Steam Turbine Blade Connecting Member Vortex Control
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Solution Overview
Problem
Long moving blades in steam turbines face challenges with increased centrifugal stress and vibration, leading to performance degradation due to the need for intermediate connecting members that either increase aerodynamic loss or risk structural integrity issues.
Innovation Solution
A turbine rotor assembly with a streamline-shaped intermediate connecting member positioned such that its downstream end is upstream of the throat between moving blades, minimizing vortex development and aerodynamic loss, while ensuring structural strength through optimized cross-sectional shapes and contact surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If long moving blades are provided to increase annular area and steam flow rate, then output and efficiency are improved, but centrifugal stress increases and natural vibration frequency decreases
Solution Approach 1:
The moving blade is divided into multiple segments along its span, with intermediate connecting members joining these segments. This segmentation allows each segment to be shorter and stronger while maintaining the overall long blade configuration needed for high output, thereby reducing centrifugal stress on individual blade sections.
Solution Approach 2:
The cross-sectional area of the moving blade is optimized with local quality variations, particularly at the intermediate connecting member positions where structural reinforcement is needed. The blade thickness and width are adjusted locally to distribute centrifugal stress more evenly throughout the blade structure.
2Reliability
If intermediate connecting members are disposed at the span intermediate portion of the moving blade to improve vibration characteristics, then detuning is achieved, but the turbine moving blade cascade shape is deformed and aerodynamic loss increases
Solution Approach 1:
The intermediate connecting member is designed with a streamlined curved shape that follows the flow direction of steam. This curved configuration minimizes flow separation and vortex formation, reducing aerodynamic loss while still providing the structural connection needed for vibration control.
Solution Approach 2:
The intermediate connecting member is positioned and shaped to minimize interference with the main steam flow path. Its cross-sectional dimensions and orientation are optimized locally to reduce drag and wake effects, thereby reducing aerodynamic loss while maintaining vibration damping functionality.
3Strength
If the downstream side end edge of the intermediate connecting member is positioned downstream of the throat, then structural connection is achieved, but vortex develops and aerodynamic loss increases
Solution Approach 1:
The intermediate connecting member is positioned upstream of the throat between moving blades, anticipating the flow convergence zone. This preliminary positioning allows the steam flow to adjust gradually around the connecting member before reaching the throat, preventing sudden flow separation and vortex development that would occur if the member were positioned downstream.
Solution Approach 2:
The streamlined curved shape of the intermediate connecting member, combined with its upstream positioning, creates smooth flow contours that guide steam around the member without sharp edges or corners that would trigger vortex formation. The curved surfaces promote attached flow throughout the blade passage.
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 aerodynamic losses and enhances vibration characteristics, maintaining high efficiency and structural integrity of the steam turbine by minimizing vortex development and optimizing the shape of the intermediate connecting member.
Implementation Method 1
minimizing vortex development and aerodynamic loss
Implementation Method 2
minimizing vortex development
Data Source
Figure 1
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AI summary
A turbine rotor assembly 10 comprises a turbine rotor and a plurality of moving blades 20 implanted in a circumferential direction of the rotor. A flow passage is formed between each of the moving blades 20 and a circumferentially adjacent moving blade 20. Each of the moving blades 20 comprises a suction side connecting member 22 protruded on a blade suction surface 21 and a pressure side connecting member 24 protruded on a blade pressure surface 23, wherein the suction side connecting member 22 of each of the moving blades 20 is configured to be connected with the pressure side connecting member 24 of the circumferentially adjacent moving blade 20 to form an intermediate connecting member 30 between the moving blade 20 and the circumferentially adjacent moving blade 20 during a rotation of the turbine rotor. A downstream side end edge 32 of the intermediate connecting member 30 is positioned at an upstream side of a throat S of the flow passage.