Triangular Tube Bank for Uniform Paper Stock Distribution
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Solution Overview
Problem
Conventional headbox distributors in papermaking machines face issues with uniform flow distribution due to pressure drop and reorientation of round tubes to rectangular nozzles, causing nonuniformities in paper web production and operational cleanliness.
Innovation Solution
A tube bank apparatus with triangular or trapezoidal shaped tubes at the discharge end, nested to minimize wall effects, and adjustable inserts for flow control, allowing for uniform pressure drop and flow acceleration while reducing cross-machine nonuniformities in consistency and velocity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If round inlet tubes are used to distribute slurry, then flow acceleration and pressure drop are achieved, but cross-machine uniformity of flow distribution deteriorates due to reorientation disturbances
Solution Approach 1:
The tube discharge ends are designed with asymmetric triangular or trapezoidal shapes instead of symmetric round shapes. This asymmetry allows the flow to exit in a direction that matches the rectangular nozzle geometry, eliminating the reorientation disturbances that occur with round tubes. The asymmetric shape creates a pressure drop that accelerates flow while maintaining cross-machine uniformity because the flow direction naturally aligns with the discharge path without requiring sharp turns or reorientation.
2Device complexity
If round tubes are used for slurry distribution, then simple structure is maintained, but wall effects and operational cleanliness deteriorate
Solution Approach 1:
The triangular or trapezoidal discharge ends create asymmetric flow patterns that reduce wall effects. The angled surfaces of the triangular/trapezoidal shapes allow flow to exit more smoothly along the tube walls rather than creating turbulent recirculation zones that occur with round tubes. This reduces the accumulation of fibers and debris near the walls, improving operational cleanliness without significantly increasing structural complexity.
Solution Approach 2:
The invention transitions from two-dimensional round cross-sections to three-dimensional triangular or trapezoidal cross-sections at the discharge end. This dimensional change allows the flow to be directed more precisely in the desired direction, reducing the harmful wall effects that occur with round tubes. The angled surfaces provide a more favorable flow path that reduces turbulence and fiber accumulation near the tube walls.
3Manufacturing precision
If triangular or trapezoidal tubes are nested to minimize wall effects, then cross-machine uniformity improves, but device complexity increases
Solution Approach 1:
The triangular or trapezoidal tubes are arranged in a nested configuration where the angled surfaces of adjacent tubes interlock and minimize gaps. This nesting approach allows the tubes to be packed more efficiently while maintaining the asymmetric discharge shapes that reduce wall effects. The nested arrangement creates a compact tube array that achieves uniform flow distribution without requiring complex external support structures or adjustments.
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 cross-machine nonuniformities in both consistency and velocity of stock flow, enhancing operational cleanliness and adaptability for various paper grades, including those with turbulence control and different entrance diameters.
Implementation Method 1
The pressure drop from the acceleration of the flow at the inlet of each tube within the array is critical to the uniformity of the flow within each tube
Implementation Method 2
The tube array is made up of individual round inlet tubes mounted in some manner to cause acceleration of the flow into each tube from a cross machine header
Implementation Method 3
The reorientation of the round tube entrance flow to the prior art eventual rectangular shape of the nozzle will create disturbances in the flow in all directions. These disturbances must be damped or reduced in some way prior to discharge out the slice
Data Source
AI summary
A tube bank apparatus is disclosed for distributing stock in a headbox of a papermaking machine. The apparatus includes a tube having a first and a second portion for the flow therethrough of the stock. The first portion defines a bore for the flow therethrough of the stock, the bore having an upstream and a downstream end. The second portion defines a passage for the flow therethrough of the stock, the passage having an upstream and a downstream extremity. The upstream extremity of the passage cooperates with the downstream end of the bore so that the stock flows from the upstream end to the downstream end of the bore and then through the upstream extremity and then the downstream extremity of the passage. A first, second and third edge define at least a part of the downstream extremity of the passage, the second edge extending between the first edge and the third edge such that a sum of a first angle defined between the first edge and the second edge and a second angle defined between the second edge and third edge is less than 180 degrees.