Download or read book Droplet Vaporization in Turbulent Flow written by Jung-Kyu Park and published by . This book was released on 1987 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fluid Dynamics and Transport of Droplets and Sprays written by W. A. Sirignano and published by Cambridge University Press. This book was released on 1999-07-28 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt: An authoritative review of the science and technology of droplets and sprays.

Download or read book Droplet Evaporation in an Active Turbulence Grid Wind Tunnel written by Ferran Marti Duran and published by . This book was released on 2012 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, we develop and test an experimental apparatus capable of examining the effect of turbulence on the evaporation of droplets when the Kolmogorov scale is smaller than the size of the drop (where size refers to the nominal droplet diameter). Traveling drop and suspended drop cases have been studied experimentally and the evaporation rate has also been predicted based on classical computations of transport rates. Cases involving still air, a mean flow with turbulence, and a mean flow without turbulence have been tested. The experimental data matches the theoretical computations for the case of still air and mean flow with no turbulence. There is no accepted computational model that can account for turbulent flow, but the experimental conditions tested so far do not show any measurable effect of turbulence on the evaporation rate. These findings suggest that turbulence is a much smaller factor in evaporation than is mean flow over the droplet. Hence, one suggestion for future work is to study traveling droplets with zero relative velocity to the air in order to focus the analysis on the effects of turbulence with no mean flow.

Download or read book An Experimental Investigation of the Effect of Fuel Droplet Size on the Vaporization Process in a Turbulent Environment at Elevated Temperature and Pressure written by Cameron Mark Verwey and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The performance of liquid-fuelled spray combustion systems has a massive impact on the efficiency of energy production in many sectors across the globe. Realistic combustors generate sub 100-μm droplets and operate under high pressure and temperature in strong turbulence. Investigations into droplet evaporation and combustion provide fundamental knowledge and validation data regarding the behaviour of sprays, and although single droplet approaches have been a staple of energy research for many decades, there is little information regarding the effect of turbulence and initial diameter, especially micro-sized, on droplet evaporation rates. The present experimental study develops, interprets, and correlates the results of almost 500 tests performed on isolated heptane and decane droplets. Droplets in the range of 110 - 770 μm (initial diameter) were generated and suspended on small intersecting micro-fibers in a spherical fan-driven chamber and exposed to quasi-zero mean turbulence of intensity up to 1.5 m/s, temperatures ranging from 25 - 100°C, and pressures between 1 and 10 bar. The results indicate that droplet size has a major influence on evaporation rate, as measured by the temporal reduction in droplet surface area, when the environment is turbulent. Evaporation rates increased with both initial diameter and turbulence intensity at all test conditions. The effectiveness of turbulence, defined as the ability of turbulence to improve the evaporation rate over the rate of a stagnant droplet at identical ambient conditions, increased with pressure but decreased with temperature. Both the ratio of Kolmogorov length scale to droplet diameter and the theoretical molar concentration gradient of fuel at the droplet surface are found to be excellent predictors of turbulence effectiveness. Correlation approaches utilizing a turbulent Reynolds number or a vaporization Damköhler number are suggested to predict the evaporation rate of a single droplet exposed to a purely turbulent flow field.

Download or read book Measurements of Droplet Vaporization in Sprays written by and published by . This book was released on 2000 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: AASERT funding was used to support graduate student research in the area of spray droplet vaporization. Droplet lasing spectroscopy (DLS) was applied to the measurement of droplet size and vaporization rates in both reacting and non-reacting rectilinear droplet streams. Ethanol, methanol and a pentane/ethanol mixture were doped with Rhodamine 6G. Lasing spectra were examined in the steady state combustion regime. In the pentane/ethanol case, measurements were carried out in a sooting region of the flame. In some cases, vaporization rates were high enough to measure the rate from consecutive droplets, yielding a quasi-instantaneous measurement. In all cases, the D2 law of droplet vaporization was evident. In addition, photographs of the flames yielded measurements of flame height and thickness. In the final year of support, a triggering and timing system was developed so that the DLS method could be applied a turbulent flow in which the trajectory and location of the tagged, fluorescent droplets was uncertain.

Download or read book Dynamics of Droplets written by Arnold Frohn and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book deals with the dynamical behaviour of single droplets and regular droplet systems. It has been written mainly for experimental researchers. After a short description of the theoretical background, the different experimental facilities and methods necessary for the investigation of single droplets are described in detail. A summary of important applications is included.

