Time integration methods are necessary for the solution of transient flow problems. In recent years, interest in transient flow problems has increased, leading to a need for better understanding of the costs and benefits of various time integration schemes. The present work investigates two common time integration schemes, namely the Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) and the Fractional Step (FS) method. Three two-dimensional, transient, incompressible flow problems are solved using a cell centered, finite volume code. The three test cases are laminar flow in a lid-driven skewed cavity, laminar flow over a square cylinder, and turbulent flow over a square cylinder. Turbulence is modeled using wall functions and the k - ε turbulence model with the modifications suggested by Kato and Launder. Solution efficiency as measured by the effort carried out by the flow equation solver and CPU time is examined. Accuracy of the results, generated using the SIMPLE and FS time integration schemes, is analyzed through a comparison of the results with existing experimental and/or numerical solutions. Both the SIMPLE and FS algorithms are shown to be capable of solving benchmark flow problems with reasonable accuracy. The two schemes differ slightly in their prediction of flow evolution over time, especially when simulating very slowly changing flows. As the time step size decreases, the SIMPLE algorithm computational cost (CPU time) per time step remains approximately constant, while the FS method experiences a reduction in cost per time step. Also, the SIMPLE algorithm is numerically stable for time steps approaching infinity, while the FS scheme suffers from numerical instability if the time step size is too large. As a result, the SIMPLE algorithm is recommended to be used for transient simulations with large time steps or steady state problems while the FS scheme is better suited for small time step solutions, although both time-stepping schemes are found to be most efficient when their time steps are at their maximum stable value.

The objective of this thesis is to develop a model that represents the dynamics of a hydraulically operated forestry crane. The model was derived with the traditional Euler-Lagrange formalism and considers the crane mechanics, three double-acting hydraulic cylinders and the valve control unit. On the basis of the derived model we reproduced the entire crane model in MATLAB in order to run simulations herewith. This gave us the possibility to do parameter changes for further studies of the crane in motion. Another major goal within the thesis work was to estimate cylinder friction of the hydraulic actuators. We built up a test rig and used double-acting cylinders for determing their frictional behaviour. For this, we ran open-loop experiments in order to create velocity-friction maps that represented the static friction force of the cylinders. In this concern, we varied system pressure and cylinder load to study their influence on the friction force. By means of the derived static friction maps we approached the cylinder’s dynamic friction behaviour and applied both step and ramp control inputs to examine the spring-damping characteristics of the microspoic bristles in the contacting area. The dynamic friction experiments have been exerted in the fashion of the LuGre model. As a result we acquired different nominal friction parameters that we necessarily used to develope adequate friction models. A third objective of this thesis was to establish a crane-tip control. Instead of a traditional control, providing a direct relationship between joystick input and cylinder extension, the focus was to build up a control for the end-effector’s trajectory in a two-dimensional frame. This could be achieved by using inverse kinematics in order to determine the required joint angles that corresponded to the desired position of the crane-tip. The work also contains a CD including all developed MATLAB models that have been written within this project.

This report was written as a result of a Bachelor Degree Project, together with Swepart Transmission AB. The report contains the construction of a hydraulic press for the assembly operation. The project started with a new construction of a hydraulic press for the bearings’ assembly. The goal within the thesis work was to fit the three bearings to the housing by only one press motion. This operation should be very safety because of the sensitive tolerance at the bearings and housing. Construction of the cylinders, rams and bolster were the most important parts at this project because this parts’ functions are very important for this assembly. The next step of this thesis was to calculate the hydraulic press components’ parameters and then choose the suitable components. The focus was to choose more useful and reliable components. The hydraulic press was modeled in the CAD program Solid Works and 2D technical drawing was drawn in the Autocad. The frame material was chosen and the frame was analysised in the Solid Works.

