9,771 research outputs found

    Ultra High Strength Steels for Roll Formed Automotive Body in White

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    One of the more recent steel developments is the quenching and partitioning process, first proposed by Speer et al. in 2003 on developing 3rd generation advanced high-strength steel (AHSS). The quenching and partitioning (Q&P) process set a new way of producing martensitic steels with enhanced austenite levels, realised through controlled thermal treatments. The main objective of the so-called 3rd generation steels was to realise comparable properties to the 2nd generation but without high alloying additions. Generally, Q&P steels have remained within lab-scale environments, with only a small number of Q&P steels produced industrially. Q&P steels are produced either by a one-step or two-step process, and the re-heating mechanism for the two-step adds additional complexities when heat treating the material industrially. The Q&P steels developed and tested throughout this thesis have been designed to achieve the desired microstructural evolution whilst fitting in with Tata’s continuous annealing processing line (CAPL) capabilities. The CALPHAD approach using a combination of thermodynamics, kinetics, and phase transformation theory with software packages ThermoCalc and JMatPro has been successfully deployed to find novel Q&P steels. The research undertaken throughout this thesis has led to two novel Q&P steels, which can be produced on CAPL without making any infrastructure changes to the line. The two novel Q&P steels show an apparent reduction in hardness mismatch, illustrated visually and numerically after nano-indentation experiments. The properties realised after Q&P heat treatments on the C-Mn-Si alloy with 0.2 Wt.% C and the C-Mn-Si alloy with the small Cr addition is superior to the commercially available QP980/1180 steels by BaoSteel. Both novel alloys had comparable levels of elongation and hole expansion ratio to QP1180 but are substantially stronger with a > 320MPa increase in tensile stress. The heat treatment is also less complex as there is no requirement to heat the steel back up after quenching due to one-step quenching and partitioning being employed on the novel alloys

    Process intensification of oxidative coupling of methane

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    Hydrodynamic scales of integrable many-particle systems

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    1. Introduction, 2. Dynamics of the classical Toda lattice, 3. Static properties, 4. Dyson Brownian motion. , 5. Hydrodynamics for hard rods, 6. Equations of generalized hydrodynamics, 7. Linearized hydrodynamics and GGE dynamical correlations, 8. Domain wall initial states, 9. Toda fluid, 10. Hydrodynamics of soliton gases, 11. Calogero models, 12. Discretized nonlinear Schr\"odinger equation , 13. Hydrodynamics for the Lieb-Liniger δ\delta-Bose gas, 14. Quantum Toda lattice, 15. Beyond the Euler time scaleComment: 178 pages, 12 Figures. This a much enlarged and substantially improved version of arXiv:2101.0652

