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The control system of an open-type headbox has a high complexity, which is associated with the need not only to stabilize the parameters of the object, but also to carry out coordinated control of it in the case of automatic transfer of a paper machine from one type of product to another for a minimum time. A mathematical model of an open-type headbox as an object of mass level control has been developed. In the model, the output variable of the control object is the level of mass in the injection chamber, and the control action is the mass flow rate supplied to the injection chamber. The model takes into account the disturbing action - the area of the discharge slot. On the basis of the developed model, two options for constructing an algorithm for controlling the pressure box during its transfer from one mode to another are considered. The structure of the algorithm for coordinated control of the pressure box is developed. An illustrative example of application of the developed algorithm is given. The calculations of the optimal transient process in the object confirm the effectiveness of the developed control algorithm. The algorithm of coordinated control is applied to the standard pressure box YANO-180. The development of the algorithm for transferring the pressure box from the working (0.485 m) to the maximum (0.575 m) height of the mass level in the pressure box for 180 seconds is demonstrated. The calculation results show that the coordinated control algorithm provides the transfer of the mass level to the maximum height for a given time. The algorithm developed on the basis of the obtained mathematical model allows to control the level of mass in such a complex object as an open-type headbox when transferring a paper machine from one mode of operation to another for the time specified by the coordinated control system., Система керування напірним ящиком відкритого типу має високу складність, що пов'язано із необхідністю не тільки стабілізувати параметри об’єкта, але й здійснювати координоване керування ним у випадку автоматичного переведення папероробної машини з одного виду продукції на інший за мінімальний час. Розроблено математичну модель напірного ящика відкритого типу як об’єкта керування рівнем маси. У моделі вихідною змінна об’єкта керування є рівень маси у напускній камері, а керувальним діянням є витрата маси, що подається до напускної камери. В моделі враховано збурювальне діяння – площу випускальної щілини. На основі розробленої моделі розглядається два варіанти побудови алгоритму керування напірним ящиком під час переведення його із одного режиму у інший. Розроблено структуру алгоритму координованого керування напірним ящиком. Наведено ілюстративний приклад застосування розробленого алгоритму. Здійснено розрахунки оптимального перехідного процесу в об’єкті які підтверджують ефективність розробленого алгоритму керування. Алгоритм координованого керування застосовано для стандартного напірного ящика ЯНО-180. Продемонстровано розробку алгоритму переведення напірного ящика з робочої (0,485 м) на максимальну (0,575 м) висоту рівня маси у напірному ящику за час 180 с. Результати розрахунків показують, що алгоритм координованого керування забезпечує переведення рівня маси на максимальну висоту за заданий час. Розроблений на основі отриманої математичної моделі алгоритм дозволяє здійснювати керування рівнем маси у такому складному об’єкті, як напірний ящик відкритого типу при переведенні папероробної машини з одного режиму роботи на інший за час, вказаний системою координованого керування.

Система керування напірним ящиком відкритого типу має високу складність, що пов'язано із необхідністю не тільки стабілізувати параметри об’єкта, але й здійснювати координоване керування ним у випадку автоматичного переведення папероробної машини з одного виду продукції на інший за мінімальний час. Розроблено математичну модель напірного ящика відкритого типу як об’єкта керування рівнем маси. У моделі вихідною змінна об’єкта керування є рівень маси у напускній камері, а керувальним діянням є витрата маси, що подається до напускної камери. В моделі враховано збурювальне діяння – площу випускальної щілини. На основі розробленої моделі розглядається два варіанти побудови алгоритму керування напірним ящиком під час переведення його із одного режиму у інший. Розроблено структуру алгоритму координованого керування напірним ящиком. Наведено ілюстративний приклад застосування розробленого алгоритму. Здійснено розрахунки оптимального перехідного процесу в об’єкті які підтверджують ефективність розробленого алгоритму керування. Алгоритм координованого керування застосовано для стандартного напірного ящика ЯНО-180. Продемонстровано розробку алгоритму переведення напірного ящика з робочої (0,485 м) на максимальну (0,575 м) висоту рівня маси у напірному ящику за час 180 с. Результати розрахунків показують, що алгоритм координованого керування забезпечує переведення рівня маси на максимальну висоту за заданий час. Розроблений на основі отриманої математичної моделі алгоритм дозволяє здійснювати керування рівнем маси у такому складному об’єкті, як напірний ящик відкритого типу при переведенні папероробної машини з одного режиму роботи на інший за час, вказаний системою координованого керування. The control system of an open-type headbox has a high complexity, which is associated with the need not only to stabilize the parameters of the object, but also to carry out coordinated control of it in the case of automatic transfer of a paper machine from one type of product to another for a minimum time. A mathematical model of an open-type headbox as an object of mass level control has been developed. In the model, the output variable of the control object is the level of mass in the injection chamber, and the control action is the mass flow rate supplied to the injection chamber. The model takes into account the disturbing action - the area of the discharge slot. On the basis of the developed model, two options for constructing an algorithm for controlling the pressure box during its transfer from one mode to another are considered. The structure of the algorithm for coordinated control of the pressure box is developed. An illustrative example of application of the developed algorithm is given. The calculations of the optimal transient process in the object confirm the effectiveness of the developed control algorithm. The algorithm of coordinated control is applied to the standard pressure box YANO180. The development of the algorithm for transferring the pressure box from the working (0.485 m) to the maximum (0.575 m) height of the mass level in the pressure box for 180 seconds is demonstrated. The calculation results show that the coordinated control algorithm provides the transfer of the mass level to the maximum height for a given time. The algorithm developed on the basis of the obtained mathematical model allows to control the level of mass in such a complex object as an open-type headbox when transferring a paper machine from one mode of operation to another for the time specified by the coordinated control system.

