Design methods for side shear of drilled shafts, including the resistance factors that should be applied, do not account for any specific construction procedure. Instead, design often relies on analysis of case studies which include all construction methods used in each geomaterial type (e.g. clays, sands and rocks), or on parametric analysis. Nonetheless, literature suggests that different construction procedures result in varying side shear. This research investigated 2 types of construction: (1) slurry stabilization in sandy soils using bentonite and polymer products that are commonly used on the field, with exposure times from near 0h to 96h, and (2) temporary casing stabilization in simulated limestone using 3 different methods for installation and extraction of the casings which included: driven, coarse-tooth rotated and fine-tooth rotated. All specimens were 1/10th scale in relation to the most common shafts sizes constructed in the field. The results showed that bentonite slurry causes a significant reduction on the side shear within relatively short periods of time (between 2h and 4h of open excavation), whereas polymer slurry did not show appreciable variations up to 96h. The driven and coarse-tooth rotated temporary casing exhibited lower side shear resistance than the fine-tooth rotated casings, which can be attributed to the larger annulus outside the casing and the additional crumbled pieces of rock that degrades the contact interface with the socket concrete. Construction-based resistance factors are suggested for each construction procedure investigated in this study and clearly show the effects from different methods.

The behaviour of cohesionless soils is known to be influenced by the method of reconstitution. It is generally accepted in the literature that different reconstitution methods produce samples of varying fabric and thus samples of varying behaviour. Very little evidence has been presented to validate this statement. The main aim of this is thesis is firstly to observe the fabric of in situ and reconstituted gold tailings samples and secondly to investigate the difference in behaviour between these samples at the same state. The investigation focused on testing in situ and reconstituted gold tailings samples obtained from 3 positions on a tailings dam; pond, middle beach and upper beach. Laboratory reconstitution methods included moist tamping and slurry deposition. Fabric analysis involved the use of SEM images to classify the observed differences in the fabric of the undisturbed and reconstituted gold tailings samples. A particle interaction model based on the observed fabric was postulated to explain the differences or similarities in behaviour. The scope of behaviour investigated included sedimentation, collapse and swell, consolidation and compressibility, creep, stiffness and shear behaviour. The fabric analysis indicates that differences in the fabric of undisturbed and reconstituted gold tailings samples are visible. Moist tamping produces an aggregated fabric while slurry deposition yields a homogeneous fabric similar to that of the undisturbed samples. Comparison of behaviour indicates that neither moist tamping nor slurry deposition can replicate the behaviour of the undisturbed sample fully. Consolidation and compression is a function of the fabric while friction angle is independent of the fabric. Available shear strength and liquifaction potential is also affected by the preparation method and the resulting fabric. / Thesis (PhD)--University of Pretoria, 2009. / Civil Engineering / PhD / Unrestricted

A vehicle flying at hypersonic speeds, i.e. at speeds greater than Mach 4, needs to be able to withstand the heat arising from friction and shock waves, which can reach temperatures of up to 3000oC. The current project focuses on producing thermal protection systems based on ultra high temperature ceramic (UHTC) impregnated carbon-carbon composites. The carbon fibres offer low mass and excellent resistance to thermal shock; their vulnerability is to oxidation above 500oC. The aim of introducing HfB2, a UHTC, as a coating on the fibre tows or as particulate reinforcement into the carbon fibre preform, was to improve this property. The objectives of this project were to: i) identify a low temperature synthesis route for group IV diborides, ii) produce a powder fine enough to reduce the difficulties associated with sintering the refractory diborides, iii) develop sol-gel coating of HfB2 onto carbon fibre tows iv) improve the solid loading of the particulate reinforcement into the carbon fibre preform, which should, in turn, increase the oxidation protection. In order to achieve the above set objectives, fine HfB2 powder was synthesized through a low temperature sol gel and boro/carbothermal reduction process, using a range of different carbon sources. Study of the formation mechanism of HfB2 revealed an intermediate boron sub-oxide and/or active boron formation that yielded HfB2 formation at 1300oC. At higher temperatures the formation of HfB2 could be via intermediate HfC formation and/or B4C formation. Growth mechanism analysis showed that the nucleated particles possessed screw dislocations which indicated that the formation of HfB2 was not only through a substitution reaction, but there could have been an element of a precipitation nucleation mechanism that lead to anisotropic growth under certain conditions. The effect of carbon sources during the boro/carbothermal reduction reaction on the size of the final HfB2 powders was analysed and it was found that a direct relation existed between the size and level of agglomeration of the carbon sources and the resulting HfB2 powders. A powder phenolic resin source led to the finest powder, with particle sizes in the range 30 to 150 nm. SPS sintering of the powder revealed that 99% theoretical density could be achieved without the need for sintering aids at 2200oC. Sol-gel coatings and slurry impregnation of HfB2 on carbon fibres tows was performed using dip coating and a 'squeeze-tube' method respectively. Crack free coatings and non-porous matrix infiltration were successfully achieved. The solid loading of the fine HfB2 into the carbon fibre preform was carried out through impregnation of a HfB2 / phenolic resin/acetone slurry using vacuum impregnation. Although the sub-micron Loughborough (LU) powders were expected to improve the solid loading, compared to the commercially available micron sized powders, due to the slurry made from them having a higher viscosity because of the fine particle size, the solids loading achieved was consequently decreased. Optimisation of the rheology of the slurry with LU HfB2 still requires more work. A comparison of the oxidation and ablation resistance of the Cf-HfB2 composites prepared with both commercial micron sized HfB2 powder and Loughborough sub-micron sized HfB2 powder, each with similar level of solid loading, was carried out using oxyacetylene torch testing. It was found that the composite containing the finer, Loughborough powders suffered a larger erosion volume than the composite with the coarser commercial powders indicating that the former offered worse ablation and oxidation resistance than the latter. A full investigation of the effect of solids loading and particle size, including the option of using mixtures of fine and coarse powders, is still required.

