Download or read book Near Field Mixing Characteristics of a Variable Density Non Reacting Jet in a Hot Vitiated Crossflow written by Kyle T Linevitch (Jr) and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The mixing characteristics in the "extreme" near field of a non-reacting jet in crossflow were experimentally investigated in an environment relevant to gas turbine combustors. A turbulent jet was injected into a hot vitiated crossflow of combustion products at 1500K. Different jet-to-crossflow momentum flux ratios and jet-to-crossflow density ratios were studied using three different jet exit velocity profiles; a fully developed turbulent pipe flow with 4% turbulence intensity (TI), a top-hat flow with 8% TI, and a turbulent pipe-like flow with 40% TI. Center-plane scalar mixing of the jet and crossflow were investigated using measured temperature fields from planar laser Rayleigh scattering. Jet trajectory, centerline concentration decay, scalar dissipation and mixing time scales were determined as a function of the above-mentioned jet parameters to characterize the jet-crossflow mixing characteristics. The observed center-plane mixing metrics indicated that better near field mixing was exhibited for lower values of the momentum flux ratio and larger values of density ratio. As the momentum flux ratio increased, windward and leeward mixing decreased. The magnitude of scalar dissipation in the windward region decreased as the momentum flux increased, while the leeward dissipation region increased in size and magnitude as momentum flux ratio increased. When the density ratio was decreased, both the windward and leeward dissipation regions reduced in size and magnitude. The top-hat and turbulent pipe jet exit velocity profiles displayed similar mixing characteristics while the 40% TI profile exhibited deeper jet penetration, slower centerline concentration decay rates, and lower scalar dissipation.

Download or read book Flow Field and Mixing Characteristics of Multiple Reacting Jets in Vitiated Crossflow written by George M. Lapaan and published by . This book was released on 2014 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mixing and Structural Characteristics of Unforced and Forced Jets in Crossflow written by Takeshi Shoji and published by . This book was released on 2017 with total page 619 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes an experimental exploration of structural and mixing characteristics of the unforced as well as forced jet in crossflow (JICF). For unforced experiments, variable jet-to-crossflow density ratios (0.35 S 1.00) and momentum flux ratios (5 J 41) were explored, for three alternative injectors with a fixed jet Reynolds number (Rej=1900). For forced jet experiments, an equidensity jet emanating from two alternative flush nozzles (Rej=1900; Rej=1500) were explored. The interplay between scalar and velocity fields for the JICF was studied using simultaneous PLIF/stereo PIV measurements in the jet's centerplane. POD analysis showed a transition from convective to absolutely instability in the upstream shear layer as J was reduced, consistent with hotwire measurements. Local strain rates were extracted from both PLIF and PIV data via the Howarth transformation. Mixing characterization with variable mixing scale lengths was explored via centerplane PLIF images. Mixing associated with stirring as well as molecular mixing could be distinguished, apparent especially in vortical structures for flush pipe injection. Sinusoidal forcing of the convectively unstable JICF demonstrated that relatively low amplitude forcing affected jet structures and mixing, especially close to the fundamental frequency. For the absolutely unstable JICF, a much higher forcing amplitude was required to alter jet characteristics, consistent with lock-in, leading to enhanced molecular mixing. Single-pulse square wave forcing created deeply-penetrating vortical structures for specific stroke ratios (L/D), even for the absolutely unstable JICF. L/D producing the greatest jet spread and penetration decreased with decreasing J, but L/D for optimal molecular mixing corresponded to different values and trends in J. Double-pulse square wave excitation, with two variable pulses within each temporal period, enabled the jet's nearfield vortex rings to interact and collide, with attendant effect on molecular mixing.

