CONFORMITIES TO LAW OF FORMING LAYER FOR POLYDISPERSE PELLET CHARGE ON SINTER BELT

Motion of pellet charge on the loading tray on a sinter belt is accompanied not only by the change of its grain-size composition, but by segregation processes, id est. by the redistribution of charge of different size particles for the most part friable material. The result of this process is formation of local discontinuity with pre-dominance of content for particles of certain factions. The traditional method for analysis of work for loading tray on the basis of factious classification does not allow to educe and analyze appearing heterogeneity in the most part friable material. It results in errors at the calculation for action of the system of the automated control by sintering process and ignoring of notational of the use of segregation of particles of friable material for optimization of technological process. The use of balance method enables to specify and spread understanding of mechanism of processes which take place during motion of pellet charge in relation to the loading tray, and also to form theoretical pre-conditions for the choice of the rational modes of operations of agglomeration separation of sintering plant. It is set that at monotonous increase of angle of slope for loading tray the segregation phenomena increase in a pellet charge, and after achievement of the defined value – go down, id est. have extreme character. Mentioned features of forming of layer for polydisperse material in the conditions of inconstancy of mechanical properties of its separate factions it is possible to take into account at the use of balance of grain-size composition of charge, loaded on a sinter belt, and charge, being on it, when conditional middle diameters of particles of their components must be equal. On the basis of the set conformities to law of forming of friable of structure of layer the method of authentication of grain-size compositions of pellet charge mixture is in theory reasonable in every its horizon taking into account a segregation during loading.

Determination of the Conditions for Carbon Materials Oxidation with Carbon Monoxide Formation at High Temperatures

In this paper, the influence of carbon material type, temperature and oxygen concentration in gas mixture on the processes of carbon monoxide formation in production of the electrodes by graphitization was explored experimentally. Specific quantity of gas formed for a definite time, reduced to mass unit of carbon loading using pitch, packing materials and charge mixture of industrial use, was calculated. It is demonstrated that pitch provides the highest rate of carbon oxidation with the release of CO and substantially exceeds packing materials and charge mixture for this index.

Materials and technologies of powder metallurgy in components of aviation and space engineering

Examples of the implementation of powder metallurgy methods and their individual elements in the processes of producing materials with special properties and products thereof are considered. The possibility is shown and the results of producing radar-absorbing and radar-transparent materials in the form of solid bodies and coatings are evaluated. The addition of technological transitions, traditional for powder metallurgy, providing in general the production of radar-transparent materials, with the processes of mechanically activated synthesis and mechanically activated self-propagating high-temperature synthesis at the stages of preparing powders for molding, makes it possible to make the transition to the production of radar-absorbing materials. The high efficiency of both has been confirmed experimentally. The transition from a single-component composition of the initial charge mixture through the formation of the phase composition of the material due to the inclusion of powder components into the mixed charge, the composition and crystal structure of which remain unchanged at all stages of its preparation, to the synthesis of the required phase composition due to the interaction of powder components at one of the stages of technological conversion makes it possible to synthesize, for example, silicon carbide ceramics directly in practically useful products, particularly, substrates of optical mirrors for remote sensing of the Earth. The technological operations developed in powder metallurgy have become a background for the production of energy-saturated heterogeneous composite materials. Actively developing additive technologies, as a relatively new branch of powder metallurgy, expands its capabilities practically boundless.

Acid-Base and Luminescent Properties of Gd2O2S: Tb Luminescent Phosphors Synthesized in a Reducing Atmosphere

Gd2O2S:Tb phosphors with different terbium content are prepared in a reducing atmosphere at various synthesis conditions. The effect of an activator and Na4P2O7 flux concentrations upon photo-and X-ray induced luminescence of the synthesized samples as well as on their acid-base properties and morphology is studied. The addition of Na4P2O7 flux into the charge mixture leads to a significant increase of the phosphor particle size. A positive correlation is found between the particle size and pH value of the phosphor aqueous slurry. The photoluminescence intensity is found to mostly depend on the activator concentration, while X-ray luminescence intensity primarily depends on the particle size and crystal structure perfectness of the phosphor matrix. Charge mixture compositions and synthesis conditions providing Gd2O2S:Tb phosphors with the highest photo-and X-ray luminescence intensity are determined. A Gd2O2S:Tb phosphor with X-ray luminescence intensity exceeding the values for the commercial phosphor KEP-45 of a similar composition is developed. The obtained phosphors can be used for the manufacture of intensifying screens applied in industrial X-ray flaw detection.

Investigation of Thermal Fields at Phase Boundaries in Powder Mixtures that are Subject to Melting and Chemical Transformation

An important part of the process of parts hardening by the induction surfacing method is the heating of hard alloy particles and flux in charge mixture. The article describes comprehensive studies on measurement and simulation of temperatures at phase boundaries in complex melting and heat-sensitive powder mixtures. To record the temperature in the induction surfacing process, it is proposed to apply CA micro-thermocouple method and the thermal indication method using SHS compositions. The developed methods for complex temperature recording in the process of induction surfacing allow to determine the melting temperature of the charge mixture and its single components.

