Axial Flow Blade Elevated Portions for Outflow Angle Control
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Solution Overview
Problem
Existing blade designs for axial flow fans, compressors, and turbines face challenges in optimizing outflow angles, particularly in the hub and tip regions, due to secondary flows caused by viscosity effects, leading to deviations from design values and performance issues.
Innovation Solution
The method involves modifying the blade by adding suction-side and pressure-side elevated portions near the trailing edge in specific spanwise regions of the hub and tip areas, utilizing a base airfoil with a leading-edge curve, an arc trailing-edge curve, and concave/convex surface curves, to adjust the outflow angle through a Coanda effect, without altering the aerodynamic design of the base blade.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an elevated portion is provided on the pressure surface near the trailing edge in the hub region or tip region, then the outflow angle is increased in the spanwise region where the elevated portion is provided, but the outflow angle becomes excessive in the blade-end region due to the combined effect of secondary flow and the elevated portion
Solution Approach 1:
The patent applies local quality by providing elevated portions only in specific spanwise regions (midspan-side tip region and midspan-side hub region) rather than uniformly across the entire blade. This localized modification allows the outflow angle to be optimized in regions where it is below the design value while avoiding excessive outflow angle in blade-end regions where secondary flow effects are already prominent.
Solution Approach 2:
The blade spanwise region is segmented into different zones: blade-end-side tip region, midspan-side tip region, blade-end-side hub region, and midspan-side hub region. The elevated portions are selectively applied to specific segments (midspan regions) while leaving other segments (blade-end regions) unmodified, allowing differential control of outflow angle across the blade span.
2Manufacturing precision
If the outflow angle is optimized in the hub region and tip region through elevated portions, then the deviation from design value is corrected in those regions, but extensive aerodynamic and structural analysis is required to determine the optimal configuration
Solution Approach 1:
The patent establishes predetermined rules for elevated portion configuration based on spanwise position criteria. The midspan-side tip region is defined as where the distance from the tip-side end is 0.05L to 0.45L, and the midspan-side hub region is where the distance from the hub-side end is 0.05L to 0.45L. These preliminary definitions provide a systematic approach that reduces the need for extensive iterative analysis.
Solution Approach 2:
The patent modifies the blade geometry by introducing elevated portions with specific height parameters (0.005c to 0.05c) and spanwise distribution patterns. By changing these geometric parameters according to the defined spanwise regions, the outflow angle is optimized without requiring comprehensive aerodynamic and structural analysis of all possible configurations.
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 approach effectively optimizes the outflow angle across the entire hub and tip regions, particularly in the blade-end-side areas, without the need for extensive aerodynamic and structural analysis, thereby improving blade performance while minimizing time and effort in design adjustments.
Implementation Method 1
the flow on the suction surface side turns around to the pressure surface side along the trailing edge of the elevated portion due to a kind of Coanda effect, and the turning of the flow is increased to increase the outflow angle
Data Source
AI summary
Provided is a blade capable of optimizing an outflow angle in substantially the entire hub region and tip region, particularly in a blade-end-side hub region and a blade-end-side tip region. The blade includes: a base blade part; a suction-side elevated portion provided on a suction surface near a trailing edge in at least one of the blade-end-side tip region and the blade-end-side hub region of the base blade part; and a pressure-side elevated portion provided on a pressure surface near the trailing edge in at least one of a midspan-side tip region and a midspan-side hub region of the base blade part. An airfoil at each spanwise position where the elevated portion is provided is such that a trailing-edge curve of a base airfoil is changed to a modified trailing-edge curve. The modified trailing-edge curve includes a portion of the trailing-edge curve of the base airfoil in the spanwise region where the elevated portion is provided, the portion being closer to the pressure side or the suction side than the trailing edge, and an elevated portion curve. The elevated portion curve includes a concave front-side curve and a convex rear-side curve.