Mathematical Model Of Combustion Research Articles

SIMULATION THE PROCESSES OF ORGANIC MATERIALS DESTRUCTION AND COMBUSTION PROCESSES CONDITION OF FIRE INTENSEICATION

Problem statement. The rapid occurrence and development of fires are caused by the occurrence of combustible materials and structures in their focus. This complicates, and in some cases makes impossible, effective firefighting, evacuation, and rescue of people and property. In order to correctly assess fire resistance, effectively increase fire resistance, and change the flammability of materials, it is necessary to study the materials burning process. The purpose of the article. To study of the combustion of easily dispersible substances and the development of gaseous reactions and their combination using the example of wood combustion. Methods. We use mathematical modeling of combustion and destructive processes under the high temperatures, taking into account the rules of thermodynamics. Research results. The conducted analysis showed that the selection of the main stages in the simulation of wood combustion is much less developed than in the case of the combustion of gas systems. It is especially difficult to do this to describe the combustion of wood, on the surface of which there is an interaction of masses (and heat) during the combustion of individual components, and the size of the front surface per unit cross-section of the sample may also change over time. Therefore, the definition of the main stage in wood burning should be used mainly in the qualitative analysis of the process, and quantitative models of wood burning should be built, if possible, taking into account all the determining factors characterizing the phenomena. Scientific novelty. For the first time, on the basis of the modeling of organic material combustion is proposed. We determine the patterns of destructive processes, which, depending on the temperature, have common patterns of qualitative and quantitative characteristics. The chemical phasing and its connection with the physical phasing of the transformation of combustible organic materials dispersed in the surface layer with the overall thermal effect of the combustion wave were determined. Practical value. The identification of stages during the wave burning of wood allows for a qualitative display of processes depending on the spatial zone and its distance from the gas zone, which allows predicting the development of protective means of organic materials against combustion.

Research on low‐carbon system of biomass combustion and solar‐energy power generation based on MP‐PIC simulation

AbstractTo vigorously reduce CO2 emission in the energy sector is an inevitable choice to achieve world's carbon emission reduction and to accelerate the construction of a modern energy system. The development of CO2 capture, utilization, and storage technology (CCUS) is of great significance for promoting low carbon utilization of traditional energy and realizing the low carbon transformation of coal power industry. The joint development of biomass combustion integrated with new energy technology and consideration of fuel conversion CO2 capture from the source is a technical solution with high efficiency and low energy consumption in coordination, which will bring new development opportunities for conventional thermal power industry. In this study, a low carbon system of collaborative renewable energy CO2 source capture is constructed. Numerical simulation method of multiphase flow coupled with thermal mass transfer and chemical reaction of the combustion mathematical model is employed to study the combustion characteristics in the biomass combustion system. The combustion efficiency, carbon conversion, and pollutant emissions are calculated compared with the conventional coal combustion system. Hydrogen production and CO2 emissions are analyzed based on life cycle assessment method. The energy integration full‐chain system of geological storage and CCUS is optimized, which is committed to achieving nearly zero carbon emission in the thermal power industry, contributing to the global low CO2 emission work.

Influence of Ambient Temperature on the Thermal Safety of Fireworks Products in Civil Aviation Transportation

Fireworks products are energy-containing materials and are hazardous during production, storage, transportation, and use. By analyzing the range of civil aviation ground ambient temperature and civil aviation cabin ambient temperature in storage and ground operation as well as establishing a spontaneous combustion mathematical model for cylindrical fireworks products based on the spontaneous combustion theory, we identified the critical temperature for spontaneous combustion of a single spray and analyzed the thermal safety of fireworks products under the civil aviation ambient temperature by example to provide theoretical support for the feasibility study of transporting fireworks products by civil aviation.

