Propagation of turbulent burning of methane-air mixtures in tubes

A simplified mathematical model for turbulent flows, which may be called a “two-phase” approximation with respect to one of possible methods of deriving corresponding equations for time-averaged quantities, is proposed. In a one-dimensional approximation, the problem of propagation of a turbulent flame that arises near the butt end of a semi-infinite smooth tube is solved. On the basis of the infinitely thin flame front model, the range of concentrations in which turbulent burning modes with a constant flame-propagation velocity exist is determined. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 3, pp. 11–16, May–June, 2000. The present work was supported by the Tomsk State University grant “Fundamental Problems in Environment Protection and Human Ecology.”     

Filtration combustion of liquid monofuels

A one-dimensional two-temperature model for filtration combustion of liquid monofuels is proposed. The model is used to analyze the filtration combustion of liquid hydrazine in narrow tubes. Two steady-state regimes are found. In regime I, the dominant mechanism of heat transfer from the combustion products in the preflame zone is heat conduction in the gas, and in regime II, this is interfacial convective heat transfer and heat conduction in the solid phase. Parameter ranges for the existence of the regimes are established. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 4, pp. 21–30, July–August, 2008.     

Theoretical modeling of simultaneous processes of coke burning and limestone decomposition in a furnace

A one-dimensional mathematical model is presented for a combined process of limestone calcination and coke burning in a reactor with allowance for kinetics of physical and chemical transformations. The model makes it possible to obtain the distributions of the gas-phase composition, temperatures of the solid and gas phases, and mass flow along the furnace as functions of the intensity of air, raw materials, and fuel supply into the furnace, their initial temperature, and the size of coke and limestone particles. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 1, pp. 63–72, January–February, 2008.     

Developing 1D nanostructure arrays for future nanophotonics

There is intense and growing interest in one-dimensional (1-D) nanostructures from the perspective of their synthesis and unique properties, especially with respect to their excellent optical response and an ability to form heterostructures. This review discusses alternative approaches to preparation and organization of such structures, and their potential properties. In particular, molecular-scale printing is highlighted as a method for creating organized pre-cursor structure for locating nanowires, as well as vapor–liquid–solid (VLS) templated growth using nano-channel alumina (NCA), and deposition of 1-D structures with glancing angle deposition (GLAD). As regards novel optical properties, we discuss as an example, finite size photonic crystal cavity structures formed from such nanostructure arrays possessing high Q and small mode volume, and being ideal for developing future nanolasers.     

Applicability conditions for inverse methods of reconstructing the nonsteady burning rate

Applicability conditions for inverse methods of reconstructing the time-dependent burning rate of solid fuels are analyzed by studying the effect of the varying burning rate on the pressure in the combustion chamber. Thermodynamic and one-dimensional gas-dynamic approximations are considered. It is shown that the thermodynamic statement of the inverse problem can be used to study processes with characteristic times longer than 0.2 of the combustion-chamber free-volume relaxation time. Making allowance for one-dimensional effects is feasible and appropriate where experimental data on butt-end burning of readily combustible fuels are treated. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 3, pp. 39–43, May–June, 2000.     

The impact of crop growth sub-model choice on simulated water and nitrogen balances

It is the aim of this study to analyse how different crop growth model routines affect the simulation of water flow and nitrogen transport of a crop rotation in agricultural fields. The model system Expert-N is briefly described and used to test the crop growth sub-models against data of a six-year field experiment on sandy soils. Expert-N is a modular soil–plant–atmosphere model system, which comprises different sub-models to simulate one-dimensional vertical transport of water, solute and heat in the unsaturated zone. It includes several sub-models to describe organic matter turnover and has three generic crop growth sub-models. The latter are derived from the crop models CERES, SPASS and SUCROS. Simulations were performed using the different sub-models for each of the cereal crops in the sugar beet, winter wheat, winter barley, winter rye crop rotation. Results show the impact of crop model choice on simulated water balances and turnover of C and N. It is concluded that the simulation of root growth and plant residue mineralisation needs some improvement.     