Download or read book Evaporation and Droplet Growth in Gaseous Media written by N.A. Fuchs and published by Elsevier. This book was released on 2013-10-22 with total page 81 pages. Available in PDF, EPUB and Kindle. Book excerpt: Evaporation and Droplet Growth in Gaseous Media deals with the evaporation of droplets of liquid in gaseous media and the reverse process of droplet growth in a medium supersaturated with the vapor of the liquid. Thediscussion is restricted to the kinetics of evaporation and growth of droplets of pure liquids (and heat transfer to the same). Comprised of three chapters, this book first examines the quasi-stationary evaporation and growth of droplets that are motionless relative to the medium and the hydrodynamic factor is absent. The Maxwell equation, the basis of the theory of evaporation of droplets in a gaseous medium, is taken into account. The influence of the Stefan flow and the concentration change at the surface on the rate of evaporation are considered, along with the evaporation of droplets in a vessel with absorbing walls and the fall in temperature of both free evaporating droplets and supported evaporating droplets. The second chapter is devoted to the quasi-stationary evaporation of droplets in a stream of gas, that is, droplets moving relative to the medium. The last chapter focuses on non-stationary evaporation and growth of droplets that either motionless or moving relative to the medium. This monograph will be of interest to students, practitioners, and researchers in inorganic and structural chemistry.

Download or read book The Effect of Turbulence on Vaporization and Mixing in Fuel Sprays written by and published by . This book was released on 1995 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental study of droplet-turbulence interactions under simulated fuel spray conditions has been conducted. The behavior of individual droplets transversely injected into laminar and turbulent flows has been characterized by measuring droplet position, shape and size as a function of time. From these measurements new information has been obtained on the effects of vaporization and unsteady curvilinear motion on droplet drag and lift in laminar flows. These measurements have also provided new data which characterize the effects of turbulence on droplet drag, dispersion and secondary breakup. jg.

Download or read book The Evaporation of Liquid Droplets in Highly Turbulent Gas Streams written by Richard Gould and published by . This book was released on 1998 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Single acetone and heptane droplets were suspended from a hypodermic needle in turbulent airflow, and the Nusselt number was obtained from direct measurements of the droplet diameter and evaporation rate. Acetone was selected because it fluoresces when irradiated with ultraviolet laser radiation while heptane was selected because of its high volatility compared with water, methanol, and ethanol which were used previously. Planar laser induced fluorescence (PLIF) measurements were made to obtain qualitative concentration measurements of gaseous acetone in the boundary layer surrounding the droplet. The goal of these measurements was to give insight as to why the evaporation rate is increased by 50 % when the gas phase turbulence is increased from the laminar flow case to the case where the freestream turbulence is 10%. The use of acetone droplets required that the influence of humidity on droplet evaporation rate be considered. Measurements of the turbulence intensity of heated freestream air were also made. Finally, many modifications to improve the experimental apparatus were made during this research project.

Download or read book Fluid Dynamics and Transport of Droplets and Sprays written by W. A. Sirignano and published by Cambridge University Press. This book was released on 2010-01-11 with total page 481 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses the theoretical foundations of spray and droplet applications relevant to the technology for active control of sprays applied to new products and applications, improved product performance, cost reductions, and improved environmental outcomes. It also covers theory related to power and propulsion; materials processing and manufacturing technologies including droplet-based net form processing, coating, and painting; medication; pesticides and insecticides; and other consumer uses.

