ANALYSIS OF TECHNOLOGICAL POSSIBILITIES OF TWO-CHAMBER IMPULSE DEVICES FOR SHEET STAMPING

Проведен анализ технологических возможностей двухкамерных устройств для листовой штамповки с одной и двумя камерами сгорания. В устройствах с одной камерой сгорания штамповка детали происходит в холодном состоянии заготовки под действием на нее гибкой среды за счет кинетической энергии поршня, ускоряемого продуктами сгорания газообразной топливной смеси. В устройствах с двумя камерами сгорания процесс штамповки совершается с нагревом заготовки воздействием на нее горячего газа, образованного при сгорании в верхней камере предварительно сжатой топливной смеси. При этом сжатие смеси осуществляется за счет энергии продуктов сгорания, образованных в нижней камере сгорания. Доказано, что устройства с одной камерой сгорания целесообразно использовать для штамповки из пластичных сортов сталей деталей разнообразной формы толщиной до 4 мм и из пластичных цветных сплавов толщиной до 8 мм. Устройства с двумя камерами сгорания целесообразно использовать для штамповки деталей из малопластичных сортов алюминиевых, титановых сплавов и других труднодеформируемых сплавов. Двухкамерные устройства для листовой штамповки обладают широкими технологическими возможностями и могут быть эффективно использованы в мелкосерийных производствах для штамповки деталей различной формы We carried out the analysis of technological capabilities of two-chamber devices for sheet stamping with one and two combustion chambers. In devices with one combustion chamber, the stamping process is carried out in the cold state of the workpiece by the action of an elastic medium on it, using the kinetic energy of the piston accelerated by the combustion products of the gaseous fuel mixture. In devices with two combustion chambers, the stamping process is carried out with the heating of the workpiece by the action of the hot gas formed during combustion in the upper chamber of the pre-compressed fuel mixture. In this case, the mixture is compressed due to the energy of the combustion products formed in the lower chamber. We established that devices with one combustion chamber are expedient to be used for stamping parts of various shapes with a thickness of up to 4 mm and from plastic non-ferrous alloys with a thickness of up to 8 mm from ductile steels. Devices with two combustion chambers are advisable to be used for stamping parts from low-plastic grades of aluminum, titanium alloys and other hard-to-deform alloys. Two-chamber devices for sheet stamping have wide technological capabilities and can be effectively used in small-scale production for stamping parts of various shapes

Improving the Environmental Safety of Combustion Products in the Development of Designs of Magnetic-Electric Activators for Industrial Gas Combustion

The aim of this research was to examine the combustion process of the magnetic-electric activation of hydrocarbon-containing waste gases for heat generation. A method for analyzing the composition of the gases was also developed. Keywords: industrial gas combustion, magnetic-electric activation, heat generation

Analysis of technological conditions for the formation and burnout of carcinogenic pahs in boiler flue gases

THE PURPOSE. The necessity of establishing emission standards for highly toxic substances with carcinogenic properties in the context of the implementation of new principles of state regulation of environmental protection activities at energy enterprises is substantiated and confirmed. The analysis of the features of the formation and burnout of carcinogenic polycyclic aromatic hydrocarbons in the flue gases of boilers during the combustion of coals in lowtemperature conditions of the furnace process is carried out. Based on the analysis, the total and partial indicators of the harmfulness of flue gases were calculated in order to assess and predict the overall toxicity of coal combustion products, taking into account the contribution of carcinogenic substances.METHODS. When calculating the overall toxicity of flue gases, a systematic analysis and generalization of experimental data on the content of carcinogenic and non-carcinogenic polycyclic aromatic hydrocarbons in the combustion products of low-power boilers was applied.RESULTS. As a result of the performed study, the contribution of carcinogenic and non-carcinogenic polycyclic hydrocarbons to the overall toxicity of boiler flue gases during the combustion of Azeysky, Mugunsky, Cheremkhovsky and Tugnuy coal was determined. It is shown that substances such as benz(a)pyrene, fluoranthene, pyrene and phenanthrene significantly affect the level of the total indicator of the harmfulness of combustion products from 38.8 to 53.6%.CONCLUSION. The obtained research results can be applied at energy enterprises at the stage of substantiating the introduction of regime-technological and environmental measures in order to develop measures to improve environmental efficiency through technological rationing of carcinogenic emissions.

Thermodynamic Analysis of a Jet Engine Using a Liquid Propellant

Combustion-chamber is a critical component of the propulsion engine, which is widelyused in the space industry and aeronautics. The goal of this article is to perform a numericalanalysis on the combustion process using a liquid-type propellant. The steps that must be followeduntil total combustion is achieved are emphasized. It concerns the fuel feeding phase, its injectionand the combustion operation. The amount of combustion products and the energy generated areevaluated. It has been shown that the liquid propellant may present an efficient alternative fuelthan the kerosene. In addition, the temperature of combustion does not exceed a certain limit toavoid structural problems in the chamber. The parametric survey allowed determining the range ofthe most influence factors, including the pressure, mixture richness, velocity and flow rates ofinjection for the fuel and oxidizer. The number and type of injectors revealed a considerableinfluence on the velocity and flow rates of injection. To maximize thrust force and systempropulsion, a careful selection of chamber material and ignition methods is required. A thorough inspection on the issues of walls cooling showed the necessary survey of maximum temperaturesthat may be reached during the combustion. Finally, an investigation of the thermal exchangethrough the walls will be very interesting.