The flow characteristics of a pulp liquid in the wake of a dispersion promoter were investigated to explore the feasibility of improving the hydraulic headbox of a papermaking machine. This research was undertaken as a basic test of a screen-type model, in which a circular cylinder has been inserted in a channel. The test was performed using a pulp liquid with a fiber concentration ranging from 0.3 to 1.0 wt% under flow velocity conditions of Ua = 0.016 0.74 m/s. The distributions of the fiber concentration were measured by transmitted light attenuation method. The obtained results are illustrated, and the influence of the flow velocity on the characteristics of the wake behind the cylinder are argued with reference to findings previously reported (Sumida and Fujimoto, 2010). The fiber-concentration distribution changes in the flow direction were large in the section from the cylinder to four times its diameter. The findings provide useful information for the development of hydraulic headboxes., Ⅲ.論文集

An experimental investigation was performed for the pulp-suspension flow in a channel with a partition plate, which is an extremely simplified model of the dispersion part of the hydraulic headbox of papermaking machines. This study was tried to make the papermaking system most suitable and was conducted to obtain the fundamental findings. To do it, flow visualization and optical measurements of the fiber concentration were made in the wake region of a flat plate. Characteristics of the pulp-suspension flow were examined for five flow cases based on the flow patterns found in the authors' previous report (2010) for a channel. The behavior of the pulp fibers and flow in the wake is strongly related to the flow states in the passages of the partition plate and also depends on the shear layer generated at the trailing edge of the plate. The partition plate is slightly effective for obtaining a uniform time-averaged fiber concentration distribution and for making the fluctuating fiber concentration lower., Ⅲ.論文集, [再録元]混相流

действующие системы управления процессом формирования бумажного полотна с регуляторами уровня массы и давления в напускном устройстве не обеспечивают желаемых показателей качества. В тоже время применение высокоточных и помехозащищенных алгоритмов управления на базе экстремальных и предиктивных регуляторов снижает быстродействие систем. Таким образом, дальнейшее повышение эффективности системы управления процессом формирования бумажного полотна возможно в рамках APC-управления и нечеткой логики. Введение в систему кросскорреляционных оптических вычислителей скорости позволит сформировать данные об основных параметрах потока бумажной массы в моменты формирования полотна на сетке машины, что является необходимым и достаточным для внедрения в экстремальные системы управления регулятора соотношения скоростей, повышающего их быстродействие. Для замещения каскадного соединения регуляторов в системах управления процессом формирования бумажного полотна предлагается использовать координирующий нечеткий регулятор и методы нечеткого управления, позволяющие “развязать” между собой выходные сигналы с экстремального регулятора, регуляторов соотношения скоростей и общего давления, предназначенные для одного исполнительного механизма – компрессора. Таким образом, применение дополнительного контура стабилизации соотношения скоростей и координирующего нечеткого управления на 59.4% повысило быстродействие систем управления процессом формирования бумажного полотна по сравнению с экстремальными регуляторами и позволило снизить дисперсию веса полотна бумаги на 1.4%, что подтверждается актами внедрения на предприятии ОАО “МАЯК”., existing control systems for the paper web formation process with mass and pressure level regulators in the inlet device do not provide the desired quality indicators. At the same time, the use of high-precision and noise-proof control algorithms based on extreme and predictive controllers reduces the performance of systems. Thus, further improvement of the efficiency of the control system for the paper web formation process is possible within the framework of APC control and fuzzy logic. The introduction of cross-correlation optical speed calculators into the system will allow generating data on the main parameters of the paper mass flow at the moments when the web is formed on the machine grid, which is necessary and sufficient for implementing a speed ratio controller in extreme control systems that increases their speed. To replace the cascade connection of regulators in the control systems for the process of forming a paper web, it is proposed to use a coordinating fuzzy controller and fuzzy control methods that allow “decoupling” the output signals from the extreme controller, speed ratio and total pressure regulators designed for a single actuator – the compressor. Thus, the use of an additional speed ratio stabilization loop and coordinating fuzzy control increased the speed of paper web formation control systems by 59.4% in comparison with extreme regulators and allowed reducing the dispersion of paper web weight by 1.4%, which is confirmed by the implementation certificates at the MAYAK enterprise., МОДЕЛИРОВАНИЕ, ОПТИМИЗАЦИЯ И ИНФОРМАЦИОННЫЕ ТЕХНОЛОГИИ, Выпуск 4 (31) 2020, Pages 2-3

