T-bar Turbulence Grid for Cascade Wind Tunnel
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Solution Overview
Problem
Conventional turbulence generating grids in cascade wind tunnels are not optimized for corner test sections and change the angle of attack on turbine blades, leading to undesirable airflow redirection and inaccurate measurements.
Innovation Solution
A T-bar grid design where the overall assembly is angled to the airflow, with individual cross and vertical bars perpendicular to the flow, maintaining constant turbulence intensity across the pitchwise location, allowing the grid to be parallel to the turbine blades and reducing airflow redirection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a conventional turbulence generating grid is placed perpendicular to the air flow, then turbulence is generated, but the airflow is redirected and the angle of attack on turbine blades changes
Solution Approach 1:
The grid is segmented into multiple bars arranged in a specific pattern, allowing turbulence generation while maintaining airflow direction. The segmented structure creates turbulence through the arrangement and spacing of individual bars rather than through a solid perpendicular barrier.
Solution Approach 2:
The grid employs an asymmetric arrangement of bars with specific spacing and orientation patterns. This asymmetric configuration generates turbulence effectively while allowing the overall grid structure to be aligned parallel to the turbine blades, avoiding airflow redirection.
2Measurement precision
If a turbulence generating grid is angled to match the turbine blades, then the angle of attack is preserved, but the turbulence distribution becomes non-uniform across the pitchwise location
Solution Approach 1:
The grid structure implements local variations in bar spacing and orientation to achieve uniform turbulence distribution. Different sections of the grid have locally optimized configurations that collectively produce uniform turbulence across the entire pitchwise location while maintaining the overall parallel alignment with turbine blades.
Solution Approach 2:
The invention transitions from a simple two-dimensional grid to a three-dimensional bar structure with specific spacing and orientation in multiple dimensions. This dimensional enhancement allows the grid to generate uniform turbulence across the pitchwise location while maintaining parallel alignment with the turbine blades.
3Quantity of substance
If a parallel mesh grid is used, then turbulence is generated, but the inlet profiles and velocity distributions are less uniform compared to T-bar grid
Solution Approach 1:
The T-bar grid structure creates dynamic turbulence characteristics through its specific bar arrangement and spacing. The configuration allows for optimized turbulence generation that naturally produces more uniform inlet profiles and velocity distributions compared to static mesh grid arrangements.
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 T-bar grid provides more uniform turbulence intensity and velocity profiles, improving inlet profiles and matching clean tunnel data better than parallel mesh grids, resulting in more accurate turbine blade wind tunnel modeling.
Implementation Method 1
A cascade wind tunnel T-bar turbulence generating grid for creating a turbulence intensity in an air flow
Data Source
AI summary
A cascade wind tunnel T-bar turbulence generating grid for creating a turbulence intensity in an air flow having an air flow volume for testing at least two turbine blades having a turbine blade dimension and a pitchwise location, the turbulence generating grid comprising a plurality of cross bars having a front surface and a cross bar gap, a plurality of vertical bars having a vertical bar front surface and a cross bar gap and at least two support bars assembled to form a plurality of air flow. The support bar at an angle θ to the air flow and about parallel to the turbine blades. The cross bars mounted to the support bar such that the cross bar front surface is perpendicular to the air flow. The vertical bars are mounted to the support bar such that the vertical bar front surface is perpendicular to the air flow and wherein the vertical bar gap and a horizontal gap provide the turbulence intensity about constant across the pitchwise location.