The Influence of Thermal Dilution on the Microstructure Evolution of Some Combustion-Synthesized Refractory Ceramic Composites

Modeling the self-sustained high-temperature synthesis (SHS) reaction via thermal dilution and transformation of the reaction heterogeneous media into a moderate exothermic one has unlimited potential for designing inorganic powders of a certain morphology beneficial for advanced consolidation. Thermal/inert dilution of the high-exothermic mixtures leads to the fluent decrease of both the combustion temperature and velocity, thus allowing to tailor the thermal regime of the combustion process, therewith contributing to high yield of reaction and governing the microstructural features of the combustion products. In the current review, we shed on light on the possibilities of this effective strategy to control the thermal behavior of the SHS process for the preparation of applicable powder precursors for the subsequent successful sintering. Since the SHS process of some refractory ceramics (MoSi2, TiB2, TiC, etc.) involves a relatively violent reaction rate and high combustion temperature, achieving a high level of microstructure control in these systems is often challenging. The challenge was tackled with a thermal dilution approach, attaining considerable enhancement in the homogeneity among phases with an increase of diluent content along with microstructure refinement.

Analysis of the use of transformable elements in intelligent tunnel ventilation systems

All main and auxiliary equipment in the tunnel with an intelligent ventilation system are designed to ensure the safety. These systems “talk” and “listen” to each other, make decisions to switch on/off certain system(s) or part(s) thereof and duly inform the tunnel operator, who is authorized to the centralized control of all systems of necessity. The present article uses the numerical models to assess the efficiency of the transformable elements ensuring safe operation of the tunnels. The idea of their use is based on an artificial increase of the tunnel aerodynamic resistance by means of a flexible element, which will hamper the dissemination of combustion products, but not the movement of people through the tunnel and will help isolate clean and polluted air masses. Such resistance will be used to swiftly divide the tunnel carriageway into smaller sections what will help extinguish the fire as early as at its initial stage, prolong the evacuation time and save lives during the strong uncontrollable fires. As for the compact transformable element, it can be used in both, the operating and the planned tunnels, as it in practice does not reduce the volume of valuable underground space.

Comparative analysis of characteristics of liquid fuel combustion for various designs of oil-steam burners

The paper presents a comparative analysis of experimental data on combustion of liquid hydrocarbon fuels in the presence of superheated steam in two designs of the developed burners. By the example of diesel fuel burnt in a spray burner it is shown that lower values of nitrogen oxide contents in the exhaust gases are achieved in comparison with an evaporative burner. At that, the content of carbon monoxide in some regimes is lower for the evaporative burner. The regimes with the minimum content of toxic combustion products are found for both designs of the burners.

Heat Exchange and Hydrodynamic Characteristics of Unified Package of Cold Layer of RAH

Heating the air in the boiler air heater with the heat of fuel combustion products performs the functions of increasing the fuel combustion temperature, increasing the temperature level of gases in convective heating surfaces, improving ignition and fuel combustion conditions, increasing boiler efficiency by utilizing waste gas heat, improving fuel quality due to its preliminary supply, etc. However, the peculiarities of the process of heating the air in the air heaters do not allow to achieve a decrease in the temperature of the exhaust gases. This is due to the unfavorable ratio of heat capacities of flue gases and air, as well as corrosion and contamination of the heating surfaces of air heaters. The research of heat transfer processes and hydraulic resistance of unified package of cold layer of RAH is depicted at this work. The graphic dependence of the change in the coefficient of hydraulic resistance and Nu number for unified packages with single line of sheets and simplified profile with corrosion resistance enamel from the Reynolds number for different values of the length of the replaced areas was constructed. The unified packing of the simplified profile has increased by 1.17 times equivalent diameter and is characterized by good operational parameters and takes into account the risk of contamination of heating surfaces due to the enamel coating.

Development of Highly Efficient Radiation-Convective Recuperator for Furnace of Secondary Aluminum Melting

The high efficient design of the radiation-convective recuperator with secondary emitters have been proposed, in which due to the rational arrangement of heating surfaces, as well as due to the installation of secondary emitters in flues, an increase in heat perception is transmitted to the secondary heat carrier – preheating air. High efficiency of air preheating is provided by two-stage heating: 1st stage of heating – the internal air ring channel with bilateral heating which is washed by combustion products from the parties of the central cylindrical and peripheral ring channels of combustion products; 2nd stage of heating – the external air ring channel in which unilateral heating by products of combustion from the peripheral ring channel of products of combustion is organized. Inner and outer annular air ducts (tanks), interconnected by bypass pipes. To increase the efficiency of heat transfer in the considered recuperator in the central channel of combustion products is placed emitter, which consisting of intersecting radial plates, and in the annular channel of combustion products are placed auxiliary emitters, which made in the form of flat radial edges. These emitters provide an increasing in total heat flux to the walls of the channels of the recuperator. On the basis of the conducted theoretical researches, engineering calculations and CFD – modelling the characteristics of operation of the recuperator for its installation on the furnace of secondary smelting of aluminium are defined. The main advantages of the new design of recuperator are high thermo-hydraulic efficiency, compactness and low metal consumption, ease of installation on the furnace and no need for placement in separate chimneys. It is established that the recuperator provides air heating ta,ex ~ 400 °C at an acceptable aerodynamic drag (pressure drop) on the air track (∆pa ~ 1000 Pa). Appropriate design documentation has been developed for the manufacture of the recuperator, which is installed on a pilot furnace of secondary aluminium smelting by California Die Casting (USA).