Deflagration Analysis of Aluminum Droplet Combustion

2012 ◽  
Author(s):  
Birce Dikici ◽  
M. L. Pantoya ◽  
B. D. Shaw
Keyword(s):  
Gas Phase ◽  
Flame Propagation ◽  
Diffusion Flame ◽  
Dominant Role ◽  
Experimental Studies ◽  
Droplet Evaporation ◽  
Combustion Model ◽  
Single Droplet ◽  
Aluminum Particles ◽  
Combustion Dynamics

The evaporation and combustion of nanometric aluminum particles with an oxidizer MoO3 is analyzed. The analysis was performed to correlate individual Al particle gasification rates to macroscopic flame propagation rates observed in flame tube experiments. Examination of various characteristic times relevant to propagation of a deflagration reveals that particles below about 1.7 nm in diameter evaporate before appreciable chemical reactions occur. Experimental studies use Al particles greater than 1.7 nm in diameter such that a diffusion flame model was developed to better understand the combustion dynamics of multiphase Al particles. The results showed that it is unlikely that droplets will fully evaporate before reacting in the gas phase. A droplet evaporation and combustion model was further applied to quantify single droplet reaction velocities in comparison to the bulk flame propagation measurements observed in the literature. The diffusion flame model predicted orders of magnitude slower propagation rates than experimentally observed. These results imply that another reaction mechanism is responsible for promoting reaction propagation or modes other than diffusion play a more dominant role in flame propagation.

scholarly journals Combustion of Laser-Induced Individual Magnesium Microparticles under Natural Convection

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1276
Author(s):  
Chengyuan Lin ◽  
Minqi Zhang ◽  
Yue Wang ◽  
Shengji Li ◽  
Xuefeng Huang ◽  
...  
Keyword(s):  
Gas Phase ◽  
High Speed ◽  
Dominant Role ◽  
Combustion Process ◽  
Particle Diameter ◽  
Combustion Model ◽  
Combustion Mechanism ◽  
Rocket Propellants ◽  
High Speed Cinematography ◽  
Ignition And Combustion

Metal magnesium (Mg) fuels have been widely used in rocket propellants. The combustion study on individual Mg microparticles is crucial to the in-depth unveiling of the combustion mechanism of Mg-based propellants. In this paper, a new experimental setup was proposed to directly observe the combustion of individual micron-sized Mg particles, based on laser ignition and microscopic high-speed cinematography. The combustion process of individual Mg microparticles could be directly and clearly observed by the apparatus at high temporal and spatial resolutions. Individual Mg microparticles took gas phase combustion, and mainly underwent four stages: expansion, melting, gasification, ignition, and combustion. The ignition delay time and total combustion time had an exponential decay on the particle diameter, and they had a linear decay on the ignition power density. The melting took a dominant role in the whole burnout time. The gas-phase combustion flame seemed thick, inhomogeneous, and ring-like structure. The combustion model of individual Mg microparticles was built through combining the experimental results with the SEM, XRD, XPS, and EDS analysis of original samples and combustion residues. This study will be beneficial to understand the combustion process and reveal the combustion mechanism of metal microparticles besides Mg.

Theoretical Evaporation Model of a Single Droplet in Laser Treatment of PWS in Conjunction With Cryogen Spray Cooling

2008 ◽  
Author(s):  
Zhifu Zhou ◽  
Hui Xin ◽  
Bin Chen ◽  
Guo-Xiang Wang
Keyword(s):  
Gas Phase ◽  
Laser Treatment ◽  
Deep Understanding ◽  
Theoretical Models ◽  
Spray Cooling ◽  
Droplet Evaporation ◽  
Evaporation Process ◽  
Single Droplet ◽  
Equilibrium Evaporation ◽  
Cryogen Spray Cooling

Cryogen spray is an effective cooling technique used for laser treatment of Port Wine Stain. The cooling process involves complex droplet evaporation and strong convective heat and mass transfer, therefore a deep understanding of spray characteristics is essential in order to optimize the nozzle design and improve the cooling efficiency of the spray. This paper improves a theoretical model to describe the equilibrium evaporation process of a single cryogen droplet in cryogen spray. The results of comparative analysis of gas phase models for single droplet heating and evaporation are presented. Six different semi-theoretical models based on various assumptions are compared and their effects on a single droplet heating and evaporation characteristics in the process of cryogen R-134a spray cooling are compared. It is pointed out that the gas phase model, in which the effect of superheat is taken into account, predicts the evaporation process closest to the experimental data. Finally, a parametric study of the influences of initial diameter and velocity on the droplet evaporation is then carried out. The results can be used to guide the Cryogen Spray Cooling of laser therapy.