This study focused on web forming at a 5–10% consistency range, termed Ultra High Consistency (UHC). The study continued work done by Gullichsen with his research groups (1981–2007) and combined it with the HC forming research done by Valmet (HC, 1999–2004). The hypothesis was that by utilizing a rotor to fluidize suspension and a wedge to eliminate the free jet and thus prevent reflocculation, web forming at UHC is feasible at commercial speeds. The research method was experimental. The bulk of the research was conducted at pilot scale. A new UHC headbox was designed and mounted on a pilot former. The key elements of the headbox are the rotor and the wedge. As fluidization forms the base for UHC forming, this was evaluated at the pilot former using image analysis. In addition, fluidization was studied using a laboratory-scale device. Besides basic paper analysis, X-ray microtomography and sheet splitting methods were utilized to analyze the sheet structure. The results show that forming is possible within the focus area, 5–10% consistency and machine speeds of 150–600 m/min, although the operation potential of the UHC former is even wider. The results demonstrate that the wedge is needed for successful UHC forming, but the rotor is not required, providing the flow rate is sufficiently high. This indicates that various forces induced by the flow itself can be adequate to fluidize suspension for forming. The critical Reynolds number of full fluidization was found to be 200–250. The Reynolds numbers were estimated utilizing the linear dependencies found between the apparent viscosity and consistency, using the maximum mean flow velocities inside the headbox, and neglecting the possible rotation of the rotor. The corresponding critical flow velocities at 10% consistency are 12 and 19 m/s for a eucalyptus and pine pulp. The velocities are on average 70 and 60% lower than those given in the literature (40–50 m/s). The results reveal that the fiber orientation of UHC sheets is planar, the floc size of the web increases with consistency, the internal bond increases linearly with the floc size, and the tensile strength appears to decrease with increasing floc size. In consequence, it is postulated that the increase in the out-of-plane strength at the expense of in-plane strength with the consistency increase results from a more flocculated structure. Tiivistelmä Tutkimus keskittyi rainanmuodostukseen 5–10 % sakeudessa. Sakeusalue nimitettiin ultra korkeaksi (lyhenne UHC). Tämä työ jatkoi Gullichsenin ja hänen tutkimusryhmiensä tutkimustyötä (1981–2007) ja samalla yhdisti sen Valmetin tekemään suursakeusrainaustutkimukseen (HC, 1994–2004). Työn hypoteesina oli, että käyttämällä roottoria massan fluidisoimiseen sekä ns. wedgeä eliminoimaan vapaa suihku ja estämään jälleenflokkaantuminen, rainanmuodostus UHC-sakeudessa on mahdollista kaupallisissa nopeuksissa. Tutkimusmetodi oli kokeellinen. Pääosa tutkimuksesta suoritettiin koekonemittakaavassa. Uusi UHC-perälaatikko suunniteltiin ja asennettiin koeformeille. Perälaatikon pääelementit ovat pyörivä roottori ja wedge. Koska fluidisointi muodostaa UHC-rainauksen perustan, fluidisointia evaluoitiin koekoneella käyttäen kuva-analyysiä sekä tutkittiin lisäksi käyttäen röntgenmikrotomografia ja arkin halkaisu -metodeja. Tulokset osoittavat, että rainaaminen on mahdollista määritellyllä fokusalueella, 5–10 %sakeudessa ja konenopeudella150–600 m/min, joskin UHC-formerin toimintapotentiaali on vieläkin laajempi. Tulokset osoittavat, että wedge tarvitaan onnistuneeseen UHC-muodostamiseen, mutta roottoria ei tarvita, mikäli virtausnopeus on riittävän suuri. Tämä tarkoittaa, että virtauksen aikaansaamat voimat voivat itsessään olla riittäviä massan fluidisoimiseksi rainaamista varten. Täyden fluidisaation kriittisen Reynoldsin luvun havaittiin olevan välillä 200–250. Reynoldsin luvut arvioitiin käyttäen löydettyjä viskositeetin ja sakeuden välisiä lineaarisia riippuvuuksia, päävirtauksen maksiminopeuksia perälaatikossa ja jättäen huomioon ottamatta mahdollinen roottorin pyöriminen. Reynoldsin lukuja vastaavat kriittiset virtausnopeudet 10 % sakeudessa ovat eukalyptus- ja mäntymassalla 12 ja 19 m/s. Nopeudet ovat keskimäärin 70 ja 60 % pienempiä kuin kirjallisuudessa annetut (40–50 m/s). Tulokset osoittavat, että UHC-arkeissa kuituorientaatio on tasomainen, rainan flokkikoko kasvaa sakeuden kasvaessa, palstautumislujuus kasvaa lineaarisesti flokkikoon kanssa ja vetolujuus näyttäisi laskevan flokkikoon kasvaessa. Näin ollen esitetään, että sakeuden kasvaessa tapahtuva palstautumislujuuden kasvu tasolujuuksien kustannuksella johtuu flokkaantuneemmasta rakenteesta.

