两种金属材料腐蚀磨损的交互作用

金属材料的腐蚀磨损率不是其腐蚀率与磨损率之和，这是由于存在腐蚀与磨损交互作用的缘故．在腐蚀磨损系统中，若忽略温度和压力等环境因素的影响，则材料的腐蚀磨损就是电化学因素与力学因素交互作用的结果．在给定的试验条件下，４５＃钢和２Ｃｒ１３不锈钢在分别含硫酸、盐酸和硝酸的石英砂浆体冲击下的腐蚀磨损率均大于各自的腐蚀率与磨损率之和，证明有交互作用发生，而且交互作用值随腐蚀率或磨损率的增高而增大．在对影响腐蚀磨损交互作用的主要因素进行分析的基础上，建立了反映材料腐蚀磨损交互作用与腐蚀率及磨损率之间数量关系和变化规律的交互作用图．利用这种图可以分析腐蚀磨损中电化学因素和力学因素对腐蚀磨损交互作用的影响，比较不同材料的腐蚀磨损交互作用受这两种因素影响的敏感程度，评价金属材料的腐蚀磨损性能     

Modeling the acidizing of a carbonate formation

Two approaches to the determination of the optimum conditions of the well bottom zone treatment in a carbonate formation are considered and compared. The first, bench approach is based on the investigation of the process of wormhole formation in rock cores, while the second approach is the mathematical modeling of the process within the framework of mechanics of multi-component seepage flows using averaged values of the reservoir porosity and permeability. A mathematical model of the process, that takes account for fluid flow and the chemical reaction between the acid and the rock matrix proceeding in the kinetic regime, is presented. Both approaches indicate the existence of an optimum rate of acid solution injection into the formation at a certain given value of the dimensionless Damköller number.     

Calculation of the concentration fields of solid and fluid phases in the flow of a chemically active fluid through a porous medium

The flow of a chemically active fluid through a porous medium is considered. Under certain assumptions, an analytical solution is obtained which describes the distribution of the concentration of the chemically active component and the variation of the solidphase porosity. On the basis of the results obtained, the optimization of the hydrochloric acid treatment of wells is considered.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 78–81, March–April, 1985.     

EFFECTS OF SURFACTANT AND ACID TYPE ON PREPARATION OF CHITOSAN MICROCAPSULES

Chitosan microcapsules were prepared by a method involving emulsification and crosslinking. The effectsof surfactants and acid type for dissolving chitosan on the characteristics of chitosan microcapsules were investigated.The results showed that the mixed surfactant consisting of Span80 and Tween60 had an obvious effect on reducing the size of the microcapsules. The two-surfactant complex, formed on the basis of hydrogen bonding, strengthened the interfacial membrane in the emulsion, thus decreasing not only the size of the microcapsules but also the coalescence of dispersed chitosan liquid drops. In the case of monoacid such as hydrochloric acid or acetic acid for dissolving chitosan,the chitosan microcapsules obtained were spherical in shape with smooth surfaces. For diacids or triacid, the chitosanmicrocapsules obtained were also spherical, but their surfaces were covered by folds and crinkles. The number of carboxyl groups in the acids used influenced the chemical crosslinking between chitosan and the crosslinker (glutaraldehyde) as well as the morphology of the particles. For diacids or triacid, physical crosslinking occured due to electrostatic force, accompanied by substantial decrease of covalent crosslinking, leading to decreased strength of the microcapsules as shown by the collapse of microcapsule walls and the formation of multiple folds and cnnkles on their surfaces.     

Rapid proton diffusion in microfluidic devices by means of micro-LIF technique

The micro-LIF (laser-induced fluorescence) technique was applied to the measurement of pH distributions in a chemically reacting flow in a microfluidic device. Two liquid streams were combined at the junction of a Y-shaped microchannel (100-m width and 33-m depth), and allowed to diffuse into each other and react. The results for non-reacting fluids (hydrochloric acid and water) show good agreement with theoretical values calculated using conventional diffusion. When a reaction occurred (hydrochloric acid and sodium hydroxide), a large difference between the measurement results and the theoretical values was observed, indicating rapid proton diffusion compared with the theoretically calculated values.     

化学镀Ni -Cu -P 镀层在3 种腐蚀介质中冲蚀行为的研究

通过改变冲蚀介质的种类与浓度、冲蚀介质流速、冲蚀时间、冲蚀攻角等,研究了化学镀Ni-Cu-P合金镀层的耐冲蚀性能.结果表明:在(wt%)2%的氢氧化钠介质中,化学镀Ni-Cu-P合金镀层耐冲蚀性能最佳;在稀盐酸中冲蚀有以下规律:随着盐酸浓度的增加,冲蚀失重逐渐增加;随着冲蚀速度的增大,试样的冲蚀失重逐渐增加,二者之间符合指数关系,冲蚀失重的变化有一临界液体流速;在攻角为45°时冲蚀失重最大.相比化学镀Ni-P镀层,化学镀N i-Cu-P镀层具有更好的耐冲蚀性能.     