Download or read book Direct Numerical Simulation of Droplet laden Isotropic Turbulence written by Michael S. Dodd and published by . This book was released on 2017 with total page 199 pages. Available in PDF, EPUB and Kindle. Book excerpt: Interaction of liquid droplets with turbulence is important in numerous applications ranging from rain formation to oil spills to spray combustion. The physical mechanisms of droplet-turbulence interaction are largely unknown, especially when compared to that of solid particles. Compared to solid particles, droplets can deform, break up, coalesce and have internal fluid circulation. The main goal of this work is to investigate using direct numerical simulation (DNS) the physical mechanisms of droplet-turbulence interaction, both for non-evaporating and evaporating droplets. To achieve this objective, we develop and couple a new pressure-correction method with the volume-of-fluid (VoF) method for simulating incompressible two-fluid flows. The method's main advantage is that the variable coefficient Poisson equation that arises in solving the incompressible Navier-Stokes equations for two-fluid flows is reduced to a constant coefficient equation. This equation can then be solved directly using, e.g., the FFT-based parallel Poisson solver. For a $1024^3$ mesh, our new pressure-correction method using a fast Poisson solver is ten to forty times faster than the standard pressure-correction method using multigrid. Using the coupled pressure-correction and VoF method, we perform direct numerical simulations (DNS) of 3130 finite-size, non-evaporating droplets of diameter approximately equal to the Taylor lengthscale and with 5~\% droplet volume fraction in decaying isotropic turbulence at initial Taylor-scale Reynolds number $\Rey_\lambda=83$. In the droplet-laden cases, we vary one of the following three parameters: the droplet Weber number based on the r.m.s. velocity of turbulence ($0.1 \leq \Webrms \leq 5$), the droplet- to carrier-fluid density ratio ($1 \leq \rho_d/\rho_c \leq 100$) or the droplet- to carrier-fluid viscosity ratio ($1 \leq \mu_d/\mu_c \leq 100$). We derive the turbulence kinetic energy (TKE) equations for the two-fluid, carrier-fluid and droplet-fluid flow. These equations allow us to explain the pathways for TKE exchange between the carrier turbulent flow and the flow inside the droplet. We also explain the role of the interfacial surface energy in the two-fluid TKE equation through work performed by surface tension. Furthermore, we derive the relationship between the power of surface tension and the rate of change of total droplet surface area. This link allows us to explain how droplet deformation, breakup and coalescence play roles in the temporal evolution of TKE. We then extend the code for non-evaporating droplets and develop a combined VoF method and low-Mach-number approach to simulate evaporating and condensing droplets. The two main novelties of the method are: (i) the VOF algorithm captures the motion of the liquid gas interface in the presence of mass transfer due to evaporation and condensation without requiring a projection step for the liquid velocity, and (ii) the low-Mach-number approach allows for local volume changes caused by phase change while the total volume of the liquid-gas system is constant. The method is verified against an analytical solution for a Stefan flow problem, and the $D^2$ law is verified for a single droplet in quiescent gas. Finally, we perform DNS of an evaporating liquid droplet in forced isotropic turbulence. We show that the method accurately captures the temperature and vapor fields in the turbulent regime, and that the local evaporation rate can vary along the droplet surface depending on the structure of the surrounding vapor cloud. We also report the time evolution of the mean Sherwood number, which indicates that turbulence enhances the vaporization rate of liquid droplets.

Download or read book Droplets and Sprays written by Saptarshi Basu and published by Springer. This book was released on 2017-12-11 with total page 433 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on droplets and sprays relevant to combustion and propulsion applications. The book includes fundamental studies on the heating, evaporation and combustion of individual droplets and basic mechanisms of spray formation. The contents also extend to the latest analytical, numerical and experimental techniques for investigating the behavior of sprays in devices like combustion engines and gas turbines. In addition, the book explores several emerging areas like interactions between sprays and flames and the dynamic characteristics of spray combustion systems on the fundamental side, as well as the development of novel fuel injectors for specific devices on the application side. Given its breadth of coverage, the book will benefit researchers and professionals alike.

Download or read book Effect of Flow Turbulence on Evaporation Rate of a Single Droplet written by A. V. Eckartsberg and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Droplet Wetting and Evaporation written by David Brutin and published by Academic Press. This book was released on 2015-05-11 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt: Droplet Wetting and Evaporation provides engineers, students, and researchers with the first comprehensive guide to the theory and applications of droplet wetting and evaporation. Beginning with a relevant theoretical background, the book moves on to consider specific aspects, including heat transfer, flow instabilities, and the drying of complex fluid droplets. Each chapter covers the principles of the subject, addressing corresponding practical issues and problems. The text is ideal for a broad range of domains, from aerospace and materials, to biomedical applications, comprehensively relaying the challenges and approaches from the different communities leading the way in droplet research and development. - Provides a broad, cross-subject coverage of theory and application that is ideal for engineers, students and researchers who need to follow all major developments in this interdisciplinary field - Includes comprehensive discussions of heat transfer, flow instabilities, and the drying of complex fluid droplets - Begins with an accessible summary of fundamental theory before moving on to specific areas such as heat transfer, flow instabilities, and the drying of complex fluid droplets

Download or read book Droplet Turbulence Interactions in Sprays Exposed to Supercritical Environmental Conditions written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-02 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this research was to experimentally characterize the behavior of droplets in vaporizing sprays under conditions typical of those encountered in high pressure combustion systems such as liquid fueled rocket engines. Of particular interest are measurements of droplet drag and lift, droplet dispersion, droplet heating, and droplet vaporization under both subcritical and supercritical conditions. A summary of the major accomplishments achieved during the period from June 1990 through June 1993, a brief description and status report on five research areas, which were directly or indirectly supported by this grant, and a list of publications and personnel associated with this research is included. Santavicca, Domenic A. Unspecified Center NAG8-160...

Download or read book Technology of Forced Flow and Once through Boiling written by Heinz Frank Poppendiek and published by . This book was released on 1975 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Droplet Transport in Turbulent Pipe Flow written by Theodore Ginsberg and published by . This book was released on 1971 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: