Transonic Blade Stacking Line Sweep for Shock Loss Reduction
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Solution Overview
Problem
Conventional transonic blades face challenges in reducing shock loss and improving stall margin, especially at increased pressure ratios, where shock waves can lead to flow separation and reduced efficiency in axial-flow rotating machines like gas turbines.
Innovation Solution
The transonic blade design features a stacking line that is monotonously swept forward with increased span, and maximum thickness positions are shifted downstream, reducing shock loss and enhancing stall margin by altering the flow velocity and pressure distribution across the blade.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the tip cross-sectional surface is shifted toward the upstream side to reduce shock loss, then shock loss is reduced, but boundary layer development increases on the hub side
Solution Approach 1:
The patent applies different stacking line configurations to different spanwise regions. The tip cross-sectional surface is shifted upstream to reduce shock loss, while the hub cross-sectional surface maintains a different configuration to suppress boundary layer development. This local differentiation allows each region to be optimized for its specific flow characteristics and loss mechanisms.
2Loss of energy
If the stacking line is modified to reduce shock loss, then shock loss decreases, but the design complexity increases
Solution Approach 1:
The stacking line is segmented into different configurations based on spanwise position. The tip region uses a forward-swept configuration to reduce shock loss, while the hub region uses a different configuration to control boundary layer development. This segmentation allows complex flow control to be achieved through modular, region-specific designs rather than a single complex configuration throughout.
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 effectively reduces shock loss and increases stall margin by shifting the shock wave position downstream, moderating gas-path width variations and suppressing flow separation, thereby improving the performance and reliability of axial-flow rotating machines.
Implementation Method 1
the shock loss tends to increase... shock loss at a transonic stage will increase... reducing shock loss... shifting the shock wave position downstream
Implementation Method 2
suppressing flow separation... a place where a large separation area induces stall
Data Source
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AI summary
An object of the present invention is to provide a transonic blade that concurrently achieves a reduction in shock loss at a design point and an improvement in stall margin in blades operating in a flow field of transonic speed or higher in an axial-flow rotating machine. To achieve the above object, the present invention provides a transonic blade used in a flow field through which an overall or partial flow passes at a transonic speed or higher. The transonic blade is formed as below. A cross-sectional surface at each of spanwise positions of the blade is shifted parallel to a stagger line 38 connecting a leading edge 34 with a trailing edge 35 of the blade. A stacking line 36 is shifted toward an upstream side of working fluid. The stacking line 36 connects together respective gravity center positions of blade cross-sectional surfaces at spanwise positions in a range from a hub cross-sectional surface 31 joined to a rotating shaft or an outer circumferential side casing of a rotating machine to a tip cross-sectional surface 33 lying at a position most remote from the hub cross-sectional surface in a spanwise direction. A maximum thickness position of the cross-sectional surface of the blade at each of the spanwise positions is shifted toward a trailing edge side of the blade in a range from the hub cross-sectional surface 31 to the tip cross-sectional surface 33.