In the papermaking process it is a well-known fact that the flow condition of a free jet entering the former section has a direct influence on the structure of the final paper. In this paper we present a systematic analysis how surface roughness and MD characteristic size of the slice jet depend on jet velocity, jet length, pulp consistency and vane geometry. The measurements are based on laser profiling and ccd-imaging.

The purpose of the headbox is to convert a flow of fiber suspension to a jet, with a thickness between 4 and 20mm and a width between 3 -8meters, depending on the paper machine model. To adjust the beam thickness, the lip adjustment arrangement is used. This master thesis was written to develop the headbox and the lip adjustment system, for paper machines with a width over 6 meters. In the beginning of the project much focus was layed on understanding the problem and develop the product and customer requirements of the Headbox. In order to utilize the entire idea space a number of idea generation methods were used. The evaluation of concepts were conducted with the method Analytic hierarchy process (AHP), which is a method for clarifying the decision pattern. From the evaluation of the concept, two concepts were chosen. A modification of the existing headbox and a new concept, which adjusts the slice opening with a number of elastic pockets and a wedge. To further evaluate the modified headbox concepts the Finite Element Method was used. During the simulations the elastic deformation was compared between the current and the modified solution. The second concept was developed by describing the new design and motivated the chosen material and structures. Overall it can be said that the modification of the current headbox solves the main problem and maintains the current quality on the paper. The new and innovative solution enables a more exact adjustment of the lip opening and allows a larger potential of modularization. Syftet med inloppslådan är att den ska transformera ett flöde av fibersuspension till en stråle som är mellan 4 och 20 mm tjock och 3-8 m bred, beroende på pappersmaskinsmodell. För att justera strålens tjocklek används läppjusteringsanordningen. Målet med detta arbete var att utveckla inloppslådan och dess läppöppningsarrangemang så att den kan användas till en pappersmaskin som är breddare än 6 meter. Projektet inleddes med att skapa en förståelse för problemet samt att undersöka vilka produkt- och kundkrav det finns på inloppslådan. För att utnyttja hela iderymden användes ett antal idegenereringsmetoder. Utvärdering av koncepten genomfördes med hjälp av en metod som heter Analytic hierarchy process (AHP) som är en metod som används för att tydliggöra beslutsvägen. Utifrån utvärdering med AHP valdes två koncept ut. En modifierad lösning av det nuvarande läppöppningsarrangemangen och ett nytt koncept vilket justerar läppöppningen med hjälp av ett antal trycksatta fickor och en vinge. För att ytterligare utveckla den modifierade inloppslådan användes Finita Elementmetoden. Under simuleringen jämfördes elastisk deformation i den nuvarande och den modifierade lösningen. Det nya konceptet utvecklades genom att den nya konstruktionen beskrevs utifrån struktur, materialval och tillverkningsmetoder. Sammantaget kan det sägas att den modifierade inloppslådan löser problemställning och bibehåller den nuvarande kvalitén på pappret. Den innovativa och nya lösningen möjliggör en mer exakt justering av läppöppningen och ökar möjligheten att modularisera inloppslådan.

