Cross-Flow Fan Guide Wall Steps for Quieter Air Conditioners
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Solution Overview
Problem
In air conditioners with cross flow fans, the semispherical dimples on the casing surface cause instability in airflow direction, leading to separation issues and increased noise, while swirl generation on the casing surface increases torque and ventilation resistance, deteriorating fan motor input and causing dew splashing due to reduced air speed at the fan's rotary shaft ends.
Innovation Solution
The implementation of a stepped portion on the guide wall with a spiral shape, featuring multiple steps that gradually expand downstream, reduces airflow separation and noise by generating swirl and negative pressure, which draws airflow closer to the center, preventing counterflow and reducing motor power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If semispherical dimples are formed on the casing surface, then separation reduction is attempted, but the airflow direction becomes unstable and separation still occurs
Solution Approach 1:
The guide wall surface is segmented into multiple stepped portions rather than using a single smooth surface or simple dimples. This segmentation creates multiple control zones that collectively manage airflow more effectively, preventing separation through distributed rather than localized features.
Solution Approach 2:
The invention transitions from two-dimensional dimples (surface depressions) to three-dimensional stepped portions (multi-level structures extending into the flow path). This dimensional change allows for more complex flow control mechanisms including swirl generation and negative pressure zone creation, which simple dimples cannot achieve.
2Reliability
If swirl generating means is disposed on the casing surface, then longitudinal swirl is generated to prevent separation, but upstream-side surface blocks fan blow-out flow causing increased torque and ventilation resistance
Solution Approach 1:
The stepped portions are positioned and designed to generate swirl and negative pressure zones in advance, upstream of critical separation-prone areas. This preliminary action prepares the airflow with favorable characteristics (swirl and pressure distribution) before it reaches regions where separation would otherwise occur, reducing the need for additional downstream intervention.
Solution Approach 2:
The invention changes key flow parameters (swirl intensity, pressure distribution, flow velocity profile) through the stepped portions design. By carefully controlling the geometry, depth, and positioning of steps, the airflow parameters are optimized to prevent separation while minimizing resistance and torque requirements.
3Object-generated harmful factors
If stepped portion is disposed on the guide wall, then separation is prevented and noise is reduced, but device complexity increases
Solution Approach 1:
The stepped portions are integrated directly into the guide wall structure itself, merging the flow control function with the existing structural component. This eliminates the need for separate attachments or additional parts, achieving complex flow control through modification of the guide wall geometry rather than adding separate devices.
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 configuration effectively prevents airflow separation, reduces noise, and conserves energy by stabilizing airflow and minimizing counterflow, resulting in a more efficient and silent air conditioner operation.
Implementation Method 1
generating swirl and negative pressure, which draws airflow closer to the center
Implementation Method 2
generating swirl and negative pressure, which draws airflow closer to the center
Implementation Method 3
prevents separation from the casing surface in an air path
Data Source
Figure 1
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Figure 3
AI summary
An inlet 2, a heat exchanger 7, a blow-out port 3, a blower 8 having an impeller 8a, disposed on the downstream side of the heat exchanger 7 and feeding said indoor air from the inlet 2 to the blow-out port 3, with a longitudinal direction of an air conditioner main body 1 as its rotary shaft direction L, a stabilizer 9 that separates a suction-side channel E1 on the upstream side of the impeller 8a and a blow-out-side channel E2 on the downstream side from each other and forms a front face side of the blow-out-side channel E2, a spiral guide wall 10 that forms a rear face side of the blow-out-side channel E2, and a stepped portion 14 disposed in a stepped shape in a blowing direction of the blower 8 at least in a part of the guide wall 10 and having a plurality of steps, each extending in a rotary shaft direction L and indented substantially in a triangular shape on a section perpendicular to the rotary shaft O of the impeller 8a are provided so that separation of a blow-out flow by a negative pressure generated by the step in the stepped shape is prevented, noise is lowered, and energy saving can be realized.