2 edition of Evaluation of a locally homogeneous model of spray evaporation found in the catalog.
Evaluation of a locally homogeneous model of spray evaporation
A. J Shearer
1979 by National Aeronautics and Space Administration, Scientific and Technical Information Office, For sale by the National Technical Information Service] in Washington, D.C, [Springfield, Va .
Written in English
|Statement||A.J. Shearer and G.M. Faeth ; prepared for Lewis Research Center under grant NGR 39-009-077|
|Series||NASA contractor report -- 3198|
|Contributions||Faeth, G. M, United States. National Aeronautics and Space Administration. Scientific and Technical Information Office, Lewis Research Center|
|The Physical Object|
|Pagination||ix,  p. :|
|Number of Pages||104|
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Evaluation of a locally homogeneous model of spray evaporation. Washington, D.C.: National Aeronautics and Space Administration, Scientific and Technical Information Office ; [Springfield, Va.: For sale by the National Technical Information Service], (OCoLC) Material Type: Government publication, National government publication.
Measurements were conducted on an evaporating spray in a stagnant environment. The spray was formed using an air-atomizing injector to yield a Sauter mean diameter of the order of 30 microns. The region where evaporation occurred extended approximately 1 m from the injector for the test conditions.
Profiles of mean velocity, temperature, composition, and drop size distribution, as well Cited by: 8. A model of spray evaporation which employs a second-order turbulence model in conjunction with the locally homogeneous flow approximation, which implies infinitely fast interphase transport rates is by: 7.
A simplified model of high pressure spray combustion Symposium (International) on Combustion, Vol. 18, No. 1 Evaluation of a locally homogeneous flow model of spray combustionCited by: A model of spray evaporation based on the locally homogeneous flow assumption and a second order turbulence model was developed and evaluated against a wide range of experimental conditions.
The turbulence was represented by a k-epsilon-g model employing a clipped Gaussian probability density function for mixture fraction by: 7.
Evaluation of a locally homogeneous model of spray evaporation Measurements were conducted on an evaporating spray in a stagnant environment.
The spray was formed using an air-atomizing injector to yield a Sauter mean diameter of the order of 30 microns.
The region where evaporation occurred extended approximately 1 m from the injector for. Evaluation of a locally homogeneous model of spray evaporation. Abstract. A model of spray evaporation which employs a second-order turbulence model in conjunction with the locally homogeneous flow approximation, which implies infinitely fast interphase transport rates is presented.
Measurements to test the model were completed for single. Back to Results. Evaluation of a locally homogeneous model of spray evaporation A model of spray evaporation which employs a second-order turbulence model in conjunction with the locally homogeneous flow approximation, which implies infinitely fast interphase transport rates is presented.
Measurements to test the model were completed for single phase constant and variable. Water spray evaporation model. evaporation in homogeneous and heterogeneous bubbling. regimes. Part II: dynamic simulation. Experimental evaluation on half-scale prototypes of these towers.
Wongsarivej, W. Tanthapanichakoon, A model for a non-uniform spray evaporator taking into account the effect of non-isothermal polydisperse droplets, International Journal of Heat and Mass Transfer, /masstransfer, 90, (), ().
Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems Evaporation is accounted for via a droplet evaporation sub-model which runs in parallel with the gas-phase solver exchanging data with it.
J., and Faeth, G. M.,“Evaluation of Locally Homogeneous Model for Spray Evaporation,” NASA. Stefan flow effect is important in high evaporation rates, while the infinite conductivity model (ICM) predicted accurately a wide range of experimental data. Evaporation modeling. The Spalding’s evaporation rate is used, coupled with an equation for the temperature of the droplet + droplet’s temperature equation D 2-law.
In the present work, an unified derivation of simple evaporation models used in spray simulation is described and a new evaporation model is formulated. In the model, the Nusselt number, Sherwood number, and evaporation mass flux are derived using the traditional film theory.
