Flow Of Combustion Products Research Articles

Application of an inertial vacuum trap for separation of the solid phase of carbon dioxide from the flow of fuel combustion products of boiler units

The technological process of low-temperature purification of fuel combustion products of boiler units from carbon dioxide by freezing it in a turboexpander and separating from the fuel combustion products flow in a separator is considered.The issue of separation of solid carbon dioxide from the flow of fuel combustion products of boiler units using a bag filter, an electric precipitator, a cyclone separator and an inertia-type separator is considered. Based on the analysis, the use of an inertial vacuum separator for separating the solid phase of carbon dioxide from the flow of fuel combustion products is proposed.Solidworks and ANSYS CFX modules were used for numerical modeling. To solve, the equations of continuity, motion, energy, and the k-ε model equations are used. The closing equation is for the effective and turbulent viscosity. There is also a description of the forces affecting the movement of the dispersed phase. The stream is considered lightly dusty.Numerical studies of the dispersed flow in the channel of an inertial-vacuum separator and in the previously used cyclone TsN-11 were carried out. The initial data for the calculation were taken based on the known mass flow rate and particle concentration, as well as from the continuity equation. From the results obtained, we can draw conclusions about a directly proportional relationship between the growth of the flow rate characteristics of the flow, the speeds along the flow path of the apparatus at the inlet and the resistance of the apparatus.Besides, based on the obtained calculation results, it was concluded that it is necessary to additionally install a rotary industrial air blower in order to create the necessary pressure drop in the inertial vacuum separator. The economic and environmental feasibility of installing a rotary air blower is consideredThe range of consumption of fuel combustion products has been determined at which the most effective purification of fuel combustion products from carbon dioxide in an inertial vacuum separator is possible within the technical characteristics of the refrigeration capacity of turborefrigeration machines.

Multiphase reactive flow and heat transfer simulations in the unlocking components of an ultra-low shock pyrotechnic separation nut

This study presents a multiphase reactive flow and conjugate heat transfer model for the unlocking components in an ultra-low shock pyrotechnic separation nut. The process of the shape memory alloy (SMA) tube heated by the heat released from the combustion of the micro gas pyrotechnic charges was simulated. The established model was validated by comparing the simulation with experimental results for the temperature of the outer wall of the SMA tube. Then, the detailed ignition and combustion of micro gas pyrotechnic charges, transient flow of combustion products, and heat transfer in the SMA tube were analyzed. The effects of the amount and burning rate of micro gas pyrotechnic charges on the unlocking time were investigated. It is found that the unlocking time decreases with an increase in the amount of micro gas pyrotechnic charges. Moreover, the reduction range of the unlocking time decreases with the increase in the amount of micro gas pyrotechnic charges. Reducing the differences in the burning rate contributes to enhancing the consistency of unlocking time.

Simulation of simultaneous tablet–emitter surface ignition by a flow of two-phase combustion products and tablet-emitter ejection from a cartridge case

Simulation of simultaneous tablet–emitter surface ignition by a flow of two-phase combustion products and tablet-emitter ejection from a cartridge case

Evaporation rates of water droplets with soluble and insoluble additives

The relevance. Caused by a wide practical use of water with typical soluble and insoluble additives in the following technologies. They are: thermal and fire purification of liquids, polydisperse fire extinguishing, combustion of waste-derived slurry fuels, cleaning of heat-loaded surfaces, creation of heat agents based on combustion products. Any change in liquid component composition leads to a change in its thermophysical properties, heating rates and phase transformations. So far, there is not enough experimental data on evaporation rates of water droplets with typical soluble and insoluble additives. The aim. Experimental determination of evaporation rate of water droplets with typical additives under various heating methods. The methods. To register sizes of moving droplets, optical registration methods based on a high-speed video camera were used. To register the temperature of combustion products, a measuring complex, consisting of an NI 9219 board and four chromel-alumel fast-response thermocouples, was used. The authors used four methods of droplet heating: in the flow of combustion products with the dominance of convective heat transfer, in a tubular muffle furnace with the dominance of radiative heat transfer, on a solid surface with the dominance of conductive heat transfer, and in a flame with the dominance of mixed (convective and radiative) heat transfer. The results. The authors have determined the ranges of change in evaporation rates of water droplets with typical (soluble and insoluble) additives for various heating methods with the dominance of convective, radiative, and conductive heat transfer. The effect of an additive type and concentration, heating method and heating medium temperature on of droplet evaporation characteristics was established.