Experimental Investigation of Side Effect of Henna Extract as a New and Ecofriendly Corrosion Inhibitor on Acid Injectivity of Calcareous Sandstone

Matrix acidizing of the oil wells is one of the most important stimulation techniques for enhancing oil production. The most common acids are hydrochloric acid (HCl), used primarily to dissolve carbonate minerals, and mixtures of HCl and hydrofluoric acid (HF) used to attack silicate minerals such as clays and feldspars. During acid stimulation treatment, the lines and tubing must be protected from corrosive attack by the acid. Among different approaches for mitigation of corrosion, inhibitors are the best to prevent destruction or degradation of metal surfaces in corrosive media. Although many synthetic compounds show inhibitive action, most of them are toxic. There is increasing concern about the toxicity of corrosion inhibitors in petroleum industry. Therefore, finding natural occurring substances as a corrosion inhibitor is subject of great practical significance. A few studies have investigated corrosion inhibition of henna extract on some metals such as aluminum, iron, zinc, and nickel in acidic and alkaline solutions, but, in these studies, henna extract evaluated only for its ability to control acid corrosion under stimulated treating conditions. Formation damage may result from insoluble materials in the inhibitor and from inhibitor adsorption on clays and other minerals present in the matrix of the rock is seldom considered. The purpose of current study is to investigate the side effect of henna extract as a new and ecofriendly corrosion inhibitor on reservoir rock grains. In present work, the inhibitive action of henna extract on corrosion of N80 API steel in HCl 10 wt% at $70\,^{\circ }\text{ C}$ was investigated through electrochemical techniques. The side effect of this inhibitor on rock grains was investigated through linear acid core flooding of calcareous sandstone samples. The analysis of pressure data from the test revealed that the core samples flooded with inhibited acid (HCl 10 wt% containing 0.4 g/l henna extract) have higher pressure drop respect to samples flooded with blank acid (HCl 10 wt%). The results of wettability analysis reveal that samples flooded with inhibited acid have higher contact angle respect to samples flooded with blank acid. It means that henna extract tends the samples toward the oil wet phase.     

Numerical Simulation of the Evolution of Intensive Convective Vortices of the Typhoon Type in a Rotating Fluid

The problem of the generation of a vortex in a rotating vessel locally heated from below is considered. The results of calculating the regime of formation of an intense vortex from a large-scale advective cell are given. The spiral vortex obtained is characterized by cyclonic rotation at a velocity of an order of magnitude greater than the vessel's rate of rotation. The vortex has the characteristic features of atmospheric typhoons. A comparison of the results with the data of analogous laboratory experiments shows that they are in good agreement. The vortex flow restructuring stages after heating is interrupted are also investigated. It is shown that in this case the development of Rayleigh-Taylor instability favours for the formation of extended spiral branches.     

Rheology of highly concentrated anionic surfactants

Surfactant solution flow behavior is of great importance to both the chemical and consumer product industries. Most studies on the flow behavior of surfactant solutions, however, have focused on the dilute regime. Seldom reported is rheology in the highly concentrated regime where typically these surfactants are processed and delivered. First, we present here the phase diagram for the ternary system: water and two anionic surfactants (sodium salt of lauric and oleic acid) at different temperatures. Then, we present both linear viscoelastic and steady shear flow results in the high (70 to 90%) surfactant regime. We find that high values of the shear modulus are directly dependent on the quantity of surfactant crystals and that the formation of a lamellar liquid crystal phase at 45°C affects both modulus and flow of the system. Lamellar crystals create a stiff network resulting in wall slip at large shear strain. Using serrated plates removes slip at the wall and we find a shear rate where microfractures localize in a preferential plane and the material flows. This behavior is reversible.     

On the interplay between strain rate and strain rate sensitivity on flow localization in the dynamic expansion of ductile rings

In this work a stability analysis on flow localization in the dynamic expansion of ductile rings is conducted. Within a 1-D theoretical framework, the boundary value problem of a radially expanding thin ring is posed. Based on a previous work, the equations governing the stretching process of the expanding ring are derived and solved using a linear perturbation method. Then, three different perfectly plastic material constitutive behaviours are analysed: the rate independent material, the rate dependent material showing constant logarithmic rate sensitivity and the rate dependent material showing non-constant and non-monotonic logarithmic rate sensitivity. The latter allows to investigate the interaction between inertia and strain rate sensitivity on necking formation. The main feature of this work is rationally demonstrate that under certain loading conditions and material behaviours: (1) decreasing rate sensitivity may not lead to more unstable material, (2) increasing loading rate may not lead to more stable material. This finding reveals that the relation between rate sensitivity and loading rate controls the unstable flow growth. Additionally a finite element model of the ring expansion problem is built in ABAQUS/Explicit. The stability analysis properly reflects the results obtained from the numerical simulations. Both procedures, perturbation analysis and numerical simulations, allow for emphasizing the interplay between rate sensitivity and inertia on strain localization.     

