Asymmetric Wedge Bar for Inertial Particle Separation
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Solution Overview
Problem
Existing wedge wire screens for water intake systems have poor particle-separation efficiency due to low inertial forces, leading to carry-through of particles and susceptibility to impingement and clogging, especially with suspended seaweed and long algae.
Innovation Solution
The use of asymmetrically profiled wedge-bars with a flow separation edge protruding into the tangential sweeping flow, creating sharply curved streamlines for high acceleration and inertial separation, while minimizing the boundary layer thickness for improved particle capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If small gap-size screens are applied to offset lack of separation efficiency, then particle separation efficiency is improved, but the screen becomes susceptible to impingement of larger particles and surface clog-up
Solution Approach 1:
The patent employs asymmetrically profiled wedge-bars with a flow separation edge on the trailing end, creating asymmetric flow patterns that enhance inertial separation forces. This asymmetric geometry allows the screen to achieve effective particle separation without requiring small gap sizes, thereby avoiding clog-up while maintaining separation efficiency.
Solution Approach 2:
The flow separation edge creates sharply curved streamlines in the boundary layer, increasing the curvature radius to enhance inertial forces. This curved flow path improves particle separation efficiency without requiring reduced gap sizes, thus preventing both particle carry-through and surface clog-up.
2Reliability
If symmetrical trapezoid shaped wire profile is used, then screen plug-up is reduced, but particle separation efficiency remains poor due to large streamline curvature
Solution Approach 1:
The patent transitions from symmetrical to asymmetrically profiled wedge-bars with a flow separation edge on the trailing end. This asymmetric geometry creates more favorable flow patterns that reduce boundary layer thickness and increase inertial separation forces, thereby improving particle separation efficiency while maintaining the plug-up resistance of the wedge profile.
Solution Approach 2:
The flow separation edge is positioned to create curved streamlines in advance within the boundary layer before particles reach the screen surface. This preliminary flow curvature enhances inertial forces that act on particles, improving separation efficiency without requiring changes to the overall screen gap size or profile symmetry.
3Ease of operation
If natural gravity or pump-induced flow is used to create tangential flow, then sweeping flow is achieved, but particle separation efficiency remains insufficient
Solution Approach 1:
The flow separation edge creates sharply curved streamlines with reduced boundary layer thickness, increasing the curvature radius and thereby enhancing inertial forces. This curved flow path significantly improves particle separation efficiency while maintaining easy operation through natural or pump-induced sweeping flow.
Solution Approach 2:
The asymmetric wedge-bar profile changes the flow parameters by creating a flow separation edge that generates curved streamlines and reduces boundary layer thickness. This parameter change increases inertial separation forces, improving particle separation efficiency without requiring additional energy input for sweeping flow generation.
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 enhances particle separation efficiency by increasing inertial forces and reducing boundary layer thickness, effectively preventing particle entrainment and surface impingement, thereby minimizing flow restriction and blockage.
Implementation Method 1
Induced local acceleration is used—typically by changing the local (small scale) flow pattern of the fluid—to induce inertial forces to the suspended particles. The inertial forces result in the partial or full separation of floating particles.
Implementation Method 2
The flow separation edge is partially protruding from the face of the screen into the tangential sweeping flow. The protruding edge facilitates a formation of sharply curved streamlines of the flow passing through the gaps of the screen for high acceleration and effective inertial separation of particles.
Implementation Method 3
The asymmetrical profile, combined with the separation edge minimizes the thickness of the entrainment boundary layer within which the small particles may pass through the screen.
Data Source
AI summary
Asymmetrically profiled wedge bar screen used for inertial separation of suspended particles, wherein the profile of the bars is a generalized trapezoid, tilted in the direction of the sweeping flow with a distinctly extended trailing edge at the aft face side of the cross section of the bar.