Forward-Swept Rotor Struts for Pressure Screen Stringing Control
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Solution Overview
Problem
Conventional pressure screen rotors for removing contaminants from pulp and slurry 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 redirect contaminants and fibers inboard towards the hub, combined with a release region at the strut-hub connection, reduces accumulation and drag by creating flow currents that prevent contaminants and fibers from collecting on the forward edge of the struts and foils.
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 strut forward edge is designed with an asymmetric swept-back configuration where the leading edge angle varies along the span, creating asymmetric flow patterns that prevent contaminant accumulation while maintaining structural integrity and manufacturability
2Device complexity
If conventional radially extending struts are used in the rotor, then the rotor structure is simple, but the accumulation of contaminants and fibers increases rotor drag requiring more motor power
Solution Approach 1:
The asymmetric swept-back forward edge geometry creates flow separation and low-pressure zones that actively repel contaminants away from the strut surface, reducing drag forces and consequently lowering motor power requirements while adding minimal structural complexity
3Device complexity
If conventional struts are used, then the rotor design is straightforward, but deposits on the forward edge interfere with pressure pulse generation
Solution Approach 1:
The asymmetric swept-back configuration prevents deposit accumulation by creating unfavorable flow attachment conditions on the forward edge, ensuring that the foils can consistently generate effective pressure pulses against the screen surface without interference from contaminant deposits
Solution Approach 2:
The geometric design of the forward edge proactively prevents contaminant accumulation before it can interfere with pressure pulse generation, eliminating the need for additional cleaning mechanisms or complex control systems
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 forward-swept struts effectively minimize stringing, reducing rotor drag and maintaining the effectiveness of pressure pulses, thereby improving the efficiency and capacity of the pressure screen cylinder.
Implementation Method 1
the fluid dynamics created by 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 of the pressure screen cylinder
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.