Improving the Characteristics of Wear-Resistant Coatings Obtained by HDTV-Boration, their Modification by Intermetallic Compounds of Fe-Al and Ni-Al Systems

Innovative technology of HDTV-borating, that is distinguished by high hardness, strength, wear resistance and corrosion resistance occupies a special place among the hardening processes for steels and construction materials. During the new technology process HDTV-boration of structural steel 65Mn (65Г in Russian) under a mix layer of charge mixture based on fused borate fluxing agent P-0.66, boron carbide and intermetallic compounds FexAly, NixAly. Using the methods of X-ray phase analysis, spectrography and metallography, the composition and structure of coatings were determined, the microhardness distribution over the coating thickness was studied. In the coatings, new phases of intermetallic compounds, the double superhard boride Fe2AlB2, were found; in the coatings, the base iron boride is FeB, what leads to an increase in their hardness and wear resistance. Modification of boride coatings formed by intermetallic compounds with melting temperatures close to the process temperature of HFC surfacing leads to a decrease in the cracks number and the appearance of new consumer qualities of the material.

Comparative Analysis of EGR and Air Dilution in Spark-Ignited Natural Gas Engines

Industrial natural gas engines are used in a wide range of applications, each with unique requirements in terms of power density, initial cost, thermal efficiency, and other factors. As a result of these requirements, distinct engine designs have evolved to serve various applications. Heavy-duty spark-ignited engines can generally be divided into two broad categories based on their charge characteristics and method of emissions control. Stoichiometric engines are widely used in applications where first cost, absolute emissions and relative engine simplicity are more important than fuel consumption. In most of the developed world, stoichiometric engines are equipped with a three-way catalyst to control emissions of nitrogen oxides (NOx) as well as products of incomplete combustion and raw unburned fuel. Dilution of the charge mixture with excess air reduces the peak combustion gas temperature and associated heat rejection. As a result, lean burn engines are generally able to achieve higher efficiency and power density without inducing excessive component temperatures or end gas knock. NOx formation is mitigated by the reduced gas temperatures, such that most regulatory standards can currently be met in-cylinder. Significant obstacles exist to meeting more stringent future emissions regulations in this manner, however. Another possible strategy is to dilute the charge mixture with recirculated exhaust gas. This offers similar benefits as air dilution while maintaining the ability to use a three-way catalyst for emissions after-treatment. While similar principles apply in either case, the choice of diluent can have a significant impact on knock resistance, emissions formation, thermal efficiency, and other parameters of importance to engine developers and operators. This work aimed to examine the unique characteristics of EGR and air dilution from a thermodynamic and combustion perspective. A combination of cycle simulation tools and experimental data from a single-cylinder test engine was applied to demonstrate the impact of diluent properties on a fundamental level, and to illustrate departures from idealized behavior and practical considerations specific to the development of combustion systems for spark-ignited natural gas engines.

Model-Based Control for Mode Transition Between Spark Ignition and HCCI Combustion

While the homogeneous charge compression ignition (HCCI) combustion has its advantages of high thermal efficiency with low emissions, its operational range is limited in both engine speed and load. To utilize the advantage of the HCCI combustion, an HCCI capable spark ignition (SI) engine is required. One of the key challenges of developing such an engine is to achieve smooth mode transition between SI and HCCI combustion, where the in-cylinder thermal and charge mixture properties are quite different due to the distinct combustion characteristics. In this paper, a control strategy for smooth mode transition between SI and HCCI combustion is developed and experimentally validated for an HCCI capable SI engine equipped with electrical variable valve timing (EVVT) systems, dual-lift valves, and electronic throttle control (ETC) system. During the mode transition, the intake manifold air pressure is controlled by tracking the desired throttle position updated cycle-by-cycle; and an iterative learning fuel mass controller, combined with sensitivity-based compensation, is used to manage the engine torque in terms of net mean effective pressure (NMEP) at the desired level for smooth mode transition. Note that the NMEP is directly correlated to the engine output torque. Experiment results show that the developed controller is able to achieve smooth combustion mode transition, where the NMEP fluctuation is kept below 3.8% during the mode transition.

Mathematical Model of Iron Reduction with Aluminothermic Method

Utilization of industrial waste in foundry engineering is one of approaches for decrease of production cost price. This technological process may be based on exothermic oxidation-reduction reaction with the resulting formation of iron from dross. Initial charge mixture consists of dispersed aluminum, iron dross and admixtures. This paper is concerned with mathematical modeling of thermite steel production. Presented model takes into account thermal, mechanical and kinetic processes occurring in aluminothermic method of steel melt production.