Turbofan Blade Coupling Gap Orientation for Noise Reduction
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Solution Overview
Problem
In turbofans with three-dimensional blades, air flowing into gaps at the coupling portion increases noise, requiring high-precision dimensional control during manufacturing.
Innovation Solution
The coupling portion between the blade main portion and the blade cover is formed in a surface region parallel to the air flow direction over the pressure surface of the blades, reducing the likelihood of air entering the gap and eliminating the need for precise dimensional control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If two components are coupled to form hollow blades with three-dimensional shape, then weight of impeller is reduced, but air flows into the gap at coupling portion increasing noise
Solution Approach 1:
The coupling portion is repositioned from the conventional shroud-side leading edge region to the suction surface or pressure surface of the blade, changing the spatial dimension and orientation of the coupling gap relative to the air flow direction. This dimensional repositioning ensures that the gap runs parallel to the air flow rather than perpendicular to it, preventing air from entering the gap and reducing noise while preserving the hollow blade structure for weight reduction.
Solution Approach 2:
The invention applies different coupling configurations to different regions of the blade. Specifically, the coupling portion is strategically placed in regions (suction surface or pressure surface) where the local geometry and flow characteristics minimize air entry into the gap. This localized optimization allows the hollow blade structure to maintain its weight-saving benefit while eliminating noise generation at the coupling portion.
2Weight of moving object
If coupling portion is positioned at shroud-side leading edge to form hollow blade, then weight reduction is achieved, but high-precision dimensional control is required during manufacture
Solution Approach 1:
By repositioning the coupling portion to the suction or pressure surface, the invention changes the orientation of the coupling gap from a position where precise dimensional control is critical (shroud-side leading edge) to a position where the gap runs parallel to air flow. This dimensional change inherently reduces sensitivity to manufacturing tolerances, as the parallel orientation prevents air entry even with moderate gap variations.
Solution Approach 2:
The invention changes the critical parameters from gap width (which requires high-precision control in conventional designs) to gap orientation relative to air flow. By orienting the gap parallel to the flow direction on the suction or pressure surface, the design becomes less sensitive to dimensional variations, allowing for more relaxed manufacturing tolerances while still achieving the weight reduction benefit of hollow blades.
3Shape
If coupling portion is formed in conventional position, then hollow blade structure is achieved, but air enters the gap causing noise increase
Solution Approach 1:
The coupling portion is relocated from the conventional shroud-side leading edge position to the suction surface or pressure surface, changing the spatial orientation of the coupling gap. This dimensional repositioning aligns the gap parallel to the air flow direction, allowing the hollow blade structure to be maintained while preventing air from entering the gap and generating noise.
Solution Approach 2:
The invention optimizes the local geometry and positioning of the coupling portion specifically on the suction or pressure surface, where the local flow characteristics and blade geometry work together to minimize air entry into the gap. This localized design approach preserves the overall hollow blade structure while eliminating the noise-generating feature at the coupling portion.
Data Source
AI summary
Provided is a turbofan producing reduced noise and easily manufactured. A coupling portion between a blade main portion and a blade cover is formed in a surface region (pressure surface) parallel to a direction of air flowing over the pressure surface of each blade. With this configuration, the air sucked from a direction of a rotation axis of a turbofan is less liable to enter a gap of the coupling portion of the blade, thereby being capable of reducing noise. Further, noise is reduced so that high-precision dimensional control of the gap of the coupling portion of the blade is not required. Consequently, dimensional control at the time of manufacture is facilitated to thereby facilitate manufacture.