The head box in a tissue machine distributes the fiber suspension to a flat jet along the width of the machine. By adjusting the so-called lip opening, the flow is regulated and the jet is accelerated to match the machine speed. In this work, ideas for alternative solutions for lip opening mechanism is generated and evaluated with a focus on making a cost saving. One of the concepts has been selected for a deeper analysis with respect to the design, strength and cost. The selected concept is based on reducing the number of jacks required by using one jack operating a shaft parallel to the apron beam. Levers convey the movement to the apron beam. The analysis show that the shaft is exposed to high torque which results in large elastic twisting of the shaft, which means that the force that supports the apron beam will not be equal over the entire width. If the difference in force is too big, the apron beam will twist which results in an uneven lip opening. The shaft stiffness is therefore crucial. For the head box with a width of 2946 mm, the number of jacks is reduced from three to one. Wider head boxes may need more than one jack since the shaft cannot be made to long without getting too much twisted. A lip opening mechanism of the current design with six 20 ton jacks can be compared to the new concept in which only two jacks is needed and the cost is reduced by 18%. There is further potential for savings if the jack, separate gear and electric motor are replaced with an actuator that has the motor mounted directly. Inloppslådan i en tissuemaskin har till uppgift att fördela fibersuspensionen till en flat stråle längs maskinens bredd. Genom att justera den så kallade läppöppningen regleras flödet och strålen accelereras för att passa maskinhastigheten. I detta arbete har idéer till alternativa lösningar för läppöppningsmekanismen genererats och utvärderats med fokus på att göra en kostnadsbesparing. Ett av koncepten har valts ut för en djupare analys med avseende på konstruktion, hållfasthet och kostnad. Det valda konceptet bygger på att reducera antalet domkrafter som behövs genom att en domkraft driver en axel parallell med utloppsbordet. Hävarmar överför rörelsen till utloppsbordet. Analysen visar att axeln utsätts för ett stort moment vilket ger en stor elastisk vridning av axeln, vilket gör att kraften som håller emot utloppsbordet inte blir lika stor över hela bredden. Om skillnaden i kraft är för stor ger det en förvridning av utloppsbordet som resulterar i en ojämn läppöppning. Axelns styvhet är alltså avgörande. För den undersökta lådan med bredden 2946 mm har antalet domkrafter reducerats från tre stycken till en. För bredare inloppslådor behövs fler domkrafter då axeln inte kan göras för lång utan att få för mycket vridning. Ett läppöppningsarrangemang som idag har sex stycken domkrafter kan jämföras med det nya konceptet där det krävs endast två domkrafter och kostnaden minskas med ca. 18%. Ytterligare potential till besparing finns om man byter ut domkraft, separat växel och elmotor till ett ställdon som har motorn direktmonterad.

Experimental results on the fibre orientation in a laboratory scale headbox are reported. A steerable filter was used to determine the orientation of bleached unbeaten birch fibres at different distances from one of the inclined walls of the headbox contraction. Due to optical limitations only dilute suspensions were studied. It is shown that the fibre orientation distribution varies with the distance from the wall. Sufficiently far upstream in the headbox a more anisotropic distribution is found closer to the wall as compared to farther away from the wall. QC 20211008

In the papermaking process it is a well-known fact that the flow condition of a free jet entering the former section has a direct influence on the structure of the final paper. In this paper we present a systematic analysis how surface roughness and MD characteristic size of the slice jet depend on jet velocity, jet length, pulp consistency and vane geometry. The measurements are based on laser profiling and ccd-imaging.