    Coating and hydrodynamics of random column packing Dixon rings

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    In this thesis, three main objectives were covered using experiments and modelling studies. Firstly, the coating of Dixon rings cheaply and repeatably using alumina sol-gel. Secondly, the new understanding of fluid flow over curved wire meshes. Thirdly, the effect of Dixon rings on process parameters such as pressure drop, liquid holdup and mass transfer coefficient were investigated using experiments and model. Packed columns are filled with solid structures to improve the heat and mixing of multiphase processes. The packing usually interacts with the fluid, increasing the mixing but creating a pressure drop. Packing are typically evaluated based on their hydrodynamic behavior, such as pressure drop, liquid holdup, and mass transfer coefficient. Packing with low-pressure drop, high mass transfer, and high flooding velocities are the preferred choice for users. Wire mesh packing are an example of packing that offer low-pressure drop and increased mass transfer. The pore openings in the mesh provide a path for the gas to flow, resulting in good mixing and low-pressure drop. Dixon rings are an example of wire mesh packings made of stainless steel and rolled into a cylindrical shape with a bisecting section in the middle. The stainless-steel structure of Dixon rings makes them resistant to high temperature and chemical constraints. Packing with such properties has great potential in water treatment, hydrocracking, and more. However, the hydrodynamic behavior of Dixon rings has not been investigated deeply in the literature. Secondly, a new understanding of fluid flow on a microscale and macroscale over curved surface of the wire mesh was achieved. The macroscale experiments were conducted in a semi-pilot plant with gas and liquid flow in counter-current for the uncoated Dixon rings. The effect of Dixon rings on pressure drop, liquid holdup, and mass transfer were measured and compared to commercial packing of similar size and material. The microscale study was focused on the liquid flow distribution, which is critical in the design and operation of packed columns. The liquid flow distribution changes the packing's wetting efficiency, affecting several hydrodynamic parameters, such as the liquid holdup and the effective surface area. The liquid wetting efficiency was evaluated using imaging experiments and CFD simulations for the coated and uncoated Dixon rings. The flow regime and several hydrodynamic parameters such as liquid holdup, effective surface area, and pressure drop were anticipated to affect the mass transfer capabilities highly. Finding smaller unit operations is required to cut down the global emission. It is not a surprise that process intensification is needed in packed columns. Packing with a tunable surface can achieve both hydrophobic and hydrophilic properties that are highly desired due to their tendency to control the liquid dispersion and wetting properties. Changing the surface properties using uniform coating is a common approach to produce tunable contact angle and surface wetting. Coating metals have been fraught with difficulties, and Dixon rings have a complex geometry which hinders their use in many applications, specifically when a coating is required. This research considered the application of a uniform adhesive coating via the sol-gel deposition method of alumina on Dixon rings. The coated film was investigated for the first time on stainless steel wire mesh for use as Dixon rings. The kinetics of deposition of the sol-gel was followed for a range of initial compositions of the coating, such as the ratios of alumina to water, acid content, polyethyleneimine binder content and the number of deposition cycles. The coated Dixon rings were characterised by surface optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Brunauer, Emmett and Teller (BET). Adhesive tests included assessing coating behaviour against shear forces, ultrasound, and temperature constraints. Well-adhered alumina with a thickness of up to 20 µm was successfully deposited. Imaging experiments and 3D volume-of-fluid modelling investigated the microscale behaviour of liquid flow over coated and uncoated Dixon rings. An alumina coating modified the surface of the wire mesh ring to reach both hydrophilic and hydrophobic characteristics. The contact angle was varied due to the coating and resulted in different mass and heat exchanges of the multiphase chemical systems. The cycle of capillary droplet flow over the uncoated ring exhibited penetration of the hydrophilic mesh openings, adherence to the surface of the ring, and accumulation as drips at the bottom region of the rings. However, over the hydrophobic ring, the droplet exhibited low adherence to the ring surface, accumulation at the top surface of the ring, no penetration of the openings, slipping by the gravitational forces over the vertical curvature and accumulation as drips at the bottom region. In agreement with the classical observations at the macroscale, the observations at the pore-scale confirmed the increase of the wetting efficiency, liquid holdup and effective surface area at increased liquid flowrate and reduced contact angle. The 3D model had a relative deviation of 7.21 % with Stichlmair’s model for the liquid holdup, particularly in the hydrophilic zone of the contact angle and low flow as well as a relative deviation of 14.24% with Linek’s model for effective area, particularly in the hydrophobic range of the contact angle. Considering the results at the pore scale, the packing material was then investigated at a larger scale using the non-coated Dixon rings exclusively. The hydrodynamic and mass transfer properties for Dixon rings packing are not currently available within the literature. A semi-pilot plant was used to evaluate the pressure drop, the liquid holdup, and the mass transfer coefficient for Dixon rings packing 5/8 and 1/4 in. The study was extended to various operational conditions for gas and liquid counter-current flow. The results were compared to commercial random packing and validated, showing that Dixon rings offer low-pressure drop, high liquid holdup, and mass transfer coefficient. This study successfully investigated a method to coat metallic wire mesh packing using sol-gel. The thickness and distribution of the coating were investigated by a parametric analysis for several ratios such as the acid, water, and Al content. Microscopic and SEM tests showed that the coating has a uniform thickness, and adhesive tests were conducted to ensure the coating is well attached to the Dixon rings’ surface. This coating method can be used for any type of metallic wire mesh substrate to produce alumina coating with tunable thickness. A microscopic study was implemented to investigate the liquid flow behaviour for coated and uncoated Dixon rings using a 3D VOF model and imaging experiments. The liquid holdup and the effective surface area from the 3D model were compared to results from the literature. The coated Dixon rings have a hydrophobic nature, while the uncoated rings have hydrophilic properties. The pressure drop, liquid holdup and mass transfer value were reported for Dixon rings for the first time on a macroscopic level. Based on the experimental data, models were developed to predict the dry pressure drop and the loading point. The model showed good reliability with a SE less than 5

    Investigation of microparticle behavior in Newtonian, viscoelastic, and shear-thickening flows in straight microchannels

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    Sorting and separation of small substances such as cells, microorganisms, and micro- and nano-particles from a heterogeneous mixture is a common sample preparation step in many areas of biology, biotechnology, and medicine. Portability and inexpensive design of microfluidic-based sorting systems have benefited many of these biomedical applications. Accordingly, we have investigated microparticle hydrodynamics in fluids with various rheological behaviors (i.e., Newtonian, shear-thinning viscoelastic and shear-thickening non-Newtonian) flowing in straight microchannels. Numerical models were developed to simulate particles trajectories in Newtonian water and shear-thinning polyethylene oxide (PEO) solutions. The validated models were then used to perform numerical parametric studies and non-dimensional analysis on the Newtonian inertia-magnetic and shear-thinning elasto-inertal focusing regimes. Finally, the straight microfluidic device that was tested for Newtonian water and shear-thinning viscoelastic PEO solution, were adopted to experimentally study microparticle behavior in SiO2/Water shear-thickening nanofluid

    Optimisation of Triboelectric Nanogenerator performance in vertical contact-separation mode