Two-Scale Mathematical Model of Combustion of Coal–Methane–Air Gas–Particle Suspension

Two-Scale Mathematical Model of Combustion of Coal–Methane–Air Gas–Particle Suspension

Analyzing the combustion oscillation of a gas turbine for syngas based on the characteristic time-scale theory

When the ambient temperature is less than −10 °C in winter, the gas turbine for syngas in Huaneng Tianjin integrated gasification combined cycle (IGCC) power station has an evident combustion oscillation phenomenon, which seriously affects the production safety and efficiency. This study used the characteristic time-scale theory to guide the operation, thereby reducing the combustion oscillation of the gas turbine for syngas. The work progressed as follows. First, the boundaries of the combustion oscillation and maximum temperature safe limitations were defined based on the operational data from the extreme ambient temperature in summer and winter in the Huaneng Tianjin IGCC power station. Then, the mathematical model of combustion with critical parameters, such as ignition delay time, the adiabatic temperature of the flame, and flame speed, was constructed using the binary quadratic regression method under various combinations of dry syngas, natural gas, and steam flow rates. Finally, an operation scheme for reducing the combustion oscillation of the gas turbine for syngas in winter was designed, as well as the limitation boundary and computation model. This operation scheme can effectively reduce the combustion oscillation in winter; this was confirmed in actual operation. The results of this study should assist gas turbine designers in improving the safety, reliability, and stability of syngas turbines.

Mathematical Modeling of the Working Process of a Two-Stroke Engine with Countermoving Pistons

Simulation of the working process of an internal combustion engine is the basis for all further calculations and studies of the engine. Of particular relevance is the availability of an adequate mathematical model of the engine process due to the fact that due to the trend of continuous improvement of engine performance, it is necessary to take into account many influencing factors to obtain a satisfactory result. The most complex and dependent on many physicochemical parameters is the process of combustion of fuel in the engine. Models of combustion in diesel engines can be divided into three groups: detailed models; empirical and semipemirical models. The analysis of world experience in research and mathematical modeling of combustion process in internal combustion engines is performed in the work. The advantages and disadvantages of different mathematical models are indicated. It is proposed to use a semi-empirical mathematical model of combustion which describes the differential characteristic of the combustion rate by two curves corresponding to the periods of the first flash and diffusion combustion. Use of such model simplifies performance of calculations and at the same time allows to receive qualitative results considering many factors of influence.

Emission Assessment of Agro-Waste Combustion

Biomass can be used to meet energy needs for electricity generation, residential and commercial buildings’ heating, industrial process heating, transportation, etc. Future of bioenergy sector depends on the availability of biomass resources and development in conversion technologies. Fluidized bed combustion is a favorable technology for biomass combustion due its fuel flexible feature and enhanced combustion efficiency. In this study, the atmospheric emissions from fluidized bed combustion of agricultural residues such as wheat straw, corn stalk, rice husk, almond shell, walnut shell and sugarcane bagasse were estimated for 1 MW thermal energy production by using a mathematical combustion model. CO2 emissions from biomass can be regarded as zero due to the carbon neutral nature of biomass. Almond shell and sugarcane bagasse has shown the lowest SO2 and NOx emissions. Sugarcane bagasse has shown lower corrosion risk compared to the biomass types examined in this study. Performance and operation of biomass combustion can be enhanced by addition of limestone and additives for sulfur capturing and reducing the risk for ash related problems, respectively.

Multi-Objective Optimization of a RCCI Engine Fueled with Diesel Fuel and Natural Gas Enriched with Hydrogen

The present study seeks to conduct the optimization of a heavy-duty diesel engine under RCCI combustion fueled with diesel fuel and natural gas enriched with hydrogen. Since NOx emission is one of the most important concerns of using hydrogen as a sole fuel or an additive to hydrocarbon fuels in an internal combustion engine like RCCI engine, thus, the main goals of this study are to overcome the NOx challenge, enhance the RCCI combustion characteristics, and reduce the fuel consumption when the conventional hydrocarbon fuels are substituted with hydrogen. In order to conduct the optimization process, an artificial neural network coupled with the design of the experiment concept was employed to identify the RCCI combustion mathematical model and provide the required population for two optimization algorithms, namely genetic algorithm, and particle swarm optimization algorithm. The results from the optimization process show that by advancing the diesel fuel injection along with the appropriate amount of exhaust gas recirculation and nitrogen as diluents, the level of EURO VI for NOx can be met. However, the losses in the RCCI engine output power is less than 5% meanwhile the gross indicated efficiency is over 50% and the reduction in hydrocarbon fuels consumption is about 40%.