The evolution of paper machines in order to get better paper grades at faster production rates imposed paper mills to operate more complex systems and gain in precision. The hydraulic injector which delivers the pulp onto a paper fabric, commonly called headbox, has not escaped from this evolution. In this work a detailed analysis and simulation of each part of a headbox was made. From these simulations and whenever possible from experimental observations and measurements, some basic questions were tried to be answered,like the need of each part in a modern papermaking operation. Two different approaches were chosen, firstly a hydrodynamical study of the pulp flowing inside the different parts, focusing especially on turbulence scales and intensities and, secondly, the reaction of this pulp to the applied energy. It was observed that water can be used to reasonably predict the behaviour of a weak consistency pulp suspension for most of the important design parameters. The geometrical parameters of a headbox were also studied in order to providealternative methods for jet control. Indeed the jet geometrical characteristics are important variables for paper production. Most of the time miscalculated by old methods, no modern solutions were proposed to get a detailed jet angle and contraction coefficient. We have shown in this work that a detailed solution for any nozzle geometry can be computed. The location of the vena contracta is also possible with the proposed method. It was also shown that the real nozzle geometry used normally in a modern headbox with a double convergent configuration, may considerably modify the jet angle., L'évolution des machines à papier pour obtenir des qualités de papier supérieures a fait évoluer leséquipements papetiers en complexité et en précision. L'injecteur hydraulique de pâte à papier, appelé caisse de tête dans l'industrie, n'a pas échappé à cette règle. Nous avons analysé chaque partie constituant une caisse de tête, en nous basant sur des observations et mesures directes quand les conditions le permettaient, ou sinon grâce à des simulations numériques, pour répondre à des questions essentielles relatives à l'utilitéet au dimensionnement de chaque partie d'une caisse de tˆete moderne. Pour cela, deux approches ont été retenues : la première est l'étude hydrodynamique de la suspension circulant dans chaque élément, surtout en termes d'´echelle et intensité de turbulence ; la deuxième est l'analyse de la réaction de la pâte à cette énergie.Nous avons remarqué que l'eau peut être utilisée au lieu d'une suspension fibreuse pour établir les paramètres de dimensionnement. Finalement, nous avons étudié les paramêtres géométriques de la buse terminale d'une caisse de tête pour donner des solutions alternatives aux méthodes actuelles servant au contrôe du jet. Nousavons démontré que les modèles existants pour caractériser le jet ne sont pas toujours applicables aux caisses de tête modernes et avons observé qu'aucune solution alternative n'est proposée actuellement pour calculer correctement l'angle et le coefficient de contraction du jet. Nous avons montré que le calcul de l'angle du jet est possible pour tout type de géométrie et avons mis en évidence la position de la veine contractée. Nousavons aussi montré que l'utilisation d'un double convergent peut modifier significativement l'angle de jet et cela devrait être pris en compte.

The evolution of paper machines in order to get better paper grades at faster production rates imposed paper mills to operate more complex systems and gain in precision. The hydraulic injector which delivers the pulp onto a paper fabric, commonly called headbox, has not escaped from this evolution. In this work a detailed analysis and simulation of each part of a headbox was made. From these simulations and whenever possible from experimental observations and measurements, some basic questions were tried to be answered,like the need of each part in a modern papermaking operation. Two different approaches were chosen, firstly a hydrodynamical study of the pulp flowing inside the different parts, focusing especially on turbulence scales and intensities and, secondly, the reaction of this pulp to the applied energy. It was observed that water can be used to reasonably predict the behaviour of a weak consistency pulp suspension for most of the important design parameters. The geometrical parameters of a headbox were also studied in order to providealternative methods for jet control. Indeed the jet geometrical characteristics are important variables for paper production. Most of the time miscalculated by old methods, no modern solutions were proposed to get a detailed jet angle and contraction coefficient. We have shown in this work that a detailed solution for any nozzle geometry can be computed. The location of the vena contracta is also possible with the proposed method. It was also shown that the real nozzle geometry used normally in a modern headbox with a double convergent configuration, may considerably modify the jet angle.; L'évolution des machines à papier pour obtenir des qualités de papier supérieures a fait évoluer leséquipements papetiers en complexité et en précision. L'injecteur hydraulique de pâte à papier, appelé caisse de tête dans l'industrie, n'a pas échappé à cette règle. Nous avons analysé chaque partie constituant une caisse de tête, en nous basant sur des observations et mesures directes quand les conditions le permettaient, ou sinon grâce à des simulations numériques, pour répondre à des questions essentielles relatives à l'utilitéet au dimensionnement de chaque partie d'une caisse de tˆete moderne. Pour cela, deux approches ont été retenues : la première est l'étude hydrodynamique de la suspension circulant dans chaque élément, surtout en termes d'´echelle et intensité de turbulence ; la deuxième est l'analyse de la réaction de la pâte à cette énergie.Nous avons remarqué que l'eau peut être utilisée au lieu d'une suspension fibreuse pour établir les paramètres de dimensionnement. Finalement, nous avons étudié les paramêtres géométriques de la buse terminale d'une caisse de tête pour donner des solutions alternatives aux méthodes actuelles servant au contrôe du jet. Nousavons démontré que les modèles existants pour caractériser le jet ne sont pas toujours applicables aux caisses de tête modernes et avons observé qu'aucune solution alternative n'est proposée actuellement pour calculer correctement l'angle et le coefficient de contraction du jet. Nous avons montré que le calcul de l'angle du jet est possible pour tout type de géométrie et avons mis en évidence la position de la veine contractée. Nousavons aussi montré que l'utilisation d'un double convergent peut modifier significativement l'angle de jet et cela devrait être pris en compte.

