Turbomachine Exhaust Casing Spline Connection Profile
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Solution Overview
Problem
The lifetime of existing exhaust casings for turbomachines is insufficient due to high stress levels caused by temperature gradients between the outer shroud and the hub, leading to premature wear in the connection portion.
Innovation Solution
The exhaust casing features a connection portion with a spline profile defined by N control points, where the first side face of each arm is connected to the endplate via a connection root that optimizes stress distribution by adjusting the lengths of segments 1 and 2 within specific ranges to reduce stress levels and prevent excessive stiffening or weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the connection portion uses a traditional circular arc profile with fixed radius, then the structure is simple to manufacture, but the stress level in the connection portion becomes excessively high leading to insufficient lifetime
Solution Approach 1:
The patent changes the geometric parameters of the connection portion from a simple circular arc with fixed radius (3mm) to a spline profile defined by multiple control points. The spline profile uses variable curvature achieved through N control points (N≥10) that define the optimal stress distribution path, transforming the connection portion geometry to reduce stress concentration while maintaining manufacturability through defined construction rules.
2Stress or pressure
If the connection portion is designed with extended length to reduce stress, then the stress distribution improves, but the weight of the casing increases
Solution Approach 1:
The patent optimizes the length parameter 1 of the first straight-line segment to lie within the specific range of 3% to 15% of the total length L. This parameter optimization achieves the dual objective of reducing stress concentration in the connection portion while controlling the weight increase, as the spline profile efficiently distributes stress without requiring excessive material.
3Reliability
If the connection portion uses a spline profile with optimized segments, then the stress distribution is improved and lifetime is extended, but the manufacturing precision requirements increase
Solution Approach 1:
The patent segments the connection portion profile into distinct geometric elements: a first straight-line segment of length 1, a second straight-line segment of length 2, and spline curves connecting them. This segmentation into N control points with defined relationships (where 1 is 3-15% of L and 2 is 25-50% of 1) breaks down the complex spline profile into manufacturable segments that can be precisely fabricated using standard manufacturing techniques.
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 effectively reduces stress in the connection portion, thereby enhancing the longevity of the exhaust casing while ensuring feasibility and minimizing weight.
Implementation Method 1
the exhaust casing is subjected to a temperature gradient between the outer shroud and the hub, which temperature gradient gives rise to stresses in the connection portion
Data Source
AI summary
A turbomachine exhaust casing with connection roots between the structural arms of the casing and the annular endplates of the hub of the casing, each of said the roots having a profile that is optimized so as to reduce the level of stress in the connection portions, and thus increase the lifetime of the exhaust casing.