Recent studies have shown that nanoparticles may be more toxic than larger particles of the same material, but the health risks associated with widespread use largely depend on the extent of exposure. When dealing with potentially toxic particles, precautionary measures have to be taken in order to minimize contact. For larger particles, mechanical filtering is commonly used. Nanoparticles, however, are too small to be effectively impeded by these filters and thus alternative methods need to be developed. Experiments are performed where clusters of carbon nanotubes are dropped vertically into a region with an electric field, generated between two parallel plates. The clusters are strongly affected by the field and move swiftly towards the electrodes. In this setup, most clusters simply bounce between the electrodes. By adding an electrically insulating layer to one of the plates, however, the particles get stuck. This implies that electrostatic filtration is an effective means of collecting airborne carbon nanotubes. Nanoparticles may enter human lung regardless if filtration is used or not. To examine the health risks, therefore, knowledge of transport and deposition properties of aerosol particles in lung flows is necessary. This information is also essential in the optimization of targeted drug delivery with pharmaceutical aerosols. In vivo and in vitro studies are cost-intensive and difficult to perform for studying particle deposition in the airways. Hence, numerical simulations constitute a valuable complement. The extent and location of particle deposition depend on particle properties, airway geometry and breathing pattern. To start with, Computational Fluid Dynamics simulations are performed for spherical particles, 15 nanometer to 50 micrometer in diameter, in a multiply bifurcated asymmetric 3D model, representing trachea to the segmental bronchi. Steady, laminar flow is considered for inhalation flow rates of 0.1 and 0.5 l/s. The largest particles are captured near the first bifurcation, whereas smaller microparticles are less efficiently, but more uniformly, deposited. The site of deposition is also affected by geometric asymmetry. The nanoparticles essentially follow the streamlines and travel unaffected through the region modeled. Thus, transport to the distal airways can be assumed extensive. Because of their specific shape, fibers may cause additional harm compared to spherical particles. Asbestos is a well-known example of hazardous fibrous materials. More recently, this has also called for concern on the extended use of nanotubes. A numerical model is developed for fiber transport in the respiratory airways. The coupled equations for fiber rotation and translation are solved using MATLAB. The model is valid for arbitrary Stokes flows at low particle concentrations and for particle sizes from nano- to the micro range. The results suggest that the potential of a fiber to reach the distal airways increases with increased fiber aspect ratio, regardless of particle size. / <p>Godkänd; 2008; 20080428 (ysko)</p>

Cellulose material is processed to pulp suspensions and MDF boards in order to produce products such as papers, magazines, laminate floors or door skins. A critical stage of these processes is when the cellulose fiber networks are compressed to specific densities and when most of the fluid originally positioned between and inside the fibers is forced to leave the network. The fiber network is then exposed to a drag force generated by the flow. The magnitude of this force is dependent upon how easy the fluid can flow through the network, which is commonly described by its permeability. In addition to the permeability, which relates to the drag on each fiber, there is a solid network force. The response to this force from the fiber network is often termed as the compressibility of it. Hence, to be able to model and predict the compression stage in cellulose material related processes these two material properties must be known. In this thesis two equipments to measure the permeability of MDF networks and pulp suspensions are evaluated and a neat model for a part of the MDF- compression stage is developed. A reference material consisting of spherical particles and relevant fiber networks are used as test objects for the equipments enabling a comparison to theoretical models and existing experimental results. The outcome is that correct enough permeability data are obtained with respective equipment as long as Reynolds number is sufficiently low. The equipments are then used to study different materials showing, for instance, that highly compressed MDF-networks are strongly anisotropic as to permeability and that the tested hardwood pulps have an overall higher permeability compared to the softwood pulps investigated. It was also found that the permeability of the pulps was not influenced by different mechanical treatments of the fiber network, as long as the geometrical dimensions of the fibers were constants. / <p>Godkänd; 2006; 20070109 (haneit)</p>