Download or read book Optimization of Jet Mixing Into a Rich Reacting Crossflow written by M. Y. Leong and published by . This book was released on 1997 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Jet Mixing in a Reacting Cylindrical Crossflow written by M. Y. Leong and published by . This book was released on 1995 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimental Investigation of Crossflow Jet Mixing in a Rectangular Duct written by D. S. Liscinsky and published by . This book was released on 1993 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mixing of Pure Air Jets with a Reacting Fuel Rich Crossflow written by and published by . This book was released on 1997 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Liquid Jet in Oscillating Crossflow written by Arvindh R. Sharma and published by . This book was released on 2015 with total page 139 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental investigation of response characteristics of a liquid jet in oscillating crossflow is undertaken to understand the behavior of a liquid fuel spray in the presence of combustion instabilities. The effect of crossflow oscillations on the liquid jet is studied in the near-field (within x/d[approximately equal]8) and the far-field (x/d[approximately equal]50) spray region. Experiments are conducted in bag breakup, multimode and shear breakup regimes by varying crossflow Weber number from 18 to 250, while momentum flux ratio is varied between 10 and 30. The crossflow is modulated in the frequency range of 90 Hz to 450 Hz, with modulation level varying between 5% and 20%, using a mechanical modulating device. High speed shadowgraph is employed to study the near-field and far-field spray movement while intensified high-speed camera images of laser Mie-scattering intensity are utilized in studying the spray cross-section in the far-field. A technique to extract time-varying momentum flux ratio from the windward trajectory of liquid jet in the near-field is developed. The response of near-field spray is quantified in terms of a ratio of the observed momentum flux ratio extracted from a correlation of upper penetration to the expected momentum flux ratio corresponding to the instantaneous crossflow velocity. The liquid jet penetration is found to respond to oscillations in the crossflow at all oscillation frequencies in the near-field. The strength of the response is found to be mainly dependent on the crossflow oscillation frequency, with the strength of response decreasing with increase in frequency. The momentum flux ratio and the modulation level are found to have relatively negligible effects on the level of normalized spray response. The spray response in the far-field is studied by observing the high-speed shadowgraphs and Mie-scattering intensity images at an axial distance of x/d=50. The spray field in the axial location is divided into ten bins and the intensity change in each bin is analyzed to quantify spray response. The spray is found to respond to crossflow oscillations by exhibiting a "flapping" behavior in the far-field. The binning method and Mie-scattering intensity image analysis suggest that the spray oscillation decreases with increasing crossflow frequency. The spray width and height fluctuate in the spray cross-section in the presence of crossflow oscillation. The amplitude of spray height fluctuation is higher in low frequency crossflow, and decreases with an increase in frequency. The total Mie-scattering intensity in the cross-section also exhibits a periodic response to crossflow oscillation, suggesting that the droplet characteristics are affected by crossflow fluctuation. The liquid spray near-field and far-field study indicates that the crossflow oscillation frequency plays a large role in determining spray response.

Download or read book Effect of Jet Configuration on Transverse Jet Mixing Process written by Sin Hyen Kim and published by . This book was released on 2011 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Unsteady Combustor Physics written by Tim C. Lieuwen and published by Cambridge University Press. This book was released on 2012-08-27 with total page 427 pages. Available in PDF, EPUB and Kindle. Book excerpt: Developing clean, sustainable energy systems is a pre-eminent issue of our time. Most projections indicate that combustion-based energy conversion systems will continue to be the predominant approach for the majority of our energy usage. Unsteady combustor issues present the key challenge associated with the development of clean, high-efficiency combustion systems such as those used for power generation, heating or propulsion applications. This comprehensive study is unique, treating the subject in a systematic manner. Although this book focuses on unsteady combusting flows, it places particular emphasis on the system dynamics that occur at the intersection of the combustion, fluid mechanics and acoustic disciplines. Individuals with a background in fluid mechanics and combustion will find this book to be an incomparable study that synthesises these fields into a coherent understanding of the intrinsically unsteady processes in combustors.

Download or read book Experimental and Analytical Investigation of Near Field Coaxial Mixing written by and published by . This book was released on 1975 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the near field of coaxial jets, the structure of the flow field undergoes rapid changes as it evolves from the boundary layers at the nozzle exit, through a quasi-two-dimensional shear-layer region, to an axisymmetric jet flow. These rapid changes in flow structure have raised questions concerning the applicability of turbulent flow models in the near field, but few experimental results are available to test predictive techniques. In this report, the results of a series of experiments concerned with the near field of coaxial, nearly constant density, air-air jets are described. The experiments were carried out at an external stream velocity of 30.5 m/sec, and at nominal inner jet-to-outer jet velocity ratios of 3:1, 2:1, and 1:1.