Larval Release Behaviors in the Caribbean Spiny Lobster, <Emphasis Type="Italic">Panulirus argus</Emphasis>: Role of Peptide Pheromones

Larval release in the Caribbean spiny lobster Panulirus argus is highly synchronous and is controlled by a “pumping pheromone” released from the hatching eggs. The pheromone induces a parent female to undergo stereotypical larval release behaviors, including rapid abdominal extensions and pleopod pumping. These behaviors help to break open the egg membranes and result in the synchronous release of larvae. Based on previous studies on larval release in brachyuran crabs, we hypothesized that larval release behaviors are induced by pheromones composed of small peptides. We quantified pleopod pumping activity upon exposure to a range of synthetic peptides to identify compounds that will induce larval release behaviors. Chemically cued pumping behavior was described in terms of the threshold concentration for response, maximum percentage response, and effective concentration range. Pleopod pumping behavior was evoked by di- and tripeptides with a neutral amino acid at the amino terminus and a basic amino acid at the carboxy terminus and also by the basic–basic dipeptide Lys–Arg. All carboxy-terminal arginine peptides tested produced a significant pumping response, with the exception of Trp–Ile–Arg. Response concentration thresholds ranged from 10⁻⁹ M for the most potent peptide (Gly–Arg) to 10⁻⁴ M for the least potent (Gly–His–Lys). The maximum percentage of lobsters responding was largely independent of the threshold concentration and ranged from 24.3 to 58.3%. Effective concentration ranges for the peptides were variable from 1 to 4 orders of magnitude. Pumping response usually declined with increasing concentration beyond the concentration that evoked the maximum response of the peptides. Our results support the conceptual model that larval release in subtidal crustaceans is controlled by small peptides that act as pheromones.     

Burning-rate response functions of nitramine-based propellants and HMX from microthermocouple data measurements

The results of experimental burning-rate and burning-surface temperature measurements, which were obtained for nitramine-based propellants and HMX at various pressures and initial temperatures, are used to determine the pressure and temperature sensitivities of the burning rate and surface temperature and the criteria of burning stability. It is shown that the one-dimensional and quasistationary approaches are valid. Based on the data obtained, the functions of burning-rate response to acoustic pressure oscillations are calculated. The estimates of calculation errors show that smoothing of the experimental dependences of the burning rates and surface temperatures allows us to obtain response functions with acceptable errors. The influence of the melted layer on the surface of burning HMX on the stability criteria and the response functions of HMX is taken into account. Introduction of HMX into the structure of catalyst-containing ballistite propellants is found to decrease appreciably the response-function amplitudes. The effect of the propellant structures on these functions is studied. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 1, pp. 12–22, January–February, 2000. This work was partially supported by the Russian Foundation for Fundamental Research (Grant No. 97-03-32076).     

Numerical study of the transfer of shock-wave loading to a screened flat wall through a layer of a powdered medium and a subsequent air gap

The two-velocity, two-temperature model with two stresses in a mixture of a gas and solid particles contacting each other is used to numerically study the dynamic effect of an air shock wave incoming onto a solid wall with a screening layer of a porous powdered medium at some distance from the wall. The process is described for the case of one-dimensional planar motion of the gaseous and disperse phases under the assumption of a viscoelastic behavior of the powder skeleton. The effect of stepwise shock waves onto the porous powdered screen is considered. The influence of parameters of the screening layer and the air gap on the dynamics of loading of the screened solid wall is analyzed. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 1, pp. 132–142, January–February, 2007.     

The problem of propagation of a gasless combustion wave over a mixture of reacting metal powders

The evolution of structural, phase, and chemical transformations in reacting powders is studied in terms of the mechanics of heterogeneous media. Based on elementary physical concepts of reaction diffusion process at the level of a mixture cell with allowance for heterogeneity and stagewise nature of transformations, a mathematical model of self-propagating high-temperature synthesis of reacting powder mixtures is proposed which allows one to calculate the final product composition from a specified content of the starting mixture components. The unsteady one-dimensional problem of gas-free-combustion-wave propagation over a mixture of two different metal powders is studied numerically. The results are in good agreement with available experimental data. Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 2, pp. 69–75, March–April, 1997.     

