Numerical Modeling Of Combustion Research Articles

Integrating Flow Field Dynamics and Chemical Atmosphere Predictions for Enhanced Sulfur Corrosion Risk Assessment in Power Boilers

In this work, we attempt to explain the phenomenon of sulfur corrosion of power boiler water walls under the conditions of large fluctuations in carbon monoxide concentrations. To assess the conditions required for corrosion formation, a criterion based on the chemical and flow field parameters of the flue gas is proposed. The formulated sulfur corrosion criterion is based on the mixture fraction variance and the turbulence time scale. Numerical modeling of coal combustion in a 250 MW power boiler is performed using ANSYS. Two cases of combustion in a boiler are analyzed, with the first simulating the boiler operated using classic high-swirl burners and the second one accounting for boiler operation with modified low-swirl burners. Calculations of pulverized coal combustion are performed using the standard k-ε turbulence model and the combustion described by the mixture fraction. The simulation results reveal that the low-swirl burner is characterized by higher values of the mixture fraction variance and a higher frequency of fluctuation of the velocity field, which is strongly related to an increased corrosion rate. The study outcomes show the validity of using the criterion of the mixture fraction variance and velocity field fluctuations to determine the areas at risk of sulfur corrosion.

Exploring the combustion mechanism of single micron-sized aluminum particles with a numerical model

In this work, we explore the combustion mechanism of single micron-sized aluminum particles using a numerical model. The Burcat database and Catoire mechanism is considered as the thermodynamic data and the kinetic mechanism for our numerical model of aluminum combustion. Two independent experiments, including particle temperature profiles, ignition delay and burning time, are selected to evaluate the performance of the numerical model. The model shows great agreement for all considered properties. A parametric study is further conducted to identify the effect of involved physical parameters on the combustion process. The diffusion coefficient (D) of oxidizers and the activation energy of surface kinetics (Esurf) and evaporation coefficient (α) of aluminum impact the particle temperature the most. Burning time is most sensitive to the activation energy of surface kinetics (Esurf). The optical measurement in a solid propellant combustion indicates that the contact angle of the oxide cap on Al particle is between 10° and 20°. It is found that the selection of contact angle of the oxide cap significantly impacts the prediction of combustion time and residual of active aluminum. The current work highlights the importance of physical properties on the prediction of Al combustion, suggesting that more detailed evaluation from experiments and theory is encouraged.

Evaluation of numerical modeling and combustion characteristics of hydrogen oxy-fuel combustion in a semi-industrial furnace

The use of hydrogen (H2) in oxy-fuel combustion (OFC) systems is a promising concept for future high-temperature industries. However, the current literature lacks a comprehensive study on the numerical modeling aspects and the relevant flame characteristics. This was tackled in the present work, as the high-impulse OFC of pure H2 was analyzed for the first time in an industrial environment based on experiments, theoretical calculations and RANS simulations. A detailed 3D CFD model of a 180 kW furnace was developed in Fluent, focusing on an accurate prediction of the temperature field and heat transfer rates. An extensive model validation was accomplished using measurement data from the conventional OFC of methane (CH4), and highly precise results could be obtained. Then, the numerical modeling of H2 OFC was scrutinized, highlighting the influence of different CFD modeling options for turbulence, combustion chemistry and thermal radiation. In the end, a detailed analysis of the combustion characteristics has been performed, using the conventional OFC of CH4 as a reference.It was found that turbulence modeling has the dominating effect on the numerical representation of the flame, while only negligible changes were noticed with different combustion and radiation models. Precise simulation results were achieved only by incorporating novel adaptations of the k-ɛ model, since the turbulent diffusion was underestimated with all common turbulence models. In terms of the flame characteristics, H2 caused an increase in the peak flame temperature by 400 K relative to CH4, which led to an improved radiative heat transfer in the flame near region. At the same time, the flame length decreased by almost 10% despite three-times higher fuel nozzle velocities. Overall, thorough insights into both the numerical modeling and the combustion characteristics of H2 OFC were provided, which should support the move toward greater sustainability in high-temperature processes.

