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Author: Richard Gould
Publisher:
ISBN:
Category :
Languages : en
Pages : 8
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Book Description
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.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
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.
Author: Miguel A. Rivas
Publisher:
ISBN:
Category :
Languages : en
Pages : 84
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Book Description
Author: N.A. Fuchs
Publisher: Elsevier
ISBN: 1483225631
Category : Science
Languages : en
Pages : 81
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Book Description
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.
Author: Weikai Gu
Publisher:
ISBN:
Category : Catalytic cracking
Languages : en
Pages : 654
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Book Description
Author: Saptarshi Basu
Publisher: Springer
ISBN: 9811074496
Category : Technology & Engineering
Languages : en
Pages : 433
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Book Description
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.
Author: David M. Mann
Publisher:
ISBN:
Category : Chemical reactions
Languages : en
Pages : 302
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Book Description
Partial contents: Supercritical droplet behavior; Fundamentals of acoustic instabilities in liquid-propellant rockets; Modeling liquid jet atomization proceses; Liquid-propellant droplets dynamics and combustions in supercritical forced convective environments; Contributions of shear coaxial injectors to liquid rocket motor combustion instabilities; High pressure combustion studies under combustion driven oscillatory flow conditions; Droplet collision on liquid propellant combustion; Combustion and plumes; Development of a collisional radiative emission model for strongly nonequilibrium flows; Energy transfer processes in the production of excited states in reacting rocket flows; modeling nonequilibrium radiation in high altitude plumes; kinetics of plume radiation, and of HEDMs and metallic fuels combustion; Nonsteady combustion mechanisms of advanced solid propellants; Chemical mechanisms at the burning surface. p15
Author: Crystal Buchanan Dale
Publisher:
ISBN:
Category : Fluid mechanics
Languages : en
Pages : 322
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Book Description
Author: Michael S. Dodd
Publisher:
ISBN:
Category :
Languages : en
Pages : 199
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Book Description
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.
Author: United States. National Advisory Committee for Aeronautics
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 324
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Book Description
Author: Frederic William Hartwig
Publisher:
ISBN:
Category : Drops
Languages : en
Pages : 68
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Book Description
