Numerical Simulation of Non-Premixed Diffusion Flame and Reaction Product Aerosol Behavior in Liquid Metal Pool Combustion

2002 ◽  
Author(s):  
Akira Yamaguchi ◽  
Yuji Tajima
Keyword(s):  
Numerical Simulation ◽  
Liquid Metal ◽  
Diffusion Flame ◽  
Flame Temperature ◽  
Feedback Mechanism ◽  
Flame Height ◽  
Liquid Sodium ◽  
Negative Feedback Mechanism ◽  
Combustion Experiment ◽  
Work Interaction

A numerical methodology has been developed to solve a non-premixed diffusion flame under natural convection and applied to the calculation of the liquid sodium pool combustion experiment at various pool temperatures and oxygen concentrations. The computations reproduce the experimental observations concerning burning rate, flame temperature and flame height, consistently. The aerosol release rates are also in good agreement with the measurement. Dominant mechanisms of the mass and heat transfer are identified through the numerical simulation. An intrinsic feature is that the liquid sodium pool combustion is self-limited and negative feedback mechanism is at work Interaction among the thermal-hydraulics, chemical reaction and aerosol behavior plays an important role in the phenomena and it has been successfully analyzed by the numerical simulation. The present method can be used to understand sodium combustion phenomena and applied to the modeling of sodium pool combustion for safety analyses of liquid metal fast reactors. The numerical simulation is a useful tool because it can easily employ various conditions by changing parameters.

scholarly journals Effects of Ethanol Blending on the Formation of Soot in n-Heptane/Air Coflow Diffusion Flame

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Yuchen Ya ◽  
Xiaokang Nie ◽  
Licheng Peng ◽  
Longkai Xiang ◽  
Jialong Hu ◽  
...  
Keyword(s):  
Working Conditions ◽  
Diffusion Flame ◽  
Soot Particle ◽  
Primary Particle ◽  
Flame Temperature ◽  
Primary Particle Size ◽  
Flame Height ◽  
High Position ◽  
Carbon Mass ◽  
Coflow Diffusion Flame

Laminar diffusion flame was used to study the effect of ethanol on n-heptane flame in terms of the morphology and microstructure of soot under atomization combustion. For the same carbon mass flux at the outlet of the burner, the ratio of ethanol doping in n-heptane was changed, and the soot was collected from the axial positions of the flame at different heights using the thermophoresis probe method. The results showed that the flame height increased significantly with the increasing ratio of ethanol doping. When the ratio of ethanol and n-heptane (CE/CN) was 1.5, the flame height increased by 10 mm compared with that of pure n-heptane flame. Besides, the temperature in the center of the flame decreased with the increasing ratio of ethanol doping, but the temperature in the low position was higher than that in the pure n-heptane flame, and the temperature in the high position was lower than that in the pure n-heptane flame. However, the flame temperature was the highest when the proportion of ethanol in the mixture was greater than that of n-heptane. The temperature at the flame center decreased with the increasing ratio of ethanol doping, while the temperature at the flame edge increased with the ratio. The primary particle size of soot (soot size hereafter) in all working conditions increased with the increase of flame height, which was in line with the general growth law of soot. Moreover, the soot size at the same height decreased with the increasing ratio of ethanol doping, and this trend was most obvious at the flame height of 20 mm and 30 mm. Compared with pure n-heptane, when CE/CN was 1.5, the soot size at 20 mm and 30 mm decreased by an average of 34.83%, indicating that ethanol could inhibit the surface growth of soot particle. Furthermore, the density of soot particles collected by a single copper net decreased significantly, indicating that ethanol could reduce the production amount of soot.

Numerical Prediction and Optimization of Depressurized Sodium-Water Reaction Experiment With Counterflow Diffusion Flame

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Akira Yamaguchi ◽  
Takashi Takata ◽  
Hiroyuki Ohshima ◽  
Yoshitaka Kohara ◽  
Yoshihiro Deguchi
Keyword(s):  
Numerical Simulation ◽  
Chemical Reaction ◽  
Diffusion Flame ◽  
Safety Evaluation ◽  
Liquid Sodium ◽  
Pressurized Water ◽  
Transfer Tube ◽  
Reaction Region ◽  
Long Time ◽  
Counterflow Diffusion Flame

Sodium-water reaction (SWR) is a design basis accident of a sodium-cooled fast reactor (SFR). A breach of the heat transfer tube in a steam generator results in contact of liquid sodium with water. Typical phenomenon is that the pressurized water blows off, vaporizes, and mixes with the liquid sodium. It is necessary to quantify the SWR phenomena in the safety evaluation of the SFR system. In this paper, a new computer program has been developed and the SWR in a counterflow diffusion flame is studied by a numerical simulation and an experiment. The experiment is designed based on the numerical simulation so that the stable reaction flame is maintained for a long time and physical and chemical quantities are measured. From the comparison of the analysis and the experiment, there exist discrepancies that may be caused by the assumptions of the chemical reaction. Hence, a new experiment is proposed to enhance the measurement accuracy and to investigate the reason of the disagreement. The authors propose a depressurized experiment and show the preliminary result of the experiment. It is found that a stable chemical reaction flame is formed. With the depressurization, it is expected that the flame location can be controlled and the reaction region becomes thicker because of decrease in the reactant gas density.