Time integration methods are necessary for the solution of transient flow problems. In recent years, interest in transient flow problems has increased, leading to a need for better understanding of the costs and benefits of various time integration schemes. The present work investigates two common time integration schemes, namely the Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) and the Fractional Step (FS) method. Three two-dimensional, transient, incompressible flow problems are solved using a cell centered, finite volume code. The three test cases are laminar flow in a lid-driven skewed cavity, laminar flow over a square cylinder, and turbulent flow over a square cylinder. Turbulence is modeled using wall functions and the k - ε turbulence model with the modifications suggested by Kato and Launder. Solution efficiency as measured by the effort carried out by the flow equation solver and CPU time is examined. Accuracy of the results, generated using the SIMPLE and FS time integration schemes, is analyzed through a comparison of the results with existing experimental and/or numerical solutions. Both the SIMPLE and FS algorithms are shown to be capable of solving benchmark flow problems with reasonable accuracy. The two schemes differ slightly in their prediction of flow evolution over time, especially when simulating very slowly changing flows. As the time step size decreases, the SIMPLE algorithm computational cost (CPU time) per time step remains approximately constant, while the FS method experiences a reduction in cost per time step. Also, the SIMPLE algorithm is numerically stable for time steps approaching infinity, while the FS scheme suffers from numerical instability if the time step size is too large. As a result, the SIMPLE algorithm is recommended to be used for transient simulations with large time steps or steady state problems while the FS scheme is better suited for small time step solutions, although both time-stepping schemes are found to be most efficient when their time steps are at their maximum stable value.

Oil feed grooves are implemented in reciprocating compressor piston applications to assure a constant supply of lubricating oil on bearing surfaces and decrease friction loss. In a hermetically sealed compressor, due to small clearances encountered, oil supply becomes critical in order not to operate in boundary lubrication regime. Due to the small size of the piston and small piston &ndash / cylinder clearance, a partial lubrication regime is present. In the current study, a model that solves Reynolds&rsquo / equation for piston-cylinder lubrication and the average Reynolds&rsquo / equation that considers the effect of roughness on partially lubricated bearing for a compressor piston with oil feed grooves is developed. A parametric study is carried out to investigate the effects of piston design parameters and then arrive at an improved piston performance by using alternative designs for oil feed groove and the other design parameters.

This study considers the elastostatic contact problem of a semi-infinite cylinder. The cylinder is compressed against a layer lying on a rigid foundation. There is a sharp-edged circular hole in the middle of the foundation. It is assumed that all the contacting surfaces are frictionless and only compressive normal tractions can be transmitted through the interfaces. The contact along interfaces of the elastic layer and the rigid foundation forms a circular area of which outer diameter is unknown. The problem is converted into the singular integral equations of the second kind by means of Hankel and Fourier integral transform techniques. The singular integral equations are then reduced to a system of linear algebraic equations by using Gauss-Lobatto and Gauss-Jacobi integration formulas. This system is then solved numerically. In this study, firstly, the extent of the contact area between the layer and foundation are evaluated. Secondly, contact pressure between the cylinder and layer and contact pressure between the layer and foundation are calculated for various material pairs. Finally, stress intensity factor on the edge of the cylinder and in the end of the sharp-edged hole are calculated.

This specific-purpose mathematical model was developed for the drying process in a multi-cylinder drying section. The unsteady state of one-dimensional heat conduction equation has been applied to mathematical model of both, cylinder shell and paper web. The internal mass transfer of the paper web has not been included in this work. The calculations of the simulation program use an implicit numerical method. The drying path length along the machine direction has been divided into 4 drying phases for each drying cylinder. Each drying phase has been divided in small sub-elements. In each sub-element, the heat and mass transfer across boundary conditions have been solved simultaneously in the simulation program, which runs with MatLAB®.