scholarly journals The Prevalence of Inorganic Mercury in Human Kidneys Suggests a Role for Toxic Metals in Essential Hypertension

Toxics ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 67
Author(s):  
Roger Pamphlett ◽  
Philip A. Doble ◽  
David P. Bishop
Keyword(s):  
Essential Hypertension ◽  
Toxic Metals ◽  
Inductively Coupled Plasma ◽  
Dominant Role ◽  
Inorganic Mercury ◽  
Experimental Studies ◽  
Human Kidney ◽  
Proximal Tubules ◽  
Age Related ◽  
Icp Ms

The kidney plays a dominant role in the pathogenesis of essential hypertension, but the initial pathogenic events in the kidney leading to hypertension are not known. Exposure to mercury has been linked to many diseases including hypertension in epidemiological and experimental studies, so we studied the distribution and prevalence of mercury in the human kidney. Paraffin sections of kidneys were available from 129 people ranging in age from 1 to 104 years who had forensic/coronial autopsies. One individual had injected himself with metallic mercury, the other 128 were from varied clinicopathological backgrounds without known exposure to mercury. Sections were stained for inorganic mercury using autometallography. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used on six samples to confirm the presence of autometallography-detected mercury and to look for other toxic metals. In the 128 people without known mercury exposure, mercury was found in: (1) proximal tubules of the cortex and Henle thin loops of the medulla, in 25% of kidneys (and also in the man who injected himself with mercury), (2) proximal tubules only in 16% of kidneys, and (3) Henle thin loops only in 23% of kidneys. The age-related proportion of people who had any mercury in their kidney was 0% at 1–20 years, 66% at 21–40 years, 77% at 41–60 years, 84% at 61–80 years, and 64% at 81–104 years. LA-ICP-MS confirmed the presence of mercury in samples staining with autometallography and showed cadmium, lead, iron, nickel, and silver in some kidneys. In conclusion, mercury is found commonly in the adult human kidney, where it appears to accumulate in proximal tubules and Henle thin loops until an advanced age. Dysfunctions of both these cortical and medullary regions have been implicated in the pathogenesis of essential hypertension, so these findings suggest that further studies of the effects of mercury on blood pressure are warranted.

Experimental and Numerical Investigation of a Large Cylindrical Oil-Fired Combustor

1983 ◽  
Author(s):  
F. M. ElMahallawy ◽  
E. E. Khalil ◽  
O. Abdel Aal
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Gas Phase ◽  
Combustion Model ◽  
Steam Boiler ◽  
Discrete Ordinate ◽  
Radiation Model ◽  
Droplet Motion ◽  
Transfer Rates ◽  
Lagrangian Equations

The present work presents measurements of velocity, temperature and heat transfer rates carried out on a segmented water-cooled cylindrical oil-fired flame tube typical of a 0.56 kg/s packaged fire-tube steam boiler. A prediction procedure, that solves the conservation equations of the various entities, was successfully used to produce computed velocities, temperatures and heat flux distributions. A two-equation turbulence model, a combustion model and a discrete ordinate radiation model were used to approximate the various characteristics of the flow. The combustion model solved the Eulerian equations of the gas phase, and the Lagrangian equations of the droplet motion, heating, evaporation and combustion.

Numerical Study of Bicomponent Droplet Vaporization in a High Pressure Environment

1996 ◽  
Author(s):  
J. Stengele ◽  
H.-J. Bauer ◽  
S. Wittig
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Gas Phase ◽  
Numerical Study ◽  
Droplet Evaporation ◽  
Single Component ◽  
Vapor Concentration ◽  
Diffusion Limit ◽  
Evaporation Process ◽  
Droplet Vaporization

