10 research outputs found

    A NUMERICAL STUDY OF A NEW SPRAY APPLICATOR

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    This study focuses on the design and development of a new spray applicator design utilizing effects of imposed pressure oscillations in conjunction with cavitation collapse energy to create distribution of fine droplets. An oscillating horn placed inside the nozzle performing high frequency oscillations is envisioned to provide the necessary pressure perturbations on the exiting liquid jet, while the nozzle geometry design in configured to amplify cavitation process. Initially, a two-zone approach modeling the nozzle interior and exterior in a separate fashion and later, a coupled strategy is proposed. Parametric studies describing the effect of horn stroke length, frequency, its position inside the nozzle in combination with different nozzle designs and liquid flow rates are explored to identify their contribution in obtaining desired cavitation characteristics. In this regard, incorporation of a backward facing step profile within the nozzle shows strong capability of generating the required cavitation and flow field distribution at the nozzle exit. The velocity modulations occuring at the nozzle exit due to oscillating horn structure result in a wide gamut of liquid structures specific to the imposed oscillation frequency and modulation amplitude. The disintegration characteristics of these modulated liquid jets are studied using a Volume-of-Fluid (VOF) interface capturing approach based on finite volume methodology employing an interface compression scheme. VOF methods are validated against experimental results and then subsequently used to study scaling parameters governing the modulated liquid jets. To perform coupled interior-exterior nozzle computations with cavitation, two new cavitation models are presented: First, a model based on Homogeneous Equilibrium assumptions for tracking cavitation events in a compressible framework is presented. Owing to its inability to simulate incompressible cavitating flows, a new cavitation event tracking model based on a Cavitation-Induced-Momentum-Defect (CIMD) correction approach is formulated utilizing a scalar transport model for vapor volume fraction with relevant transport, diffusion and source terms. Validations of both the models against experimental observations are detailed. Coupled internal-external liquid flow computations from the proposed atomizer design using a VOF-CIMD strategy shows strong potential for rapid drop formation in the presence of cavitation effects. A prototype model of a new spray applicator design is presented

    Tidal Energy and Coastal Models: Improved Turbine Simulation

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    Marine renewable energy is a continually growing topic of both commercial and academic research sectors. While not as developed as other renewable technologies such as those deployed within the wind sector, there is substantial technological crossover coupled with the inherent high energy density of water, that has helped push marine renewables into the wider renewable agenda. Thus, an ever expanding range of projects are in various stages of development.As with all technological developments, there are a range of factors that can con-tribute to the rate of development or eventual success. One of the main difficulties, when looking at marine renewable technologies in a comparative view to other en-ergy generation technologies, is that the operational environment is physically more complex: Energy must be supplied in diverse physical conditions, that temporally fluctuate with a range of time scales. The constant questions to the iteration to the local ecology. The increased operational fatigue of deployed devices. The financial risk associated within a recent sector.This work presents the continual research related to the computational research development of different marine renewable technologies that were under develop-ment of several institutional bodies at the time of writing this document.The scope has a wide envelopment as the nature of novel projects means that the project failure rate is high. Thus, forced through a combination of reasons related to financial, useful purpose and intellectual property, the research covers distinct projects

    Turbine Engine Hot Section Technology, 1984

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    Presentations were made concerning the hot section environment and behavior of combustion liners, turbine blades, and waves. The presentations were divided into six sessions: instrumentation, combustion, turbine heat transfer, structural analysis, fatigue and fracture, and surface properties. The principal objective of each session was to disseminate research results to date, along with future plans. Topics discussed included modeling of thermal and fluid flow phenomena, structural analysis, fatigue and fracture, surface protective coatings, constitutive behavior, stress-strain response, and life prediction methods

    Flow Control for Loads Control

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    Six Decades of Flight Research: An Annotated Bibliography of Technical Publications of NASA Dryden Flight Research Center, 1946-2006

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    Titles, authors, report numbers, and abstracts are given for nearly 2900 unclassified and unrestricted technical reports and papers published from September 1946 to December 2006 by the NASA Dryden Flight Research Center and its predecessor organizations. These technical reports and papers describe and give the results of 60 years of flight research performed by the NACA and NASA, from the X-1 and other early X-airplanes, to the X-15, Space Shuttle, X-29 Forward Swept Wing, X-31, and X-43 aircraft. Some of the other research airplanes tested were the D-558, phase 1 and 2; M-2, HL-10 and X-24 lifting bodies; Digital Fly-By-Wire and Supercritical Wing F-8; XB-70; YF-12; AFTI F-111 TACT and MAW; F-15 HiDEC; F-18 High Alpha Research Vehicle, F-18 Systems Research Aircraft and the NASA Landing Systems Research aircraft. The citations of reports and papers are listed in chronological order, with author and aircraft indices. In addition, in the appendices, citations of 270 contractor reports, more than 200 UCLA Flight System Research Center reports, nearly 200 Tech Briefs, 30 Dryden Historical Publications, and over 30 videotapes are included

    Index to 1983 NASA Tech Briefs, volume 8, numbers 1-4

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    Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1983 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

    Modelling challenges of stationary combustion in inert porous media

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    Thanks to strong heat recirculation, submerged combustion within porous media presents unique technological features such as broadened flammability limits and extended power range. The associated possibility to burn ultra-lean mixtures with minimal CO/NOx emissions makes porous media combustion a potential alternative in the industry, for instance in domestic heat generation or clean aviation where low pollutant emissions and robust operability are of paramount importance. However, even though this combustion mode has been studied for decades, there remains many open questions regarding the intertwined flame structure and the validity of associated low-order modelling. To date, volume-averaged models are mostly based upon ad hoc hypotheses and still present large discrepancies with experiments. Aiming to chal- lenge and strengthen these models, the present work presents analytical and numerical studies of the volume-averaged equations, followed by 3D direct pore-level simulations of methane-air and hydrogen-air combustion. Chapters 1 and 2 provide a critical review of concepts associated to flows and flames within porous media, with a focus on non-adiabatic combustion and macroscopic effective characteriza- tion. A classification of gaseous flames in terms of the thermal Péclet number is proposed, and the upscaling procedure on the pointwise equations is presented. Chapter 3 presents asymptotic results based on the volume-averaged equations, and the proposed theoretical framework un- veils the first fully-explicit formulae for flame speed in infinite and finite-length porous burners. Multi-layered burners are also considered theoretically for the first time, and the important con- cept of contact resistance between two stacked porous plates is underlined. Chapter 4 proposes a general classification of porous media combustion in three distinct regimes for increasing inter- phase heat transfer, only based on two reduced parameters, in order to reconcile the literature frameworks of local thermal equilibrium (LTE) and non-equilibrium (LTNE). Chapter 5, 6 and 7 present 3D pore-level direct numerical simulations of flames within porous media using complex kinetics, for various structural topologies and pore sizes. As a major technical hurdle encountered during the thesis, the meshing workflow from X-ray tomography to conformal computational mesh is given for practical use in the community. These DNS unveil the internal flame structure of methane-air and hydrogen-air flames within typical porous burners, and it is shown that when the pore size is larger than the flame thickness, sharp and locally- anchored flame fronts are observed. These local discontinuities related to the strongly non-linear reaction rates are shown to be in direct violation of the classical volume-averaged hypotheses. This demonstrates that new volume-averaged models are required, and accordingly a closure for reaction rates based upon phenomenology and observations in the 3D DNS is proposed. Eventually, the pore-level specificities of hydrogen combustion at pore scale are described

    Aeronautical Engineering - A special bibliography with indexes /supplement 1/

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    Annotated reference bibliography on aeronautical engineering document
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