Simulation Of Combustion Process Research Articles

Numerical simulation of combustion, flow, and heat transfer process of an oilfield heating furnace under different production conditions

AbstractHeating furnace is an important energy‐consuming equipment in oilfield. In order to evaluate the operation status of heating furnace more accurately, in this paper, the production process of heating furnace in an oilfield is studied by numerical simulation technology, and the specific reasons affecting its thermal efficiency are deeply explored. First, the numerical simulation model of oilfield heating furnace production process is established, which is to digitize the geometric structure of the heating furnace, study the characteristics of the geometric shape, and generate the appropriate calculation grid. Second, numerical simulation and analysis are carried out for the working process of the heating furnace under rated and nonrated conditions, respectively. The medium flow characteristics, flame shape, temperature distribution, and pipe temperature distribution in the heating furnace under different conditions are systematically discussed. Finally, through the simulation analysis, it is found that the burner rotating device is beneficial to strengthen the heat transfer, and the change of load will affect the efficiency of the heating furnace. Under the rated working condition, design exhaust temperature is 260℃, numerical result is 225.8℃, and the error is −13.2%; design export temperature of water is 60℃, numerical result is 58.1℃, and the error is −3.2%; design temperature difference between inlet and outlet of water is 30℃, numerical result is 28.1℃, and the error is −6.3%. The working process of oilfield heating furnace is a complex coupling heat transfer process of combustion, flow, and heat transfer. The numerical results show that the working process of oilfield heating furnace could be successfully realized by means of numerical simulation. Under variable load conditions, in order to ensure that the export temperature of water is close to design temperature, it is necessary to change the fuel quantity in equal proportion to the water quantity. It is hoped that the reported results provide interesting information among the oilfield heating furnace operators.

RETRACTED: Numerical simulation of combustion process in different heating furnaces

The physical field of different heating furnaces and its related aspects were studied by numerical simulation method. Firstly, by studying the heating furnaces of different shapes, namely triangle furnace, square furnace and cylindrical furnace, it was found that: square furnace and cylinder furnace combustion was more full, high temperature range was larger, different furnace tube heat intensity distribution was more uniform, the amount of heat loss was lower, the outlet NOx emission was higher. By studying the cylindrical furnaces with different dip angles of 95°, 93°, 90°, 87° and 85°, it was found that with the decrease of the dip angle, the inner reflux decreases, the reaction rate decreases, the range of higher temperature increases, the heat absorption of the furnace tube was larger, and the NOx concentration at the outlet was lower.

Combined ReaxFF and Ab Initio MD Simulations of Brown Coal Oxidation and Coal-Water Interactions.

In this manuscript, we use a combination of Car–Parrinello molecular dynamics (CPMD) and ReaxFF reactive molecular dynamics (ReaxFF-MD) simulations to study the brown coal–water interactions and coal oxidation. Our Car–Parrinello molecular dynamics simulation results reveal that hydrogen bonds dominate the water adsorption process, and oxygen-containing functional groups such as carboxyl play an important role in the interaction between brown coal and water. The discrepancy in hydrogen bonds formation between our simulation results by ab initio molecular dynamics (CPMD) and that by ReaxFF-MD indicates that the ReaxFF force field is not capable of accurately describing the diffusive behaviors of water on lignite at low temperatures. The oxidations of brown coal for both fuel rich and fuel lean conditions at various temperatures were investigated using ReaxFF-MD simulations through which the generation rates of major products were obtained. In addition, it was observed that the density decrease significantly enhances the generation of gaseous products due to the entropy gain by reducing system density. Although the ReaxFF-MD simulation of complete coal combustion process is limited to high temperatures, the combined CPMD and ReaxFF-MD simulations allow us to examine the correlation between water adsorption on brown coal and the initial stage of coal oxidation.