Detonation in van der Waals Gas

Solving problems of detonation control is associated with obtaining detailed information about the gas dynamics accompanying the detonation process. This paper focuses on the dynamics of real gas flow through a plane detonation wave. The influence of real gas parameters on the Chapman–Jouguet detonation process has been studied. The process is described using the Rankine–Hugoniot system of equations. To model the thermodynamic properties of a real gas, the van der Waals equation of state is used. Equations are obtained to determine the ratio of speeds and pressures during the passage of a wave. The influence of van der Waals parameters on changes in the parameters of the detonation process was elucidated. An increase in parameter A slows down the increase in pressure in the detonation wave, and an increase in parameter B enhances it. Differences in the speed of combustion products for ideal and real gases are shown. For an ideal gas, combustion products flow from the detonation front at a critical (sonic) speed. For a van der Waals gas, the speed of combustion products may be greater than the critical one. Moreover, both factors, additional pressure (A) and additional volume (B), lead to acceleration of combustion products. Effects of heat release on the process parameters were elucidated.

Generatsiya elektricheskogo polya v pylevoy plazme

A nonuniform dusty plasma, micrometer-size particles or microdroplets of which are located in a dense gas or in atmospheric air, is excited by an energy pulse leading to the weak ionization of the gas. As a result, the particles charge through the attachment of gaseous ions to them. The stability of dusty plasma is determined by the low mobility of charged microparticles. The conditions under which the separation of negative and positive charges occurs in a dusty plasma with the creation the electric field are considered. The criteria are presented for the generation of atmospheric electricity in a dense cloud as a result of the gravitational falling of charged water microdroplets in the atmosphere, the weak ionization of which occurs under the action of cosmic rays. It is shown that this is possible only under a nonuniform space distribution of water microdroplets in the cloud. The peculiarities of a dusty plasma are considered. This plasma exists in Saturn’s rings and in the flow of coal combustion products, as well as in the dusty atmosphere of a coal mine.

Drag and Heat Transfer of Metal and Oxide Agglomerates in a Flow of Solid-Propellant Combustion Products

Drag and Heat Transfer of Metal and Oxide Agglomerates in a Flow of Solid-Propellant Combustion Products

Численное моделирование течения продуктов сгорания энергетического конденсированного материала в проточном тракте с учетом эрозионного эффекта

Численное моделирование течения продуктов сгорания энергетического конденсированного материала в проточном тракте с учетом эрозионного эффекта

Drag and heat transfer of metal and oxide agglomerates in flow of combustion products of solid propellant

Modeling and simulation of the motion of agglomerates with a complex composition and shape in the flow of combustion products is of interest for problems related to design and optimization of solid propellant rocket motors. An approach is developed for modeling of unsteady processes that occur when a particle consisting of an aluminum droplet and a condensed oxide particle attached to it (aluminum droplet with oxide cap) is transported by a viscous incompressible fluid flow. Methods are proposed to take into account the sliding of an attached oxide particle over the surface of the aluminum droplet. The results of numerical computations are used to find the drag and heat transfer coefficients of a non-spherical particle at flow velocities corresponding to the formation of separation zones. The constructed model is one of the components of a more general mathematical model designed to calculate two-phase flows of combustion products based on a multi-scale approach to the simulation of two-phase flows in a complex environment.

The influence of wind on smoke propagation to the lower layer in naturally ventilated tunnels

A tunnel fire is a dangerous accident, which may lead to serious injuries and deaths. This work studies the flow of combustion products during naturally ventilated tunnel fires, i.e., without a mechanical ventilation system. In such an event, two stratified layers with opposing velocity directions are formed. The safety of tunnel users is compromised if the smoke, initially flowing in the upper layer, contaminates the lower one, which has been found to happen abruptly at a distance xc from the fire. This is caused by the cooling of the jet leading to a large enough decrease in momentum for the smoke to be entrained by the lower layer. Natural ventilation may be an effective and inexpensive smoke control strategy if the fire-to-portal distance is shorter than xc. However, there is a lack of research to predict under which conditions this occurs and how xc is influenced by factors such as natural wind. An open-source Computational Fluid Dynamics (CFD) code, fireFoam, was used to conduct Large Eddy Simulations (LES) of naturally ventilated tunnel fires. The numerical model was validated by performing a simulation of a large-scale tunnel fire test. Additionally, 7 fire scenarios with varying wind velocities were simulated. The contamination distance xc was found to decrease for higher wind velocities. Furthermore, a simple semi-analytical model was employed to obtain quick estimates of xc, by calculating ceiling jet properties using balance equations and empirical correlations. Model coefficients were calculated using the CFD results.

