Theoretical Study on Premixed Flames of Nano Aluminum Particles and Water Mixture

2013 ◽  
Vol 284-287 ◽  
pp. 567-571
Author(s):  
Jun Su Shin ◽  
Hong Gye Sung
Keyword(s):  
Reaction Zone ◽  
Aluminum Particle ◽  
Particle Diameter ◽  
Initial Pressure ◽  
Combustion Products ◽  
Flame Speed ◽  
Computational Domain ◽  
Water Mixture ◽  
Aluminum Particles ◽  
Preheat Zone

A theoretical model is proposed to investigate premixed combustion characteristics of Nano aluminum particles - water mixture. The effects of particle size, initial pressure, and temperature were considered as well. Computational domain is divided into 3 regions; preheat zone 1, preheat zone 2, and reaction zone. No reaction occurs in either of the preheat zones. Reaction zone, consisting of nano aluminum particles–steam mixture and the combustion products, is the region where reaction and heat-release occurs. Energy conservation is considered separately at each zones. The flame speed and temperature distribution are derived by solving the energy equation in each regime and matching the temperature and heat flux at the interfacial boundaries. Combustion time correlation of nano aluminum particle is also considered to imply complex aluminum combustion kinetics. Normalized flame speed is calculated as a function of pressure, initial particle diameter, and equivalence ratio and compared with experimental data.

An analytical study of radiation effects on the premixed laminar flames of aluminium dust clouds

2010 ◽  
Vol 224 (8) ◽  
pp. 1679-1695 ◽  
Author(s):  
M Bidabadi ◽  
A Shabani Shahrbabaki ◽  
M Jadidi ◽  
S Montazerinejad
Keyword(s):  
Gas Phase ◽  
Reaction Zone ◽  
Radiation Effects ◽  
Flame Temperature ◽  
Flame Speed ◽  
Propagation Mechanism ◽  
Preheat Zone ◽  
Phase Temperature ◽  
Lean Limit ◽  
Rich Mixtures

A new analytical model of a quasi one-dimensional non-adiabatic dust flame is developed with the assumption that the particle burning rate in the flame front is controlled by the process of oxygen diffusion. In this model, the flame propagation mechanism is considered to be radiation, conduction, and convection. Algebraic equations defining the laminar flame speed were obtained in two limiting cases: lean and rich mixtures. The flame structure is assumed to consist of a preheat zone, a reaction zone, and a postflame zone for lean mixtures and a preheat zone and a reaction zone for rich mixtures. Under the lean mixture approximation, values of the flame speed, lean limit, and flame temperature were calculated by adding the radiation term; flame temperature in the preheat zone increased, while it decreased in the postflame zone. This phenomenon may be attributed to the radiative heat transfer from the postflame zone to the preheat zone. Also, when the radiation term was considered, the flame speed increased but the lean limit decreased. In addition, radiation in the rich mixture resulted in the increase of the flame speed and the gas phase temperature in the preheat zone, whereas in the flame zone, the gas phase temperature decreased. Calculated values of the flame speed and flame temperature are in a good agreement with the experimental data in the literature.

The Influence of Singlet Oxygen and Ozone on the Combustion in Methane-Air Mixture

2013 ◽  
Vol 699 ◽  
pp. 111-118
Author(s):  
Rui Shi ◽  
Chang Hui Wang ◽  
Yan Nan Chang
Keyword(s):  
Singlet Oxygen ◽  
Chemical Kinetics ◽  
Mole Fraction ◽  
Ignition Delay ◽  
Delay Time ◽  
Ignition Delay Time ◽  
Laminar Flame ◽  
Combustion Products ◽  
Flame Speed ◽  
Air Mixing

