3 edition of Effects of turbulence mixing, variable properties, and vaporization on spray droplet combustion found in the catalog.
Effects of turbulence mixing, variable properties, and vaporization on spray droplet combustion
1990 by Dept. of Mechanical Engineering, University of Alabama in Huntsville in Huntsville, AL .
Written in English
|Statement||Y.M. Kim and T.J. Chung.|
|Series||NASA-CR -- 186463., NASA contractor report -- NASA CR-186463.|
|Contributions||Chung, T. J., 1929-, United States. National Aeronautics and Space Administration.|
|The Physical Object|
Two-dimensional direct numerical simulation is applied to spray flames stabilized in a laminar counterflow, and the detailed behavior is studied in terms of the droplet group combustion. The stretch ratio of the laminar counterflow is 40 l/s. n-decane (C10H22) is used as a liquid spray fuel, and a one-step global reaction is employed for the combustion reaction model. Despite progress in laser-based and computational tools, an accessible model that relies on fundamentals and offers a reasonably accurate estimation of droplet size and velocity is lacking, primarily due to entangled complex breakup mechanisms. Therefore, this study aims at using the integral form of the conservation equations to create a system of equations by solving which, the far-field. In K. K. Kuo (Ed.), Recent Advances in Spray Combustion. Vol. (pp. ). AIAA Progress in Astronautics and Aeronautics. C. M., Rangel, R. H. (). Non-Ideal Vaporization of Dilating Binary Droplets with Variable Properties. Int. J. Heat Flame and Droplet Interaction Effects during Droplet-Stream Combustion at Zero. Transient heating and liquid-phase mass diffusion in droplet vaporization. In: Zung, JT (ed.) Evaporation combustion of fuels (Advances in chemistry series, vol. ). Washington, DC: American Chemical Society, , pp. 3 – Google Scholar | Crossref.
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The effect of the turbulence is caused mainly by producing more uniform spatial distribution of droplets and reducing the interdroplet interactions which hamper droplet vaporization. Faster evaporation leads to the situation where both the fuel and air mix Cited by: Get this from a library.
Effects of turbulence mixing, variable properties, and vaporization on spray droplet combustion. [Y M Kim; T J Chung; United States.
National Aeronautics and. Download Citation | Effects of turbulence on dispersion and vaporization of droplets in spray combustion | Interactions between liquid-fuel spray combustion and turbulent fluctuations were.
Firstly, the effects of turbulence intensity variations on the turbulent droplet dispersion, vaporization and mixing for non-reacting sprays (with and without swirl) are pointed out. The objective of this work is twofold. Firstly, the effects of turbulence intensity variations on the turbulent droplet dispersion, variable properties and mixing for non-reacting sprays (with and without swirl) are pointed out.
Secondly, the effects of the coupling of the turbulence modulation with external parameters, such as swirl intensity, on turbulent spray combustion are analyzed in Cited by: The droplet Reynolds number, Red, is changed in the range (60–), and turbulence intensity varied between 0 % and 11 %.
The major findings of this study showed that the droplet’s vaporization rate, which is deduced from the steady-state linear variation of the droplet squared diameter, increases with increasing turbulence intensity. droplet evaporation process characteristics on spray combustion [1, 4, 8].
An accurate capture of the turbulence characteristics that strongly influence the spray dispersion is determinant for an accurate prediction of evapora-tion, that in turn, affects significantly the spray combustion along with the spray flame structure .
Abstract-The re-examination of the classical droplet vaporization model is made in order to develop the simple but sticiently accurate calculation algorithm which can be used in spray combustion calculations. The new model includes the effects of variable thermophysical properties, non-unitary Lewis number in.
Droplet vaporization model for spray combustion calculations Modele de vaporisation de gouttelette pour les calculs de la The new model includes the effects of variable thermophysical properties, non-unitary Lewis number in the gas film, the effect of the Stefan flow on heat and mass transfer between the droplet and the gas, and the effect.
A multicomponent droplet vaporization model, the Diffusion-Limit Model, is modified to account for the variation of liquid properties due to large temperature gradients as well as considerable concentration gradients within the droplet. The effects on the vaporization behavior are analysed for an isolated bicomponent droplet consisting of.
1. Introduction. The performance of spray combustion relies heavily on liquid fuel breakup and the resulting droplet vaporization process. Therefore, a thorough physical understanding of fuel droplet evaporation and combustion is vital for improving the output and efficiency of power generation systems.
