Propeller Fan Blade Inclination Angle Variation for Tip Vortex Stabilization
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Solution Overview
Problem
The variation in tip vortex size during the rotation of a propeller fan leads to increased noise and decreased efficiency due to changes in air flow rate and pressure, affecting the performance of the fan.
Innovation Solution
The propeller fan design features blades with a gradually increasing inclination angle from an intermediate position to the trailing blade end, which helps in stabilizing the tip vortex size, and a camber ratio that decreases from the blade root to the end, reducing turbulence and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the blade inclination angle is increased to stabilize tip vortex size, then noise is reduced and fan efficiency is improved, but blade complexity increases
Solution Approach 1:
The blade is designed with non-uniform inclination angles along its span, where the inclination angle varies specifically in the region from 0.7R to R (R being the blade outer diameter). This local differentiation allows the blade to stabilize tip vortex size and reduce noise in critical areas without unnecessarily complicating the entire blade structure.
Solution Approach 2:
The inclination angle parameter is changed along the blade span, transitioning from a constant value to a variable value in the region from 0.7R to R. This parameter variation optimizes airflow characteristics and tip vortex stability while maintaining manufacturing feasibility through defined geometric progression relationships.
2Stress or pressure
If the inclination angle varies significantly to control airflow, then pressure distribution improves, but tip vortex stability deteriorates
Solution Approach 1:
The inclination angle is designed to vary only in the specific region from 0.7R to R, while remaining constant or varying less significantly in the inner region (0 to 0.7R). This localized variation allows improved pressure distribution at the blade end without causing excessive tip vortex instability.
Solution Approach 2:
Rather than varying the inclination angle along the entire blade span, the invention applies inclination angle variation only partially in the region from 0.7R to R. This partial action is sufficient to control airflow and pressure distribution while avoiding the excessive variation that would destabilize the tip vortex.
3Productivity
If the blade inclination angle is optimized for airflow, then fan efficiency increases, but manufacturing complexity increases
Solution Approach 1:
The inclination angle parameter is changed in a controlled manner using geometric progression relationships, which provides a systematic approach to manufacturing. The parameter variation follows defined mathematical relationships that can be implemented through standard manufacturing processes while achieving optimized airflow and fan efficiency.
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 design stabilizes the tip vortex, reduces noise, and enhances fan efficiency by minimizing power consumption and airflow turbulence, while maintaining effective air blowing ability.
Implementation Method 1
air flows from the positive pressure surface side to the negative pressure surface side via the blade end of the blade, so that a tip vortex is generated
Implementation Method 2
air flows from the positive pressure surface side to the negative pressure surface side via the blade end of the blade
Data Source
AI summary
In a blade of a propeller fan, an inclination angle (φ) is made by a straight line passing through an outer circumferential side end and an inner circumferential side end of a radial cross section of the blade with a second plane orthogonal to a center axis of a hub. In a blade end of the blade, one end in front of the other end viewed in the rotation direction of the propeller fan is a leading blade end, while the other end behind the leading blade end is a trailing blade end. The blade is shaped such that the inclination angle (φ) monotonically increases, in the direction from the intermediate position toward the trailing blade end, in an area extending from an intermediate position between the leading blade end and the trailing blade end to the trailing blade end.