The understanding of multicomponent droplet evaporation in a high pressure and high temperature gas is of great importance for the design of modern gas turbine combustors, since the different volatilities of the droplet components affect strongly the vapor concentration and, therefore, the ignition and combustion process in the gas phase. Plenty of experimental and numerical research is already done to understand the droplet evaporation process. Until now, most numerical studies were carried out for single component droplets, but there is still lack of knowledge concerning evaporation of multicomponent droplets under supercritical pressures. In the study presented, the Diffusion Limit Model is applied to predict bicomponent droplet vaporization. The calculations are carried out for a stagnant droplet consisting of heptane and dodecane evaporating in a stagnant high pressure and high temperature nitrogen environment. Different temperature and pressure levels are analyzed in order to characterize their influence on the vaporization behavior. The model employed is fully transient in the liquid and the gas phase. It accounts for real gas effects, ambient gas solubility in the liquid phase, high pressure phase equilibrium and variable properties in the droplet and surrounding gas. It is found that for high gas temperatures (T = 2000 K) the evaporation time of the bicomponent droplet decreases with higher pressures, whereas for moderate gas temperatures (T = 800 K) the lifetime of the droplet first increases and then decreases when elevating the pressure. This is comparable to numerical results conducted with single component droplets. Generally, the droplet temperature increases with higher pressures reaching finally the critical mixture temperature of the fuel components. The numerical study shows also that the same tendencies of vapor concentration at the droplet surface and vapor mass flow are observed for different pressures. Additionally, there is almost no influence of the ambient pressure on fuel composition inside the droplet during the evaporation process.

Flame propagation of nano/micron-sized aluminum particles and ice (ALICE) mixtures

2013 ◽  
Vol 34 (2) ◽  
pp. 2221-2228 ◽  
Author(s):  
Dilip S. Sundaram ◽  
Vigor Yang ◽  
Terrence L. Connell ◽  
Grant A. Risha ◽  
Richard A. Yetter
Keyword(s):  
Flame Propagation ◽  
Aluminum Particles

scholarly journals CHEMICALLY RESISTANT FLAME RETARDING COATINGS BASED ON EPOXY-AMINE COMPOSITES MODIFIED WITH COPPER(II) CARBONATE

Fire Safety ◽  
2019 ◽  
pp. 66-71
Author(s):  
P. V. Pastuhov ◽  
V. V. Kochubei ◽  
O. I. Lavrenyuk ◽  
B. M. Mykhalichko
Keyword(s):  
Flame Propagation ◽  
Epoxy Resins ◽  
Experimental Studies ◽  
Gravimetric Method ◽  
Fire Retardant ◽  
Propagation Rate ◽  
Binding Agent ◽  
Corrosive Media ◽  
Epoxy Amine ◽  
Effect Of Copper

Introduction. The development of modern technologies and the elaboration of new materials facilitates the wide use of epoxy resins for instance in industries. Particular attention deserves the various fire retardant coatings making. These coatings are increasingly used to increase fire resistance of details and designs made of metals, plastics, wood in various industrial and civil constructions, and in transport. The very perspective mode producing the effective fire retardant coatings is the direct introduction into the polymeric matrix of epoxy resins of reactive fire retardant agents. Purpose. The aim of this work is to study the effect of the elaborated fire retardant on the ability of epoxy-amine composites modified with copper(II) carbonate to resist the spread of the flame, as well as the effects of water and chemicals. Metods. The flame propagation rate on the surface of horizontally located experimental samples was determined according to all-State Standard 28157-89. Water and chemical resistance were evaluated by a gravimetric method on the polymer mass film change after exposure to distilled water and corrosive media for a certain period of time. Results. The results of experimental studies have shown that samples of the epoxy-amine composites containing 20, 40 and 80 mass parts of CuCO3 per 100 mass part of the binding agent do not propagate the flame horizontally at all. At that, duration of free combustion of these polymer samples did not exceed 2 min. It has been found too that the penetrability of water and chemicals through films based on epoxy-amine composites modified with CuCO3 is reduced due to the formation of chemical bonds between copper(II) carbonate and polyethylenepolyamine. The lowest level of the equilibrium absorption in water and 10% aqueous solutions of H2SO4 and NaOH was watched for samples of those composites that contained 20 mass parts of CuCO3 per 100 mass parts of binder. Conclusion. When studying the effect of copper(II) carbonate on the flame propagation rate, it was found that the epoxy-amine composites containing >20 mass parts of CuCO3 per 100 mass parts of the binding agent, do not propagate the flame and so these are self-extinguishing. The copper(II) carbonate addition to epoxy polymers reduces their sorption capacity in water and solutions of alkalis and acids. These data are the basis to future develop the chemically resistant fire retarding coatings based on epoxy-amine composites modified with copper(II) carbonate. Keywords

Sign in / Sign up

Export Citation Format

Share Document