Coupled simulation and deep-learning prediction of combustion and heat transfer processes in supercritical CO2 CFB boiler

The supercritical CO2 (S-CO2) power cycle has a wide application prospect in coal-fired power generation field because it’s highly effective, compactly structured, and flexible of operation. To observe more accurate heat transfer and coal combustion characteristics in the circulating fluidized bed (CFB) with the distinctive S-CO2 boundary, a 3D computational fluid dynamics (CFD) simulation of the furnace-side combustion process treated by the multiphase particle-in-cell (MP-PIC) method was conducted in a 600 MW S-CO2 CFB boiler coupled with the heat transfer process on working fluid side based on the polynomial fitting calculation model. Furthermore, a novel method to predict simulation results via Radial Base Function (RBF) neural network was proposed to simplify the computational process, enhance the sample data fusion, and improve the prediction accuracy. Results show that staggered high-temperature fluid and high heat flux was a major concern in S-CO2 heating surface arrangement. The temperature rise of wall heaters was less than the conventional steam CFB, and the heat flux of spiral and vertical heat transfer tubes decreased along the tube. The predicted temperature distribution of tubes and cold walls was in a good agreement with the coupling simulation results, whose accuracy can meet the engineering requirements.

Approach to combustion calculation using neural network

Numerical simulations of combustion processes in rocket engines requires a long run time of supercomputer systems even for a very short physical time. Therefore, creating digital twins of rocket engines needs enormous processor time, and is not very effective. This computational time surpasses the actual physical time of the process in many orders of magnitude. To speed up numerical simulations the paper presents a solution of the chemical kinetics problem using artificial neural network approach. Using the architecture of a multilayer neural network with bypass connections, namely residual network, it is possible to obtain a fast and reliable solution to the problem. The neural network is trained to predict the state of the system only one time step ahead. Using it in a recursive mode, it is possible to forecast for thousands of steps without loss of accuracy.

Applying detailed chemistry for the dual-fuel engine combustion process simulation using CFD approach

Modern research in the area of internal combustion engines is focused on searching and investigating the technologies that will improve fuel efficiency and decrease emissions. The application of dual-fuel engines is considered a potential solution to these problems. In the dual-fuel engine, the natural gas-air mixture is ignited by a small amount of diesel fuel directly injected into a combustion chamber. This paper aims to develop a detailed chemistry mechanism for 3D simulation of the combustion process of a dual-fuel engine, providing sufficient convergence with the experimental data. It should be noted that sufficient convergence must also be provided in terms of such parameters as pilot fuel ignition delay and premixed air-fuel mixture flame propagation speed. In the course of the research, the analysis of the most commonly used detailed chemistry mechanisms for calculation of the combustion process and mechanisms’ disadvantages was performed. The results obtained with the use of the detailed mechanisms were compared with the results obtained without using detailed chemistry and with the experimental data as well.

Numerical Modeling of Combustion and Detonation in Aqueous Foams

Combustible aqueous foams and foamed emulsions represent prospective energy carriers. This paper is devoted to the overview of model assumptions required for numerical simulations of combustion and detonation processes in aqueous foams. The basic mathematical model is proposed and used for the analysis of the combustion development in the wet aqueous foam containing bubbles filled with reactive gas. The numerical results agree with the recent experimental data on combustion and detonation in aqueous foams containing premixed hydrogen–oxygen. The obtained results allowed for distinguishing the mechanisms of flame acceleration, transition to detonation, detonation propagation, and decay.

A Shortcut Method to Predict Particle Size Changes during Char Combustion and Gasification under regime II Conditions

ABSTRACT In most industrial applications, combustion and gasification of char progresses under regime II conditions. Unlike in other regimes, both particle size and density change simultaneously in regime II due to non-uniform consumption of carbon inside the particles. In this work, mathematical predictions of diameter changes in regime II were made by a one-dimensional simulation tool, where transient species balances are resolved locally inside the particle. This simulation is computationally expensive and usually not appropriate for the implementation in comprehensive CFD simulations of combustion or gasification processes. To overcome this restraint, an alternative shortcut method with affordable computation time has been developed and validated against the detailed model. This method allows the calculation of diameter changes during combustion and gasification from precalculated effectiveness factors. Additionally, the change of particle size has been investigated experimentally in a single particle converter setup. Therein, particles are fixed on a sample holder placed in the hot flue gas of a flat flame burner. Size and temperature trends are optically assessed by a 3CCD camera.

Numerical Simulation of Turbulent Non-premixed Combustion Processes for Methane and Dimethyl Ether Binary Fuels.

