Steam Turbine Blade Boundary Layer Separation Control
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Solution Overview
Problem
In steam turbines, separation on the negative-pressure surface leads to decreased blade performance, and existing structures do not adequately address this issue to improve efficiency.
Innovation Solution
The steam turbine blade features a blade body with a concave positive-pressure surface and a convex negative-pressure surface, including first and second flow paths to inject higher-pressure steam from the positive-pressure surface and negative-pressure surface opening holes, respectively, to suppress boundary layer development and separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If main steam flows along the negative-pressure surface, then the drive force is generated, but separation occurs and blade performance decreases
Solution Approach 1:
The invention applies preliminary anti-action by introducing higher-pressure steam through the first flow path to counteract the separation tendency before it fully develops on the negative-pressure surface. This preventive measure maintains the boundary layer attachment and prevents the harmful separation effect from occurring, thereby preserving blade performance while maintaining drive force generation.
Solution Approach 2:
The invention converts the harmful separation effect into a beneficial outcome by using the pressure difference between the positive-pressure and negative-pressure surfaces. The higher-pressure steam from the positive-pressure side is redirected through the first flow path to the negative-pressure surface, where it suppresses separation. Thus, the pressure difference that could cause separation is instead utilized to prevent separation and improve blade performance.
2Object-generated harmful factors
If extraction slit is formed on ventral surface to draw in wakes, then wake suppression is achieved, but blade performance decrease due to separation on negative-pressure surface remains
Solution Approach 1:
The invention segments the blade surface into distinct functional zones: the positive-pressure surface with the second flow path for wake extraction, and the negative-pressure surface with the first flow path for separation suppression. This segmentation allows each surface to address specific problems independently - wakes are drawn in from the positive-pressure side while separation is prevented on the negative-pressure side, achieving comprehensive performance improvement.
Solution Approach 2:
The first flow path acts as an intermediary mechanism that transports higher-pressure steam from the positive-pressure surface region to the negative-pressure surface. This intermediary flow path enables the positive-pressure steam to intervene and suppress separation on the negative-pressure surface, resolving the issue that cannot be addressed by wake extraction alone.
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 effectively suppresses separation on the negative-pressure surface, improving blade efficiency and reducing steam backflow, thereby enhancing the overall operation efficiency of the steam turbine.
Implementation Method 1
steam having a pressure higher than that of the main steam to which the positive-pressure surface and the negative-pressure surface are exposed flows
Implementation Method 2
the development of a boundary layer around the negative-pressure surface can be suppressed
Implementation Method 3
the steam ejected from the negative-pressure surface opening hole can be joined to the flow of the main steam flowing along the negative-pressure surface
Data Source
AI summary
A blade of a steam turbine includes a plurality of turbine blade rows which are fixed to a radially outer side of a rotor shaft rotating about an axis, and are arranged in an axial direction in which the axis extends, and a turbine vane row which is disposed to be adjacent to an upstream side of the turbine blade row in the axial direction for each of the plurality of turbine blade rows, the blade of a steam turbine including a blade body which is disposed in a steam main flow path which is formed around a rotary shaft such that main steam flows through the steam main flow path, the blade body having an airfoil cross section in which a concave positive-pressure surface and a convex negative-pressure surface are continuous to each other via a leading edge and a trailing edge.