ОСОБЕННОСТИ РАСПРОСТРАНЕНИЯ ПЛАМЕНИ В УГЛЕ-ПРОПАНО-ВОЗДУШНОЙ ГАЗОВЗВЕСИ

The mathematical model of combustion for a reactive gas suspension of coal dust in a propane-air mixture is developed. The parametric study of the problem is carried out. The observed burning velocity of the propane-air mixture with an admixture of coal particles is determined. Dependences of the observed burning velocity of the propane-air gas suspension on the equivalence ratio and on the radius of the particles are obtained. It is shown that, the observed burning velocity decreases with an increase in the radius of the particles. On the contrary, with an increase in the radius of the particle, the observed burning velocity increases for high-propane mixtures. Moreover, in the case of high-propane mixtures, the observed burning velocity of the gas suspension can be increased by reducing the mass of the particles. The observed burning velocity for a propane-air mixture with particles is significantly less than that for a mixture without particles.

PEMODELAN TEMPERATUR DARI PROSES PEMBAKARAN DI REFORMER FURNACE PADA INDUSTRI BAJA

Conversion processes that involve large amounts of energy include processes in furnace reformers inthe steel industry. The reformer unit used to convert the process gas, namely a mixture of gas andsteam into CO and H2 gas with the help of a nickel catalyst. The heat energy used in the process is theresult of combustion from natural gas using combustion located above the furnace. The most importantthing in the conversion process is the radiative heat transfer in the combustion chamber to the reactionpipe wall so that enough energy is obtained to carry out the conversion process. One way to determinethe heat distribution of the reformer combustion chamber is to know the temperature profile along thereaction pipe, including the pipe wall temperature, the process gas temperature, and the temperatureof the combustion gas used as energy for the process in the reformer furnace. The performanceevaluation of the reformer furnace uses a mathematical model for combustion in the furnace which canlater be developed by knowing the fitting composition of the conversion results. The type of reformerstudied is the top-fired reformer. The results of modeling using data from the steel industry obtained thehighest temperature from the combustion of gas from the burner which is in the reaction pipe at aposition 3-4 meters from the upper end of the reformer around 1300 oC and the temperature of naturalgas-steam in the pipe reaches 860 oC at the end of the pipe. reaction. The pipe wall heating with naturalo ogas fuels provides a maximum temperature ranging from 890 C - 895 C on the outer wall of thereaction pipe, and the pressure inside the reaction pipe ranges from 8.0-8.5 atm.

Effect of Particle Size on Boron Combustion in Air

Mathematical modeling of combustion of micron-sized and nanometer boron particles in air with allowance for changes in the heat and mass transfer mechanism and a decreasing particle size is carried out. The Knudsen number is taken as an indicator of a transition from one state to another: a continuous medium assumption is valid for describing the heat and mass transfer mechanisms in the case where Kn $$<$$ 0.01, the free molecular regime takes place for Kn $$>$$ 10, and a transient state occurs for 0.01 $$<$$ Kn $$<$$ 10. Particle sizes at which different heat and mass transfer regimes occur with respect to boron combustion in air at pressures of 0.1–4 MPa are estimated. The time it takes for boron particles to combust within the framework of the assumption of a continuous medium and in a free molecular mode is determined. It is shown that calculation models for determining the burning time of boron particles with initial sizes close to micron-sized and nanodispersed ones should take into account a change in the heat and mass transfer mechanism with variation in the current particle radius during burnout.

Mathematical model and calculation results of the kerosene aerosol combustion rate

This paper presents a mathematical combustion model of the kerosene aerosol and the calculation results of the combustion front normal velocity. The model is based on the dynamic equations of the two-phase reacting medium and consists of the energy equations for the gas and kerosene droplets, taking into account heat exchange, evaporation and heat release from the kerosene-oxygen reaction in the air; mass conservation equations for the gas, droplets, oxygen and kerosene, controlling the mass exchange between the phases and the burning of the reagents; the motion equation of the droplets; the particle number equations for the of droplets per unit volume; the ideal gas equation. The model assumes the isobaric conditions of the aerosol combustion. The obtained (calculated) propagation velocity of the kerosene aerosol combustion front, depending on the kerosene mass concentration and the initial temperature of the mixture, is in good agreement with the experimental data.