The C1ε = 1.6 standard k – ε equation combined with the steady flamelet model was applied to a methane/dimethyl ether swirl combustion field, and the effects of the dimethyl ether (DME) blending ratio and operating pressure on the flame behavior, including species variation, reaction zone behavior, and flame entrainment, were investigated. The results demonstrated that selected models could better reproduce the trends of the experimental measurements. The downstream reaction zone achieved better calculation accuracy than the outer shear layer of the first recirculation zone. The addition of DME accelerated the accumulation process of H2, O, H, and OH radicals. The intermediate radical CH2O was rapidly developed by the influence of the H extraction rate under a constant fuel volume flow rate. The reaction zone dimensions were approximately linearly and positively correlated with the DME blending ratio, whereas flame entrainment expressed a lower DME concentration dependence in the high-DME mass-dominated system. The operating pressure significantly impacted the distribution of reactive radicals in the turbulent flame; meanwhile, the flame and reaction zone length showed nonlinear inverse behavior with pressure variation, while the thickness of the reaction zone was always linearly and negatively correlated with pressure. Moreover, the peak flame entrainment rate also experienced a nonlinear decline with pressure elevation; however, the peak positions were not sensitive to pressure fluctuation. Concurrently, the response surface functions for the reaction zone dimensions were established covering the range of 0–1 for the DME blending ratio and 1–5 atm operating pressure, which could provide assistance for combustion condition optimization and combustion chamber design.

Experimental Study on Spontaneous Combustion Prediction System of No.12 Coal Seam in TongXin Coal Mine

To reduce coal spontaneous combustion hazards, establishing accurate and reliable prediction system, with 12# coal seam with TongXin ore as object, using the large platform of coal spontaneous combustion simulation of coal spontaneous combustion process, the oxygen consumption rate, exothermal intensity and other characteristic parameters were analyzed, and based on the method of index gases, temperature programmed experiments, summarizes the characteristics of the temperature and gas change rule. The experimental results show that the oxygen consumption rate and heat release intensity increase with the increase of coal temperature. At 70.1 °C, it reaches the critical temperature of coal; at 132.7 °C, the dry cracking temperature of coal is reached;when the temperature is 244.8 °C, it reaches the growth temperature of coal; when the coal temperature is between 22.9.1-70.1 °C, CO and C2H6/CH4 can be selected as the main index gas of No.12 coal seam in TongXin Mine; when the coal temperature is between 132.7-320.5 °C, CO can be selected as the index gas. Since C2H4 can only be detected when the coal temperature reaches about 85 °C, C2H4 and C2H4/CH4 can be used as auxiliary marker gas.

Kinetic model study on biomass pyrolysis and CFD application by using pseudo-Bio-CPD model

Pyrolysis is the key step in biomass thermochemical conversion process. The network model can accurately predict the pyrolysis process but generally cannot incorporate the combustion and gasification sub-models due to its complexity. This paper used the Bio-CPD model to predict the pyrolysis products of softwood and hardwood respectively; based on the predicted results, two empirical-simple forms of pyrolysis models were further optimized. The ultimate kinetic parameters obtained are suitable for biomass pyrolysis at high heating rate. For softwood, after being optimized, the apparent frequency factor and E/R of single rate are 4.3106e + 07 s−1, 10042 K respectively. While for two-competing rates model, the parameters are, α1 = 0.75, α2 = 0.89, A1 = 7992 s−1, E1/R = 7000 K, A2 = 8.3e + 09 s−1, E2/R = 14520 K, respectively. The numerical simulation of biomass pyrolysis and combustion process were performed by using CFD code Ansys Fluent. The results reveal that the release of volatile predicted by the default parameters have a delay compared with the actual process and is not appropriate for biomass simulation, while the optimized parameters in two simple models are accurate enough to simulate the biomass pyrolysis at high heating rate (103–105 K/s).