Den här rapporten presenterar ett examensarbete som har utförts på Boliden Mineral AB. Arbetet handlar om att förbättra pumphoarnas konstruktion för att minimera slitage och sedimentering av slurryn. Pumphoarna sitter i anslutning till slurrypumparna i anrikningsverket för att reglera flödet av slurry. Arbetet följer Boliden Mineral ABs egna projektmodell, från början till slut. Syftet med projektet är att få bättre kunskap om pumphoarna, hur slurryn rör sig samt hur och var slitage uppstår. Målet med projektet är att utveckla en standardiserad design av pumphoar för slurrypumpning, samt att standardisera sättet för att ta fram dessa i framtiden. Nuvarande konstruktion av Bolidenområdets pumpho utvärderas med hjälp av CFD-simuleringar. Resultatet visar slitage som uppstår vid pumphons inlopp, områden där sedimentering kan förekomma samt strömlinjer för partiklarna i slurryn. Nya koncept för att förbättra pumphons konstruktion tas fram. Koncepten genereras för att minimera slitaget vid inloppet på pumphon samt minska risken för sedimentering av slurryn. De framtagna koncepten utvärderas med hjälp av CFD-simuleringar, på samma sätt som för den nuvarande konstruktionen. Koncepten jämfördes sedan med den nuvarande pumphon. En kombination av två koncept valdes som den slutgiltiga konstruktionen då den uppfyllde arbetets mål bäst.

Slush is a two phase flow of solid particles (crystals) and liquid at the triple point temperature, and constitutes an appealing alternative to liquid propellants for space launchers. The crystals give to the mixture higher density and lower specific enthalpy than liquid, enabling reduced tank volume storage and larger fuel holding time. However, the presence of solid crystals significantly modifies the thermo-hydraulics of the fuel transport, and requires novel predictive tools and diagnostic techniques for efficiently exploiting slush propellants. This thesis contributes to both aspects. In particular, this work studied the flow pressure losses and the heat transfer of solid-liquid mixtures in pipelines, combining experimental and numerical methods. Hydraulic and thermal flow features were analyzed separately with substitute mixtures chosen to mimic the behavior of slush flows in engine fuel feed systems. A dedicated facility was designed and built. The pipeline mounted conventional probes for pressure, temperature and mass flow rate measurements. Moreover, a capacitance-based density meter was developed and validated to measure the mixture's solid content. Optical flow visualization and image processing routines were combined to retrieve particulate phase distribution and velocity fields. The experimental work was complemented with 3D Unsteady Reynolds Averaged Navier Stokes simulations in OpenFOAM. The simulations coupled the Euler-Euler approach with the granular kinetic theory for the treatment of the solid dispersed phase. The model was validated with the experimental results on the pressure drop, heat transfer and solid volume fraction.The resulting physical insights and the proposed empirical correlations on the pressure drop and heat transfer in solid-liquid flows contribute to move a step forward towards slush propelled space launchers. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

This diploma thesis deals with the solution of ammonia separation from waste raw materials of agricultural production. It focuses on determining the efficiency of desorption from an experimental stripping device depending on the measurement temperature. Ammonia water solutions and liquid digestate samples from technical practice were used to verify the functionality of the equipment. Increasing separation efficiency with increasing temperature has been demonstrated. The device was gradually improved during the measurement for a better profitability of the separation process. The results of the experiments are discussed concerning the theoretical assumptions and compared with other methods of ammonia separation.

