Forward-Swept Pressure Screen Rotor Struts to Prevent Stringing
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Solution Overview
Problem
Conventional pressure screen rotors for removing contaminants from solid suspensions suffer from stringing, where contaminants and fibers accumulate on the forward edge of struts and foils, increasing rotor drag and reducing the effectiveness of pressure pulses.
Innovation Solution
The use of forward-swept struts that extend between the hub and foils, creating flow currents to move contaminants and fibers inboard towards the hub, reducing accumulation and drag, 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 structural simplicity is maintained, but stringing occurs where 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 configuring the struts with a swept-back angle relative to the radial direction. This asymmetric orientation creates a leading edge and trailing edge on the struts, which directs flow patterns to prevent contaminant accumulation on the forward edge, thereby eliminating stringing while maintaining structural integrity and screening effectiveness
2Device complexity
If conventional radially extending struts are used in the rotor, then the device complexity is low, but rotor drag increases due to contaminant accumulation on the struts
Solution Approach 1:
The asymmetric swept-back strut configuration modifies the flow field around the struts, creating a hydrodynamic pattern that prevents contaminant deposition. This reduces the wetted surface area where contaminants could accumulate, thereby decreasing rotor drag and energy loss without requiring additional components or complex mechanisms
3Device complexity
If conventional struts are used, then the rotor structure is simple, but the foils become less effective in dislodging contaminants due to interference from accumulated deposits
Solution Approach 1:
The swept-back angle of the struts creates a flow pattern that keeps the foil leading edges clear of contaminant deposits. By directing the slurry flow along the struts in a specific pattern, the asymmetric design prevents buildup that would otherwise interfere with foil operation, maintaining reliable contaminant dislodgement functionality
Solution Approach 2:
The struts act as intermediaries that manage the flow of slurry between the hub and the foils. By optimizing their orientation, they mediate the flow patterns to ensure clean leading edges of the foils, allowing the foils to effectively perform their contaminant-dislodging function without direct interference from accumulated deposits
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, and minimizing power requirements.
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
rotation of the rotor traverses the plurality of foils circumferentially around the inner surface of the pressure screen cylinder. Movement of the foils along the inner surface of the pressure screen cylinder causes pressure pulses that remove contaminants and fibers matted to the inner surface
Data Source
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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.