Download or read book A Comprehensive Analysis of the Near Field Axisymmetric Jet Mixing Layer and the Flow Field Downstream of a Lobed Mixer Using a Pseudo Flow Visualization Method written by David P. Wick and published by . This book was released on 1991 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Effect of Hole Geometry on the Near Field Character of Crossflow Jets written by Brenda A. Haven and published by . This book was released on 1996 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Investigation of Field scale Convective Mixing Processes in Heterogeneous Variable density Flow Systems Using High resolution Adaptive Mesh Refinement Methods written by Douglas Jay Cosler and published by . This book was released on 2006 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Three-dimensional, field-scale (~ 100 m) convective mixing processes in heterogeneous porous media are examined. The focus is on fluid mixing rates and density-dependent macrodispersion, and the influence of small-scale (~ centimeters) instability development on large-scale variable-density flow and solute transport behavior. Dynamic adaptive mesh refinement methods (AMR) and a higher-order (solute advection term), mass-conservative Eulerian-Lagrangian discretization scheme for the solute transport equation are used to construct a new numerical code (DensTransAMR) that automatically adjusts to multiple scales of convective mixing processes by translating and adding/removing telescoping levels of progressively finer subgrids during a simulation. Because the flow and transport solutions for each subgrid are computed independently, field-scale simulations are broken into multiple smaller problems that can be modeled more efficiently and with finer detail. Two types of numerical experiments are performed: freshwater injection in a saltwater aquifer and dense fluid injection in a freshwater aquifer. Convective mixing rates are related to the geostatistical properties of the aquifer (variance and mean of the log permeability distribution, horizontal and vertical correlation scales), the fluid density difference, the magnitude of local small-scale dispersion, the effects of different permeability field realizations, the injection well size and orientation, hydraulic parameters such as injection rate and regional hydraulic gradient, and the spatial resolution. Convective mixing in heterogeneous porous media is shown to be more amenable to prediction than previously concluded. Computed three-dimensional fluid mixing rates are related to mathematical expressions for density-dependent macrodispersivity that are based on stochastic flow and solute transport theory and are a function of log permeability variance, the correlation scale, and a time-dependent parameter. Different instability patterns are generated when a different permeability field realization is used, the source location changes, or the mesh spacing is varied. However, long-term fluid mixing rates (i.e., after the mixing zone becomes large compared with the correlation scale) do not change if the fluid and macroscopic porous media properties (mean permeability, variance, and correlation lengths) remain constant. Porous media variability on scales smaller than the correlation lengths has an effect on the fluid mixing zone volume but does not affect long-term mixing rates.

Download or read book Manipulation and Control of Jets in Crossflow written by Ann R. Karagozian and published by Springer. This book was released on 2014-05-04 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fundamental Non-Reactive Jets in Crossflow and Other Jet Systems; Background on Modeling, Dynamical Systems, and Control; Reactive Jets in Crossflow and Multiphase Jets; Controlled Jets in Crossflow and Control via Jet Systems;

Download or read book Simulation of Turbulent Flows with and without Combustion with Emphasis on the Impact of Coherent Structures on the Turbulent Mixing written by Cunha Galeazzo, Flavio Cesar and published by KIT Scientific Publishing. This book was released on 2016-10-14 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: The analysis of turbulent mixing in complex turbulent flows is a challenging task. The effective mixing of entrained fluids to a molecular level is a vital part of the dynamics of turbulent flows, especially when combustion is involved. The work has shown the limitations of the steady-state simulations and acknowledged the need of applying high-fidelity unsteady methods for the calculation of flows with pronounced unsteadiness promoted by large-scale coherent structures or other sources.

Download or read book Multicomponent Flow Modeling written by Vincent Giovangigli and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 334 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this is book to give a detailed presentation of multicomponent flow models and to investigate the mathematical structure and properties of the resulting system of partial differential equations. These developments are also illustrated by simulating numerically a typical laminar flame. Our aim in the chapters is to treat the general situation of multicomponent flows, taking into account complex chemistry and detailed transport phe nomena. In this book, we have adopted an interdisciplinary approach that en compasses a physical, mathematical, and numerical point of view. In par ticular, the links between molecular models, macroscopic models, mathe matical structure, and mathematical properties are emphasized. We also often mention flame models since combustion is an excellent prototype of multicomponent flow. This book still does not pretend to be a complete survey of existing models and related mathematical results. In particular, many subjects like multi phase-flows , turbulence modeling, specific applications, porous me dia, biological models, or magneto-hydrodynamics are not covered. We rather emphasize the fundamental modeling of multicomponent gaseous flows and the qualitative properties of the resulting systems of partial dif ferential equations. Part of this book was taught at the post-graduate level at the Uni versity of Paris, the University of Versailles, and at Ecole Poly technique in 1998-1999 to students of applied mathematics.