The main goal of this work was to develop numerical models for studying the behaviour of fibres in an accelerated flow. This is of special interest for e.g. papermaking. The early stage of the paper manufacturing process determines most of the final properties of a paper sheet. The complexity of studying the flow of fibre suspensions both experimentally and numerically emphasises a need for new ideas and developments. By means of solving the evolution of a convective-dispersion equation, i.e. the Fokker-Planck equation, a fully 3D approach with respect to the position and the two fibre angles, polar and azimuthal angles, following a streamline is presented. As an input to the fibre orientation model the turbulent flow field is solved by Computational Fluid Dynamics (CFD) with second-order closure in the turbulence model. In this work two new hypotheses have been presented for the variation of the non-dimensional rotational diffusivity with non-dimensional fibre length, Lf /η and the Reynolds number based on the Taylor micro-scale of the turbulence, Reλ Parameters for the two new hy- potheses and earlier models are determined with the aim of achieving a general relation and a value of the rotational dispersion coeffcient of stiff fibres in an anisotropic turbulent fluid flow. Earlier modelling work has been focused on solving the planar approach, i.e. assuming all fibres to be in one plane. This planar approach is discussed and compared with the fully 3D approach and its validity is evaluated. The optimization of parameters for the different hypotheses correlated on a central streamline, showed a good agreement with an independent experimental result in the undisturbed region. Moreover, it is particularly interesting that the boundary layer region and the wake region are predicted fairly well and the phenomena are well described, which has not been the case earlier. It seems that the new hypothesis based on the variation of the non-dimensional fibre length, Lf /η gives the best correlation in these shear-layer regions. Further- more it was established that the planar approach fails to predict shear layers, i.e. the boundary layer and the wake regions. As emphasized in the theory section, the planar formulation is strictly valid only if all fibres are oriented in one plane, which is not the case in the shear layers. In the undisturbed region, the 3D and the planar approaches, agree in their results. This leads to the conclusion that both approaches are suitable when shear layers are not studied. QC 20100812

Introducción: La administración de oxígeno en lactantes que lo requieren se realiza preferentemente con halo, lo cual origina un mayor consumo del gas con respecto a una cánula nasal. Hipótesis: "La transición de halo a cánula nasal, se traducirá en una disminución no inferior a un tercio del flujo de O2 necesario para mantener invariable la saturación arterial de O2 (SaO2) en los pacientes con compromiso respiratorio en fase de estado o resolutiva". Material y Método: Se estudiaron lactantes de 1 a 24 m, con infecciones respiratorias agudas (IRA) estables y fracción inspirada de O2 (FiO2) £ 0,4, sin patologías agravantes asociadas. Se controló la FiO2 del halo, frecuencia respiratoria (FR), SaO2 y retracciones intercostales pre y post transición. Se colocó una naricera con flujo de O2 calculado. A las 2 horas se controló el flujo y se reajustó. Se usaron promedios, desviación estándar, X² de Mc Nemar y test de Student. Resultados: Ingresaron 41 pacientes cuya edad fue 6,3 ± 4,7 meses, peso 8,4 ± 3,1 kg, respectivamente. La FR no se modificó significativamente durante el estudio. El flujo de O2 requerido descendió en promedio de 7,0 a 1,1 l/min (p < 0,001). Las manifestaciones clínicas mostraron una respuesta favorable, con disminución de las retracciones en 14 niños, con p < 0,002. Conclusión: Se verificó la hipótesis planteada. La transición de halo a cánula nasal se tradujo en una disminución promedio de 5,9 l/min del O2, lo que representa un 84,2% menor, manteniendo invariable la SaO2, en los pacientes con compromiso respiratorio en fase de estado o resolutiva Change from headbox to nasal cannula, an efficient oxygen therapy in toddlers with acute low respiratory tract infection Introduction: Oxygen (O2) administration in toddlers who require it is performed mainly through a headbox, which produces a high cost in gas consumption in relation to nasal cannula. Hypothesis: The transition from headbox to nasal cannula will cause a decrease in oxygen flow around 1/3 or more needed to maintain an arterial oxygen saturation (Sat O2), without significant variation in patients at the end-stage of a respiratory disease. Methods: Toddlers between 1 and 24 months-old at a stable phase of a respiratory infection, without any other concomitant disease and with an oxygen inspired fraction (FiO2) £ 0,4 were admitted in the study. Headbox FiO2, breath rate (BR), Sat O2 and intercostal retraction were evaluated before and after the transition. A nasal cannula was used with a measured oxygen flow, being controlled and adjusted two hours later. Average, standard desviation, Mc Nemar’s X², and Student’s test were used to analyze the results. Results: 41 patients were admitted to the study, with age 6.3 ± 4.7 months and weight 8.4 ± 3.1 kg. BR did not experiment significative changes and the required oxygen flow decreased from 7.0 to 1.1 l/min (p < 0.001). Clinical manifestations showed a positive response, with decrease in intercostal retraction on 14 children (p < 0.002). Conclusions: The hypothesis was verified. In stable patients with respiratory disease in resolution, the transition from headbox to nasal cannula implicated a decrease in oxygen flow of 5.9 l/min, representing 84,2% less used oxygen without changes in Sat O2

