Turbomachine Blade Shroud with Recessed Pockets
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Solution Overview
Problem
Turbomachine blades with shrouds face increased centrifugal loads and stresses due to the weight of the outer shroud, which affects the blade root and overall lifetime, and require balanced mass distribution and prevention of creep curling, while hardfacing on edges must be supported effectively under circumferential loads.
Innovation Solution
A blade design featuring a shroud with circumferential webs, recessed pockets to reduce mass, and hardfacing on edges supported by a supporting wall, allowing for a lightweight and balanced structure that distributes stress effectively and prevents creep curling, with additional pockets forming reinforcement ribs for further weight reduction and stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the shroud is made heavier to provide sufficient support for hardfacing under circumferential loads, then the support strength for hardfacing is improved, but the centrifugal load on the blade increases, affecting blade root stresses and overall lifetime
Solution Approach 1:
The shroud features localized thickening specifically at the hardfacing support area where strength is needed, while other regions maintain reduced thickness. This creates non-uniform wall thickness distribution that provides targeted support exactly where the hardfacing requires it, without unnecessarily increasing weight in other areas of the shroud.
Solution Approach 2:
The shroud structure is segmented into regions of different thickness - a thicker support region beneath the hardfacing and thinner regions elsewhere. This segmentation allows the design to optimize strength where needed while minimizing weight overall, resolving the contradiction between local support requirements and global weight reduction.
2Weight of moving object
If the shroud mass is reduced for lightweight design, then the centrifugal load and stresses on blade root and disc are reduced, but the support capability for hardfacing under circumferential loads is compromised
Solution Approach 1:
Instead of uniformly thickening the entire shroud, the design applies localized thickening only in the specific area that supports the hardfacing. This ensures minimal weight increase while providing sufficient local strength to handle circumferential loads on the hardfacing, directly addressing the contradiction between weight reduction and support capability.
Solution Approach 2:
The shroud is divided into functional zones with different thickness characteristics - a reinforced zone for hardfacing support and lighter zones for vibration damping and weight reduction. This zonal segmentation allows simultaneous optimization of both weight and support capability.
3Weight of moving object
If pockets are recessed in the outer surface of the shroud for weight reduction, then the shroud mass is reduced, but the structural strength and stiffness of the shroud may be compromised
Solution Approach 1:
The shroud design segments the structure into solid load-bearing regions and recessed pockets. The pockets are strategically positioned and sized to remove non-critical material for weight reduction, while key structural areas maintain sufficient thickness to preserve overall strength and stiffness. The reinforced area beneath hardfacing ensures critical load paths are maintained.
Solution Approach 2:
Different regions of the shroud have different thickness qualities - pockets create local thinning for weight reduction in non-critical areas, while localized thickening creates reinforcement in critical areas. This spatial variation in material distribution optimizes the strength-to-weight ratio by applying material only where structurally necessary.
Data Source
Figure 1
Figure 2~3
AI summary
The invention refers to a blade for a turbomachine comprising a shroud (12) which is positioned on a tip side of the blade (10) having an outer surface (14) having at least one circumferential web (16) arranged thereon, at least one pocket (21, 22, 23, 24, 25) recessed in the outer surface (14) and a hardfacing (26, 27) provided on at least one edge (31, 32) of the shroud (12) wherein a pocket (22) recessed in the outer surface (14) is arranged adjacent to the hardfacing (26) and a side face (22a) of the pocket (22) joins the supporting wall (28) with a radius (R) corresponding at least to the length of the shorter extension (28a) of the supporting wall (28) and at most to 1.5 times the length of the larger extension (28b) of the supporting wall (28).