The evaporation of spray droplets is a phase transition process by which molecules in a liquid overcome their intermolecular attraction forces and escape into the surrounding gaseous environment.
Self-similar pressure-atomized sprays - Volume - H. Hinterbichler, H. Steiner, G. Brenn. In the homogeneous model, the droplets movement adopts the gas velocity and can be easier to carry by the gas.
Thus the spatial distribution of the droplets is much wider in the homogeneous model than that in the Lagrangian model. Download: Download high-res image (KB) Download: Download full-size image; Fig.
The comparison of the spray. The model overcomes problems of high computational demand, normally required in the implementation of chemical kinetics models describing low-temperature alkane oxidation.
Two test cases are computationally simulated: a “single” spray evaporation case, serving to validate the CFD code, and a “cool flame evaporation” case, used for. The model was created with Balas® simulation software linked with MS Excel.
The description of the model is presented in PowerPoint slides, ChemSep – report slides. This document, instead, acts as a theory source for the use of the model. In this document, the classification of separation processes into heterogeneous and homogeneous separation.
ABSTRACT. This work presents an implementation and evaluation of the Σ-Υ atomization model for Diesel spray CFD simulations. The Σ-Υ model is based on an Eulerian representation of the spray atomization and dispersion by means of a single-fluid variable density turbulent flow within a RANS framework.
The locally homogeneous flow approach has been applied in order to develop a spray vaporization model. First, the evaporation of a single droplet is considered from a general point of view by means of the conservation equations for mass, species and energy of the liquid and gas phases.
Subsequently, additional assumptions and simplifications are discussed which lead to simpler evaporation models suitable for use in CFD spray calculations. Liquid evaporation is involved in numerous processes, including the water cycle, coating processes, dryers, and combustion.
This phenomenon is characterized by continuous energy and mass transfer in a wide range of scales .Hence, the complexity of evaporation makes its modeling cumbersome in the scale of a practical device, leading to the need for model simplification .
Evaporation. See also what's at Wikipedia, your library, or elsewhere. Broader terms: Chemistry; Moisture; Evaluation of a locally homogeneous model of spray evaporation / (Washington, Evaluation of the effects of surface water and groundwater interactions on regional climate and local water resources /.
The mathematical model considers the evaporation and ignition of a monodispersed spray cloud in a homogeneous gas phase. To isolate the effect of preferential evaporation from transport in the gaseous mixture we consider the droplet evaporation into a homogeneous gas phase.
Spray evaporation model sensitivities ﬁltered and represents an average over the computational cell in which the drop resides. Y d,s is the mass fraction of gas-phase fuel at the drop’s surface. A frequently used model.
The ignition criterion, which judges the droplet stage between pure evaporation and burning, and the droplet combustion correlation, which integrates the micro-scales droplet burning effects into point source term frame, are both selected from pioneer’s experimental work and added to the present existing widely used multi-phase combustion model.
Hence, the rate of droplet evaporation is equal to the rate of vapour diffusion from the droplet surface to ambient gas. These are known as the hydrodynamic models of droplet evaporation. The analysis starts with empirical correlations which are not directly linked with any evaporation model.
A theoretical model for exergy analysis of the process of spray evaporation has been developed to predict the second law efficiency of the process in terms of pertinent controlling parameters like free stream temperature, initial Reynolds number and initial drop size distribution of the spray.
Model results are supported by our experimental results and concur with previously published studies which, in general, show suppressed evaporation rates (on the order of tens of percentage points) for saline solutions from a free surface [Salhotra et al., ], as well as from homogeneous porous media [e.g., Chen, ; Fujimaki et al., To support such a conjecture, we performed a set of simulations in which evaporation of cloud water was allowed to proceed as in a traditional model (i.e., the delay of evaporation was excluded by assuming ).
