Pressure Screen Rotor With Forward-Swept Struts to Reduce Stringing
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Solution Overview
Problem
Conventional rotors for pressure screen cylinders experience stringing, where contaminants and fibers accumulate on the forward edge of struts and foils, increasing rotor drag and reducing the effectiveness of pressure pulses, leading to increased motor power requirements.
Innovation Solution
The use of forward-swept struts that create flow currents to convey contaminants and fibers inboard towards the hub, reducing accumulation on the forward edge of the struts and foils, and incorporating a release region with increased thickness to facilitate fiber sliding off the struts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional radially extending struts are used in the rotor, then the rotor structure is simple and easy to manufacture, but contaminants and fibers accumulate on the forward edge of the struts, increasing rotor drag and reducing screening effectiveness
Solution Approach 1:
The patent applies asymmetry by changing the strut configuration from conventional radially extending straight struts to forward-swept struts that curve forward in the direction of rotation. This asymmetric geometry prevents contaminants and fibers from accumulating on the forward edge, thereby reducing rotor drag and maintaining screening effectiveness without significantly complicating manufacturing
Solution Approach 2:
The patent employs curvature by designing the struts with a forward-swept curved profile instead of straight radial extensions. The curved geometry creates favorable flow patterns that reduce contamination buildup on the forward edge, improving rotor performance while remaining manufacturable using standard fabrication techniques
2Force
If conventional struts are used, then the rotor drag is lower initially, but stringing occurs and rotor drag increases over time, requiring increased motor power
Solution Approach 1:
The forward-swept strut geometry is designed in advance to prevent stringing before it occurs. The curved forward-swept profile creates flow currents that continuously clear contaminants away from the forward edge during rotation, preventing accumulation that would otherwise increase drag and power requirements over time
Solution Approach 2:
The patent converts the potentially harmful effect of rotating struts through contaminated slurry into a beneficial self-cleaning action. The forward-swept geometry utilizes the rotational motion and slurry flow to create currents that actively remove contaminants from the strut surfaces, transforming what would be a drag-increasing condition into a self-maintaining system
3Productivity
If foils traverse the inner surface to dislodge contaminants, then screening effectiveness is maintained, but stringing on foils and struts interferes with pressure pulse production
Solution Approach 1:
The forward-swept asymmetric strut geometry prevents stringing from forming on the struts, which eliminates interference with the foils' ability to produce pressure pulses. The asymmetric design creates flow patterns that keep the foil and strut surfaces clear, maintaining consistent pressure pulse generation and screening effectiveness
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
Reduces stringing and rotor drag, maintaining foil effectiveness in dislodging contaminants and fibers, thereby decreasing the power required to rotate the rotor.
Implementation Method 1
The forward-swept struts create flow currents or flow fields that move fibers and contaminants, which are dislodged from the pressure screen cylinder or from the general local flow field, inboard towards the hub of the rotor
Implementation Method 2
The release region is a region of the struts proximate the inboard end of the struts that has a thickness greater than the thickness of the strut. The greater thickness of the release regions allow for the forward edge of the struts at the inboard end of the struts to have a greater radius of curvature so that contaminants and fibers do not get caught on the forward edge of the strut
Data Source
AI summary
The present disclosure is directed to rotors for pressure screens with cylinders for screening solid contaminants from a solid slurry. The rotor includes a cylindrical hub, a plurality of foils spaced radially outward from the hub, and a plurality of struts coupling the plurality of foils to the hub. The struts include a forward edge having a forward-swept shape that creates streamlines that move contaminants and fibers from the general local flow field and those dislodged from the inner surface of the pressure screen cylinder radially inboard towards the hub. The streamlines produced by the forward-swept struts can reduce or prevent deposition of solid contaminants on the forward edge of the strut and on the leading edge of the foil. The struts can also include a release region proximate the inboard end of the strut.