Based on GRI3.0, we study the main chemical kinetics process about reactions of singlet oxygen O2(a1Δg) and ozone O3 with methane-air combustion products, inherit and further develop research in chemical kinetics process with enhancement effects on methane-air mixed combustion by these two molecules. In addition, influence of these two molecules on ignition delay time and flame speed of laminar mixture are considered in our numerical simulation research. This study validates the calculation of this model which cotains these two active molecules by using experimental data of ignition delay time and the speed of laminar flame propagation. In CH4-air mixing laminar combustion under fuel-lean condition(ф=0.5), flame speed will be increased, and singlet oxygen with 10% of mole fraction increases it by 80.34%, while ozone with 10% mole fraction increase it by 127.96%. It mainly because active atoms and groups(O, H, OH, CH3, CH2O, CH3O, etc) will be increased a lot after adding active molecules in the initial stage, and chain reaction be reacted greatly, inducing shortening of reaction time and accelerating of flame speed. Under fuel rich(ф=1.5), accelerating of flame speed will be weakened slightly, singlet oxygen with 10% in molecular oxygen increase it by 48.93%, while ozone with 10% increase it by 70.25%.

scholarly journals Measurements in Solid Propellant Plumes at Ambient Conditions

2011 ◽  
Author(s):  
Jonathan L. Height ◽  
Burl A. Donaldson ◽  
Walter Gill ◽  
Christian G. Parigger
Keyword(s):  
Temperature Distribution ◽  
Solid Propellant ◽  
Aluminum Particle ◽  
Burning Surface ◽  
Ambient Conditions ◽  
Aluminum Particles ◽  
Open Atmosphere ◽  
Particle Ignition ◽  
Accident Scenarios ◽  
Color Pyrometer

The study of aluminum particle ignition in an open atmosphere propellant burn is of particular interest when considering accident scenarios for rockets carrying high-value payloads. This study investigates the temperature of an open atmosphere Atlas V solid propellant burn as a function of height from the burning surface. Two instruments were used to infer this temperature: a two-color pyrometer and a spectrometer. The spectra were fitted to a model of energy states for aluminum monoxide. The temperature which provided the best match between the model and data was taken as the reaction temperature. Emissions above 30 inches from the surface of the propellant were not sufficiently strong for data reduction, perhaps obscured by the alumina smoke cloud. The temperature distribution in the plume increased slightly with distance from the burning surface, presumably indicating the delay in ignition and heat release from the larger aluminum particles in the propellant. The pyrometer and spectrometer results were found to be in excellent agreement indicating plume temperatures in the range of 2300K to 3000K.

Consolidation Features of Aluminum-Alumina Compositions by Powder Metallurgy Methods

2016 ◽  
Vol 254 ◽  
pp. 110-115
Author(s):  
Mihai Ovidiu Cojocaru ◽  
Mihaela Raluca Condruz ◽  
Florică Tudose
Keyword(s):  
Solid Phase ◽  
Particle Diameter ◽  
Aluminum Matrix ◽  
Aluminum Matrix Composites ◽  
Average Particle ◽  
Matrix Composites ◽  
Aluminum Particles ◽  
Transmission Electron ◽  
Tapped Density ◽  
Powder Metallurgy Methods

In this paper was followed the processing flow of aluminum-alumina compositions (10÷20% alumina) in powder state, aiming to obtain aluminum matrix composites reinforced with alumina particles, starting from selecting and mixing the grading fraction of both components reaching up to sintering; it was analyzed the way in which reflects the variation of grading fraction ratio (expressed through average particle diameter in the analyzed fractions limits) on the level of technological interest features: apparent density, tapped density, flowability, presability and on densification after sintering (in various environments). By transmission electron microscopy was observed that aluminum particles showed on the surface a nanoscale oxide film, so the sintering occurs between congeneric areas – by solid phase sintering mechanisms [1, 2, 3]. The analysis of thermophysical properties revealed a decrease of thermal diffusivity at an increase of alumina, simultaneous with the decrease of the densification level.

scholarly journals Effects of Silica-Particle Coating on a Silica Support for the Fabrication of High-Performance Silicalite-1 Membranes by Gel-Free Steam-Assisted Conversion

Membranes ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 46 ◽  
Author(s):  
Kyohei Ueno ◽  
Hideyuki Negishi ◽  
Takuya Okuno ◽  
Hiromasa Tawarayama ◽  
Shinji Ishikawa ◽  
...  
Keyword(s):  
High Performance ◽  
Silica Particle ◽  
Particle Diameter ◽  
Silica Particles ◽  
Steam Treatment ◽  
Water Mixture ◽  
Silica Support ◽  
Chemical Waste ◽  
Silica Source ◽  
Particle Layer