Interaction of rarefaction waves with a finite-thickness layer near a rigid boundary. Equilibrium approximation

Interaction of a rarefaction wave with a layer of solid particles near the end face of a shock tube is considered. A one-dimensional unsteady approximation of mechanics of heterogeneous media with identical pressures of the phases and with allowance for a finite volume concentration of particles in the layer is used as a mathematical model. The wave pattern of the flow and the mechanism of wave interaction with the layer, including the dynamics of the layer boundary depending on the layer thickness and rarefaction-wave width, are determined. The mathematical model proposed is verified against the dependence of the layer-boundary coordinate on time and also the dependence of the velocity of upward motion of the layer on the difference in pressures between the high-pressure and low-pressure chambers. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 5, pp. 126–135, September–October, 2007.     

Large-scale Synthesis of β-SiC Nanochains and Their Raman/Photoluminescence Properties

Although the SiC/SiO₂ nanochain heterojunction has been synthesized, the chained homogeneous nanostructure of SiC has not been reported before. Herein, the novel β-SiC nanochains are synthesized assisted by the AAO template. The characterized results demonstrate that the nanostructures are constructed by spheres of 25–30 nm and conjoint wires of 15–20 nm in diameters. Raman and photoluminescence measurements are used to explore the unique optical properties. A speed-alternating vapor–solid (SA-VS) growth mechanism is proposed to interpret the formation of this typical nanochains. The achieved nanochains enrich the species of one-dimensional (1D) nanostructures and may hold great potential applications in nanotechnology.     

Modeling and simulation of biomass air-steam gasification in a fluidized bed

By considering the features of fluidized-bed reactors and the kinetic mechanism of biomass gasification, a steady-state, isothermal, one-dimensional and two-phase mathematical model of biomass gasification kinetics in bubbling fluidized beds was developed. The model assumes the existence of two phases — a bubble and an emulsion phase — with chemical reactions occurring in both phases. The axial gas dispersion in the two phases is accounted for and the pyrolysis of biomass is taken to be instantaneous. The char and gas species CO, CO₂, H₂, H₂O, CH₄ and 8 chemical reactions are included in the model. The mathematical model belongs to a typical boundary value problem of ordinary differential equations and its solution is obtained by a Matlab program. Utilizing wood powder as the feedstock, the calculated data show satisfactory agreement with experimental results and proves the effectiveness and reliability of the model. __________ Translated from Chemical Engineering (China), 2007, 35(10): 23–26 [译自: 化学工程]     

One-Dimensional Nanostructures and Devices of II–V Group Semiconductors

The II–V group semiconductors, with narrow band gaps, are important materials with many applications in infrared detectors, lasers, solar cells, ultrasonic multipliers, and Hall generators. Since the first report on trumpet-like Zn₃P₂ nanowires, one-dimensional (1-D) nanostructures of II–V group semiconductors have attracted great research attention recently because these special 1-D nanostructures may find applications in fabricating new electronic and optoelectronic nanoscale devices. This article covers the 1-D II–V semiconducting nanostructures that have been synthesized till now, focusing on nanotubes, nanowires, nanobelts, and special nanostructures like heterostructured nanowires. Novel electronic and optoelectronic devices built on 1-D II–V semiconducting nanostructures will also be discussed, which include metal–insulator-semiconductor field-effect transistors, metal-semiconductor field-effect transistors, and p–n heterojunction photodiode. We intent to provide the readers a brief account of these exciting research activities.     

Analysis of unsteady solid-propellant combustion models (review)

Recent studies of solid-propellant combustion models are briefly analyzed. The models are divided into purely one-dimensional (classical and phenomenological models with various generalizations of the Zel’dovich approach) and non-one-dimensional. The latter include models with local non-one-dimensionality, which is always accompanied by local unsteadiness. This all can be eliminated by averaging. The main disadvantage of unsteady solid-propellant combustion models, which is no fault of their authors, is the same as in the case of steady-state models: the lack of detailed information on chemical and physical processes in the condensed phase. Impropriety of extending the purely one-dimensional approach to the instability region is noted. Possible directions for further development of unsteady (and quasi-steady-state) solid-propellant combustion models for homogeneous compositions may involve accounting for local non-one-dimensionality and the unsteadiness due to instability of the subsurface reactions zone and verification of the possibility of the existence of chemical instability capable of causing similar non-one-dimensionality and unsteadiness. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 1, pp. 35–48, January–February, 2008.     

