Yankee Drying Hood Helical Distributor Conduits
Solution Overview
Problem
Yankee drying hoods often result in uneven heating across the cross machine direction, leading to undesirable variations in the moisture profile of the paper web, which is not in line with current standards requiring more uniform performance.
Innovation Solution
The Yankee drying hood arrangement is designed with nozzle boxes equidistantly spaced around an imaginary axis, forming a curved structure that follows the cylindrical surface of the Yankee drying cylinder, and distributor conduits oriented in a helical pattern to ensure consistent hot air distribution along the axial extension, compensating for temperature variations across the machine direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional air supply system with parallel distributor conduits is used, then the structure is simple, but the heating uniformity across cross machine direction deteriorates
Solution Approach 1:
The distributor conduits are arranged asymmetrically with respect to the nozzle boxes, following a helical path rather than parallel lines. This asymmetric arrangement ensures that hot air is distributed more uniformly across the cross machine direction by compensating for temperature variations at different axial positions, thereby improving heating uniformity without requiring excessive structural complexity
Solution Approach 2:
The distributor conduits transition from a two-dimensional parallel arrangement to a three-dimensional helical configuration. This dimensional change allows the conduits to access multiple nozzle boxes at different axial positions and circumferential locations, enabling more uniform hot air distribution across the cross machine direction while maintaining structural feasibility
2Manufacturing precision
If hot air is supplied through conventional distributor conduits, then the device complexity is low, but the moisture profile uniformity deteriorates
Solution Approach 1:
The asymmetric helical arrangement of distributor conduits creates non-uniform flow paths that compensate for the natural temperature drop in hot air. By strategically positioning conduit connections to different nozzle boxes at varying axial positions, the system achieves more uniform moisture removal across the web width, improving moisture profile uniformity while keeping the configuration manageable
Solution Approach 2:
Different sections of the distributor conduit system are designed with locally optimized characteristics. The helical path allows specific conduit segments to supply hot air to nozzle boxes at different axial positions with appropriate temperature compensation, creating locally adapted air supply that results in globally uniform moisture profile
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 design achieves a more even temperature distribution and impingement velocity profile, resulting in a uniform moisture profile across the paper web, enhancing the drying efficiency and meeting modern standards for tissue machines.
Implementation Method 1
The air that is supplied is heated such that it can contribute to achieve evaporation of the water that is present in the paper web
Implementation Method 2
Through the openings in the nozzle box, a fluid such as hot air can exit the nozzle boxes and stream towards the circular cylindrical surface of the Yankee drying cylinder... contribute to achieve evaporation of the water that is present in the paper web
Data Source
AI summary
The invention relates to a Yankee drying hood arrangement (1) which is shaped to be fitted over a Yankee drying cylinder (2) such that the drying hood arrangement (1) can cover a part (4) of the circular cylindrical surface (3) of a Yankee drying cylinder (2). The Yankee drying hood arrangement (1) comprises a plurality of nozzle boxes (5) distributed equidistantly around an imaginary axis (X) such that, when the Yankee drying hood arrangement (1) is fitted over a Yankee drying cylinder (2), the nozzle boxes (5) are spaced from the circular cylindrical surface (3) of the Yankee drying cylinder (2) but form a curved structure (6) that follows the outer contour of the circular cylindrical surface (3) of the Yankee drying cylinder (2). Each nozzle box (5) has a longitudinal extension in a direction parallel to the axial extension of the Yankee drying cylinder (2) and each nozzle box (5) has openings (7) distributed along the longitudinal extension of the nozzle box (5) through which openings (7) a fluid such as hot air can exit the nozzle boxes (5) and stream towards the circular cylindrical surface (3) of the Yankee drying cylinder (2) at different points at different points along the axial extension of the Yankee drying cylinder (2). The Yankee drying arrangement further comprises a plurality of distributor conduits (8) for a fluid such as hot air and the distributor conduits (8) extend in the circumferential direction around the curved structure (6) formed by the nozzle boxes (5). Each distributor conduit (8) is in communication with several nozzle boxes (5) such that a fluid such as hot air can stream from each distributor conduit (8) to several different nozzle boxes (5). At least one main supply conduit (9, 10) for a fluid such as hot air is in communication with the distributor conduits (8) such that a fluid such as hot air can stream to the distributor conduits (8). The distributor conduits (8) are oriented around the curved structure (6) of the nozzle boxes (5) in such a pattern that, when one and the same distributor conduit (8) communicates with different nozzle boxes (5), it does so at different points along the longitudinal extension of the different nozzle boxes (5). The invention also relates to a Yankee drying cylinder fitted with the inventive Yankee drying hood arrangement and to a method of drying a fibrous web.