Coanda Nozzle Air Stabilization for Web Profile Control
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Solution Overview
Problem
Current air stabilizers for papermaking machines fail to maintain a sufficiently flat profile of the moving paper web, leading to inaccurate thickness measurements due to misalignment of sensor heads and inadequate non-contact support, which results in debris accumulation and contamination issues.
Innovation Solution
The use of two parallel, opposite-facing elongated Coanda nozzles positioned above or below the moving web, with each nozzle exhausting gas in opposite directions to create local tension and regulate the web's contour, ensuring a planar profile and improved clamping capacity by optimizing air pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a single Coanda nozzle is used to support the web, then non-contact support is achieved, but the web profile becomes curved (sombrero-type) rather than flat
Solution Approach 1:
The single Coanda nozzle is divided into two separate nozzles positioned on opposite sides of the web. Each nozzle independently generates a jet that applies force to one side of the web, allowing the forces to be balanced and the web profile to remain flat rather than curved.
Solution Approach 2:
The two nozzles are positioned asymmetrically on opposite faces of the web, with each nozzle's jet directed toward the web from its respective side. This asymmetric positioning allows the system to generate balanced opposing forces that maintain a flat web profile.
2Measurement precision
If contacting methods are used to stabilize the web, then measurement accuracy improves, but debris and contaminants accumulate on sensing elements
Solution Approach 1:
A jet of gas serves as an intermediary between the stabilizing mechanism and the web. The gas jet applies force to the web without physical contact, preventing debris accumulation on sensing elements while still achieving the necessary web stabilization for accurate measurement.
Solution Approach 2:
The mechanical contacting stabilization system is replaced with a pneumatic system using Coanda nozzles. The gas jet provides the stabilizing force through fluid dynamics rather than mechanical contact, eliminating the problem of debris accumulation on contact surfaces.
3Productivity
If high-speed manufacturing is maintained, then productivity increases, but web stability for measurement becomes difficult to achieve
Solution Approach 1:
The Coanda jet system is designed to dynamically adapt to high-speed web movement. The gas jet maintains attachment to the web surface through the Coanda effect even at high speeds, providing continuous stabilization force that maintains web flatness during rapid manufacturing processes.
Solution Approach 2:
The system adjusts gas flow parameters (pressure, velocity) to match the web speed. By changing these parameters, the stabilization force remains effective across a range of manufacturing speeds, maintaining web flatness from slow to high-speed operation.
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 solution enables accurate thickness and other measurements by maintaining a flat web profile, reducing debris accumulation, and minimizing contact, thus enhancing measurement precision and maintaining web stability during high-speed manufacturing.
Implementation Method 1
The air stabilizer employs two opposite-facing nozzles that direct jets of gas onto the moving web thereby imparting tension in the web
Implementation Method 2
By regulating the speeds of the two jets of gas that are exhausted from the opposite-facing nozzles, the profile of the web as it passes over the air stabilizer can be controlled
Data Source
AI summary
An air stabilization system employing two parallel, opposite-facing Coanda nozzles, with each nozzle exhausting gas at opposite directions, subjects a moving flexible web to opposing forces effective to create local tension within the web. Each nozzle includes an elongated slot that is perpendicular to the path of the moving web. The nozzles serve as separate points along the machine direction for controlling the height of the web. The operative surface with the nozzles can exhibit a flush surface. The nozzles can be formed on elevated structures on the operative surface. The operative surface can be covered with a transparent substrate to minimize shape distortions on the moving web and to prevent debris from collecting around the sensor. By modulating the velocities of gases exiting the nozzles, the shape of the web can be manipulated to present a planar contour. The air stabilization system can be incorporated into a caliper scanner.