Scaling effect in dynamic fracture (spallation) of brittle and ductile material

Results are presented from an experimental study of the spallation strength of lead (S1) and a metal-ceramic (Al+20% SiC) as representatives of materials that are more ductile and brittle than those studied before. The dimensions of the samples changed by factors of 4–5. It was found that during fracture of these materials under high velocity one-dimensional deformation, significant scaling effects are observed which originate in the energy characteristics. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 1, pp. 108–114, January–February 1999.     

Scale effect in high-rate (spall) failure

Experimental results on the spall strength of copper in which the scale of the system was changed by a factor of ten show that the scale effect for high-rate one-dimensional strain depends on energy. The spall energy per unit surface area for failure increases with time. Arzamas-16. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 6, pp. 88–93, November–December, 1993.     

Spinning of poly-p-phenylenebenzobisthiazole fibres

The effect of the intrinsic viscosity and concentration of polymer in LC solution on the mechanical properties of PPBT yarn was demonstrated. In examining the spinning stability of PPBT yarns, use of spinnerets with an opening diameter of 0.25 mm and conditions ensuring cooling of the jets of heated LC solutions in an air gap are preferred. The isometric conditions of drawing of jets of a LC solution of PPBT with a ratio greater than 7–8 initiate one-dimensional flow with stable pulsation of the diameter. The phenomenon is known as draw resonance. All-Russian Scientific-Research Institute of Polymer Fibres, Mytishchi. Translated fromKhimicheskie Volokna, No. 1, pp. 23–28, January–February, 2000.     

On the Hydrodynamic Thickness of Cellular Detonations

The characterization of the detonation dynamic parameters (detonability limits, direct initiation energy, critical tube diameter, etc.) requires a characteristic length scale for the detonation wave in the direction of propagation. However, most detonations are unstable, their reaction zones are turbulent, and their structure departs significantly from the idealized one-dimensional Zel'dovich-Von Neumann-Doring model. It is argued that the most suitable length scale to characterize a turbulent detonation wave is the location of the sonic surface, which separates the statistically stationary flow of the reaction zone structure from the unsteady expansions behind the wave. Previous real and numerical experiments are reviewed in order to determine the relation between the global location of the mean sonic surface and the chemical, mechanical, and thermodynamic relaxation processes occurring in the detonation wave structure. Based on the experimental evidence, we postulate that the structure of turbulent detonations can be modeled in the one-dimensional Zel'dovich-Neumann-Doring framework, with the turbulence effects as source terms in the momentum and energy equations. These source terms involve the relaxation rates for the mechanical fluctuations, thermal fluctuations and the chemical exothermicity towards equilibrium. In the framework of the idealized one-dimensional structure with source terms, the sonic surface location is governed by the balance between the competing source terms satisfying the generalized Chapman-Jouguet criterion. We recommend that future work in detonation research should be focused at: 1) acquiring a large experimental database for the mean detonation properties (detonation velocity, location of sonic surface and mean reaction zone profiles); 2) the development of the appropriate source terms involving the turbulent fluctuations in the averaged equations of motion. __________ Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 6, pp. 157–180, November–December, 2005.     

Effect of size, manufacturing and prestrain on high-rate failure (spall) of PT-3V titanium alloy and 12Kh18N10T steel

Experimental results are presented on the spall strength of PT-3V titanium alloy and 12Kh18N10T steel as the system size is changed by a factor of five. The effects of a 0.5–5% dynamic prestrain and of the direction of the load relative to the manufacturing rolling direction on spall failure were also studied for the titanium alloy. It was established that failure of these metals under high-rate one-dimensional strain shows significant energy-related size effects. Effects of the rolling direction and prestrain were less pronounced for the titanium alloy than for steel. All-Union Research Institute of Experimental Physics, 607200 Sarov. Translated from Fizika Goreniya i Bzryva, Vol. 31, No. 6, pp. 130–139. November–December, 1995.