Simulation of Combustion Process of Diesel and Ethanol Fuel in Reactivity Controlled Compression Ignition Engine

Reactivity controlled compression ignition (RCCI) engine give advantages over conventional diesel engine with the promising engine power and good control on NOx and soot emission. The trend of the RCCI concept is still new and Is very important to control the ignition in order to control the combustion progress and emission. The objective of this study is to provide data on the combustion characteristics and emission of diesel as high reactive, and ethanol as the low reactive fuel in the RCCI engine. The engine speed and injection timing were varied. Simulation work was conducted by using the Converge CFD software based on the Yanmar TF90 diesel engine parameter. Results show that operating the engine at low speed resulting in better engine performance and low carbon emissions due to the sufficient oxygen contents. For the high-speed engine, advancing the injection timing improves the fuel and air reactivity and steeper the equivalence ratio gradient, which result in a complete combustion process.

Molecular level simulations of combustion processes using the DSMC method

A technique called the Direct Simulation Monte Carlo (DSMC) method is used for simulating laminar one-dimensional hydrogen-air flames with an aim to establish the feasibility of molecular-level simulations for combustion using the Quantum-Kinetic (QK) reaction model. In DSMC, simulation particles are employed which represent many molecules with similar properties. The DSMC method effectively solves the Boltzmann equation by decoupling the motion of molecules into two phases: a Move phase and a Collision phase. Chemistry is treated using the Quantum-Kinetic model in which the total energy exchange resulting from molecular collision determines the outcome of the chemical reactions. A major advantage of DSMC is that it avoids using continuum Arrhenius reaction rates or simplified gradient laws for the diffusivities of mass, momentum and heat. Instead, any such laws and their parameters emerge naturally from the DSMC results. Simulations of one-dimensional hydrogen-air flames using the DSMC method with a detailed chemical scheme show promising results for molecular-level simulations of combustion. An adjustment to the activation energy of a key reaction is made in order to achieve the correct flame speed. The species and temperature profiles from DSMC show reasonable agreement with those obtained from Direct Numerical Simulation (DNS) using a conventional continuum approach. Likewise, the molecular diffusivity of hydrogen and oxygen also show reasonable agreement with the DNS results, although differences in the results still exist, especially for oxygen diffusivity. These are expected to improve with further development in the DSMC method for combustion.

Numerical simulation of in-cylinder combustion characteristics of LNG-diesel dual-fuel engine

Three - dimensional numerical simulation of diesel engine cylinder combustion process was carried out by using computational fluid Dynamics (CFD) software AVL-FIRE. The combustion characteristics of LNG under different ignition diesel ratio, cylinder pressure were studied. Through the simulation calculation of pilot diesel ratio, cylinder pressure, combustion heat release rate, the analysis results showed that the minimum value of pilot diesel ratio was not less than 0.5. During a cycle, there was no cliff-like change in cylinder pressure. CFD simulation has guiding significance for optimizing combustion chamber structure parameters and improving diesel engine performance. CFD simulation is instructive for the optimization of diesel engine performance.

Features of modeling the combustion processes of flammable liquids with high ignition temperature in FDS software

The article describes the features of modeling the dynamics of fire during the combustion of flammable liquids, linked with dependence of the velocity of spreading along the liquid surface from a large number of factors. The method of computer simulation of combustion processes of flammable liquids with high ignition temperature is viewed via the Fire Dynamics Simulator software on the example of turbine oil. The influence of the linear velocity of flame spreading over the surface of turbine oil on the dynamics of temperature changes of the gaseous medium in the room is explored. The results of dynamic modeling of turbine oil combustion for cases of a simultaneously ignited area of the spilled flammable liquid and spreading of the flame over its surface from the ignition point with a calculated linear speed. The conclusion is made that it is expedient to use the described method for estimating the linear velocity of flame movement over the liquid surface when modeling combustion over large areas of flammable liquids with a high ignition temperature.

DESIGN BY PROGRAM ANSYS FLUENT PROCESSES IN HEATING OF CALDRON OF TPP-210А

Numerical modeling of processes in the furnaces of power boilers serves as a tool for assessing the impact of the proposed structural or operational changes on the ongoing processes and characteristics of the boiler. Using the ANSYS FLUENT program, three-dimensional numerical simulation of anthracite combustion processes in the furnace of a TPP-210A boiler with liquid slag removal was performed. The initial data for the calculation — component costs, composition and calorific value of coal — are taken from the boiler passport for the nominal operating mode. Air suction into the furnace has been taken into account. As the boundary conditions on the walls of the furnace, their thermal resistances are set, the values of which are determined by the results of the zone calculation of the furnace by the normative method. The turbulence model was used in the modification of a realizable, non-premixed combustion model of particle combustion in a single mixture fractions formulation, discrete phase model of the movement of coal particles, P-1 emission model, two-competing-rates model of volatile output, kinetics/diffusion-limited model of coal combustion. Obtained as a result of the distribution of heat flux densities and wall surface temperatures («contaminants») within each of the zones is substantially uneven, which confirms the validity of the type of boundary condition used on the walls. The change in the height of the furnace of the mass-average temperature of the flow, the heat flux densities into the walls, the distribution of the mechanical underburning of the fuel along the height of the furnace according to the simulation results are compared with the data of a well-known experimental study of S.L.Shagalova and I.N.Shnitser processes in the boiler under consideration, as well as with the data of the zone calculation of the boiler by the normative method. On this basis, a conclusion was made about satisfactory simulation results. Ref. 12, Fig. 7, Tab. 3.

Numerical Simulation of Combustion and Air Supply Process and Optimal Design of Traditional Top Combustion Hot Blast Stoves

The combustion performance and flue gas flow pattern of hot blast stoves significantly affect the temperature distribution of the combustion chamber and regenerator, as well as the air supply temperature and duration. In this study, a 3D fluid flow heat transfer model coupled with turbulence, combustion, heat radiation, and heat exchange models is established to study the combustion and air supply characteristics of a traditional hot blast stove. The results indicate that the nozzle arrangement on the traditional stove causes the flue gas to exhibit a high‐speed swirling flow. Due to the expansion of the flue gas and the centrifugal effect of the swirling flow, the “attachment” phenomenon of the fluid (i.e., a high edge velocity and a low center velocity) occurs in the combustion chamber, resulting in an unreasonable temperature distribution in the combustion chamber and regenerator. Accordingly, an improved design of a top combustion hot blast stove is proposed to solve this problem, and its performance is evaluated and compared with that of the original design via numerical simulations.

Numerical simulation of combustion process of petroleum coke partially substituting heavy oil in combustion space of float glass furnace

Numerical simulation of combustion process of petroleum coke partially substituting heavy oil in combustion space of float glass furnace

Predicting the Temperature and Composition – Dependent Density and Viscosity of Diesel Fuel – Ethanol Blends

Density and viscosity are very important fuel properties which have a major influence not only on the fuel production, transportation and distribution processes but also on the processes that take place in an internal combustion engine. Developing robust and high precision density and viscosity models for stabilized diesel fuel – ethanol blends helps the production of fuel to adhere to the quality requirements regarding density and viscosity and the modeling and simulation of injection and combustion processes. For modeling the density and the viscosity of diesel fuel – ethanol blends, five mixtures were prepared with ethanol content up to 15 % (v/v) and were stabilized by adding tetrahydrofuran as a surfactant at room temperature. The temperature-dependent density and viscosity of the blends were measured at four different temperatures (0, 15, 40 and 50 °C) using an SVM 3000 type apparatus. Based on experimental data, several mixing rules were fitted to them and three new models were developed, of which two need only one experimental value. These models yield very good accuracies, presenting average relative deviations of 0.0604 % in the case of density and 3.8931 % in the case of viscosity.

Predicting the Density and Viscosity of Biodiesels and Biodiesel Blends by the Regular-Solution Theory

Accurately predicting density and viscosity is required by the production of biodiesels and biodiesel blends that can meet the required quality standards, by the modeling and simulation of injection and combustion processes, and by the design of reactors, distillation units, and separation processes. Here, the regular-solution theory is used to develop novel predictive equations for the density of biodiesels and the density and viscosity of the (biodiesel + biodiesel) and (biodiesel + petrodiesel) blends. Systematic comparisons with experimental data and with the most widely used equations are made. The new density equation provides accurate predictions for the biodiesels and the above-mentioned blends, but Kay’s mixing rule cannot provide satisfactory predictions for the biodiesels. The new viscosity equation gives good predictions for the above-mentioned blends; particularly, its predictions are much better than those of the Grunberg–Nissan equation, even though the Grunberg–Nissan equation uses a blend-specific parameter determined from the blend viscosity.