Cross-Flow Fan Impeller Layout for Air Conditioner Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional cross-flow fans fail to adequately reduce noise frequencies of 2NZ to 3NZ sounds, which are exacerbated by the proximity of the fan to the heat exchanger, leading to increased noise levels.
Innovation Solution
The air conditioner incorporates 17 to 25 impellers with a specific skew angle and a compact design, where the length of each impeller is less than 40% of its diameter, and the heat exchanger is positioned with a clearance of 10% or less, to effectively cancel out 2NZ to 3NZ sound frequencies and maintain efficient air blowing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the number of impellers is increased to reduce 2NZ to 3NZ noise, then noise cancellation improves, but air blowing resistance increases
Solution Approach 1:
The patent optimizes the number of impellers to a specific range (17-25) to achieve the best balance between noise cancellation and air blowing performance. This parameter optimization ensures that enough impellers are present to cancel 2NZ to 3NZ noise while preventing excessive impeller count that would increase air blowing resistance and reduce productivity.
2Length of moving object
If the length of impeller is reduced to make the air conditioner compact, then device size decreases, but air blowing amount may be insufficient
Solution Approach 1:
The patent specifies that the length dimension of each impeller in the rotation axis direction should be equal to or less than 40% of the diameter. This parameter constraint allows the air conditioner to maintain a compact size while ensuring sufficient air blowing amount through optimized impeller geometry and the collective effect of multiple impellers.
3Length of moving object
If the clearance between heat exchanger and cross-flow fan is reduced to make the device compact, then device size decreases, but 2NZ to 3NZ noise increases
Solution Approach 1:
The patent optimizes the clearance between the heat exchanger and cross-flow fan to a specific range (equal to or less than 10% of the diameter) to achieve the best compromise between compactness and noise reduction. This parameter optimization ensures the device remains compact while minimizing the increase in 2NZ to 3NZ noise that would result from reduced clearance.
4Reliability
If the number of impellers is set to 17 or more to reduce noise variation, then noise stability improves, but air blowing resistance becomes too large
Solution Approach 1:
The patent establishes an upper bound of 25 impellers to prevent air blowing resistance from becoming excessive. This parameter constraint ensures that while enough impellers are included to achieve noise stability and reduce 2NZ to 3NZ noise variation, the impeller count does not exceed the threshold where air blowing performance deteriorates.
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 significantly reduces noise levels of 2NZ to 3NZ sounds, enhances air blowing performance, and allows for a compact air conditioner design while maintaining high quietness and efficient operation.
Implementation Method 1
a cross-flow fan produces a noise having a frequency of the product of the number N of revolutions per second and the number Z of blades arranged on the circumference of a circle (N × Z)
Implementation Method 2
the noises of 2NZ to 3NZ sounds produced in the respective impellers can be sufficiently cancelled with each other
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Provided is a highly quiet air conditioner in which a noise of 2NZ to 3NZ sounds is reduced. The air conditioner (10) includes a heat exchanger (30) and a cross-flow fan (40). The cross-flow fan (40) having a cylindrical shape includes a plurality of impellers (41), each of the impellers (41) including a plurality of blades (42) arranged in a circumferential direction. The heat exchanger (30) is disposed on the upstream side of an air flow of the cross-flow fan (40) with a clearance (In) having a dimension of equal to or less than 20% of the diameter of each of the impellers (41) therebetween. The impellers (41) are arranged with at least one of the blades displaced between each adjacent two of the impellers (41). In the cross-flow fan (40), 14 or more and 30 or less impellers (41) are arranged along a rotation axis.