通气空泡生成和溃灭特性试验研究

为了研究通气流量对超空泡生成和溃灭的影响,在西北工业大学高速水洞实验室进行了系列通气超空泡生成和渍灭特征的试验.结果表明:空泡生成过程中,空泡长度和直径的变化特性与空泡溃灭时的变化特性相反;通气流量对空泡生成和溃灭均有较大影响,数据显示通气量对空泡生成的影响大于对空泡溃灭的影响.此研究为进一步研究超空泡的快速稳定生成提供了实验基础.     

The simulation of gas production from oceanic gas hydrate reservoir by the combination of ocean surface warm water flooding with depressurization

A new method is proposed to produce gas from oceanic gas hydrate reservoir by combining the ocean surface warm water flooding with depressurization which can efficiently utilize the synthetic effects of thermal, salt and depressurization on gas hydrate dissociation. The method has the advantage of high efficiency, low cost and enhanced safety. Based on the proposed conceptual method, the physical and mathematical models are established, in which the effects of the flow of multiphase fluid, the kinetic process of hydrate dissociation, the endothermic process of hydrate dissociation, ice-water phase equilibrium, salt inhibition, dispersion, convection and conduction on the hydrate dissociation and gas and water production are considered. The gas and water rates, formation pressure for the combination method are compared with that of the single depressurization, which is referred to the method in which only depressurization is used. The results show that the combination method can remedy the deficiency of individual producing methods. It has the advantage of longer stable period of high gas rate than the single depressurization. It can also reduce the geologic hazard caused by the formation deformation due to the maintaining of the formation pressure by injected ocean warm water.     

Aircraft atmospheric aerosols and ecological problems

The formation and development of atmospheric aerosols as a result of subsonic aircraft emissions are considered. The sequence of hydrodynamic and physicochemical processes in the combustion chamber, the engine duct, the jet, and the external atmosphere, leading to heterogeneous and homogeneous condensation and the formation of dispersed phases of various composition in the upper troposphere and lower stratosphere, is analyzed. The latest data are used to predict the amount of aircraft aerosol at these altitudes, which by the beginning of the next century may be comparable with traditional geological, anthropogenic and atmospheric factors. Attention is drawn to the fundamental effect — the formation of sulfur aerosols in the exhaust jet. Approximate models in which the important part played by binary condensation of a water-sulfuric acid mixture with the formation of fine droplets of sulfuric acid are proposed.Based on a paper read at the Seventh Congress on Theoretical and Applied Mechanics, Moscow, August 1991. Presented by V. V. Gogosov.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.6, pp. 57–72, November–December, 1992.The authors are grateful to A. B. Lebedev for actively assisting them with their work and discussing the results.     

Application of novel pressure-sensitive paint formulations for the surface flow mapping of high-speed jets

The principle of pressure-sensitive paints (PSPs) is based upon excitation of the luminophore molecules at a certain wavelength and the emission of this absorbed energy at a higher wavelength. By isolating these two wavelengths we insure that the results obtained are not affected by any background radiation. Various international research groups, such as: the Central Aero-Hydrodynamic Institute (Russia), the University of Washington, NASA Ames, Boeing and McDonnell Douglas (USA), have developed their PSP formulations and some are commercially available.Two paints, which have been developed in-house at the Aero-Physics Laboratory (APL) at the University of Manchester, are studied here. One formulation uses hydrochloric acid (PSP1–HCl) and the other acetone as the solvent (PSP2–Ace). The current study employs the well known schlieren photography technique together with the relatively new PSP method, with comparison to discrete measurements, to examine the flow through a two-dimensional air-ejector system and examines the efficacy of the PSP formulations in providing an accurate global pressure field of the aforementioned setup. Detailed analysis of the errors and drawbacks involved in PSP measurements along with possible solutions to overcome them are also presented. Fully expanded jet Mach numbers in the range of 0.52 ? M_j ? 1.36 were examined.     

