http://calliope.dem.uniud.it/CLASS/EPFL-COURSE/Tomyama-Zun-CES-2002.pdf

Transverse migration of single bubbles in simple shear flows

Current status of droplet and liquid combustion

The present understanding of spray combustion in rocket engine, gas turbine, Diesel engine and industrial furnace applications is reviewed. In some cases, spray combustion can be modeled by ignoring the details of spray evaporation and treating the system as a gaseous diffusion flame; however, in many circumstances, this simplification is not adequate and turbulent two-phase flow must be considered. The behavior of individual droplets is a necessary component of two-phase models and recent work on transient droplet evaporation, ignition and combustion is considered, along with a discusssion of important simplifying assumptions involved with modeling these processes. Methods of modeling spray evaporation and combustion processes are also discussed including: one-dimensional models for rocket engine and prevaporized combustion systems, lumped zone models (utilizing well-stirred reactor and plug flow regions) for gas turbine and furnace systems, locally homogeneous turbulent models, and two-phase models. The review highlights the need for improved injector characterization methods, more information of droplet transport characteristics in turbulent flow and continued development of more complete two-phase turbulent models.

Terminal velocity of single bubbles in surface tension force dominant regime

An investigation of the effects of various physical properties, drop size, and drop velocity on drop shape was carried out for nonoscillating liquid drops falling through stationary liquid continuous phases. The data of forty-five dispersed-continuous phase systems were studied with continuous phase viscosities varying from 0.3 to 46 centipoise and interfacial tensions varying from 0.3 to 42 dyne/cm. A theoretical relation was obtained from the Taylor and Acrivos analysis which quite accurately predicts drop eccentricities for drop Reynolds numbers less than about 20, but is highly inaccurate at higher Reynolds numbers. Relatively simple empirical relations involving the Weber number, Eotvos number, and viscosity ratio were obtained which enable the prediction of the eccentricity of nonoscillating drops over a wide range of Reynolds numbers (6.0 to 1,354) with average deviations of 6 to 8%. These relations may be useful in the estimation of the interfacial area, velocity, and continuous phase mass transfer coefficient of drops distorted from spherical shape.

Shape of liquid drops moving in liquid media

A relatively simple and explicit mathematical expression has been developed for estimating the enhancement factors for mass transfer accompanied by a second-order irreversible chemical reaction. The development is based on asymptotic characteristics, i.e., limiting solutions, for second-order enhancement factors. The resulting mathematical relation and other approximate analytical formulations previously presented in the literature have been critically compared with a numerical solution for the diffusion-reaction process based on film theory.



On a mis au point une expression mathematique relativement simple et explicite pour evaluer les facteurs de promotion d'un transfert de masse accompagne d'un reaction chimique irreversible et de second ordre. Ledit developpement est base sur des caracteristiques asymptotiques, c'est-a-dire des solutions limiteuses, pour les facteurs de promotion de second ordre. On a compare d'une maniere critique la relation mathematique qui en resulte, et d'autres formulations analytiques et approximatives anterieurement presentees dans la litterature, avec une solution numerique pour le procede de reaction et diffusion base sur la theorie des pellicules.

Enhancement factors for gas‐absorption with second‐order irreversible chemical reaction

All existing relations describing mass transfer within oscillating droplets were critically compared with experimental data in which resistance to transfer is predominantly inside the droplet Several new relations are also developed to estimate oscillating droplet extraction efficiencies, one of which is recommended in view of its theoretical appeal, accuracy, and ease of application

The most accurate relation currently available is an empirical expression developed by Skelland and Wellek

R. M. Wellek

Papers

Shape of liquid drops moving in liquid media

Enhancement factors for gas‐absorption with second‐order irreversible chemical reaction

Mass transfer within oscillating liquid droplets

Extraction with single turbulent droplets

Mass transfer inside liquid droplets and gas bubbles accompanied by a second‐order chemical reaction