Noise control and sound quality analysis are important, since noise has been registered to be a predominant factor in stress and a source of great annoyance. Traffic noise is a problem and a major part of this noise comes from heavy vehicles. The only legislative requirement for heavy-duty trucks regarding noise emissions, is that the noise level does not exceed an Aweighted sound pressure level of 80 dB. The specification of an A-weighted sound pressure level is, however, not an adequate description of psychoacoustic annoyance and therefore work towards defining a better description of loudness is one of the principal fields of acoustics today. Sound radiation from trucks is speed-related. At medium and high speeds, the overall noise level is comprised mainly of the tyre noise, whereas at low speed and during acceleration, exhaust noise and noise from the engine and transmission structure are predominant. In front of the truck, the noise from the engine and especially that from the timing transmission cover, the torsional damper and the oil sump, comprises a greater proportion of the total noise. The aim of sound quality analysis of diesel engines is to find cost-efficient methods of reducing sound radiation and of changing the character of the sound in order to minimise annoyance. This thesis concerns the development of experimental methods for analysing the sound quality of diesel engines, and focuses on measurement of acoustic intensity, multivariate data analysis, structural modification and subjective assessment of engine noise. The applicability of the FFT-based sound intensity method is evaluated. It is found that the intensity measurements may be influenced by high reactivity, interference due to partlycoherent sources, difficulties in performing the spatial average, real-time limitations and engine speed variations. Scanning the intensity probe, preferably by a robot, is necessary when measuring within narrow bands to avoid interference problems. Scanning achieves more reliable estimates of sound power and intensity vectors. Experimental design and the multivariate techniques, principal components analysis (PCA) and partial least squares (PLS) were utilised to facilitate interpretation of intensity measurements. The results show that PCA and PLS enable independent phenomena in the sound field to be extracted and which can thereby be visualised by principal spectra and principal radiating patterns. The characteristics of sound radiation are determined by designed experiments, sound intensity measurements and operational deflection shape estimations. These methods enable the effects on sound radiation of structure modifications to be predicted. An annoyance index for in-line 6-cylinder diesel engines in stationary running conditions was developed using multivariate statistics. The index is based on engine sounds resulting from structure modifications and changes in fuel. The annoyance level was measured during listening tests of sound stimuli recorded in stereo and reproduced by loudspeakers under anechoic conditions. The different sound stimuli were ranked using paired comparisons or the method of successive intervals. It was found that 94% of the variance of annoyance can be explained by a model based on loudness (Sone), sharpness (Acum) and harmonic ratio (rumble). Impulsiveness, roughness and tonality were other important criteria used in the study and which were found to have a relationship with specific speed ranges. The annoyance was minimised by an increase in stiffness in the lower part of the engine achieved by using a ladder frame in combination with a bearing beam. / Godkänd; 1996; 20061214 (biem)

Sprays are used in a wide range of engineering applications, in the food and pharmaceutical industry in order to produce certain materials in the desired powder-form, or in internal combustion engines where liquid fuel is injected and atomized in order to obtain the required air/fuel mixture. The optimization of such processes requires the detailed understanding of the breakup of liquid structures. In this work, we focus on the secondary breakup of medium size liquid drops that are the result of primary breakup at earlier stages of the breakup process, and that are subject to further breakup. The fragmentation of such drops is determined by the competing disruptive (pressure and viscous) and cohesive (surface tension) forces. In order to gain a deeper understanding on the dynamics of the deformation and breakup of such drops, numerical simulations on single drops in uniform and shear flows, and on dual drops in uniform flows are performed employing a Volume of Fluid method. The studied parameter range corresponds to an intermediate Weber number of 20, sufficiently high so that breakup occurs, but much lower than the limit for catastrophic breakup, and a range of Reynolds numbers covering the steady wake regime for liquid drops, Re = 20-200. In order to account for liquids in various applications, a set of different density and viscosity ratios are considered, ρ*=20-80, and μ*=0.5-50 respectively. Single drop simulations show that depending on the Reynolds number and density and viscosity ratios, various breakup modes besides classical bag and shear breakup may be observed at a constant Weber number. The characteristics of the deformation process and the time required for breakup are considerably different for these modes; furthermore, both are significantly altered by velocity gradients in the flow. Dual drop simulations show that the relative position of the two drops, in addition to the Reynolds number and density and viscosity ratios, plays a crucial role in determining the interaction scenario. It is found that the behaviour of drops in tandem may be predicted based on data obtained for single drops: the breakup time and the length of the wake behind the drop. The region where collision is most likely to occur is identified as a two diameters wide and eight diameters long streak, however, weaker forms of interaction may occur up to twenty diameters behind the drop. Results presented in this thesis may be applied to formulate enhanced breakup models regarding the deformation, breakup, and interaction of liquid drops employed in spray simulations. / <p>QC 20170825</p>

The thesis comprises six papers with the overall theme of measurement, assessment and control of diesel engine noise, with an emphasize on control. The radiation of noise is shown to be dominated by the low end of the engine sides and by the engine front. The mode shapes of the crankcase, the oil sump and the timing transmission cover are investigated. The vibrations are measured and analysed through running mode, modal analyses and SEA. The noise radiation is explored in detail with near-field measurements of sound intensity. In the engine front, the noise radiation is shown to have contributions from the timing casing, the oil-sump front and the crankshaft torsion vibration damper. The radiation from the torsion damper is analysed by a regression analysis of measured intensity data and the vibrations of the damper are investigated with a laser-doppler vibrometer. The results show that the damper vibrates in the axial directions with vibration modes that both radiate noise and interfere with the radiation from the engine structure. It is shown that there in the engine front are strong coupled vibration modes between the timing cover and the oil sump front m the frequency range 500 Hz - 1 kHz. The importance of the strong vibration modes in the crankcase and the oil-sump sides is shown. The propagation paths of noise and vibration to the engine front have been examined with an SEA powerflow analysis and by opening the front cover to measure the sound power from the timing gears. The main excitations of the front cover are found to be by engine block vibrations below 1.25 kHz and by tuning gears noise above 2 kHz. Various constructions to control the noise are tested. Two stiffeners are designed and tested to reduce vibrations m the engine low end, one ladder frame introducing stiffness at the crankcase flange and one bearing beam introducing stiffness at the main bearing caps. The stiffeners have hem evaluated by sound intensity measurements and mobility measurements. The ladder frame gave good noise reductions but the bearing beam merely caused frequency shifts of the bearing modes. A decoupling of the oil sump resulted in significant noise and vibration reductions. The timing cover is modified by increasing the damping and by decrease the radiation efficiency. Various interior panels are tested, like plexiglass and aluminium panels of different thicknesses, a rubber damping layer and a combined rubber/steel-sheet damping layer. A thin plastic sheet has low radiation efficiency and may thereby lower the noise emission. A slightly improved model for calculation of radiation efficiency of small irregularly shaped plates is suggested. The traditional SEA prediction model is shown to be ill-conditioned for engine applications. An improved model using geometric averaging is suggested and evaluated. The results show that the new SEA model is working well for frequencies down to 800 Hz for predictions of damping treatments, decoupling of the oil sump and for power-flow determinations. The concept of equivalent mass is found valuable and validations are made according to the consistency and reciprocity theories. A hemi-anechoic engine laboratory is constructed and evaluated. New efficient low-cost diffusing absorbers have been designed, the performance is evaluated with standard deviation analysis of sound pressure measurements. The performance of the absorbers is found to be compeatable with much more expensive commercial designs. Measured sound intensity in three-dimensional vectors is a powerful tool to identify and illustrate sound fields. When used in near-fields to identify complex noise sources large errors may occur. It is shown that the low relative levels of vector components and the reactivity of the sound field give large errors m repeated measurements. Analyses and comparisons are performed on a simple source and on an engine. A two- and a six-microphone probe were used that were hand-held and robot-controlled. It is concluded dig in point-intensity measurements on engineering noise sources, a 4-6 microphone probe and a precision positioner should be used to get reliable measurements. / Godkänd; 1994; 20061214 (biem)

