Free-Tipped Axial Fan Blade Tip Geometry for Tip Gap Management
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Solution Overview
Problem
Free-tipped axial-flow fans used in automotive engine cooling face efficiency and noise issues due to tip gaps, which are not adequately accounted for in design, leading to compromised performance.
Innovation Solution
The design of the free-tipped axial fan assembly features a blade tip radius that maximizes camber distribution and blade angle, with a significant increase as the tip radius is approached, and a shroud barrel configuration that accounts for the tip gap, ensuring optimal loading and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a free-tipped fan design is used to reduce material cost and mass, then manufacturing cost and weight are reduced, but fan efficiency decreases and noise increases due to tip gap
Solution Approach 1:
The blade geometry is modified locally at the tip region with increased camber and blade angle specifically where the tip gap exists, while the rest of the blade maintains its original design. This localized modification compensates for the adverse effects of the tip gap without requiring a complete redesign of the entire blade or adding tip bands.
2Weight of moving object
If a free-tipped fan design is used to reduce mass, then the fan weight is reduced, but fan efficiency decreases due to tip gap
Solution Approach 1:
The blade geometry is modified locally at the tip region with increased camber and blade angle specifically where the tip gap exists, while the rest of the blade maintains its original design. This localized modification compensates for the adverse effects of the tip gap without requiring a complete redesign of the entire blade or adding tip bands.
3Stability of the object's composition
If a free-tipped fan design is used to improve balance, then rotational balance is improved, but fan efficiency decreases and noise increases due to tip gap
Solution Approach 1:
The blade geometry is modified locally at the tip region with increased camber and blade angle specifically where the tip gap exists, while the rest of the blade maintains its original design. This localized modification compensates for the adverse effects of the tip gap without requiring a complete redesign of the entire blade or adding tip bands.
4Reliability
If a significant tip gap is designed to accommodate manufacturing tolerances and deflection, then reliability is improved, but fan efficiency decreases and noise increases
Solution Approach 1:
The blade tip camber and blade angle parameters are increased specifically at the tip region to compensate for the tip gap effects. This parameter modification allows the fan to maintain design blade loading despite the presence of the tip gap, thereby improving efficiency without reducing the necessary gap for reliability.
Data Source
Figure 1a~1b
Figure 1c~2c
Figure 2a~2b
AI summary
A free-tipped axial fan assembly includes fan having a blade tip geometry which provides a desired blade loading in the presence of a tip gap. The maximum camber exhibits a sudden and significant increase as the blade tip radius R is closely approached in the direction of increasing radial position. In some constructions, the maximum camber at the blade tip radius R is at least 10 percent greater than the maximum camber at a radial position r where r/R = 0.95. In some constructions, the blade angle increases by more than 0.01 radians from a radial position r where r/R = 0.95 to the blade tip radius R. The maximum camber at the blade tip radius R is at least 0.06 times the chord length in some constructions.