Численное моделирование сажеобразования в восстановительных газогенераторах кислородно-метановых жидкостных ракетных двигателей

A method for numerical simulation of operating processes in reducing gas generators with calculation of the condensed phase (soot) formation process detailed structure has been developed. It is assumed that soot is formed from gas-phase fuel in two stages. At the first stage, active radical nuclei are formed, and at the second stage, carbon black particles are formed from these nuclei. Numerical modeling of processes, fuel mixing and combustion, as well as soot formation in model reducing oxygen-methane gas generators with gas-liquid coaxial mixing elements of jet-jet type has been performed. Gas generators of this type can be used in promising oxygen-methane liquid rocket engines operating on open and closed circuits with reducing gas generators, as well as on the gas-gas circuit having reducing and oxidizing gas generators. A comparative analysis of soot formation features in gas generators with single- and multi-nozzle mixing heads has been performed. It is shown that a decrease in the pitch between the mixing elements leads to a significant change in the mixture formation processes, fuel combustion and the flow of combustion products (all other conditions being equal), which significantly reduces the intensity of condensed phase formation in reducing gas generators. The numerical simulation method will be used for studies of fuel combustion and condensed phase formation in regenerative gas generators of modern and advanced liquid rocket engines at the stages of development, design and improvement

Investigating the radiation-convective heat exchange of a metal-ceramic plate

The paper presents the experimental data on heat exchange during thermo-cyclic interaction of a flame jet with a thermal barrier ceramic coating. Cooling due to radiant heat transfer into the environment allows organizing heat exchange in such a way that when a flow of combustion products with a temperature of 1500 °C flows onto the sample, the temperature on the surface of the TBC does not exceed 1200 °C. The thickness of TGO after 1500 thermal cycles was 9.5 microns

The efficiency analysis of the turbo air refrigerators for producing solid carbon dioxide from the boiler combustion products flow

The paper considers the efficiency analysis of the turbo air refrigerators for producing solid carbon dioxide from the boiler combustion products flow. The process of obtaining solid carbon dioxide in the turbo air refrigerating machine was modelled. A numerical study of the process and degree of solid carbon dioxide freezing in the turbo air refrigerating machine was performed. The range of the boiler power characteristics, where the most effective solid carbon dioxide freezing is possible within the technical specifications of the turbo air refrigerating machines, was determined.

НЕСТАЦИОНАРНОЕ ПОВЕДЕНИЕ ЗАРЯДА ТТ БЕССОПЛОВОГО РДТТ ПОД ДЕЙСТВИЕМ ГАЗОДИНАМИЧЕСКОЙ НАГРУЗКИ

The numerical solution to a conjugate problem of an unsteady flow of combustion products in a flow path of the nozzleless solid rocket motor (SRM) and the oscillation of a solid propellant charge under the action of the forces directed from combustion products is considered. The Navier-Stokes equations for a compressible viscous gas are used to mathematically describe the flow of the combustion products. To model the charge oscillations, the equations of solid mechanics are applied, which take into account the propellant hyperelasticity. Pressure distributions and the propellant burning rate along the charge channel are presented for different models of the propellant burning rate. It is revealed that at the stage of SRM design, the use of the burning rate law, determined by pressure in the head of the combustion chamber, is more preferable in order to assess the internal ballistic characteristics. The solution to the conjugate problem shows that in the nozzleless SRM with the propellant having low Young's modulus, resonance can occur, which causes uncontrolled charge oscillations.

Developing mathematical model of the 3D turbulent flow of combustion products in solid propellant rocket engines

Developing mathematical model of the 3D turbulent flow of combustion products in solid propellant rocket engines

Digital Simulation of a High-Energy System Using a Boron–Aluminum Admixture as a Fuel

Numerical modeling of the flow of combustion products of a fuel containing a boron–aluminum admixture in the nozzle of a solid-propellant rocket engine has been carried out. The advantage of boron–aluminum over aluminum in using in composite solid propellants has been shown.

Theoretical Study of the Coagulation of Ash Particles in Waste Gases during the Vibrating Combustion of Solid Biofuel

Consideration has been given to the influence of acoustic oscillations on the process of coagulation of soot particles suspended in the flow of combustion products of wood and peat. It has been shown that at the characteristic parameters of vibrating combustion of these materials, the main factor of growth of the soot particles in the process of their coagulation is the deposition of small particles well entrained by the gas on large ones that are streamlined by the gas but are poorly entrained by it.