This thesis covers research in the floor vibration field. Although lightweight steel framed constructions have been in focus, many results are applicable to floors in common and to some extent also to vibrations in general. Whether a floor is treated as "good" or "bad" by the occupants is an interaction of a) the dynamic properties of the floor and of b) human vibration perception. Both these factors are covered. Two steel framed floors were tested in laboratory condition with respect to its dynamic. Modal testing was used to obtain the modal parameters, i.e. natural frequencies, damping and mode shapes. Both floors were tested for numerous set-ups where for example the effect of different supports, top layers, ceiling joists and simulated partitions were investigated. For one of the floors, subjective opinions were collected for correlation with the measured data. The research of floor dynamic has lead to a creative new method that utilizes strategically positioned small pieces of visco-elastic material to increase the damping of the floor. It was found out that this economic and proportionally easy method significantly increases the damping for some specific type of modes. The human vibration sensitivity was tested in a new developed motion simulator. Absolute threshold values for single sinusoidals were tested in the frequency range of 5-31.5 Hz. For validation of the test setup, the results were compared with data from other similar studies. The obtained thresholds agreed satisfactorily with previously reported results. More innovated tests were performed concerning multiple frequency signals of two to five discrete frequency components. The results show that a signal's composition in terms of number of frequency components and their mutual amplitude relation significantly affect the subjective perception. Therefore, it can be argued that multiple natural frequencies of a floor should be considered when it comes to design rules. This is in opposition to many floor design criteria of today since these often rely upon the fundamental frequency only. A prediction model, where the acceptance is calculated as a function of the frequency weighted total acceleration amplitude in combination with the fundamental frequency is suggested. The presented model does take into account the presence of possible multiple response frequencies. / Godkänd; 2006; 20061205 (haneit)

Godkänd; 2002; 20070110 (biem)

The increasing demands from governments on the engine manufactures to lower the fuel consumption, lower the exhaust emissions and to reduce the noise have lead to an intensive research in the combustion process. Measurement of the combustion process inside the cylinder is only suitable in laboratory environment due to a number of limitations; the pressure transducer needed to measure the pressure is expensive, difficult to mount in the cylinder and has a limited lifetime that is much shorter than the engine's lifetime. Demands of on-board diagnostics where the combustion process is continuously monitored, on production vehicles have created a need for a method to indirectly measure the combustion process. The two main indirect methods are vibration measurement based reconstruction and crankshaft angular speed measurement reconstruction. The combustion process give rise to vibrations in the engine body that in the former method is measured with an accelerometer and the pressure can be reconstructed by using inverted transfer functions. The idea behind the latter method, the crankshaft angular speed reconstruction method, is that when one cylinder fires the produced torque is higher than the load torque and the crankshaft accelerates. As next cylinder goes into compression the total load torque increases and the crankshaft speed will decrease. This is repeated when the next cylinder fires and the produced crankshaft speed fluctuations will then contain information about the combustion and compression that caused it. In this thesis an indirect method to predict the maximum cylinder pressure is developed based on the crankshaft speed fluctuations combined with neural networks. The speed fluctuations were measured on a 6-cylinder inline diesel engine at 9 speed-load-combinations. A two layer (one hidden and one output layer) feedforward neural network was trained with the backpropagation algorithm. The prediction accuracy for pmax was found to be better than ±5 % at 95%-confidence interval for the validation set. Another important parameter for the engine control and for optimising the fuel efficiency at the same time as the exhaust emissions are kept to a minimum, is the position of the pistons most upper position, TDC (top dead centre). The TDC position is normally measured mechanically with means that need access to the cylinders (the cylinder head has to be removed). This method is time consuming and therefore expensive and because of that not used on production engines. Several indirect methods to measure the TDC- positions have been suggested. Either based on measured cylinder pressures, that again need a pressure transducer mounted in the cylinder, or on the crankshaft speed fluctuations. An indirect method based on the speed fluctuations, that are measured when the starter motor rotates the engine with turned off ignition, is developed. From the measured crankshaft speed fluctuations the TDC-positions can be determined either by curve fitting or with neural networks. The TDC position determined by curve fitting has a bias error, due to the out-of-phase acceleration component in the crankshaft that are induced by the starter motor, but also caused by heat exchange between the compressed gas and the cylinder walls and gas. The results from the neural network were found to be better and the TDC-position for all 6 cylinders was determined within ±0.1 degree crank angle at 95%-confidence interval. / <p>Godkänd; 2001; 20070110 (biem)</p>

På grund av allt hårdare miljökrav från EU och nedläggningen av kärnkraften så kommer vattenkraft, vilket redan spelar en stor roll för dagens energiproduktion, behöva utökas. På grund av detta behövs en hållbarare och billigare lösning på tekniska fiskvägar, vilka idag oftast gjuts i betong. En av lösningarna som företaget Composite Service Europe AB föreslår är att göra detta i komposit, då det är lättare att underhålla och specialdesigna. För att enklare kunna specialdesigna och se så den uppfyller alla krav som ställs så kommer detta examensarbete presentera en simulering av en dessa fiskrännor samt validering av denna simulering. En ränna modellerades upp i Siemens NX vilken sedan simulerades med ANSYS CFX. Från denna simulering togs sedan flödesfältet och hastighetskonturen från den tredje bassängen ut och jämfördes mot experimentella flöden. De experimentella flödena är framtagna i kursen Experimentella Metoder och gav en indiktation för hur flödet borde se ut i bassängen. Då det experimentella arbetet var gjort på ett sådant sätt att inga hastigheter eller andra kvantiteter för flödet fanns, så kan inte flödet räknas som helt validerat utan vidare experimentellt arbete krävs. Men det som jämförelsen tyder på är att det simulerade flödet följer det experimentella. Vidare måste simuleringstiden sänkas då denna simuleringen tog 21 dagar, vilket inte är gångbart ute i industrin. Några sätt att göra det på som föreslås är att göra en nätstudie och se om det går att simulera en bassäng.

The present research focuses on flow properties of the elbow draft tube. This element has a major function in low head turbines, since up to half of the losses may arise there at part load. The use of computational fluid dynamic (CFD) to redisign a draft tube necessitates detailed knowledged of the boundary conditions. They are generally not available and qualified guesses must be made. This applies in particular to the radial velocity at the inlet. A method to estimate this component in swirling flow from experimental values of the axial and tangential velocities is derived. The method uses a two dimensional non- viscous description of the flow, the Squire-Long formulation. It is tested against swirling flow in a diffuser and applied to the Turbine-99 draft tube flow. As several other boundary conditions are difficult to estimate and many input parameters are available to perform a simulation, the use of factorial design is proposed as an alternative to design simulations in a systematic, objective and quantitative way. The method allows the deternmination of the main and joint effects of input parameters on the numerical simulation. The input parameters may be experimental uncertainty on boundary conditions, unknown boundary conditions, grid and turbulence models. The method is applied to the Turbine-99 test case, where the radial velocity, the surface roughness, the turbulence length scale and the grid were the factors investigated. The inlet radial velocity is found to have a major effect on the pressure recovery. The flow in water turbines is highly unsteady due to the runner blade rotation, guide vanes and stay vanes. Unsteady pressure measurements on a Kaplan prototype point out unsteadiness in the high and low pressure regions of the turbine. Since model and prototype are not running in dynamically similar conditions, the influence of unsteadiness on the losses is of interest. The derivation of the variation of the mechanical energy for the mean, oscillating and turbulent fields point out the contribution of unsteadiness to the losses and the turbulent production. Application to turbulent channel flow reveals that the contribution is a function of the amplitude of the oscillation, the frequency and the friction velocity. Turbulent pulsating flow in a generic model of the rectangular diffuser found at the end of elbow draft tube is studied in detail with laser Doppler anemometry (LDA). Three frequencies, corresponding to the quasi-steady, relaxation and quasi-laminar regimes with an amplitude of about 10% are investigated. The results indicate no alteration of the mean flow by the excitation of a single frequency. Furthermore. the existence of the different regimes, as found in turbulent pulsating turbulent pipe and channel flows, is confirmed. / Godkänd; 2003; 20061108 (haneit)