scholarly journals One Dimensional Modeling of Jet Diffusion Flame

2018 ◽  
Vol 16 (4) ◽  
Author(s):  
Angan Sengupta ◽  
A.K. Gupta ◽  
I.M. Mishra ◽  
S. Suresh
Keyword(s):  
Diffusion Flame ◽  
Flame Temperature ◽  
Flame Height ◽  
Mixing Efficiency ◽  
Entrainment Rate ◽  
Flame Velocity ◽  
Runge Kutta Method ◽  
Efficiency Parameter ◽  
Entrained Air ◽  
Constant Slope

This paper reports on the determination of the flame height of a flare system using theoretical approach based on the laws of conservation of mass, momentum and energy. The set of ordinary differential equations at steady state conditions are solved numerically by fourth order Runge–Kutta method. The extent of reaction between the fuel and the entrained air has been studied by introducing the reaction mixing efficiency parameter, as the reaction rate is fixed by local entrainment rate. The reaction mixing efficiency parameter is a key measure to determine the height of the flame and its variation with the source velocity is limited by the flame width and the maximum vertical flame velocity at the tip of the flaming region. The variation of different parameters as vertical flame velocity, flame geometry and flame temperature with flame height are shown in plots. It is found that the flame geometry undergoes an initial necking up to a certain height, followed by an increase in its spread thereafter. The flame geometry and the flame dynamics depend exclusively on the burner design and the stack exit velocity. The flame height to burner diameter ratio of the jet diffusion flame is found to vary linearly with Froude number with a constant slope in the logarithmic plot.

Sodium-Water Reaction Elucidation With Counter-Flow Diffusion Flame Experiment and Its Numerical Simulation

2010 ◽  
Author(s):  
Akira Yamaguchi ◽  
Takashi Takata ◽  
Hiroyuki Ohshima ◽  
Joji Sogabe ◽  
Yoshihiro Deguchi ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Diffusion Flame ◽  
Exothermic Reaction ◽  
Reaction Model ◽  
Liquid Sodium ◽  
Counter Flow ◽  
Pressurized Water ◽  
Sodium Fast Reactor ◽  
Transfer Tube ◽  
Design Basis Accident

Sodium-water reaction (SWR) is a design basis accident of a Sodium Fast Reactor (SFR). A breach of the heat transfer tube in a steam generator (SG) results in contact of liquid sodium with water. Typical phenomenon is that the pressurized water blows off, vaporizes and mixes with the liquid sodium. The consequence of the accident are: thermal-hydraulic and chemical impact on the heat transport equipment and structure induced by the heat of exothermic reaction and caustic reaction product. The purpose of the present paper is to delineate the mechanism and process of the SWR by a counter-flow diffusion flame experiment and a numerical simulation. Based on the numerical simulation, the most appropriate and optimum condition in which stable and continuous diffusion flame of sodium and water vapor is obtained. Key idea is to perform the experiment in a depressurized reaction vessel. According to the experiment, spatial distributions of chemical reactants and products, temperature and particles are measured in detail. The characteristics of the SWR are explained from the present study and the chemical reaction model currently used in the analytical tool of the SWR is appropriate.

Ultrastructural morphology of nontumorous lactotrophs in human pituitaries exposed to high prolactin levels

1987 ◽  
Vol 45 ◽  
pp. 896-897
Author(s):  
S. Jalalah ◽  
K. Kovacs ◽  
E. Horvath
Keyword(s):  
Anterior Pituitary ◽  
Secretory Activity ◽  
Pituitary Hormones ◽  
Feedback Mechanism ◽  
Endocrine Activity ◽  
Hormone Synthesis ◽  
Anterior Pituitary Hormones ◽  
Negative Feedback Mechanism ◽  
Ultrastructural Morphology ◽  
Transmission Electron

Lactotrophs, as many other endocrine cells, change their morphology in response to factors influencing their secretory activity. Secretion of prolactin (PRL) from lactotrophs, like that of other anterior pituitary hormones, is under the control of the hypothalamus. Unlike most anterior pituitary hormones, PRL has no apparent target gland which could modulate the endocrine activity of lactotrophs. It is generally agreed that PRL regulates its own release from lactotrophs via the short loop negative feedback mechanism exerted at the level of the hypothalamus or the pituitary. Accordingly, ultrastructural morphology of lactotrophs is not constant; it is changing in response to high PRL levels showing signs of suppressed hormone synthesis and secretion.By transmission electron microscopy and morphometry, we have studied the morphology of lactotrophs in nontumorous (NT) portions of 7 human pituitaries containing PRL-secreting adenoma; these lactotrophs were exposed to abnormally high PRL levels.

scholarly journals Influence of a Standing Wave Flow-Field on the Dynamics of a Spray Diffusion Flame

Fluids ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 27
Author(s):  
J. Barry Greenberg ◽  
David Katoshevski
Keyword(s):  
Liquid Phase ◽  
Flow Field ◽  
Standing Wave ◽  
Diffusion Flame ◽  
Stokes Number ◽  
Flame Height ◽  
Wave Flow ◽  
Two Dimensional ◽  
Governing Equations ◽  
First Time

A theoretical investigation of the influence of a standing wave flow-field on the dynamics of a laminar two-dimensional spray diffusion flame is presented for the first time. The mathematical analysis permits mild slip between the droplets and their host surroundings. For the liquid phase, the use of a small Stokes number as the perturbation parameater enables a solution of the governing equations to be developed. Influence of the standing wave flow-field on droplet grouping is described by a specially constructed modification of the vaporization Damkohler number. Instantaneous flame front shapes are found via a solution for the usual Schwab–Zeldovitch parameter. Numerical results obtained from the analytical solution uncover the strong bearing that droplet grouping, induced by the standing wave flow-field, can have on flame height, shape, and type (over- or under-ventilated) and on the existence of multiple flame fronts.

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