Hindered-bed separators have been used in several different mineral processing fields for many years. Recent improvements in designs have led to the development of the CrossFlow separator. This new design employs a tangential feed system that has shown promise in several applications. This paper investigates the use of this relatively new technology to upgrade heavy mineral concentrates using Florida type ores. The intended use of this separatory device in this particular application is the removal of gangue quartz from other valuable heavy minerals such as ilmenite, leucoxene, rutile, zircon, and staurolite. The results of two different pilot-scale in-plant testing investigations are discussed. In general, quartz rejections in excess of 80% were achieved while maintaining TiO2 and heavy mineral recoveries above 98% and 99%, respectively. In addition to field test work, two separate unit models have been developed. The first model is an empirical investigation into understanding unit operation and functionality. The second model is a statistical prediction of unit operation based on specific field test work. These models can be used to effectively scale-up a CrossFlow unit for full-scale installation at any Florida heavy mineral sands operation. Emphasis is placed on unit capacity and other operational parameters such as elutriation flowrate and bed level. / Master of Science

This Research explores hydrogen combustion in a Jet-in-Crossflow configuration through computational fluid dynamics using ANSYS Fluent commercial CFD software. Three fuel-only hydrogen jets with a momentum flux ratio J of 10, 50, and 115 were introduced axially, using a large eddy simulation with a WALE sub grid model. Detailed chemistry was computed directly with a 9 species hydrogen/air kinetic mechanism. The 4mm jet and crossflow domain utilized an automatic mesh adaptation method centered around the flame shear layer. The study models the second stage of a lab-scale gas turbine test facility at a pressure level of 5atm,a crossflow temperature of 1620K, and crossflow velocity of 75m/s. The models were compared to physical experiments conducted and analyzed with line-of-sight CH* chemiluminescence to create more insight into the phenomena of the combustion process. Flame position along the windward and leeside stabilization points were overlaid, and the validated CFD model utilized to characterize reaction progress as a function of jet entrainment with hot oxidizer. At elevated momentum flux ratio, increased reaction rates along the shear layer of the diffusion flame were attributed to the enhanced contact area between the fuel jet and crossflow oxidizer. The results outline the potential of carbon-free combustion technology and highlight the importance of tuning the operating condition for application in gas turbines.

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Many fuel spray characterization studies to date have been conducted in quiescent environments with single-hole fuel injectors. However, in actuality, multi-hole injectors spray into direct injection engine cylinders where significant air swirling and tumbling exist to promote fuel atomization and air-fuel mixing, which result in more efficient combustion. For this reason, researchers have begun developing correlations for fuel sprays where a jet of air acts perpendicularly to the fuel spray, also known as a cross airflow or crossflow, so as to more realistically predict fuel spray characteristics in direct injection engines. Accordingly, there is a need for a foundation of experimental data reflecting the specific conditions of fuel spray in cross airflow which can then be used for model validation and future engine design and development. In this study, fuel sprays are characterized with a commercial 8-hole fuel injector in a wind tunnel enclosure capable of cross airflows upwards of 200m/s. Particle image velocimetry was used to measure air velocities and capture pulsed spray events of biodiesel, diesel, and biodiesel-diesel blend fuels. Spray images were processed and analyzed in LaVision's DaVis and in MATLAB to calculate spray penetration length and axis deflection angle under varying cross airflow velocities, fuel injection pressures, and fuel types. Results show that strong cross airflows can decrease spray penetration by up to 44% and deflect the spray axis by up to 10.5° when compared to the same spray in a quiescent environment. Additional experiments reveal that biodiesel experiences slower spray progression when compared with diesel, resulting in shorter spray penetrations in the early phase of the spray development (up to 0.7ms after the start of injection, or ASOI). The angle between the fuel injector axis and the air jet axis plays an important role in determining the resultant spray characteristics. This angle should be considered in future correlations.

Transverse jets in crossflow are widely used to enhance mixing between two flow streams. Such jets exhibit complex flow features, and are highly sen- sitive to a wide variety of operating conditions. The focus of this work is the mixing of relatively low Reynolds number jets that are often encountered in the chemical processing industry. The main objective is to determine if the the jet mixing characteristics can be sufficiently altered by changing the nature of the jet inflow. In particular, we study the effect of jet shape and inflow veloc- ity profile on the mixing properties. Four different jet shapes including circle, square, upstream triangle, and downstream triangle are considered. It is found that the jet shape has tremendous impact on the near field dynamics, gener- ating unique vortical structures for each shape. However, the overall mixing rate is unaffected and is controlled by the evolution of the coherent vortex pair (CVP) in the far-field of the jet. Analyses of turbulence modeling constraints and structure of reaction zones for consecutive-competitive reactions are also presented. / text

