Rotor Blade Center-of-Gravity Threading for Stress Optimization
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Solution Overview
Problem
Conventional rotor blades in high-speed low-pressure turbines of aircraft gas turbines experience local stress peaks and uneven utilization due to increased centrifugal forces and hot gas forces, leading to unfavorable stress profiles.
Innovation Solution
The rotor blade design features a threading axis that extends within a cone with an opening angle of 0.5° to 2°, deviating maximally 1° from the radial direction, and is inclined in the axial or circumferential direction to optimize stress profiles and counteract centrifugal and hot gas forces, with the shroud element's centers of gravity aligned on the threading axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional rotor blades are used in high-speed low-pressure turbines, then the blades can operate at higher speeds, but local stress peaks and uneven utilization occur due to increased centrifugal forces
Solution Approach 1:
The patent changes the geometric parameters of the rotor blade by defining a specific threading axis orientation within a cone (opening angle 0.5°-2°) rather than using conventional radial or inclined threading. This parameter change optimizes the distribution of centrifugal forces and hot gas forces, eliminating local stress peaks while enabling high-speed operation
Solution Approach 2:
The threading axis is positioned asymmetrically within the cone defined by the blade cross-sectional areas, rather than following the conventional radial symmetry. This asymmetric positioning within the narrow angular range creates optimal force distribution that prevents stress concentration at specific locations
2Productivity
If the threading axis is inclined at larger angles (2.5°-4.5°) to the radial direction, then blade utilization is improved for conventional turbines, but stress peaks occur in high-speed turbines
Solution Approach 1:
The patent fundamentally changes the threading axis inclination parameter from conventional values (2.5°-4.5° or larger) to a narrow range (0.5°-2°) measured from the radial direction. This parameter optimization simultaneously achieves uniform blade utilization and eliminates local stress peaks in high-speed turbine conditions
Solution Approach 2:
Instead of using full conventional inclination angles that cause stress peaks, the patent applies a partial inclination (narrower angle range of 0.5°-2°) that provides sufficient blade utilization while avoiding the harmful effects of excessive inclination in high-speed operation
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 achieves more uniform rotor blade utilization and eliminates local stress peaks, ensuring optimized stress profiles for high-speed low-pressure turbines by strictly limiting deviations from the radial direction.
Implementation Method 1
Due to the changed, in particular higher speed of the low-pressure turbine compared to conventional aircraft (gas turbines), the rotor blades, which are attached to a rotor of a turbine stage, are exposed to higher centrifugal forces.
Data Source
Figure 1~2
Figure 3A~4
AI summary
The invention relates to a turbine blade for a gas turbine, in particular an aircraft turbine, comprising a blade root element and a jet deflection section which adjoins the blade root element (12) in the longitudinal direction (RR) of the blade, wherein the respective centers of gravity (24) of blade cross-sectional areas of the jet deflection section lie on a common threading axis (26). According to the invention, it is proposed that the threading axis (26) extends from a first center of gravity (24) of a first blade cross-sectional area adjoining the blade root element (12) within a cone (28) whose apex lies at the first center of gravity (24) and whose cone height (KH) extends orthogonally to the plane of the blade cross-sectional area, wherein the opening angle (β) of the cone (28) is greater than 0° and less than or equal to 4°, preferably greater than or equal to 0.5° and less than or equal to 2°.