Step Diffuser Fan Structure for Low-Noise Pressure Recovery
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fans face issues with increased noise levels and efficiency loss under high pressures, particularly in axial and diagonal designs with limited space or low pressures.
Innovation Solution
Incorporation of a step diffuser with an abrupt expansion in the flow cross section downstream of the impeller, combined with a redirection device and secondary flow management, stabilizes the flow and enhances pressure recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If axial fans without cover rings are used, then the structure is simple, but noise level increases considerably under rising pressures
Solution Approach 1:
The flow path is segmented into distinct regions: an inlet nozzle that directs flow onto the impeller, a cover ring that surrounds the impeller, and a step diffuser downstream. This segmentation allows each component to be optimized for its specific function, with the step diffuser specifically designed to control noise under pressure
Solution Approach 2:
The step diffuser acts as an intermediary structure between the impeller outlet and the housing outlet. This abrupt expansion structure mediates the flow transition, reducing noise generation while maintaining pressure recovery, thus resolving the contradiction between structural simplicity and noise control
2Volume of moving object
If freely running diagonal wheels are used, then lateral space is reduced, but power and noise level become problematic at low pressures
Solution Approach 1:
The inlet nozzle is designed to dynamically direct the main flow onto the impeller at optimal angles, maximizing power transfer efficiency. The nozzle geometry can be optimized to maintain high power output at low pressures while keeping the overall lateral footprint compact
Solution Approach 2:
The design optimizes flow parameters (velocity, direction, pressure) through the inlet nozzle and step diffuser configuration. By carefully controlling these parameters, the fan achieves high power output at low pressures within a compact lateral space
3Object-generated harmful factors
If a step diffuser with abrupt expansion is added, then pressure recovery is enhanced and noise is reduced, but device complexity increases
Solution Approach 1:
The step diffuser introduces local geometric complexity only at the critical downstream expansion region where noise control and pressure recovery are most needed. The rest of the housing maintains a simpler cylindrical form, balancing overall structural simplicity with localized noise reduction functionality
4Object-generated harmful factors
If the cross-sectional expansion ratio is increased to >=105%, then noise reduction and pressure recovery are maximized, but the housing volume increases
Solution Approach 1:
The step diffuser utilizes the axial dimension for expansion rather than requiring proportional increases in radial dimensions. By expanding the flow cross-section primarily in the axial direction downstream of the impeller, the design achieves the required >=105% expansion ratio for noise control while minimizing the increase in overall housing volume
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
The solution results in a low-noise, highly efficient fan design with improved pressure recovery and reduced throughflow rate, facilitated by the interaction of the step diffuser and secondary flow, suitable for various manufacturing methods.
Implementation Method 1
a step diffuser in the form of an abrupt expansion in the flow cross section is formed downstream of the impeller... the provision of a step diffuser in the form of an abrupt expansion in the flow cross section very substantially eliminates the disadvantages occurring in the prior art
Implementation Method 2
A secondary flow, as a partial flow of the air emerging from the impeller, flows back between the cover ring and the contour of the housing and enters the region of the impeller again... The secondary flow regularly has heavy swirling imparted to it, as it is influenced by the rotational movement of the impeller
Data Source
AI summary
A fan, in particular an axial or diagonal fan, comprising a housing and an impeller arranged therein and driven by an electric motor and having vanes extending between a hub ring and a cover ring, wherein a step diffuser is formed in the form of an abrupt expansion of the flow cross-section in the direction of flow downstream of the impeller and after exiting the region of the cover ring.