Turbomachine Rotor Blade Root Angles for Stress Distribution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing designs for turbomachine rotor blades and discs face challenges in optimally distributing stress and mechanical load across the contact faces between the root and slot, leading to potential damage and breakage due to centrifugal forces during rotation.
Innovation Solution
The design incorporates a firtree-shaped root and slot with specific contact face angles, where the first contact face angle is smaller than the second and third, and the second and third angles are equal, optimizing stress distribution by initially concentrating pressure on the second and third faces before it is applied to the first face, thereby reducing the risk of damage and breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a firtree profile is used for the root and slot, then accurate placement and structural strength are improved, but stress concentration and risk of breakage occur at contact sections
Solution Approach 1:
The invention applies different contact face angles to different root lobes, making each lobe's contact face locally optimized for its specific position and load characteristics. The first root lobe has a first contact face angle, while the second and third root lobes have different contact face angles, allowing each region to handle stress appropriately based on its location and mechanical demands.
Solution Approach 2:
The invention changes the geometric parameter of contact face angles across different root lobes. By varying the contact face angle parameter from one lobe to another, the stress distribution is optimized to prevent concentration at any single location, thereby reducing breakage risk while maintaining overall strength.
2Ease of manufacture
If uniform contact face angles are used across all root lobes, then manufacturing simplicity is maintained, but stress distribution is suboptimal leading to potential damage
Solution Approach 1:
Instead of uniform contact face angles, the invention implements local quality by assigning different contact face angles to different root lobes. This allows each lobe to be optimized for its specific stress conditions while maintaining a relatively simple overall firtree profile structure that can still be manufactured efficiently.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
In accordance with the invention there is provided a turbomachine rotor blade with a firtree shaped root, arranged to be secured in a rotor disc, the rotor disc being rotatable around a rotor axis. In a plane perpendicular to the rotor axis the root comprises a first root lobe with a first root contact face, a second root lobe with a second root contact face and a third root lobe with a third root contact face. The first root contact face is angled relative to a radial root bottom axis with a first root angle, the second root contact face is angled relative to the radial root bottom axis with a second root angle and the third root contact face is angled relative to the radial root bottom axis with a third root angle. The turbomachine rotor blade is characterised in that the first root angle is smaller than the second root angle and the second root angle is substantially equal to the third root angle. Analogously, there is provided a turbomachine rotor disc with a firtree shaped slot comprising a first slot angle, a second slot angle and a third slot angle, the first slot angle being smaller than the second slot angle and the second slot angle being substantially equal to the third slot angle. Furthermore, there is provided a turbomachine rotor comprising the turbomachine rotor blade and the turbomachine rotor disc. Finally, there is provided a gas turbine engine comprising the turbomachine rotor.