Turbine Blade Root Webs for Load Distribution
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Solution Overview
Problem
Turbine blades experience increased stresses and potential early fatigue due to uneven load distribution and differential thermal expansion, exacerbated by coolant channels in the blade roots, leading to reduced component lifetime.
Innovation Solution
Incorporating multiple webs between coolant channels in the blade roots with a well-defined web-to-channel ratio to stiffen the root and distribute loads more evenly, while maintaining sufficient coolant flow and mechanical integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If coolant channels are introduced into blade roots, then cooling efficiency is improved, but elastic deformation is enlarged and stresses are enhanced
Solution Approach 1:
The blade root is segmented into multiple load-bearing sections by introducing webs between coolant channels. This segmentation divides the continuous root structure into discrete load-bearing segments, allowing the root to maintain structural integrity while accommodating cooling channels. The webs act as structural dividers that prevent excessive deformation in each segment.
Solution Approach 2:
Different regions of the blade root are given different structural qualities. The regions between coolant channels are reinforced with webs to provide local stiffening, while the channel regions maintain their cooling function. This creates a non-uniform structural quality where load-bearing areas are strengthened and cooling areas remain open.
2Strength
If blade root is stiffened by adding material, then mechanical properties are improved, but overall material cross-section increases
Solution Approach 1:
Instead of increasing material cross-section in the traditional radial direction, the invention introduces webs that extend in the spanwise direction between coolant channels. This dimensional approach allows stiffening to occur along the length of the blade root rather than increasing the root's cross-sectional area, maintaining a compact profile while improving mechanical properties.
3Reliability
If webs are added between channels, then load distribution is improved, but device complexity increases
Solution Approach 1:
The webs serve multiple functions simultaneously: they act as structural stiffeners, load-bearing elements, and flow separators for the coolant channels. By merging these functions into a single structural feature, the design achieves improved load distribution without proportionally increasing complexity, as the same web structure provides multiple benefits.
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 configuration reduces maximum deformation and peak stresses, enhancing component lifetime by evenly distributing loads and maintaining mechanical integrity without increasing the overall material cross-section.
Implementation Method 1
the elastic deformation of a blade root upon loading is further enlarged in the region where the channels are arranged
Implementation Method 2
A coolant flow is introduced into hollow blade airfoils through openings and channels in the blade roots
Implementation Method 3
Differential thermal expansion between the airfoil and the blade root further contributes to said bending
Data Source
Figure 1~2
Figure 3
AI summary
A turbine blade comprising an airfoil (11) and a fir tree root (12). The fir tree root has a lengthwise direction (I), a crosswise direction extending between two lateral sides of the fir tree root, and a span direction (s) extending from a root base (13) towards an airfoil tip. The fir tree root comprises at least one longitudinal groove arranged on each lateral side and extending along and defining the lengthwise direction. The fir tree root has a root thickness measured between the two lateral sides, said width varying along the span direction. The fir tree root comprises at least two channels (31, 32, 33) extending in the span direction, each of said channels having a channel length (I1, I2, I3) measured along the lengthwise direction, the root further comprises a web (34, 35) interposed between each pair of neighboring channels, each of said at least one webs having a web length (I4, I5) measured along the lengthwise direction. For each web, a web-to-channel ratio with each of the two neighboring channels is chosen to be larger than or equal to 0.5 and is smaller than or equal to 0.85 at least at a position where the root width is a minimum load bearing root width in a load bearing section (26) of the fir tree root. In another aspect of the disclosure an overall web-to-channel ratio defined as a ratio between the sum of all web lengths (I4, I5) and the sum of all channel lengths (I1, I2, I3) is larger than or equal to 0.3 and is smaller than or equal to 0.6 at least at a position where the root width is a minimum load bearing root width in a load bearing section (26) of the fir tree root.