Diffusion-reaction compromise the polymorphs of precipitated calcium carbonate

Diffusion is seldom considered by chemists and materialists in the preparation of materials while it plays an important role in the field of chemical engineering. If we look at crystallization at the atomic level, crystal growth in a solution starts from the diffusion of ions to the growing surface followed by the incorporation of ions into its lattice. Diffusion can be a rate determining step for the growth of crystals. In this paper, we take the crystallization of calcium carbonate as an example to illustrate the microscopic processes of diffusion and reaction and their compromising influence on the morphology of the crystals produced. The diffusion effect is studied in a specially designed three-cell reactor. Experiments show that a decrease of diffusion leads to retardation of supersaturation and the formation of a continuous concentration gradient in the reaction cell, thus promoting the formation of cubic calcite particles. The reaction rate is regulated by temperature. Increase of reaction rate favors the formation of needle-like aragonite particles. When diffusion and reaction play joint roles in the reaction system, their compromise dominates the formation of products, leading to a mixture of cubic and needle-like particles with a controllable ratio. Since diffusion and reaction are universal factors in the preparation of materials, the finding of this paper could be helpful in the controlled synthesis of other materials.     

Mechanism of wave formation at the interface in explosive welding

Some of the main progress on the investigation of the mechanism of the wave formation in explosive welding at the Institute of Mechanics is summarized and others' previous works are reviewed. Our systematic experiments and analysis do not substantiate the theory of wave formation based on Karman vortex-street analogy or Helmholtz instability. On the contrary, they show that material strength insensitive to strain rate plays an important role. A simple hydro-plastic model is presented to explain the main features regarding the interfacial wave formation and to estimate the magnitude of wave length. The result is in broad agreement with experiment.     

Possible classification of the self-oscillatory spouting regimes of plane vertical submerged jets of a heavy fluid

New results of an experimental investigation of self-oscillatory regimes of plane vertical jet spouting from beneath the free surface of a heavy incompressible fluid are discussed. The experiments were performed on a setup with discharge over a weir. The range of dimensionless jet submergence values on which bifurcation change of spouting regime is observable is studied. It is established that on the Froude number and dimensionless jet submergence ranges considered in the study six characteristic spouting regimes differing in free surface shape and self-oscillation frequency can exist. It is shown that these regimes can be subdivided into three typical groups with respect to the dependence of the self-oscillation period on the jet flow rate. A dimensionless parameter that makes it possible to identify the boundaries of the bifurcation change in spouting regimes is obtained for each of these groups. For certain spouting regimes without the formation of free jets numerical calculations are carried out using the STAR-CD software package; the calculated results are in good agreement with experimental data.     

The effect of oxidant flow rate on a coaxial oxy-fuel flame

The effect of oxidant flow rate on temperature, heat transfer, and NO_x formation of an oxy-fuel flame is investigated using numerical simulation. The finite volume approach is used to solve the governing equations. The realizable k-ε turbulence model and β-PDF model are adopted to simulate the turbulence-combustion interaction. There is a good agreement between the present numerical results and the reference experimental data. The exhaust temperature is decreased with decreasing the oxidant inlet flow rate. As an important result, the adiabatic flame temperature can be considered a key parameter in the oxy-fuel flame applications. Also, it is observed that increasing oxygen inlet angle causes a decrease in NO formation.     

Natural convection induced in a fluid by the hot inner walls of a “submerged” channel

The jet flows induced around a submerged channel due to the hot inner channel walls and the flow inside the channel are calculated. The formation of high-and low-density regions at the inlet and outlet of the channel is detected. The dependence of the flow rate on the channel orientation relative to the gravity force is analyzed. The onset of coherent flow structures results in the development of unsteady oscillating flows. Natural convection in the fluid is studied using the JoinCAD/FEM program package. The regularized Oberbeck-Boussinesq equations are solved using a finite-element method with the same order of the approximating functions.     

Influence of the erection regime on the stress state of a viscoelastic arched structure erected by an additive technology under the force of gravity

We study the influence of gravity forces on additively constructed objects of a viscoelastic aging material (in a special case, of a purely elastic material) in the absence of additional surface loads and prestresses in the accreted material elements. It is shown that the stress-strain state of such objects crucially depends on how the process of their gradual formation evolves in time. The main tendencies whose interaction determines the process of deformation of these objects under a given formation regime are revealed and analyzed. The general reasoning is illustrated by the results of numerous numerical experiments performed in the framework of the model of linear mechanics of accreted bodies, which was developed by the authors for studying the essentially two-dimensional engineering problem on the erection of a heavy circular arched structure (a semicircular vault) on a smooth horizontal base by the method of layer-by-layer thickening of a blank structure previously erected on the base. This problem is used as an example in the detailed studies of the influence of the erection regime of a viscoelastic aging structure on the development of its stress state. We show that it is very important to take into account the influence of gravity forces during the entire process of erection of heavy objects rather than in their final configuration. It is conclusively shown that, without considering this influence, one can arrive at completely false conclusions about the current and resulting states of the erected structures such as overestimation of their strength and stability at the stage of formation and of their bearing capacity in their operation. The possibilities of efficient control of the stress state of the considered arch structure by varying the rate of the additional material accretion to the structure are demonstrated.