<p> This thesis investigates the characteristics of noise generation in the gas wiping process, including the effects of the various parameters manipulated in the process and countermeasures used to reduce noise levels. The process of gas wiping is used in many industrial applications such as drying of pulp and paper, photograph production and some high performance cooling applications. One of the most important industrial applications of gas wiping is the production of hot-dipped galvanized sheet steel. Gas wiping is a very efficient and reliable process to control coating thickness and uniformity of galvanized steel products, and can be used for very high line speeds and production rates. Changing the various process parameters such as the jet to strip distance (z), the jet slot width (h), plenum pressure (P) and jet inclination angle (α) allows manufacturers to control the coating thickness and quality of the finished product.</p> <p> The gas wiping process is also responsible for the generation of very high levels of noise, which can be a factor in limiting the overall production rates and indirectly increase production costs for manufacturers. To maintain a constant coating thickness as the line speed and production rate is increased, the plenum pressure supplied to the jets and thus the incident jet velocity must be increased, or the jet-to-strip distance must be decreased. Noise production in the gas wiping process is acknowledged to be proportional to the incident jet velocity and inversely proportional to the jet-to-strip distance. Thus, for a given coating thickness, as the production rates increase, the noise generated by the process must also increase. Ergonomic restrictions in the workplace, which limit the exposure to high sound pressure levels and audible acoustic tones, may indirectly limit the maximum line speed for a steel sheet with a given coating thickness. This limitation is particularly relevant to the production of high quality automotive sheet steels, which often have very thin coating thicknesses and have higher than normal coating uniformity tolerances, which necessitate the use of high plenum pressures and small jet-to-strip distances.</p> <p> At present, the state of knowledge for noise generation in the gas wiping process is very limited. Only two previous investigations have been devoted to this problem, and the experiments for these studies have only modeled specific individual cases, with no attempt at a comprehensive modeling of noise in this process. For the current study, measurements have been performed in both an actual manufacturing environment and on a scaled galvanizing simulator in a laboratory environment. A comprehensive set of experiments over a wide range of gas wiping parameters was performed in order to provide a broad overview of noise generation in the gas wiping process and allow for process optimization to reduce noise and allow higher production rates and efficiency. The creation of noise maps, modeling the overall sound pressure level and tone intensity for gas wiping as function of the various operating parameters of the process, as well as a set of equations and models to determine the frequency of discrete acoustic tones are presented. A full analysis of the frequency response, as well as the acoustic modes generated in various jet impingement regions has also been provided.</p> / Thesis / Master of Applied Science (MASc)

This thesis describes the unstable dynamics of a gas jet impinging on a falling liquid film. This flow configuration is encountered in the jet wiping process, used in continuous coating applications such as the hot-dip galvanizing to control the thickness of a liquid coat on a moving substrate. The interaction between these flows generates a non-uniform coating layer, of great concern for the quality of industrial products, and results from a complex coupling between the interface instabilities of the liquid film and the confinement-driven instabilities of the impinging jet.Combining experimental and numerical methods, this thesis studied the dynamics of these flows on three simplified flow configurations, designed to isolate the key features of their respective instabilities and to provide complementary information on their mutual interaction. These configurations include the gas jet impingement on a falling liquid film perturbed with controlled flow rate pulsation, the gas jet impingement on a solid interface reproducing stable and unstable liquid film interfaces and a laboratory scaled model of the jet wiping process. Each of these configurations was reproduced on dedicated experimental set-up, instrumented for non-intrusive measurement techniques such as High-Speed Flow Visualization (HSFV) and Time-resolved Particle Image Velocimetry (TR-PIV) for the gas jet flow analysis, Laser Induced Fluorescence (LIF) tracking of the liquid interface, and 3D Light Absorption (LAbs) measurement of the liquid film thickness. To optimize the performances of these measurement techniques, several advanced data processing routines were developed, including a novel image pre-processing method for background removal in PIV and a dynamic feature tracking for the automatic detection of the jet flow and the liquid film interface from HSFV, LIF, and PIV videos.To identify the flow structures driving the unstable response of the jet flow, a novel data-driven modal decomposition was developed. This decomposition, referred to as Multiscale Proper Orthogonal Decomposition (mPOD), was validated on synthetic, numerical and experimental test cases and allowed for better feature extraction than classical alternatives such as Proper Orthogonal Decomposition (POD) or Dynamic Mode Decomposition (DMD).The experimental work on these laboratory models was complemented with the analysis of several numerical simulations, including a classical 2D Unsteady Reynolds Averaged Navier Stokes (URANS) modeling of the gas jet impingement on a fixed interface, a 2D Variational Multiscale Simulation (VMS) with anisotropic mesh refinement of the gas jet impingement on a pulsing interface, and a 3D simulation of the jet wiping process combining Large Eddy Simulation (LES) on the gas side with Volume of Fluid (VOF) treatment of the liquid film flow. The experimental modal analysis on the dynamic response of the gas jet and the characterization of the pressure-velocity coupling in the numerical investigation allowed for a complete picture of the mechanism driving the jet oscillation and its possible impact on the liquid film.In parallel, several flow control strategies to prevent the jet oscillation were developed, tested numerically and experimentally in simplified conditions, and later implemented on the design of a new nozzle for the jet wiping process. This new nozzle was finally tested on a laboratory scale of the wiping process and its performances compared to single jet and multiple jet wiping configurations. In these three cases, the experimental work presents the modal analysis of the gas field using TR-PIV and mPOD, the liquid interface tracking via LIF, and the final coating thickness characterization via LAbs.The large spatiotemporally resolved experimental database allowed to give a detailed description of the jet wiping instability and to provide new insights on this fascinating fundamental and applied problem of fluid dynamics. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