Silicalite-1 membranes with high pervaporation performance were prepared successfully on a silica-particle-coated tubular silica support using a gel-free steam-assisted conversion (SAC) method. The effects of the silica-particle layer formed on the top surface of the silica support and the physical properties of the silica particles themselves on the membrane-formation process were investigated. The silica particles coated served as the additional silica source for growing the silicalite-1 seed crystal layer into the silicalite-1 membrane. As a result, it was possible to form a dense and continuous membrane even under gel-free conditions. Furthermore, it was found that the properties of the silica particles, such as their primary particle diameter, had a determining effect on their solubility during the steam treatment, that is, on the supply rate of the silica source. The silicalite-1 membrane obtained using the spherical-silica-particle-coated support had an approximately 9-μm-thick separation layer and showed very high pervaporation performance, exhibiting a separation factor of 105 and a flux of 3.72 kg m−2 h−1 for a 10 wt % ethanol/water mixture at 323 K. Thus, the gel-free SAC method can be used with a silica support coated with silica particles to readily prepare high-performance membranes without producing any chemical waste.

The Diffusion Stratification Effect in Bunsen Flames

1974 ◽  
Vol 96 (4) ◽  
pp. 530-535 ◽  
Author(s):  
G. I. Sivashinsky
Keyword(s):  
Reaction Zone ◽  
Reaction Rate ◽  
Lewis Number ◽  
Combustion Products ◽  
Bimolecular Reaction ◽  
Adiabatic Temperature ◽  
Strong Temperature Dependence ◽  
Light Component ◽  
Stratification Effect ◽  
Bunsen Flames

The thermal diffusion flame model for a bimolecular reaction under stoichiometry conditions of the fresh mixture was examined. The structure of the flame tip of the Bunsen cone was studied. A local breakdown in the stoichiometry in the vicinity of the reaction zone was found such that the light component is always insufficient. For Lewis numbers greater than unity, the flame front is continuous. The temperature at the exit from the reaction zone exceeds the adiabatic temperature of the combustion products. For a Lewis number of the light component less than unity, either a flame with a continuous front, the temperature of which is less than the adiabatic temperature, or a flame with an exposed tip is possible. The problem is solved on the assumption of a strong temperature dependence of the reaction rate.

The theory of flame phenomena with a chain reaction

1956 ◽  
Vol 249 (957) ◽  
pp. 1-25 ◽  
Keyword(s):  
Reaction Zone ◽  
Flame Propagation ◽  
Reaction Rate ◽  
Laminar Flame ◽  
Combustible Mixture ◽  
Flame Speed ◽  
Spontaneous Ignition ◽  
Chain Reaction ◽  
Hydrazine Decomposition ◽  
A Chain

For single-step reactions there is a unique relation between reaction rate and reactedness for a given combustible mixture at a specified pressure and initial temperature. This paper examines whether the relation is still unique when chain reactions are present, by considering three types of flame—spontaneous ignition, laminar-flame propagation, and the homogeneous steady-flow reaction zone—with a chain-reaction scheme proposed by Adams & Stocks for the decomposition of hydrazine. It is found that the relation is not unique but that similarities exist between the relation for laminar-flame propagation and the relation for the homogeneous reaction zone. Incidentally, a general method of calculating laminar-flame speeds with reaction schemes of arbitrary complexity is presented. When applied to the hydrazine decomposition flame the predictions of the theory are in fair agreement with experimental results. In particular, the variation of flame speed with temperature is correctly predicted. It is shown that the use of the Karman-Penner 'steady-state assumption' would lead to an overestimate of the flame speed. Consideration of the changes which would result if the chain reaction should branch shows that there would once again tend to be a unique reaction rate versus reactedness relation, and that the laminar-flame speed would be increased by a factor of about three for the hottest flame considered but by larger factors for cooler flames.

