Turbine Blade Cascade End Wall Projections
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Solution Overview
Problem
Turbine blades with large outflow angles experience increased secondary flow loss due to cross flow and whirling of flow on the suction side, which is not effectively addressed by existing nonaxisymmetric shapes on turbine blade cascade end walls.
Innovation Solution
A turbine blade cascade end wall design featuring gentle to steep projections and recesses, specifically a first projection extending downward from the trailing edge, and a recess on the suction and pressure sides, reduces static pressure downstream of the trailing edge, thereby smoothing flow and reducing cross flow and secondary flow loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the outflow angle of blades is increased to improve turbine performance, then the turbine can convert kinetic energy more effectively, but the secondary flow loss in association with cross flow increases
Solution Approach 1:
The invention applies local quality by creating a specific geometric feature (the first projection) at a localized position on the end wall. This projection is positioned to specifically address the flow characteristics in the region immediately downstream of the trailing edge, where pressure stagnation occurs. By localizing the modification rather than changing the entire end wall geometry, the solution targets the specific problem area without affecting other regions.
Solution Approach 2:
The invention employs asymmetry through the nonaxisymmetric configuration of the first projection on the end wall. The projection extends downward from the trailing edge in a specific direction and position, creating an asymmetric geometry that disrupts the symmetric flow patterns. This asymmetric structure is specifically designed to counteract the cross flow and whirling motion that cause secondary flow loss, while maintaining the overall asymmetric blade configuration for optimal performance.
2Loss of energy
If nonaxisymmetric shapes are formed on the turbine blade cascade end wall to reduce cross flow, then secondary flow loss may be reduced, but the effect varies depending on blade shape and does not specifically address large outflow angle blades
Solution Approach 1:
The invention segments the end wall modification into a distinct first projection feature that can be independently optimized. By separating the end wall geometry into the base surface and the added projection element, the design allows for independent optimization of each component. The projection is specifically dimensioned and positioned to address the problems of large outflow angle blades, while the base end wall geometry can be optimized separately for different blade shapes.
Solution Approach 2:
The invention utilizes parameter changes by carefully controlling the geometric parameters of the first projection, including its position, size, and shape. The projection is designed with specific dimensional ratios and spatial coordinates that are optimized for large outflow angle blades. By adjusting these parameters, the solution can be adapted to different blade configurations while maintaining effectiveness in reducing secondary flow loss for the target application.
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
The design effectively reduces cross flow and secondary flow loss, improving turbine performance, especially for blades with large outflow angles, and achieves this effect irrespective of blade shape, leading to enhanced efficiency and reduced energy loss.
Implementation Method 1
a static pressure in the vicinity of a first projection located immediately downstream of the trailing edge of the blade decreases by the effect of the first projection
Implementation Method 2
a so-called 'cross flow (secondary flow)' is generated from the pressure side of one turbine blade toward the suction side of the adjacent turbine blade
Implementation Method 3
the cross flow and whirling up of flow on the suction side of the blade is accelerated
Data Source
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AI summary
In the turbine blades set to a large outflow angle, the performance of the entire turbine is improved by reducing a cross flow generated on the turbine end wall and a whirling up of flow on the suction side of a blade irrespective of the difference of the blade shape, thereby reducing the loss. There is provided a turbine blade cascade end wall positioned on the hub-side and/or the tip side of a plurality of turbine blades arranged in an annular shape, including a first projection having a ridge extending downward from the trailing edge of a turbine blade toward the downstream side gently at the beginning and steeply at the end, and along the suction side of an adjacent turbine blade.