<p>The objective of this thesis is to develop a model that represents the dynamics of a hydraulically operated forestry crane. The model was derived with the traditional Euler-Lagrange formalism and considers the crane mechanics, three double-acting hydraulic cylinders and the valve control unit. On the basis of the derived model we reproduced the entire crane model in MATLAB in order to run simulations herewith. This gave us the possibility to do parameter changes for further studies of the crane in motion.</p><p>Another major goal within the thesis work was to estimate cylinder friction of the hydraulic actuators. We built up a test rig and used double-acting cylinders for determing their frictional behaviour. For this, we ran open-loop experiments in order to create velocity-friction maps that represented the static friction force of the cylinders. In this concern, we varied system pressure and cylinder load to study their influence on the friction force. By means of the derived static friction maps we approached the cylinder’s dynamic friction behaviour and applied both step and ramp control inputs to examine the spring-damping characteristics of the microspoic bristles in the contacting area. The dynamic friction experiments have been exerted in the fashion of the LuGre model. As a result we acquired different nominal friction parameters that we necessarily used to develope adequate friction models.</p><p>A third objective of this thesis was to establish a crane-tip control. Instead of a traditional control, providing a direct relationship between joystick input and cylinder extension, the focus was to build up a control for the end-effector’s trajectory in a two-dimensional frame. This could be achieved by using inverse kinematics in order to determine the required joint angles that corresponded to the desired position of the crane-tip.</p><p>The work also contains a CD including all developed MATLAB models that have been written within this project.</p>

<p>This report was written as a result of a Bachelor Degree Project, together with Swepart Transmission AB. The report contains the construction of a hydraulic press for the assembly operation.</p><p>The project started with a new construction of a hydraulic press for the bearings’ assembly. The goal within the thesis work was to fit the three bearings to the housing by only one press motion. This operation should be very safety because of the sensitive tolerance at the bearings and housing. Construction of the cylinders, rams and bolster were the most important parts at this project because this parts’ functions are very important for this assembly.</p><p>The next step of this thesis was to calculate the hydraulic press components’ parameters and then choose the suitable components. The focus was to choose more useful and reliable components.</p><p>The hydraulic press was modeled in the CAD program Solid Works and 2D technical drawing was drawn in the Autocad. The frame material was chosen and the frame was analysised in the Solid Works.</p>

The creping process and the conditions on the Yankee cylinder dryer are key factors in a tissue paper mill, and they therefore need to be kept under good control in order to maintain a high and uniform quality. To this end it would be valuable to be able to make on-line measurements of Yankee coating thickness as well as the crepe structure of the tissue paper. The adhesion of paper to the cylinder affects the creping process and more information about the parameters that affect the adhesion is therefore of interest. To perform trials on a full scale or in a pilot plant is very costly and laboratory creping equipment is therefore sought after in order to be able to measure the adhesion force. The coating layer for use on the cylinder was analysed. It contained a large amount of carbohydrates and could not be considered transparent. The thickness of the coating layer was measured on a laboratory cylinder with a method based on fluorescence. An optical brightener was added to the coating chemicals and the coating layer was subjected to UV-radiation. The intensity of the light emitted by the optical brightener was measured and gave an indication of the thickness of the coating layer. The equipment has to be further investigated before it is possible to implement the new sensor on-line. New creping equipment and an adhesion method were developed for use on a laboratory scale. The equipment can operate with different creping angles and the force needed to crepe the paper can be measured. The highest creping force was obtained for papers of high grammage, low dryness at adhesion, high drainability, high fines content and high hemicellulose content. A more direct method is to analyse the structure of the produced paper. Measurements were made on a tissue paper with an optical fibre sensor while the paper was travelling at low speed. The collected signal was mathematically analysed and the characteristic wavelength was calculated for different paper samples. These values were close to the wavelengths measured with an off line method by a commercial crepe analyser. / Baksidestext The creping process is the heart of tissue paper manufacture. To control the process better, on-line measurements of paper structure and coating thickness are sought after. The creping is highly dependent on the adhesion of the paper to the Yankee dryer. To be able to measure the adhesion, laboratory creping equipment was also required. Different pulp parameters affect the adhesion and some of them have been investigated in this work. The coating on the Yankee cylinder consisted mainly of fiber fragments and could not be considered as transparent, which had to be considered when choosing a method to measure coating thickness. A method based on the light emitted from an optical brightener in the coating when subjected to UV-irradiation was used, but has to be further improved before it can be used on-line. A new laboratory creping method was developed to determine the adhesion between paper and metal, and the force needed to scrape off the paper with a doctor blade was measured. The highest creping force was obtained for papers made of pulp with a high drainability, high fines content and high hemicellulose content. An optical method using reflected light to measure crepe wavelength on-line was developed. The paper travelled under a sensor and the light collected was mathematically analyzed to determine the most common wavelength.