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    Triboelectric nanogenerator (TENG) is one of the most promising energy harvesters – a technology that uses repeated or reciprocating contact of suitably chosen materials to generate charge via the triboelectric effect (TE) and utilizes this as usable voltage and current. TENGs are attractive as they can continuously generate charge over a wide range of operating conditions and have several valuable advantages such as light weight, simple structure, low cost and high efficiency. Therefore, TENGs have been explored in a wide range of applications, including self-powered wearable electronics, powering electronics and even for harvesting ocean wave/wind energy. One of the major limitations of TENGs is their low power output (usually <500 W/m2). This thesis focuses of a few specific approaches to optimising TENG output performance. This thesis begins by presenting a solution to this challenge by optimizing a low permittivity substrate beneath the tribo-contact layer. The open circuit voltage is found to increase by a factor of 1.3 in moving from PET to the lower permittivity PTFE. TENG performance is also believed to depend on contact force, but the origin of the dependence had not previously been explored. Herein, we show that this behaviour results from a contact force dependent real contact area Ar as governed by surface roughness. The open circuit voltage Voc, short circuit current Isc and Ar for a TENG were found to increase with contact force/pressure. Critically, Voc and Isc saturate at the same contact pressure as Ar suggesting that electrical output follows the same evolution as Ar. Assuming that tribo charges can only transfer across the interface at areas of real contact, it follows that an increasing Ar with contact pressure should produce a corresponding increase in the electrical output. These results underline the importance of accounting for real contact area in TENG design, as well as the distinction between real and nominal contact area in tribo-charge density definition. High-performance ferroelectricassisted TENGs (Fe-TENGs) are developed using electrospun fibrous surfaces based on P(VDFTrFE) with dispersed BaTiO3 (BTO) nanofillers in either cubic (CBTO) or tetragonal (TBTO) form in this thesis. TENGs with three types of tribo-negative surface were investigated and output increased progressively. Critically, P(VDF-TrFE)/TBTO produced higher output than P(VDFTrFE)/ CBTO even though permittivity is nearly identical. Thus, it is shown that BTO fillers boost output, not just by increasing permittivity, but also by enhancing the crystallinity and amount of the β-phase (as TBTO produced a more crystalline β-phase present in greater amounts)

    Response of saline reservoir to different phaseCOâ‚‚-brine: experimental tests and image-based modelling

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    Geological CO₂ storage in saline rocks is a promising method for meeting the target of net zero emission and minimizing the anthropogenic CO₂ emitted into the earth’s atmosphere. Storage of CO₂ in saline rocks triggers CO₂-brine-rock interaction that alters the properties of the rock. Properties of rocks are very crucial for the integrity and efficiency of the storage process. Changes in properties of the reservoir rocks due to CO₂-brine-rock interaction must be well predicted, as some changes can reduce the storage integrity of the reservoir. Considering the thermodynamics, phase behavior, solubility of CO₂ in brine, and the variable pressure-temperature conditions of the reservoir, there will be undissolved CO₂ in a CO₂ storage reservoir alongside the brine for a long time, and there is a potential for phase evolution of the undissolved CO₂. The phase of CO₂ influence the CO₂-brine-rock interaction, different phaseCO₂-brine have a unique effect on the properties of the reservoir rocks, Therefore, this study evaluates the effect of four different phaseCO₂-brine reservoir states on the properties of reservoir rocks using experimental and image-based approach. Samples were saturated with the different phaseCO₂-brine, then subjected to reservoir conditions in a triaxial compression test. The representative element volume (REV)/representative element area (REA) for the rock samples was determined from processed digital images, and rock properties were evaluated using digital rock physics and rock image analysis techniques. This research has evaluated the effect of different phaseCO₂-brine on deformation rate and deformation behavior, bulk modulus, compressibility, strength, and stiffness as well as porosity and permeability of sample reservoir rocks. Changes in pore geometry properties, porosity, and permeability of the rocks in CO₂ storage conditions with different phaseCO₂-brine have been evaluated using digital rock physics techniques. Microscopic rock image analysis has been applied to provide evidence of changes in micro-fabric, the topology of minerals, and elemental composition of minerals in saline rocks resulting from different phaseCO₂-br that can exist in a saline CO₂ storage reservoir. It was seen that the properties of the reservoir that are most affected by the scCO₂-br state of the reservoir include secondary fatigue rate, bulk modulus, shear strength, change in the topology of minerals after saturation as well as change in shape and flatness of pore surfaces. The properties of the reservoir that is most affected by the gCO₂-br state of the reservoir include primary fatigue rate, change in permeability due to stress, change in porosity due to stress, and change topology of minerals due to stress. For all samples, the roundness and smoothness of grains as well as smoothness of pores increased after compression while the roundness of pores decreased. Change in elemental composition in rock minerals in CO₂-brine-rock interaction was seen to depend on the reactivity of the mineral with CO₂ and/or brine and the presence of brine accelerates such change. Carbon, oxygen, and silicon can be used as index minerals for elemental changes in a CO₂-brine-rock system. The result of this work can be applied to predicting the effect the different possible phases of CO₂ will have on the deformation, geomechanics indices, and storage integrity of giant CO₂ storage fields such as Sleipner, In Salah, etc
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