0.64-1.11; forward radial thickness to middle thickness: 1.40-2.93) to achieve desired natural frequency tuning. These controlled parameter changes minimize structural distress by avoiding resonant conditions, while the defined ranges provide manufacturing guidance to balance precision requirements with practical fabrication capabilities.
3Reliability
If the airfoil geometry is altered to change natural frequency, then natural frequency tuning is achieved, but aerodynamic performance is compromised
Solution Approach 1:
The patent segments the airfoil system into two independent components: the airfoil geometry (responsible for aerodynamic performance) and the shroud structure (responsible for natural frequency tuning). By modifying only the shroud thickness ratios while keeping the airfoil geometry unchanged, the patent achieves natural frequency tuning without compromising aerodynamic performance, as each component can be optimized independently for its specific function.
Solution Approach 2:
The patent applies local quality by making specific modifications only to the shroud portions (forward and middle sections) while leaving the airfoil geometry intact. The shroud's local thickness variations in specific regions allow natural frequency tuning without affecting the global aerodynamic characteristics of the airfoil, enabling independent optimization of structural and aerodynamic properties.
Data Source
AI summary
A vane stage assembly includes an airfoil including a leading edge and a trailing edge. An inner shroud extends from the leading edge to the trailing edge for supporting the airfoil. The shroud includes a forward portion including an axial width and a forward thickness extending in a radial direction. A ratio of the forward radial thickness divided by the forward axial thickness is between 0.64 and 1.11 for defining a natural frequency of the airfoil. A gas turbine engine and method are also disclosed.