Blower Impeller Blade Outlet Angle Variation
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Solution Overview
Problem
Multi-blade centrifugal fans experience noise and reduced blowing efficiency due to air flow separation at the rim and backing-plate sides of the blades, as the angle of air flow into and out of the impeller differs between these areas, leading to pressure losses and noise generation.
Innovation Solution
The blower design includes an impeller with blades having different outlet angles at their trailing edges and features a flat surface on the pressure or suction surfaces of the second blade segment, which reduces air flow separation and disturbance by aligning the outlet angles with the discharge angle, thereby stabilizing the air flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the blade outlet angle is uniform across the entire blade surface, then the manufacturing is simple, but air flow separation occurs at the rim side or backing-plate side leading to noise and reduced blowing efficiency
Solution Approach 1:
The blade is designed with different outlet angles at different radial positions: the first blade segment (near the backing plate) has a first outlet angle, while the second blade segment (near the rim) has a second outlet angle that differs from the first. This local variation in geometric parameters prevents air flow separation at the rim side by matching the outlet angle to the local flow direction, thereby improving blowing efficiency without significantly complicating manufacturing
Solution Approach 2:
The blade is divided into two distinct segments along the radial direction: a first blade segment adjacent to the backing plate and a second blade segment adjacent to the rim. Each segment is assigned a different outlet angle configuration optimized for its specific operational conditions. This segmentation allows the blade to handle the varying flow angles at different radial positions effectively, reducing air flow separation and improving overall blowing efficiency
2Ease of manufacture
If the blade outlet angle is uniform across the entire blade surface, then the manufacturing is simple, but noise is generated due to air flow separation
Solution Approach 1:
The blade is designed with different outlet angles at different radial positions: the first blade segment (near the backing plate) has a first outlet angle, while the second blade segment (near the rim) has a second outlet angle that differs from the first. This local variation in geometric parameters prevents air flow separation at the rim side by matching the outlet angle to the local flow direction, thereby improving blowing efficiency without significantly complicating manufacturing
Solution Approach 2:
The blade is divided into two distinct segments along the radial direction: a first blade segment adjacent to the backing plate and a second blade segment adjacent to the rim. Each segment is assigned a different outlet angle configuration optimized for its specific operational conditions. This segmentation allows the blade to handle the varying flow angles at different radial positions effectively, reducing air flow separation and improving overall blowing efficiency
3Device complexity
If air flows into the impeller from one side only, then the structure is simple, but the angle of air flow into and out of the impeller differs between rim side and backing-plate side causing pressure losses
Solution Approach 1:
The blade is designed with different outlet angles at different radial positions: the first blade segment (near the backing plate) has a first outlet angle, while the second blade segment (near the rim) has a second outlet angle that differs from the first. This local variation in geometric parameters prevents air flow separation at the rim side by matching the outlet angle to the local flow direction, thereby improving blowing efficiency without significantly complicating manufacturing
Solution Approach 2:
The blade is divided into two distinct segments along the radial direction: a first blade segment adjacent to the backing plate and a second blade segment adjacent to the rim. Each segment is assigned a different outlet angle configuration optimized for its specific operational conditions. This segmentation allows the blade to handle the varying flow angles at different radial positions effectively, reducing air flow separation and improving overall blowing 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 enhances the efficiency and reduces noise of the blower by minimizing air flow separation and disturbance, particularly at the second blade segment, resulting in improved performance and reduced noise levels.
Implementation Method 1
separation of air flow from the blade surfaces occurs at the rim side or the backing-plate side of the blades
Data Source
AI summary
A blower includes a volute shaped casing having an air inlet, and an impeller including a disk-shaped backing plate, a ring-shaped rim, and a plurality of blades supported between the backing plate and the rim. The impeller is housed in the casing. Each of the blades includes a first blade segment adjacent to the backing plate, and a second blade segment provided between the first blade segment and the rim. Each of the blades has a blade outlet angle at a trailing edge of the second blade segment different from a blade outlet angle at a trailing edge of the first blade segment. At least one of a pressure surface of the second blade segment and a suction surface of the second blade segment includes a flat surface extending toward a leading edge of the second blade segment from the trailing edge of the second blade segment.