Turbomachine Blade Platform Contouring for Secondary Flow Reduction
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Solution Overview
Problem
Existing turbomachines face challenges in reducing secondary flows, which lead to turbulence and pressure losses due to the influence of side wall surfaces on fluid flow, despite previous attempts at contouring these surfaces.
Innovation Solution
A blade cascade segment with a contoured upstream platform edge featuring a dimple indentation that extends up to 10% of the grid width, positioned entirely upstream of the leading edges, to minimize secondary flows by altering the flow dynamics without protruding into the intermediate blade strips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If sidewall contours are incorporated into the flow channel to reduce secondary flows, then pressure losses are reduced, but the device complexity increases due to additional manufacturing requirements
Solution Approach 1:
The invention applies a localized recess contour specifically at the upstream platform edge where secondary flows originate, rather than modifying the entire sidewall surface. This targeted approach reduces secondary flows and pressure losses while minimizing the complexity increase, as only a specific local region is contoured rather than the whole flow channel.
Solution Approach 2:
The recess contour is designed as a distinct segmented feature with specific dimensional constraints (extending at most 10% of the grid width into the blade gap). This segmentation allows the contour to be manufactured as a discrete feature, potentially simplifying the manufacturing process compared to complex continuous sidewall contours while still achieving the flow control objective.
2Productivity
If larger contours are incorporated into the side walls to reduce secondary currents, then flow efficiency is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The recess contour is designed to extend only partially into the blade gap (at most 10% of the grid width), which is sufficient to influence the secondary flows at their origin point without requiring the full depth that would be needed for conventional sidewall contours. This partial action achieves the flow efficiency improvement while reducing the manufacturing precision demands compared to deeper, more extensive contours.
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 reduces secondary flows and associated losses, enhancing the efficiency of the turbomachine by optimizing the interaction between the platform edges and blade channels.
Implementation Method 1
Flow layers close to these surfaces are deflected more strongly due to their lower velocity than flow layers further away from the side walls. This creates a secondary flow superimposed on the axial main flow, leading in particular to eddies and pressure losses.
Data Source
Figure 1~2
AI summary
A blade grid segment (1, 1') for a turbomachine blade grid is disclosed, comprising a platform (10) and at least two blades (20, 30) whose leading and trailing edges (23, 33, 24, 34) on the platform surface define a blade space (11) with axial grid width (g). An upstream platform edge (10a) has a contour with a recess (13, 13'). This recess extends axially into the blade space (11) by at most 10% of the grid width (g). A corresponding platform, a blade grid, a blade channel, and a turbomachine are also disclosed.