The purpose of this thesis is to investigate an alternative control strategy for a multi-variate non-linear process in a paper machine called the headbox. The proposed solution was intended to be able to be adopted on two different headbox types, currently controlled by different concepts. The methodology was to first create black-box models of the two different systems based on measurements, at one working point. Secondly, various control strategies were investigated. A more sophisticated multi-input multi-output controller MPC, or model predictive control, and a less sophisticated one, a single-input single-output, decentralised PI-controller. With help of simulations the performances of the both strategies were tested. Finally, only the decentralised control solution was implemented and evaluated through trial runs on a pilot machine. The main issue regarding the decentralised controller was the input-ouput pairing. Since the multi-variate system had four outputs and only three inputs, analysis had to be made in order to select three of those four, to form a square system. This analysis was based on the relative gain array (RGA). The resulting performance of the decentralised controller showed stability and adequate response times, surpassing the older system and making one component obsolete through the pairing changes. The MPC controller showed even better performance during simulations and shall also be taken into account if further investigatin is possible.

The purpose of this thesis is to investigate an alternative control strategy for a multi-variate non-linear process in a paper machine called the headbox. The proposed solution was intended to be able to be adopted on two different headbox types, currently controlled by different concepts. The methodology was to first create black-box models of the two different systems based on measurements, at one working point. Secondly, various control strategies were investigated. A more sophisticated multi-input multi-output controller MPC, or model predictive control, and a less sophisticated one, a single-input single-output, decentralised PI-controller. With help of simulations the performances of the both strategies were tested. Finally, only the decentralised control solution was implemented and evaluated through trial runs on a pilot machine. The main issue regarding the decentralised controller was the input-ouput pairing. Since the multi-variate system had four outputs and only three inputs, analysis had to be made in order to select three of those four, to form a square system. This analysis was based on the relative gain array (RGA). The resulting performance of the decentralised controller showed stability and adequate response times, surpassing the older system and making one component obsolete through the pairing changes. The MPC controller showed even better performance during simulations and shall also be taken into account if further investigatin is possible.

Process industries are in general depending, in one way or the other, on fluid mechanics.Specifically, paper manufacturing, which probably is the dominant processindustry in Sweden, is depending on the flow of cellulose fibres suspended in water.As a part of the process the suspension, consisting of fibres in water, is spread out onor between two moving permeable weaves, i.e. wires. The speed of this is usually 10–30 m/s and the suspension is spread out by a plane jet issuing from a headbox nozzle.It has been show that the conditions in the headbox and jet have a large influence onthe quality of the final paper sheet. Primarily, streaks in the paper sheet are believedto be the result of streamwise streaks in the headbox jet.The thesis is aimed at the flow phenomena which occur in the headbox jet. Theinvestigations have been made with numerical calculations, stability theory and modelexperiments using water, as well as experiments with a real paper machine headboxand fibre suspension. In the thesis an introduction to the hydrodynamics of planeliquid jets is presented together with a description of the paper forming process andthe fluid mechanics of headbox flow.The basic flow and stability of a two-dimensional plane liquid jet has been investigatedby numerical calculations, stability theory and experiments. The calculationsof the laminar basic flow is successfully compared to pitot-tube measurements of thestreamwise velocity profile. By visualisations of the flow it is found that wave disturbanceson the jet has a severe effect on the flow. These waves can be predicted bylinear stability theory, which shows the presence of five convectively unstable modes.These can be divided into three types and by comparison with the experiments thetype of the visible waves is determined. These waves seem to initiate a break-up ofthe jet, which leads to strong streamwise streaks inside the jet.By flow visualisation of headbox flow of an experimental paper machine, togetherwith analysis of the resulting paper structure using the wavelet method the correspondencebetween flow disturbances and paper quality was investigated. It was shownthat the wave instability, which is present on the low Reynolds number water jet, alsocan be found in the real the headbox jet. It is shown that these waves play an importantrole in the dynamics of the headbox jet and also have an influence on the final papersheet. QC 20100825