Inlet Nozzle Recessed Edge for Fan Flow Separation
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Solution Overview
Problem
Existing radial, diagonal, or axial fans experience flow detachments and turbulence at small inlet radii, leading to increased sound values and performance losses.
Innovation Solution
A single-stream nozzle with a curved surface featuring a ring-shaped truss or back-up edge, designed to counteract turbulent border layers and prevent flow detachments, is implemented.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a small inlet radius is used, then the overall size of the inlet nozzle is reduced, but flow separation occurs leading to increased noise levels and power losses
Solution Approach 1:
The invention applies a specific geometric feature (outwardly recessed edge) at a critical location (inlet radius area) to locally modify flow characteristics. This localized modification creates turbulent boundary layers precisely where needed to prevent flow separation, without requiring changes to the overall nozzle size or geometry elsewhere.
Solution Approach 2:
The invention changes the geometric parameters of the inlet radius area by introducing an outwardly recessed edge with specific dimensions (depth between 0.01-0.5 times the inlet radius, length between 0.1-10 times the inlet radius). This parameter modification transforms the flow regime from laminar to turbulent in the boundary layer, preventing separation even at small inlet radii.
2Volume of moving object
If a small inlet radius is used, then the overall size of the inlet nozzle is reduced, but flow separation occurs leading to increased sound levels
Solution Approach 1:
The outwardly recessed edge creates localized turbulent boundary layers at the critical inlet radius position, which suppresses flow separation and the associated noise-generating vortices. This local modification eliminates the harmful acoustic effects without requiring a larger overall nozzle design.
3Loss of energy
If conventional measures in the outlet area of the inlet nozzle are applied, then some flow separation is reduced, but significant flow detachments and turbulence remain
Solution Approach 1:
Instead of attempting to correct flow problems in the outlet area, the invention applies the outwardly recessed edge feature in advance at the inlet radius area. This preliminary action creates turbulent boundary layers before the flow enters the critical regions, preventing flow separation and turbulence from developing in the first place.
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 effectively reduces sound values and performance losses by preventing flow detachments and optimizing airflow, even at small inlet radii.
Implementation Method 1
a measure or a flow element on or in the curved surface of the inlet section, in particular for forcing turbulent boundary layers in the flow, which counteract/can counteract flow separation in this area
Implementation Method 2
insufficiently large radii can lead to flow separation in the inlet area or in the area of the inlet radius
Data Source
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AI summary
The invention relates to an inlet nozzle (1) for a radial, diagonal or axial-flow fan, comprising an inlet section (3) that is circular in cross-section, has a radius of curvature, and tapers in diameter in the direction of flow (4), characterised by the presence of a measure or a flow element on or in the curved surface (5) of said inlet section for the purpose of forcing turbulent boundary layers in the flow, which can counteract a stall in this region. A radial, diagonal or axial-flow fan comprises a corresponding inlet nozzle (1).