This master’s thesis is concerned about the flow of hydro-mixture in pipelines. In the first part, I am reviewing the characteristics of disperse systems, pumps and pipelines used in hydro-mixture transportation. Slurry pumps and polyethylene HDPE pipelines receive an extra attention. In the second part, I am working with data obtained from the co-operation with the PROGROUPE Sediment Removal company. These data were measured during revitalization of the water dam Gabčíkovo. In the next step, I use the data to suggest the required characteristic for the slurry pump for pump station in project of revitalizing Borovoe lake, situated in Kazakhstan.

Heat transfer and flow characteristics of phase change material slurry flow in microchannels with constant heat flux at the base were investigated. The phase change process was included in the energy equation using the effective specific heat method. A parametric study was conducted numerically by varying the base fluid type, particle concentration, particle size, channel dimensions, inlet temperature, base heat flux and melting range of PCM. The particle distribution inside the microchannels was simulated using the diffusive flux model and its effect on the overall thermal performance of microchannels was investigated. Experimental investigation was conducted in microchannels of 101 [micro]m width and 533 [micro]m height with water as base fluid and n-Octadecane as PCM to validate the key conclusions of the numerical model. Since the flow is not fully developed in case of microchannels (specifically manifold microchannels, which are the key focus of the present study), thermal performance is not as obtained in conventional channels where the length of the channel is large (compared to length of microchannels). It was found that the thermal conductivity of the base fluid plays an important role in determining the thermal performance of slurry. The effect of particle distribution can be neglected in the numerical model under some cases. The performance of slurry depends on the heat flux, purity of PCM, inlet temperature of the fluid, and base fluid thermal conductivity. Hence, there is an application dependent optimum condition of these parameters that is required to obtain the maximum thermal performance of PCM slurry flows in microchannels.

A novel concept has been developed for the direct carbon fuel cell (DCFC) based on molten carbonate recirculating electrolyte. In the cathode, co-current flow of electrolyte with entrained gases carbon dioxide and oxygen is sent in the upward direction through a porous bed grid. In the anode, co-current flow of a slurry of electrolyte entrained with carbon particles is sent in the downward direction through a porous bed grid. The gases carbon dioxide and oxygen in the cathode react on the grid surface to form carbonate ions. The carbonate ions are then transported via conduction to the anode for reaction with carbon to produce carbon dioxide for temperatures under 750 deg C. A mathematical model based on this novel DCFC concept has been developed. The model includes governing equations that describe the transport and electrochemical processes taking place in both the anode and cathode and a methodology for solving these equations. Literature correlations from multi-phase packed-bed chemical reactors were used to estimate phase hold-up and mass transfer coefficients. CO production and axial diffusion were neglected. The results demonstrated that activation and ohmic polarization were important to the cell output. The impact of concentration polarization to the cell output was comparatively small. The bed depths realized were of the order of 10cm which is not large enough to accommodate the economies of scale for a large scale plant, however thousands of smaller cells (10 m^2 area) in series could be built to scale up to a 10 MW industrial plant. Limiting current densities of the order of 1000-1500 A/m^2 were achieved for various operating conditions. Maximum power densities of 200-350 W/m^2 with current densities of 500-750 A/m^2, and cell voltages of 0.4-0.5 V have been achieved at a temperature of 700 deg C. Over temperatures ranging from 700 to 800 deg C, results from the modeled cell are comparable with results seen in the literature for direct carbon fuel cells that are similar in design and construction. / Ph. D.

In this doctoral dissertation, two laser-based sensors were evaluated for different applications. Laser Induced Incandescence (LII) is a technique which can provide nonintrusive quantitative measurement of soot and it provides a unique diagnostic tool to characterize engine performance. Since LII is linearly proportional to the soot volume fraction, it can provide in situ, real time measurement of soot volume fraction with high temporal and spatial resolution. LII has the capability to characterize soot formation during combustion. The soot volume fraction from both flames and a soot generator was investigated with LII. The effects of experimental parameters, such as laser fluence, gate delay, gate width and various laser beam focusing, on LII signal was studied. Laser Induced Breakdown Spectroscopy (LIBS), a diagnostic tool for in situ elemental analysis, has been evaluated for on-line, simultaneous, multi-species impurity monitoring in hydrogen. LIBS spectra with different impurity levels of nitrogen, argon, and oxygen were recorded and the intensity of the spectral lines of Ar, O, N, and H observed were used to form calibration plots for impurities in hydrogen measurements. An ungated detection method for LIBS has been developed and applied to equivalence ratio measurements of CH4/air and biofuel/air. LIBS has also been used to quantitatively analyze the composition of a slurry sample. The quenching effect of water in slurry samples causes low LIBS signal quality with poor sensitivity. Univariate and multivariate calibration was performed on LIBS spectra of dried slurry samples for elemental analysis of Mg, Si and Fe. Calibration results show that the dried slurry samples give good correlation between spectral intensity and elemental concentration.