Center for Turbulence Research Proceedings of the Summer Program 25 Accounting for spray vaporization in turbulent combustion modeling By J. R eveillon1 AND L. Vervisch1 Three dimensional Direct Numerical Simulations (DNS) of droplet vaporization in the presence of turbulent micromixing have been performed.
The transport. Vaporization and Gas-Phase Mixing in Turbulent Sprays. We have developed a new laser diagnostic method to measure fuel vapor and gas phase mixing in the presence of droplets in turbulent sprays using Filtered Rayleigh Scattering (FRS).
Our FRS method provides a gas-phase measurement without inteference from the dispersed phase. In Sectionit was asserted that the effect of turbulence and droplet size on the evaporation rate depend primarily on two interrelated factors; namely, the ratio of the smallest length scale eddies to initial droplet size, η/d 0, and the stagnant concentration fuel gradient at the droplet surface, X F,s /r 0.
The new model includes the effects of variable thermophysical properties, non-unitary Lewis number in the gas film, the effect of the Stefan flow on heat and mass transfer between the droplet and.
Abstract. The dispersion characteristics of a selection of non-evaporating non-reacting, evaporating non-reacting, and reacting dilute spray jets issuing in ambient air (Gounder et al, Combust Sci Technol –, ; Masri and Gounder, Combust Flame –, ) and in a hot coflow (Oloughlin and Masri, Flow Turbul Combust –35, ) are analysed.
Part I: Effect of Partial Fuel Vaporization on Spray Combustion. Chapter in Experiments and Numerical Simulations of Diluted Spray Turbulent Combustion, Proceedings of the 1st International Workshop on Turbulent Spray Combustion, Series: ERCOFTAC Series, Vol.
17, Merci, Bart; Roekaerts, Dirk; SADIKI, AMSINI (Eds.), Google Scholar. The present article is concerned with the influence of turbulent gas-velocity fluctuations on both droplet dispersion and droplet-gas slip velocity in the context of spray simulation. The role of turbulence in generating slip and thus enhancing interphase heat and mass transfer has so far received little attention and is investigated in this work.
A model for turbulent gas-velocity. However, in reality, what is not accounted for in the d 2 law are the effects of multicomponent fuels, transient droplet heating, fuel vapor depletion or accumulation between the droplet and the flame, and various gas-phase transport properties (as functions of concentration and temperature).
Experiments have shown that droplet combustion often. The first example deals with the effects of turbulence properties on droplet dispersion, vaporization and mixing of a non-reacting spray. The second example includes the swirl intensity effects and focuses on the conjugate spray combustion.
In contrast to existing works, advanced models for turbulence, evaporation and modulation are combined. The laminar mixing layer separating a hot-air stream from a monodisperse spray carried by either an inert gas or air is investigated numerically and analytically in an effort to increase understanding of the ignition process leading to stabilization of high-speed spray combustion.
The turbulence effect on the mono-component and bicomponent droplet combustion rates before extinction was found to be negligible compared with the stagnant case. View Show abstract. Mixing of initially distinct substances plays an important role in our daily lives as well as in ecological and technological worlds.
From the continuum point of view, which we adopt here, mixing is complete when the substances come together across smallest flow scales determined in part by molecular mechanisms, but important stages of the process occur via the advection of substances by.
For the combustion, the conditioned progress variable approach based on the Bray-Moss-Libby model has been adapted and used to account for both premixed and partially premixed combustion. Dobashi, R., Hirano, T.: Effect of turbulence on vaporization, mixing, and combustion of liquid-fuel sprays.
Modeling and simulation of droplet and. This investigation reports on the study of the ambient turbulent effects on the droplet vaporization in the fuel spray combustion.
For tractability, this discussion considers a single droplet in an infinite turbulent this numerical study, the low-Reynolds-number version of k-ε turbulence mo. This work aims to understand the phenomena that occur in a combustion chamber where multi-component fuel droplets are injected.
Many evaporation models exist but the influence of turbulence on spray vaporization is not yet well understood. This study gives a useful database to improve these models. The objective of the work is to measure the dispersion and the evaporation of.
Droplet vaporization model for spray combustion calculations International Journal of Heat and Mass Transfer, Vol. 32, No. 9 Unsteady vaporization of stationary dodecane and alcohol droplets suspended in a hot non-reactive environment.
Droplet dispersion, vaporization and fuel–air mixing are crucial stages in combustion of liquid fuel sprays in many industrial applications, such as internal combustion engines, gas turbines and rocket engines, and their understanding is central to optimal performance of these devices and for reduction of pollutant emissions.