Prescribed mixing scenarios with α = 0 and α = 1 were used as in SGPM12 in the mixing-related part of the total cloud evaporation. evaporation than the film evaporation. Smaller is the droplet size; greater is the rate of evaporation and to achieve the smaller droplet size, a mist spray nozzle,and the spinning disc is used to generate fine mist spray at a very low pressure of water.
In fine mist evaporation method, each fine water particle is covered with an air. McNaughton, Evaporation and advection II: evaporation downwind of a boundary separating regions having different surface resistances and available energies, Quarterly Journal of the Royal Meteorological Society, /qj, (), ().
were performed for droplets in homogeneous isotropic turbulent non-reacting ﬂows . Two approaches were proposed to approx- imate the instantaneous carrier ﬂuid velocity ﬁeld. One approach is a random walk model, in which the instantaneous velocity is rep- resented as the sum of the local mean (or LES-ﬁltered) velocity.
A Model-Based Analysis on Size Distribution and Rate of Evaporation for Fuel Drops in a Gasoline Spray in the Engine Good understanding of fuel sprays in the engine cylinder is crucial to optimizing the operation of direct injection gasoline engines. Drag-law: Dynamic model. In-nozzle Flow Homogeneous Relaxation Model (HRM) Time step Variable based on spray, evaporation, combustion processes.
Turbulence-chemistry interactions model. Direct Integration of detailed chemistry: well-mixed model. Representative Interactive Flamelet (RIF) Model. Understanding and prediction of flash-boiling spray behavior in gasoline direct-injection (GDI) engines remains a challenge.
In this study, computational fluid dynamics (CFD) simulations using the homogeneous relaxation model (HRM) for not only internal nozzle flow but also external spray. The model accounts for the behavior of the spray zone and fuel evaporation including sub-models for spray breakup, improved zone velocity estimations with transient fuel injection, spray penetration and tracking of evaporated fuel components.
Each sub-model deals with multi-component fuel surrogates to simulate the real fuel effects. LIST OF TABLES M" o, 0 Table No. Effects of Recirculation Liquor Solids Predicted Effect of Surface Tension on the Penetration through a Venturi Scrubber Performance Evaluation Parameters Routine Inspection Points Fan Data Temperature Correction Major Types of Wet Scrubbers Preformed Scrubber Evaluatclon^Data^.
^.•., Packed Tower Evaluation During the s, with new advances in turbulence research in hand (e.g., Monin and Obukhov ), simple models of duct height were able to exploit a theoretical framework describing surface-layer temperature and humidity profiles for diabatic us groups—for example, in the United States, Japan, Germany, and the former Soviet Union—quickly set up evaporation-duct.
The data is compared to local site data for significant differences. Then the maximum pond temperature is predicted. Five programs model performance of an ultimate heat sink spray pond. The cooling performance, evaporative water loss, and drift water loss as a function of windspeed are estimated for a spray.
In this study, a systematic flash boiling spray model for a multi-hole injector is built to investigate the flash boiling spray. The key physics involved in flash boiling, including bubble formation, bubble growth, as well as bubble breakup are added to the traditional spray model in KIVA-3V to describe the development process of flash boiling spray.
The nozzle produces a homogeneous fuel spray with wider cone patterns up to 68° and finer droplet sizes less than 22 microns. The concentration of fuel droplets is a few orders of magnitude lower vs.
conventional Diesel sprays. These spray patterns result in higher mixing /evaporation rates.A turbulent methanol/air spray flame is simulated using the present method.
Detailed chemistry is implemented through the spray flamelet model. The precalculated spray flamelet library for methanol/air combustion comprises 23 species and elementary reactions.
Thus, the model is capable of predicting the formation of radicals and of pollutants. Here, u(z) is the mean velocity of the flow at the level z, τ is the tangential stress at the spray–sea boundary, and ρ is the air rmore, α s is an analog of the turbulent Prandtl number, which we will assume constant and equal to 2; γ is a constant that was evaluated from the experimental data for the flow of a homogeneous fluid, γ ≃ ; a is the velocity of the free.