МАТЕМАТИЧЕСКАЯ МОДЕЛЬ СЖИГАНИЯ ЖИДКОГО ТОПЛИВА В АППАРАТЕ

The article deals with the mathematical combustion model of organic liquid fuel in&#x0D; the technological furnace. The main factors influencing on the process are considered. The formula for&#x0D; the calculation of the oxygen concentration at the reactionary surface is obtained. The material balance of oxygen including equations for the diffusive and dense parts is compiled. The calculation results are shown in the diagrams.

ВИЗНАЧЕННЯ КРИТИЧНИХ РЕЖИМІВ РОЗВИТКУ ПРОЦЕСІВ ГОРІННЯ ПІРОТЕХНІЧНИХ НІТРАТНО-МЕТАЛЕВИХ СУМІШЕЙ В УМОВАХ ЗОВНІШНІХ ТЕРМІЧНИХ ДІЙ

Currently, models of combustion of mixtures based on Mg + NaNO3 have been developed and investigated in detail to calculate the combustion rates of pyrotechnic mixtures. As for other pyrotechnic mixtures, the results of theoretical studies on the modeling of their combustion processes under different external conditions are very limited, and in most cases absent. The purpose of this work is to develop a model of combustion of compacted mixtures of Ti powders and nitrate-containing oxidizing agent (NaNO3, Ba(NO3)2, Sr(NO3)2) to determine the critical modes of their persecution by calculating the dependence of the propagation of the combustion front on charges and technological factors conditions. Developed mathematical model of combustion of pyrotechnic nitrate-metal mixtures allows to determine with accuracy of 8… 10 % the influence of high heating temperatures and external pressures (for a wide range of change of component ratios and dispersion) on the stage of design and subsequent bench testing of pyrotechnic articles with precision and dispersion, sustainable propagation of combustion in conditions of thermal impact. This makes it possible to predict different fire situations that occur in the external thermodynamic conditions to which the products are exposed during their operation. The mechanism is established and mathematical models of the pyrotechnic nitratemetal combustion process are used, which use kinetic characteristics of the processes of thermal decomposition of oxidizer, high-temperature oxidation, ignition and combustion of metal fuel particles on the combustion surface of the mixtures. The example of nitrate-titanium mixtures shows that models with a relative error of 8…10 % allow to determine the dependence of the rate of development of the combustion process of the mixture on the parameters of external thermal actions (increased heating temperatures and external pressures) for different values of their technological parameters (the ratio of components and dispersion), which makes it possible to find critical modes of combustion, the excess of which leads to the explosive destruction of pyrotechnic articles.

Peculiarities of mathematical modeling of combustion of hydrogen-air mixtures

Paper presents a comprehensive study of contemporary opportunities in the numerical analysis of transient combustion regimes on the example of the topical problem of hydrogen combustion. The elementary processes determining the development of combustion under different conditions are considered. In view of this analysis, it is concluded that the most appropriate for numerical modeling of classic deflagration inside confined space is the low-dissipation numerical schemes of low (second) order of approximation. For near-critical conditions where distinct mechanisms determine the combustion development one is able to utilize the simplifications such as low Mach number approximation.

Multi-objective combustion optimization based on data-driven hybrid strategy

In order to reduce pollutant discharge and improve boiler efficiency, data-driven hybrid strategy is proposed to solve the problem of multi-objective combustion optimization. First, massive historical operation data of a coal-fired power station are preprocessed (including resampling, steady-state detection, data cleaning and cluster analysis), so as to divide the whole boiler working condition into different partitions. Next, combustion association rules based multi-objective optimal strategy is applied to extract a combustion optimal rule from every partition, and a combustion optimal rule-base is built up by merging all the rules, so that the preliminary combustion optimization can be quickly finished based on the combustion optimal rule-base. Meanwhile, combustion mathematical model based multi-objective optimal strategy is applied to develop the LSSVR (least square support vector regression) model of boiler combustion process for every partition, and a combustion optimal model-base, which contains all the LSSVR models, is built up. After that, an improved multi-objective particle swarm optimization algorithm is presented to calculate Pareto optimal solutions depend on the corresponding LSSVR model with the constraint of real-time boiler working condition. To achieve further combustion optimization, the method of multiple attribute decision making is used to determine the unique solution from all the Pareto optimal solutions. Data-driven hybrid strategy is to combine the above two strategies. Simulation experiments verified the validity and feasibility of data-driven hybrid strategy on multi-objective test function ZDT1. Taking advantage of data-driven hybrid strategy, the comprehensive average of NOx emissions dropped by 29.63% and the comprehensive average of boiler efficiency increased by 0.69% in the application experiments with historical operation data under some boiler working conditions. Data-driven hybrid strategy based multi-objective combustion optimization makes the integration of instantaneity and effectiveness, so that it is suitable for online application.

Mathematical Model and Calculation of the Rate of Combustion of a Frozen Aqueous Suspension of a Nanodisperse Aluminum

A mathematical model of combustion of a frozen aqueous suspension of a nanodisperse aluminum, making possible the determination of the parameters of this process with account of the dependence of the specific heat, evaporation heat, and boiling point of water on the pressure at the vaporization surface of the suspension without the predetermination of the ignition temperature of aluminum particles, is presented.

Filtration Combustion of a Two-Layer System

A system consisting of two layers with different porosities is considered. Unlike the boundary between the layers, the upper and lower boundaries of the investigated region are impermeable to heat and gas. One layers is capable of chemical interaction with a gas filtered through both ends of the system. Ignition occurs at one end. Assuming a linear dependence of powder permeability on porosity, a two-dimensional mathematical combustion model of a two-layer sample is studied numerically. Patterns of the gas flow’s movement are shown, and the reasons for the change in the velocity of the combustion front during its motion are explained. The rates of the reactive powder reactant’s combustion are compared, depending on the thickness of the fuel layer, the permeability of the powder reactant, and the degree of fuel compaction.

Nitrogen oxides reduction and performance enhancement of combustor with direct water injection and humidification of inlet air

In this study, nitrogen oxides emission reduction is investigated with humid combustion in a non-premixed combustion chamber of a gas turbine that burns natural gas using computational fluid dynamics. For humidification of the combustion chamber, two methods are studied: direct water injection into the combustion chamber and increasing the inlet air humidity. The mathematical model of combustion, governing equations, numerical method, and the combustion chamber properties are extensively discussed. The mathematical model is first validated. The two approaches are then simulated and compared for low water and steam flow rates. The results show that at the water to fuel ratio of about 1, direct water injection is 1.69 times more efficient than increasing inlet air humidity in reducing nitrogen oxide emission. Finally, it is concluded that direct water injection is appropriate at low flow rates (up to the fuel flow rate) and for situations where reducing nitrogen oxide emission is highly relevant. Furthermore, increasing the humidity of the inlet air up to 25% is suitable and increases the combustion efficiency and reduces pollutants, while the outlet temperature is not decreased too much.

Mathematical Modelling of Diesel Engine Operational Performance Parameters in Transient Modes

This study presents innovative methods for solving practical challenges that occur during the operation of heavy diesel engines (DEs). The novelty of the method arises from the combined use of an artificial neural network, a single-zone DE combustion mathematical model, and data from real operation conditions. Using the proposed method, DE transient mode energy efficiency has been analysed, and the primary influencing factors have been identified: qcycl and dqcycl/dt. The adequacy of the method has been tested for CAT3512B-HD series engines installed on freight locomotives. The difference between the model results and experimental data has been 3–4%. CAT3512B-HD series DE transient operation studies have shown that at the low-load range of qcycl (up to 36% of nominal), the fuel consumption during transient operation increases by 10% compared to steady state operation. Transient operation efficiency is not influenced by the operation rate (dqcycl/dt) in the analysed -0.016 to 0.016 g/s range. Near the nominal power (qcycl increases up to 0.5 g/cycle), it is necessary to limit the dqcycl/dt range to 0.006 g/s to avoid overexploitation of the fuel by more than 100%. The proposed method has been recommended for practical use in optimizing vehicle operation load cycle structure by adapting the engine control to the concrete operation conditions, as well as for overall efficiency improvement.