ТЕПЛОФИЗИЧЕСКИЕ ХАРАКТЕРИСТИКИ И ТЕРМОЭРОЗИОННАЯ СТОЙКОСТЬ КЕРАМИЧЕСКОГО МАТЕРИАЛА НА ОСНОВЕ КАРБИДА БОРА

A study of the thermophysical characteristics, heat resistance, and thermal erosion resistance of high-temperature structural ceramics (SC), which was developed at NTUU "I. Sikorsky Kyiv Polytechnic Institute" under the supervision of Corresponding Member of the National Academy of Sciences of Ukraine, Professor P. I. Loboda was made. This high-temperature structural ceramics is intended for use in aerospace engineering, in particular - for the manufacture of aerodynamic surfaces of reusable hypersonic aircraft and heat-stressed elements of the gas-dynamic paths of their engines. The samples of B4C-SiC-B6Si ceramics of two compositions (No. 1 and No. 2) were studied, which differ in the mass content of the initial components. Temperature dependences of the specific heat and thermal conductivity of the spacecraft, radiation coefficient, heat resistance in an oxidizing environment, and the thermal erosion resistance in supersonic flow of combustion products of an air-kerosene fuel mixture were determined. The temperature dependence of the specific heat was determined using an IT-c-400 instrument (in the range of 40 °C - 440 °C) and by the calculation of the temperature dependences of the specific heat capacity of the system components following the Reno rule (up to 2100 °C). The temperature dependence of the thermal conductivity coefficient of the SC of composition No. 1 was determined by solving the inverse heat conduction problem on a computer model based on experimental data. Temperature fields and heat fluxes were obtained under conditions of one-sided heat-ing with a reducing flame of a propane-oxygen welding burner. The thermal conductivity coefficient of SC composition No. 1 increases from 11 W/(m×K) at 20 °С to 25 W/(m×K) at 1400 °С. Its radiation coefficient in the temperature range 1000 °С - 1400 °С is ε = 0.96 ± 0.02. Heat resistance of SC of both compositions in the oxidizing flame of an oxygen welding burner at a surface temperature of 1400 °C has demonstrated that after two hours of heating, the average values of mass ablation for the two tested samples of compositions №1 and № 2 respectively 2.1% and 1.4% (a sample thickness of 4 mm). Tests in the supersonic flow of combustion products at the same surface temperature confirm the high resistance of the material to thermoerosion in the oxidizing medium. The change in the morphology of the heated surface of the sample after six five-minute heating cycles was manifested only by an increase in its roughness without visible oxidation. High thermal conductivity, heat and thermoerosion resistance, radiation coefficient of the studied SC at a temperature of 1400 °C in combination with low density (2.7 g / cm3) make this high-temperature structural material of aerospace technology promising for use.

Расчетная оценка геометрических параметров спринклерных установок водяного пожаротушения высотных стеллажей

Рассмотрены вопросы, связанные с применением спринклерных автоматических установок водяного пожаротушения стеллажей. Проанализированы соответствующие нормативные документы. Описаны варианты решения задач определения расхода воды из оросителя, координат места его установки, а также углов распыла огнетушащего вещества и наклона оси оросителя. Приведены примеры расчета геометрических параметров спринклерных автоматических установок водяного пожаротушения стеллажей. Fires at objects whith high-rack storage of combustible materials are particularly dangerous because of the rapid spread of the flame vertically, the risk of collapse of the racks and the damaging effects of high temperature on structural elements of the building. The main method of extinguishing such fires at the initial stage is the use of automatic sprinkler fire extinguishing systems (AUP). The requirements for AUP parameters (types of detectors and sprinklers, their characteristics and distances) depending on the height of the room and storage are currently set out in two normative documents: the set of rules (SP 241.1311500.2015) and the organization standard (VNPB 40-16). Unlike the SP, where there is provided only the supply of a fire extinguishing substance (FES) - water vertically down with high-flow sprinklers of type SOBR (ESFR) and there are no requirements for the type of fire detectors, VNPB provides the use of different types of detectors (aspiration, smoke, heat), forced start-up of AUP sprinklers, which reduces the time of free fire development and the supply of FES by a flow shaper with the spray angle ≈ 600 at an angle  to the vertical both to the horizontal and lateral surfaces of the racks. This article discusses the issues of determining the parameters of automatic sprinkler systems for water fire extinguishing of racks. Variants of solving synthesis problems are given - the choice of the places for installing sprinklers depending on the height and width of the racks, their axis of inclination, and also the spray angle. To solve these problems, the computer program called struja.exe was created, a series of calculations on which showed a negligible effect of aerodynamic drag due to relatively small distances. Examples are given. Thus, the features of the sprinkler AUP for the protection of rooms with high-rack storage and the task of determining its geometric parameters are considered. In this case, forced activation of the sprinkler follows in order to avoid a delay in the start of extinguishing. In the future, it is also desirable to conduct additional field experiments with sprinkler water supply and also (if possible) evaluate the effect of ascending flows of combustion products on the water flow from the sprinkler.

Numerical simulation of submicron particles formation during the combustion of coals, taking into account coagulation and dust content of combustion products

Homogeneous-heterogeneous bulk condensation of potassium sulfate vapor has been numerically simulated in a dusty vapor-gas flow of coal combustion products upon their cooling along a technological path. A closed model that we have proposed for the formation of submicron particles in coal combustion products has been employed. Data on the concentration of particles formed at varied parameters of heterogeneous condensation sites have been obtained. Variations in the relative contributions of the homogeneous and heterogeneous mechanisms with variations in flow dustiness have been considered. Data on the influence of coagulation processes on the parameters of submicron particles resulting from coal combustion have been presented.