Turbomachine Rotor Blade Inner Platform Convex Curvature
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Solution Overview
Problem
Existing rotor blade designs for turbomachines face challenges in robustness against centrifugal loads due to mass increases from traditional stiffening methods, which can negatively impact blade root and rotor loads.
Innovation Solution
The design incorporates a geometry with convex curvature toward the blade root and straight or curved portions in the connecting lines of the inner rotor blade platform, increasing the area moment of inertia without significant mass addition, ensuring stability and aerodynamic continuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional stiffening methods (wedge shape and/or pads) are used to counteract centrifugal loading, then the inner rotor blade platform becomes more robust against bending loads, but the blade mass increases which negatively affects blade root load and rotor load
Solution Approach 1:
The connecting lines are given a convex curvature specifically in their central portion (which may extend up to the circumferential end faces), creating localized geometric features that increase the area moment of inertia and provide stiffening exactly where needed to counteract bending loads, rather than uniformly increasing mass throughout the entire blade structure
Solution Approach 2:
The connecting lines feature a convex curvature (bulge) toward the blade root in their central portion, which increases the area moment of inertia of the inner rotor blade platform. This curved geometric feature provides structural stiffening against centrifugal loading while avoiding the mass penalty of traditional additive stiffening methods
2Stability of the object's composition
If the area moment of inertia is increased through traditional methods, then the bending load is counteracted and rotor blade stability is improved, but the blade root load increases
Solution Approach 1:
The convex curvature is applied specifically to the central portion of the connecting lines, which are located at the cross section of connection between the inner rotor blade platform and the rotor blade. This localized geometric modification increases the area moment of inertia precisely where the bending moments are highest, providing optimal stiffening to counteract centrifugal loading and improve stability without unnecessarily increasing blade root load
3Strength
If the inner rotor blade platform is stiffened with pads, then the bending load is counteracted, but the manufacturing complexity increases
Solution Approach 1:
The stiffening feature is integrated directly into the geometry of the inner rotor blade platform by forming the convex curvature as part of the connecting lines themselves. This merges the structural platform with the stiffening element into a single integrated component, eliminating the need for separate pads or wedge-shaped additions and thereby reducing manufacturing complexity
Solution Approach 2:
The geometry of the connecting lines is modified by introducing a convex curvature in their central portion. This parameter change in the geometric shape of the connecting lines directly increases the area moment of inertia and provides the necessary stiffening against centrifugal loading, replacing complex additive structures with a refined geometric parameter
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 enhances the rotor blade's robustness against bending loads, extends service life, and maintains aerodynamic efficiency by preventing turbulence and reducing unwanted mass distribution during rotation.
Implementation Method 1
Due to the rotation of the rotor blade assembly, the inner rotor blade platform, which may be abstracted as a beam that is clamped at one end, is subjected during operation to centrifugal loading and is mainly loaded in bending.
Implementation Method 2
The resulting increase in the area moment of inertia of the inner rotor blade platform counteracts the bending load and thus assists in stabilizing the rotor blade.
Data Source
AI summary
A rotor blade (20) for a rotor blade assembly (10) of a turbomachine (1) is provided, having an inner rotor blade platform (40) which extends axially from the rotor blade (20) with respect to a longitudinal turbomachine axis (2) and has two opposite circumferential end faces (41) and a free axial end (42) whose cross section is radially inwardly and radially outwardly bounded by circular arcs of two concentric circles. The inner rotor blade platform (40) has a cross section of connection (45) with the rotor blade (20) which is bounded radially inwardly by an inner connecting line (46) and radially outwardly by an outer connecting line (47). Each of the connecting lines (46, 47) has a central portion (61) having a convex curvature.