Cross-Flow Fan End Casing Gaps for Quieter Indoor AC Units
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Solution Overview
Problem
The existing air conditioning indoor units with cross flow fans experience blade passing frequency noise due to the inhibition of air flow from the end portion casing, which restricts the air flow from the outer circumferential surface of the cross flow fan.
Innovation Solution
The air conditioning indoor unit design includes a housing with a cross flow fan, a rear guider, a stabilizer, and an end portion casing with varying gaps and inclined surfaces to guide air flow smoothly, preventing air from entering the fan and reducing noise generation. The second gap between the air outflow region and the end portion casing is wider than the first gap, and the second inner surface is inclined to direct air towards the center of the fan, alleviating turbulence and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the end portion casing is disposed to face the second outer circumferential surface with a slight gap, then the reverse flow of indoor air is suppressed, but the air flow from the cross flow fan is inhibited and blade passing frequency noise is generated
Solution Approach 1:
The end portion casing is divided into a first portion and a second portion with different gap characteristics. The first portion has a first gap for suppressing reverse flow, while the second portion has a second gap that is wider than the first gap to allow air flow from the air outflow region. This local differentiation resolves the contradiction by applying different gap qualities to different regions of the same component.
Solution Approach 2:
The patent introduces asymmetry in the gap design between the first and second portions of the end portion casing. The first gap and second gap are intentionally made different in width to serve different functions: the first gap suppresses reverse flow while the wider second gap prevents noise generation. This asymmetric design allows simultaneous achievement of both objectives.
2Object-generated harmful factors
If the second gap is made wider than the first gap, then the air flow from the air outflow region is unobstructed and noise is reduced, but the reverse flow suppression capability may be compromised
Solution Approach 1:
Different gap widths are applied to different portions of the end portion casing to achieve different local functions. The first portion maintains a smaller first gap for reverse flow suppression, while the second portion has a wider second gap for noise reduction. This local quality differentiation ensures that neither function compromises the other.
Solution Approach 2:
The end portion casing is segmented into functionally distinct first and second portions, each with optimized gap characteristics for its specific purpose. This segmentation allows independent optimization of reverse flow suppression and noise reduction without mutual interference.
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 effectively suppresses the generation of blade passing frequency noise by ensuring unobstructed air flow from the cross flow fan's outer surface, reducing the likelihood of indoor air entering the fan and minimizing noise interference.
Implementation Method 1
a cross flow fan that is accommodated in the housing, extends in a width direction of the housing, and is provided with an outer circumferential surface, the outer circumferential surface including a first outer circumferential surface corresponding to an air inflow region into which air after the heat exchange flows and a second outer circumferential surface corresponding to an air outflow region from which air after the heat exchange flows out
Implementation Method 2
a heat exchange unit that is accommodated in the housing and performs heat exchange with the air sucked through the air inlet port
Implementation Method 3
an end portion casing that is provided for an end portion of the cross flow fan and is provided with a first portion and a second portion, the first portion being provided with a first inner surface forming a first gap between the first inner surface and the first outer circumferential surface positioned at the end portion of the cross flow fan and the second portion being provided with a second inner surface forming a second gap between the second inner surface and the second outer circumferential surface positioned at the end portion of the cross flow fan, in which the second gap is wider than the first gap
Data Source
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AI summary
An air conditioning indoor unit includes an end portion casing (22) that is provided for an end portion of a cross flow fan main body (31) and is provided with a first portion (48) and a second portion (49), the first portion (48) being provided with a first inner surface (48a) forming a first gap (48G) between the first inner surface (48a) and a first outer circumferential surface (31b) corresponding to an air inflow region and the second portion (49) being provided with a second inner surface (49a) forming a second gap (49G) between the second inner surface (49a) and a second outer circumferential surface (31c) corresponding to an air outflow region. The second gap (49G) is wider than the first gap (48G).