The main aim of this master's thesis is to propose a technological preparation of the wiping plate production. Elaboration is divided into four chapters. The first chapter describes forming tool (function and construction). In the second chapter is technologies overview, which are used for the wiping plate production. The most important is the third chapter, because it deals with the main output, and the actual proposal of technological preparation of the production. In the fourth chapter, production is reviewed economically.

För att kunna framföra ett fordon på ett säkert sätt är vindrutetorkning är en viktig del. Men, bara för att det är en viktig del i användandet innebär det inte att det är en viktig del i utvecklingen. Detta har visat sig genom att funktionen och designen av vindrutetorkare på lastbilar har varit densamma i årtionden. När hytten till Scanias senaste lastbilsmodell designades så minskades tjockleken på torpedväggen för att spara vikt. Detta minskade även styvheten i hytten, vilket fick de vibrationer som inducerades vid körning av vindrutetorkarna att nå en kritisk gräns. Problemställningen för detta exjobb var därför att förstå ursprunget till dessa vibrationer och hur delsystemen interagerar med varandra genom att utföra modellbaserad utveckling (MBD). Uppgiften var att undersöka vilka ändringar som behövde genomföras i styrningen av vindrutetorkarna och systemspecifikationen för den inbyggda styrenheten för att reducera vibrationerna och säkerställa Scanias position som premiummärke även i framtiden. Vindrutetorkarsystemet modellerades i Simulink, med både Simulink-block och Simscapemodeller. En strömberoende spänningskontroller för rörelsestyrning utvecklades för att sedan verifieras på nuvarande hårdvara. Rekommendationer för framtida arbete på ECU gällande systemfrekvens för mätning samt algoritmdesign gjordes, samt helhetstänket vid design av ett nytt system poängterades. Resultaten visar att styrning av en likströmsmotor med ström som ingångsparameter är komplicerat då strömmen varierar kraftigt på grund av störningar. Algoritmen som behandlar mätdatat måste därför vara väldigt robust eftersom filtrering påverkar systemet genom att lägga till fas i kontrollern, vilket ger eftersläpningar. Kommande arbetsinsatser bör fokusera på hur man väljer komponenter som matchar varandra gällande likströmsmotor och ECU. Desto mer logik som placeras i motorn, desto mindre datorkraft behövs i den inbyggda styrenheten. / Windscreen wiping is an important part of driving safety and vehicle maneuverability. However, importance does not automatically imply progression, and the wiping functionality for heavy commercial vehicles have remained roughly the same through decades. When redesigning the cab for the latest truck generation at Scania, the thickness of the firewall was reduced to save weight.This reduced the stiffness of the cab, which made the vibrations in the throttle pedal from actuating the windscreen wiper rise to a critical level.The problem definition in this thesis was to understand the root-cause and cooperation in the system by doing modelling and Model-Based Design (MBD), rather than starting with experimental verification. The task was to investigate what changes needed to be made in the controlling of the wiper motor and system specification of the ECU to reduce vibrations and ensure Scania's position as a premium brand in the future. The windscreen wiping system was modelled in Simulink, with both Simulink blocks and Simscape models. A current-measuring voltage-controller for motion-profiles was developed and verified on real production hardware. Recommendation for future development of next ECU generation regarding sampling time and controller design was made and the importance of considering the whole system design was emphasized. Results showed that controlling with current measurement of DC-motors as input parameter is avolatile approach due to disturbances. The algorithms depending on this measurement needs to be very robust, since filtering adds unwanted delay to the control loop. Further investigations should be made in the component selection when mapping motors with the correct driver. The more logic placed in the motor, the less need for a complex ECU and vice versa.

The topic of this thesis is the interaction between gas jet flow and a liquid film dragged by a solid substrate. This method, known as jet-wiping, is used in several industrial processes. Hot-dip galvanization of steel strips is an important application, where jet wiping is used to control the thickness of the liquid zinc that is applied on a continuous steel substrate. Unsteady phenomena in the process lead to the creation of waves on the liquid film, which is known as undulation. This unwanted phenomenon deteriorates the quality of the final product.<p>The aim of the current study is to identify the causes of the undulation and propose possible solutions to tackle the problem. This is achieved through studying the hydrodynamic interaction between the gas jet flow and the liquid film. Experiments on a laboratory test facility and numerical simulations with 3 different Computational Fluid Dynamics (CFD) codes are employed for that purpose. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished