<p>This thesis work has been performed at the department of diagnosis and dependability at Volvo Car Company, Torslanda. The background of this project is based on interest in ascertaining how different factors possibly can affect a diagnosis method, which has been developed to find leaks in the fuel tank and evaporation system. According to the OBD II requirements leaks with an orifice diameter larger or equal to 0,5 mm, must be detected. The idea of the diagnosis method is to create an over pressure in the system with an air-pump. The current through the pump is measured and correlates to the power consumed by the pump. As the power is a function of the pressure difference over the pump, the pump current correlates to the pressure in the tank. Thus, the pump current can be used as a measure of the impenetrability. Changes in the system pressure, not caused by the pump, are accordingly disturbances to the method. </p><p>The object of this work was to develop mathematical models, describing the lapse where the system is pressurized by the pump under the influence of different physical factors. The model is for instance considering variations in temperature and height, flow resistance in lines and valves, component characteristics, fuel evaporation, leaks etc. Furthermore the pump current is treated by the diagnosis evaluation algorithm with purpose to judge whether there is a leak in the system. </p><p>The model has been implemented in Matlab/Simulink and it can consequently be used in dynamic simulations according to the over pressure leakage detection concept. Numerical experiments can be done in purpose to examine how changes in environmental conditions or component characteristics will affect the diagnosis method. Good agreement has been found between measurements and simulated results. The diagnosis function produces correct decisions under different conditions with disparity in leak sizes, additionally confirming the reliability of the model.</p>

One of the most fundamental human needs is fresh air. It has been estimated that people spend comparatively much time in indoor premises. That creates an elevated need for high-quality ventilation systems in buildings. The ventilation airflow rate is recognised as the main parameter for measuring the indoor air quality. It has been shown that the ventilation airflow rates have effects on respiratory diseases, on “sick building syndrome” symptoms, on productivity and perceived air quality. Ventilation is necessary to remove indoor-generated pollutants by diluting these to an acceptable level. The choice of ventilation airflow rate is often based on norms or standards in which the airflow rate is determined based on epidemiological research and field or laboratory measurements. However, the determination of ventilation flow rate is far more complex. Indoor air quality in the occupied zone can be dependent of many factors such as outdoor air quality, airflow rate, indoor generation of pollutants, moisture content, thermal environment and how the air is supplied into the human occupied zone. One needs to acknowledge the importance of air distribution which clearly affects the comfort of occupants. To design a ventilation system which considers all aspects of room ventilation can only be achieved by computer modelling. The objective of this thesis is to investigate air diffusion, indoor air quality and comfort issues by CFD (computational fluid dynamics) modelling. The crucial part of the CFD modelling is to adopt BCs (boundary conditions) for a successful and accurate modelling procedure. Assessing the CFD simulations by validated BCs enabled constructing the ventilation system virtually and various system layouts were tested to meet given design criteria. In parallel, full-scale measurements were conducted to validate the diffuser models and the implemented simplified particle-settling model. Both the simulations and the measurements reveal the full complexity of air diffusion coupled with solid contaminants. The air supply method is an important factor for distribution of heat, air velocity and solid contaminants. The influence of air supply diffuser location, contaminant source location and air supply method was tested both numerically and by measurements to investigate the influence of different parameters on the efficiency of room ventilation. As example of this, the well-known displacement ventilation is not fully able to evacuate large 10 μm airborne particles from a room. Ventilation should control the conditions in the human breathing zone and therefore the ventilation efficiency is an important parameter. A properly designed ventilation system could use less fresh air to maintain an acceptable level of contaminant concentration in the human breathing zone. That is why complete mixing of air is not recommended as the ventilation efficiency is low and the necessary airflow rate is relatively high compared to other ventilation strategies. Especially buoyancy-driven airflows from heat sources are an important part of ventilation and should not be hampered by supply airflow from the diffusers. All the results revealed that CFD presently is the only reliable method for optimising a ventilation system considering the air diffusion and contaminant level in all locations of any kind of room. The last part of the thesis addresses the possibility to integrate the CFD modelling into a building design process where architectural space geometry, thermal simulations and diffuser BCs could be embedded into a normal building design project. / QC 20101007

This thesis work has been performed at the department of diagnosis and dependability at Volvo Car Company, Torslanda. The background of this project is based on interest in ascertaining how different factors possibly can affect a diagnosis method, which has been developed to find leaks in the fuel tank and evaporation system. According to the OBD II requirements leaks with an orifice diameter larger or equal to 0,5 mm, must be detected. The idea of the diagnosis method is to create an over pressure in the system with an air-pump. The current through the pump is measured and correlates to the power consumed by the pump. As the power is a function of the pressure difference over the pump, the pump current correlates to the pressure in the tank. Thus, the pump current can be used as a measure of the impenetrability. Changes in the system pressure, not caused by the pump, are accordingly disturbances to the method. The object of this work was to develop mathematical models, describing the lapse where the system is pressurized by the pump under the influence of different physical factors. The model is for instance considering variations in temperature and height, flow resistance in lines and valves, component characteristics, fuel evaporation, leaks etc. Furthermore the pump current is treated by the diagnosis evaluation algorithm with purpose to judge whether there is a leak in the system. The model has been implemented in Matlab/Simulink and it can consequently be used in dynamic simulations according to the over pressure leakage detection concept. Numerical experiments can be done in purpose to examine how changes in environmental conditions or component characteristics will affect the diagnosis method. Good agreement has been found between measurements and simulated results. The diagnosis function produces correct decisions under different conditions with disparity in leak sizes, additionally confirming the reliability of the model.

Three experimental studies were conducted to quantify the effects of system cycling, evaporator airflow, and condenser coil fouling on the performance of residential air conditioners. For all studies, the indoor dry-bulb (db) temperature was 80°F (26.7°C) db. The cycling study consisted of twelve transient tests conducted with an outdoor temperature of 95°F (35°C) db for cycle times of 6, 10, 15, and 24 minutes. Indoor relative humidities of 40%, 50%, and 60% were also considered. The evaporator airflow study consisted of twenty-four steady-state tests conducted with an indoor condition of 67°F (19.4°C) wet-bulb (wb) for evaporator airflows ranging from 50% below to 37.5% above rated airflow. Outdoor temperatures of 85°F (29.4°C) db, 95°F (35°C) db, and 105°F (40.6°C) db were also considered. The coil fouling study used a total of six condensers that were exposed to an outdoor environment for predetermined amounts of time and tested periodically. Three of the condensers were cleaned and retested during the periodic testing cycles. Testing consisted of thirty-three steady-state tests conducted with an indoor condition of 67°F (19.4°C) wb for outdoor exposure times of 0, 2000, 4000, and 8000 hours. Outdoor temperatures of 82°F (27.8°C) db and 95°F (35°C) db were also considered.

Modeling of airflow resistance in grain bulk requires knowledge of the tortuosity and velocity of the air flow through the grain bulk. In this study, experiments were carried out to determine these characteristics of airflow paths by analyzing digital images of smoke-visualized airflow paths inside a grain bulk obtained with a high speed camera. Colored smoke with approximately the same density as air was introduced into the test box for the visualization of the airflow through the grain bulk. Soybeans with a moisture content of 8.82% on wet basis were used in this study. The high quality videos obtained by recoding the fast movement of the smoke through the grain bulk was first separated into frames using a commercial software, VirtualDub (CRIM, Montreal, Québec, Canada), and the 512× 384 pixel RGB image files (frames) extracted from the recorded videos and read into ImageJ an image processing Java-based software developed by the United State National institute of Health, to track the movement of the smoke in the images, frame by frame to determine lengths, tortuosities of the different flow paths, as well as their velocities.

Modeling of airflow resistance in grain bulk requires knowledge of the tortuosity and velocity of the air flow through the grain bulk. In this study, experiments were carried out to determine these characteristics of airflow paths by analyzing digital images of smoke-visualized airflow paths inside a grain bulk obtained with a high speed camera. Colored smoke with approximately the same density as air was introduced into the test box for the visualization of the airflow through the grain bulk. Soybeans with a moisture content of 8.82% on wet basis were used in this study. The high quality videos obtained by recoding the fast movement of the smoke through the grain bulk was first separated into frames using a commercial software, VirtualDub (CRIM, Montreal, Québec, Canada), and the 512× 384 pixel RGB image files (frames) extracted from the recorded videos and read into ImageJ an image processing Java-based software developed by the United State National institute of Health, to track the movement of the smoke in the images, frame by frame to determine lengths, tortuosities of the different flow paths, as well as their velocities.

Airflow into, out of, and within buildings is fundamental to their design and operation as it can affect occupant health and comfort, building durability, and energy consumption. This thesis works to develop the understanding of airflow patterns and pressure regimes in high-rise multi-unit residential buildings which are both unique and complex due to the combination of their height, typical inclusion of operable windows, and compartmentalized layout. Specific attention is directed towards the performance of corridor pressurization based ventilation systems which are used pervasively within industry to ventilate and control contaminant transfer in these buildings. Airflow is caused by pressure differences which for buildings are created by the driving forces of wind, stack effect, and mechanical ventilation systems. These airflows are resisted by the air permeance (i.e. airtightness) of building elements including the exterior enclosure and interior compartmentalizing elements. Using an experimental program at a case study building, this thesis assesses the interaction of these driving forces of airflow with the physical building to create the airflow patterns for a typical high-rise multi-unit residential building. Perflourocarbon tracer (PFT) testing was performed to measure in-service airflows into and out of the suites. This testing found that the air change rates of upper suites are significantly higher than that of lower suites and that most suites receive small fractions of modern ventilation rates or are over ventilated. Airflow measurements of the supply of ventilation air to each corridor indicate that these low flow rates are in part due to leakage of air from the supply duct. The PFT testing also found that significant airflow occurred from the parking garage below the building into the occupied building spaces indicating significant potential for transfer of harmful air contaminants. The air permeance of the exterior enclosure and interior compartmentalizing elements were measured using neutralized fan pressurization and depressurization techniques and found to be within typical ranges. In particular this testing found that only 20% of the flow paths out of the corridor were to the adjacent suites through the suite entrance doors and that flows to the elevator shaft and stairwells could create a significant inefficiency in the ventilation system. A long-term monitoring program was implemented at the case study building primarily to monitor exterior environmental conditions including wind and exterior temperature and to correlate these with measured pressure differences. A strong correlation was found between building pressure and exterior temperature. Nearly 70% of the theoretical stack effect pressure was measured to act across the corridor to suite pressure boundary which creates a significant pressure differences to be overcome by the ventilation system, likely contributing to the uneven distribution of ventilation rates. Both wind and stack effect pressures were found to often be of similar or greater magnitude than mechanically induced pressure differences and thus can overwhelm the ventilation system. Overall, the corridor pressurization based ventilation system at the case study building does not effectively or efficiently ventilate the building and also does not provide sufficient control of air contaminants. As the case study building was found to be relatively representative of a typical multi-unit residential building, the findings from this building can be extended to many other buildings. Effective ventilation and airflow control in multi-unit residential buildings likely requires suite compartmentalization and direct supply of ventilation via ducted or in-suite systems.

The rise velocity of injected air phase from the injection point toward the vadose zone is a critical factor in in-situ air sparging operations. It has been reported in the literature that air injected into saturated gravel rises as discrete air bubbles in bubbly flow of air phase. The objective of this study is to develop a quantitative technique to estimate the rise velocity of an air bubble in coarse porous media. The model is based on the macroscopic balance equation for forces acting on a bubble rising in a porous medium. The governing equation incorporates inertial force, added mass force, buoyant force, surface tension and drag force that results from the momentum transfer between the phases. The momentum transfer terms take into account the viscous as well as the kinetic energy losses at high velocities. Analytical solutions are obtained for steady, quasi-steady, and accelerated bubble rise velocities. Results show that air bubbles moving up through a porous medium equilibrate after a short travel time and very iv short distances of rise. It is determined that the terminal rise velocity of a single air bubble in an otherwise water saturated porous medium cannot exceed 18.5 cm/sec. The theoretical model results compared favorably with the experimental data reported in the literature. A dimensional analysis conducted to study the effect of individual forces indicates that the buoyant force is largely balanced by the drag force for bubbles with an equivalent radius of 0.2-0.5 cm. With increasing bubble radius, the dimensionless number representing the effect of the surface tension force decreases rapidly. Since the total inertial force is quite small, the accelerated bubble rise velocity can be approximated by the terminal velocity.

Vocal fold vibration results from an alternating balance between subglottal air pressure that drives the vocal folds apart and muscular, elastic, and restoring forces that draw them together. The aim of the present thesis is to present quantitative data of normal vocal function using a noninvasive method. Measurements are made on the inverse filtered airflow waveform, of estimated average trans glottal pressure and glottal airflow, and of sound pressure for productions of syllable sequences. Statistical results are used to infer mechanisms that underlie differences across ( 1 ) normal, loud, and soft voice, (2) normal, high, and low pitch, and (3) between female and male voices. Interspeaker variation in group data and intra speaker variation across repeated recordings is also investigated. The results showed no significant female-male differences in pressure, suggesting that differences in other measures were not primarily due to differences in the respiratory systems . Most glottal waveforms showed a DC flow offset, suggesting an air leakage through a posterior glottal opening. Results suggested (indirectly) that the males in comparison with the females had significantly higher vocal fold closing velocities (maximum flow declination rate), larger vocal fold oscillations (AC flow), and relatively longer closed portions of the cycle (open quotient) in normal and loud voice. In soft voice, female and male waveforms were more alike. In comparison with normal voice, both females and males produced loud voice with significantly higher values of pressure, vocal fold closing velocity, and AC flow. Soft voice was produced with significantly lower values of these measures and increased DC flow. Correlation analyses indicated that several of the airflow measures were more directly related to vocal intensity than to pitch. Interspeaker variation was large, emphasizing the importance of large subject groups to capture normal variation. Intraspeaker variation across recording sessions was less than 2 standard deviations of the group means. The results should contribute to the understanding of normal voice function, and should be useful as norms in studies of voices disorders as well. / Härtill 5 uppsatser.För att köpa boken skicka en beställning till exp@ling.su.se/ To order the book send an e-mail to exp@ling.su.se

In this study, Computational Fluid Dynamics Modeling (CFD) was applied to model a room-and-pillar mining working area to investigate the airflow patterns for dust control. Room-and-pillar mining is a conventional underground mining technique used for the extraction of coal by cutting excavations called "rooms" using a continuous mining machine and leaving the remaining coal as "pillars" for supporting the coal seam. The FLUENT software was used to analyze the airflow in the mine whose structure was designed and meshed in GAMBIT. The analysis was carried out in four different stages. First, airflow patterns were studied in the roadway without any equipment. Next, a line curtain, which extends along the height of the coal seam, was simulated in the roadway to direct the flow of air towards the active mining face. In the third stage, a continuous miner was inserted between the mining face and the end of the line curtain. Three and six meters deep box and slab cuts were simulated and the airflow patterns were investigated. In the final stage, a wet scrubber was simulated as an integral part of the continuous miner and the effect of the scrubber on the airflow in the box and slab cuts were studied. Dead zones (areas with limited airflow) and recirculation areas were observed using velocity distribution contours. A parametric study was conducted to evaluate the effects of distance of the curtain from the pillar rib (Dcr), scrubber pressure (Psc) and height of the coal seam (Ho). The data were plotted as functions of selected dimensionless variables. It was seen that wet scrubber increased the air in the LOXC (Last open cross cut) by 7.6% and was also proved that extension of line curtain along with the cut. The results of these studies are being used to develop guidelines for dust control in the face area.