Cross-Flow Blower Outlet Geometry to Prevent Noise and Backflow
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In cross-flow fans used in air conditioners, the blown air tends to flow towards one wall portion rather than another, leading to reduced flow rates and potential reverse flow, causing noise and surging, especially during high-load operations and when filters are clogged.
Innovation Solution
The cross-flow fan design includes a blow-out path with a narrowed portion whose cross-sectional area decreases from a rectangular to a trapezoidal shape, with the distance between the first and second wall portions decreasing from the upstream to the downstream side, and inclined surfaces that are recessed inward, allowing for smoother airflow and reduced friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the blow-out path has a uniform cross-sectional area, then the structure is simple and easy to manufacture, but the airflow distribution becomes uneven causing noise and surging
Solution Approach 1:
The blow-out path is designed with varying cross-sectional area along its length, creating different flow characteristics in different sections. The cross-sectional area is larger near the fan rotor to accommodate high-velocity flow, and gradually reduces toward the blow-out port to control flow distribution and prevent separation, thereby eliminating noise and surging while maintaining manufacturability.
Solution Approach 2:
The cross-sectional area parameter of the blow-out path is changed along the flow direction to optimize airflow. By gradually reducing the cross-sectional area from upstream to downstream, the flow velocity and pressure distribution are controlled to prevent flow separation at the second wall portion, eliminating the harmful effects of noise and surging.
2Speed
If the cross-sectional area of the blow-out path is reduced, then the airflow velocity increases, but the flow rate at end portions decreases causing reverse flow
Solution Approach 1:
The blow-out path is designed with non-uniform cross-sectional area that is larger at the end portions near the second wall portion to maintain adequate flow rate, and smaller in the central region to maintain velocity. This localized variation in cross-sectional area prevents reverse flow at the end portions while maintaining overall airflow efficiency.
Solution Approach 2:
The cross-sectional shape of the blow-out path is changed from a simple rectangle to a more complex geometry with varying dimensions in different directions. The cross-section includes a first dimension (width) that varies along the length and a second dimension (height) that is maintained or varied differently, creating a three-dimensional flow distribution that prevents reverse flow while maintaining velocity.
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 airflow distribution, reduces noise, and prevents backflow by maintaining airflow at the end portions of the blow-out path, even during high-load operations, thereby improving the overall performance of the air conditioner.
Implementation Method 1
the flow rate of the blown air decreases as the blown air flows downstream due to friction with the side wall portions of the housing
Data Source
AI summary
Disclosed is a cross-flow fan including a fan rotor and a housing. The cross-flow fan has a blow-out path defined by first and second extension wall portions and two sidewalls. The first extension wall portion continuously extends from a tongue portion of the housing to the blow-out port. The second extension wall portion faces the first extension wall portion. The two sidewalls are respectively provided at axial ends of the fan rotor. The two sidewalls are formed such that the blow-out path has a narrowed portion whose cross-sectional area decreases as its cross-sectional shape changes from a rectangular shape to a trapezoidal shape from an upstream side toward a downstream side thereof, the trapezoidal shape having a portion near the second extension wall portion smaller in width than a portion near the first extension wall portion.