On-Demand Hydrogen Generator Based on the Reaction between Aluminum Slurry and Alkaline Solution

2011 ◽  
Vol 347-353 ◽  
pp. 3242-3245
Author(s):  
Xia Ni Huang ◽  
Shu Liu ◽  
Chao Wang ◽  
Da Chen ◽  
Yue Xiang Huang
Keyword(s):  
Surface Active Agent ◽  
Aluminum Particle ◽  
Active Agent ◽  
Dew Point ◽  
Hydrogen Generator ◽  
X Ray Diffraction ◽  
Aluminum Particles ◽  
Hydrogen Flow ◽  
Surface Active ◽  
Diffraction Patterns

In the present work, the aqueous slurry containing 30 wt% solid aluminum particles was prepared, using paraffin oil and oleic acid dispersant and surface active agent respectively. The results showed that no obvious aluminum particle sediment was observed even after being kept it at room temperature in air up to 15 days. The hydrogen generator based on the reaction of the aluminum slurry and sodium hydroxide aqueous solution was manufactured and could supply a maximum hydrogen flow rate of 20 NL/min. The dew point of the hydrogen from the generator was lower than -40oC, indicating the high purity of the as-obtained hydrogen. As expected the X-ray diffraction patterns revealed that the byproduct was bayerite.

scholarly journals Acceleration and heating of metal particles in condensed matter detonation

2012 ◽  
Vol 468 (2142) ◽  
pp. 1564-1590 ◽  
Author(s):  
Robert C. Ripley ◽  
Fan Zhang ◽  
Fue-Sang Lien
Keyword(s):  
Reaction Zone ◽  
Volume Fraction ◽  
Density Ratio ◽  
Particle Diameter ◽  
Solid Particles ◽  
Metal Particles ◽  
Solid Loading ◽  
Shock Propagation ◽  
Zone Length ◽  
Detonation Shock

For condensed explosives, containing metal particle additives, interaction of the detonation shock and reaction zone with solid inclusions leads to high rates of momentum and heat transfer that consequently introduce non-ideal detonation phenomena. During the time scale of the leading detonation shock crossing a particle, the acceleration and heating of metal particles are shown to depend on the volume fraction of particles, dense packing configuration, material density ratio of explosive to solid particles and ratio of particle diameter to detonation reaction-zone length. Dimensional analysis and physical parameter evaluation are used to formalize the factors affecting particle acceleration and heating. Three-dimensional mesoscale calculations are conducted for matrices of spherical metal particles immersed in a liquid explosive for various particle diameter and solid loading conditions, to determine the velocity and temperature transmission factors resulting from shock compression. Results are incorporated as interphase exchange source terms for macroscopic continuum models that can be applied to practical detonation problems involving multi-phase explosives or shock propagation in dense particle-fluid systems.

Computational Study on Influence of Water Injection Angle to Aluminum/Water Reaction Motor

2012 ◽  
Vol 248 ◽  
pp. 539-544
Author(s):  
Zheng He ◽  
Xuan Gu ◽  
Ye Gao
Keyword(s):  
Computational Study ◽  
Aluminum Particle ◽  
Specific Impulse ◽  
Water Injection ◽  
Water Droplets ◽  
Aluminum Particles ◽  
Injection Angle ◽  
Influence Of Water ◽  
Afterburning Chamber ◽  
Multi Phase

In Aluminum/Water Reaction Motor chamber, water injection angle plays an important role on mixture of aluminum particle fuel and water droplets and can affect motor performance further. On the basis of FLUENT software and taking phase transition and reaction between water droplets and aluminum particles into account, numerically simulated cases of different water injection angles by Particle Stochastic Trajectory Model. Computed total evaporation rate of water droplets, reaction rate of aluminum particles and specific impulse for the motor. Furthermore judged injection angle effect from these parameters. By comparison and analysis, it is found that hybrid injection case could get best multi-phase mixture effect and specific impulse performance for the motor. Namely axial injection angle with 45°in the main chamber and tangential injection angle with 60°in the afterburning chamber is the best case. The conclusion could provide a new idea for motor working process design.

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