Many fuel spray characterization studies to date have been conducted in quiescent environments with single-hole fuel injectors. However, in actuality, multi-hole injectors spray into direct injection engine cylinders where significant air swirling and tumbling exist to promote fuel atomization and air-fuel mixing, which result in more efficient combustion. For this reason, researchers have begun developing correlations for fuel sprays where a jet of air acts perpendicularly to the fuel spray, also known as a cross airflow or crossflow, so as to more realistically predict fuel spray characteristics in direct injection engines. Accordingly, there is a need for a foundation of experimental data reflecting the specific conditions of fuel spray in cross airflow which can then be used for model validation and future engine design and development. In this study, fuel sprays are characterized with a commercial 8-hole fuel injector in a wind tunnel enclosure capable of cross airflows upwards of 200m/s. Particle image velocimetry was used to measure air velocities and capture pulsed spray events of biodiesel, diesel, and biodiesel-diesel blend fuels. Spray images were processed and analyzed in LaVision's DaVis and in MATLAB to calculate spray penetration length and axis deflection angle under varying cross airflow velocities, fuel injection pressures, and fuel types. Results show that strong cross airflows can decrease spray penetration by up to 44% and deflect the spray axis by up to 10.5° when compared to the same spray in a quiescent environment. Additional experiments reveal that biodiesel experiences slower spray progression when compared with diesel, resulting in shorter spray penetrations in the early phase of the spray development (up to 0.7ms after the start of injection, or ASOI). The angle between the fuel injector axis and the air jet axis plays an important role in determining the resultant spray characteristics. This angle should be considered in future correlations.

The effect of a nozzle’s internal geometry was studied experimentally to determine the breakup of the emitted water jet when it was injected perpendicularly into a quiescent atmosphere or a subsonic air crossflow. The nozzle’s diameter, nominal surface roughness, length-to-diameter ratio and contraction angle were varied, together with the injection pressure, to find the water column’s breakup length. Photographs of the water jet at the nozzle’s exit, gave a clue as to identify the occurrence of cavitation and a hydraulic flip. On the other hand the water column’s breakup length and trajectory, in a subsonic crossflow, were measured by using a stroboscope in conjunction with a high speed CCD camera. Results agreed with previous literature that the breakup length grew with greater liquid/air momentum flux ratios for non-cavitating flows. This was true regardless of the injector nozzle. The rate of increase decreased at the inception of cavitation. On the other hand even shorter breakup lengths were observed at the inception of a hydraulic flip due to the detachment of the water jet from the internal surface of the nozzle. Increasing the nozzle’s length-to-diameter ratio eliminated the occurrence of hydraulic flip. The jet’s trajectory was correlated with the liquid/air momentum flux ratio and the nozzle’s exit diameter. The results showed that higher water jet trajectories were measured under non-cavitating conditions. Even shorter jet trajectories were measured at the inception of a hydraulic flip.

The effect of a nozzle’s internal geometry was studied experimentally to determine the breakup of the emitted water jet when it was injected perpendicularly into a quiescent atmosphere or a subsonic air crossflow. The nozzle’s diameter, nominal surface roughness, length-to-diameter ratio and contraction angle were varied, together with the injection pressure, to find the water column’s breakup length. Photographs of the water jet at the nozzle’s exit, gave a clue as to identify the occurrence of cavitation and a hydraulic flip. On the other hand the water column’s breakup length and trajectory, in a subsonic crossflow, were measured by using a stroboscope in conjunction with a high speed CCD camera. Results agreed with previous literature that the breakup length grew with greater liquid/air momentum flux ratios for non-cavitating flows. This was true regardless of the injector nozzle. The rate of increase decreased at the inception of cavitation. On the other hand even shorter breakup lengths were observed at the inception of a hydraulic flip due to the detachment of the water jet from the internal surface of the nozzle. Increasing the nozzle’s length-to-diameter ratio eliminated the occurrence of hydraulic flip. The jet’s trajectory was correlated with the liquid/air momentum flux ratio and the nozzle’s exit diameter. The results showed that higher water jet trajectories were measured under non-cavitating conditions. Even shorter jet trajectories were measured at the inception of a hydraulic flip.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / In Latin America, the lack of electricity has been a serious problem for over several years. To overcome this lack of supply in electricity supply, hydraulic energy is now being used in a greater proportion to fulfill the electricity needs in the rural areas. Investigations have been conducted to assess the environmental conditions of these rural areas to optimize the functionality of turbines used for hydraulic energy generation. However, there are very few focused on turbines of less than 0.5 kW generation. The proposed study aims to analyze the positioning of the blades of the cross-flow turbines and designing an electric generation system for rural dwellings. A simulation of each evaluated design was performed, and the power generated from these turbines was calculated. The results show that the power outputs initially were high and stabilized at a value of approximately 180 W, hence satisfying the minimum demands of a rural house.

Jet-in-crossflow is an interaction between a fuel jet and air crossflow commonly found in jet engines. The crossflow is used to break up or atomize the fuel jet for downstream combustion. This interaction between fluids while at low speeds, is predictable, varies greatly at higher speeds. This investigation seeks to (1) create a mechanism for jet-in-crossflow, using mechanical pintles, that is independent of velocity to help increase the predictability and reliability of jet engines and (2) identify key design parameters that will lead to flow independence. Parameters investigated in this experiment include pintle height, angle, and percent of pintle coverage into the jet orifice. Pintles that covered 100 percent of the jet showed a strong deviation from the traditional interaction with no pintle. Relationships were also found between the angle, height, and penetration depth although none as ubiquitous as the jet coverage.