The droplet. Numerical simulation is now a standard tool to optimize turbulent combustion pro-cesses in such devices. If purely gaseous problems are well-known with a wide range of suggested closures, it is not the case for two-phase ﬂows where detailed information is needed about the physics of the triple interactions: spray/turbulence/ combustion.
The effects of evaporation, droplet breakup, collisions (coalescence or deflection) and viscous and turbulent interactions with the •Numbers in brackets designate references at end of paper. ambient gas are accounted for. The effects of turbulence are represented by a k-e model modified to include the effects of spray interaction.
Effect of the turbulent mixing upon the spray flame characteristics has been investigated experimentally. Simple control of turbulence was realized by means of the grids of different mesh size, placed in front of the nozzle. The results show that insertion of a grid of sufficiently fine mesh enhances vaporization.
This study presents new experimental results on the vaporization process of hydrocarbon droplet in a turbulent environment at elevated ambient pressure and temperature conditions.
n-Heptane and n-decane, which provide a wide range of hydrocarbons properties, were tested. The initial droplet diameter was on the order of 1 mm, and its surrounding. injection location is seen to depend fundamentally on the value of the droplet Stokes num ber, St, defined as the ratio of the droplet acceleration time to the mixing-layer strain time close to the stagnation point.
Two different regimes of spray vaporization and combustion. Transcritical Liquid Oxygen Droplet Vaporization: Effect on Rocket Combustion Instability.
Transient Droplet Evaporation with Variable Properties and Internal Circulation at Intermediate Reynolds Numbers. Transient Evaporation and Combustion of a Fuel Droplet Near Its Critical Temperature.
flamelets, flamelet progress-variable approach, presumed PDF. Spray-combustion fundamentals: Liquid-fueled burners, lean direct injection, droplet heating, droplet vaporization and droplet combustion, group combustion, characteristic scales and regime diagrams, Lagrangian and Eulerian approaches.
Reference Textbooks. droplet sizes and the effects of evaporation on sprays, as well as droplet breakup, collision, and coalescence . Spray computations show the sensitivity of the results to the droplet life-time that is, in turn, dependent on the vaporization process.
The vaporization models have. RESOLVING TURBULENCE-CHEMISTRY INTERACTIONS IN MIXING-CONTROLLED COMBUSTION WITH LES AND DETAILED CHEMISTRY CONVERGE CFD 4 Figure 1(a): Instantaneous distribution of velocity, mixture fraction, mass fractions of CO2 and CO, and SGS velocity at the y = 0 plane from case A ( mm).
Figure 1(b): Small subsection [white box from Figure 1(a) above] of the instantaneous. The effects of orifice geometry on inner nozzle flow, spray, and combustion processes are examined by coupling the injector flow and spray simulations.
Results indicate that conicity and hydrogrinding reduce cavitation and turbulence inside the nozzle orifice, which slows down primary breakup, increasing spray penetration, and reducing dispersion. This work presents Large Eddy Simulations of the unconfined CORIA Rouen Spray Burner, fed with liquid n -heptane and air.
Turbulent combustion modeling is based on the Filtered TAbulated Chemistry model for LES (F-TACLES) formalism, designed to capture the propagation speed of turbulent stratified flames. Initially dedicated to gaseous combustion, the filtered flamelet model is challenged for.
CONVERGE is a CFD code with the ability to perform 3-D flow simulations as well as turbulence, combustion, and spray modeling. As shown in Figure 1, this engine has a side-mounted direct injector which is used to inject the fuel directly into the combustion chamber.
Table 1 provides a summary of the engine specifications. CFD spray modeling with RANS turbulence models in combination with Volume-of-Fluid spray/wall impingement simulations for deposition modeling. Accomplishments: i) Performed first set of calculations with UWS spray vaporization and thermal decomposition; ii) Executed detailed VoF simulations of multiple droplet impingement on a heated surface.Spray Formation; Flame Lift-Off; In-Cylinder Mixing Enhancement; φ-T Maps; Spray Formation Fuel Atomization.
The first step in the mixture formation process in the conventional, mixing controlled diesel engine combustion is spray formation. Figure 1 shows a spray formed by injecting fuel from a single hole in stagnant air .Upon leaving the nozzle hole, the jet becomes completely.
Turbulence effects on the combustion of single hydrocarbon droplets Proceedings of the Combustion Institute, Vol. 28, No. 1 Results of a Computer Model of Droplet Thermodynamic and Dynamic Behaviour in the Port of a Port-Injected Engine.