Numerical modeling of combustion in gas engines with prechamber ignition

A numerical model is developed to predict the combustion processes in large-bore gas engines featuring prechamber ignition systems and being coupled with Computational Fluid Dynamics (CFD). The proposed combustion model is based on the simultaneous modeling of premixed and partially-premixed flames by an extended progress variable approach. By introducing an additional fuel scalar to track the externally injected fuel of the scavenged prechamber and depending on a gradient criteria of the fuel scalar, regions of locally premixed or partially-premixed state can be differentiated. The reaction rate for premixed combustion is described through a turbulent flame speed closure approach, whereas the partially-premixed combustion is described by a pre-tabulated flamelet chemistry approach. For the validation of the combustion model and its performance in the different flame propagation phases, that is, prechamber flame ignition and main-chamber flame propagation, experimental data of two large-bore gas engines with different operating conditions, prechamber configurations and engine geometries are taken into account. A good agreement of the simulations with the experimental results is shown for the variety of operating conditions and engine configurations. The developed combustion model is able to predict the combustion process in the prechamber as well as the ignition of the main chamber charge by means of the protruding flame jets through the prechamber nozzles. The prechamber ignition system accelerates the early flame phase and hence shortens the burning duration due to the deep-penetrating and turbulence-inducing flame jets in comparison to a conventional spark plug engine.

Numerical investigation on the exhaust gas combustion of an SOFC in a catalytic multichannel burner

The utilization of the exhaust gas of a solid oxide fuel cell is important to improve the energy efficiency and control pollutant emission. In this work, the combustion of solid oxide fuel cell exhaust gas (H2/CO) in a honeycomb ceramic catalytic burner is investigated numerically. A 2D numerical combustion model with 17 channels is built to analyze the influence of channel position on thermal performance and combustion characteristics. The high burnout of H2 and CO is obtained as 96.75% and 97.75%, respectively. The channels can be divided into three groups from the inside to the outside as follows: part 1, from the 9th channel to the 13th channel; part 2, from the 14th channel to the 16th channel; and part 3, the 17th channel. The channels in the same group presented the same results of flow, temperature, and combustion. Compared with the other channels, the outermost channel shows notable differences in depressing the temperature of the whole channel, moving the maximum temperature downstream, enlarging the temperature bias of the lower and upper walls, and enlarging the combustion zone. H2 and CO perform different combustion processes in the honeycomb ceramic catalytic burner. Compared with H2, the initial position of CO conversion is more affected by channel distribution. In the 17th channel, the CO oxidation rate is controlled mostly by the slower oxygen adsorption and the resulting low O(s) coverage. In the 9th channel, the CO oxidation rate is controlled mostly by the wall temperature and fuel-limited. The burnout rate of H2 changes from 95% to 99.9% with the channel position, but the burnout of CO varies little. The closer the channel to the outer wall, the higher the proportion of heterogeneous reaction and the more the generated heat. The generated heat by the channel can present a diversity of 4%.

Numerical Modeling of Chemical Kinetics, Spray Dynamics, and Turbulent Combustion towards Sustainable Aviation

With growing interest in sustainable civil supersonic and hypersonic aviation, there is a need to model the combustion of alternative, sustainable jet fuels. This work presents numerical simulations of several related phenomena, including laminar flames, ignition, and spray flames. Two conventional jet fuels, Jet A and JP-5, and two alternative jet fuels, C1 and C5, are targeted. The laminar burning velocities of these fuels are predicted using skeletal and detailed reaction mechanisms. The ignition delay times are predicted in the context of dual-mode ramjet engines. Large Eddy Simulations (LES) of spray combustion in an aeroengine are carried out to investigate how the different thermodynamic and chemical properties of alternative fuels lead to different emergent behavior. A novel set of thermodynamic correlations are developed for the spray model. The laminar burning velocity predictions are normalized by heat of combustion to reveal a more distinct fuel trend, with C1 burning slowest and C5 fastest. The ignition results highlight the contributions of the Negative Temperature Coefficient (NTC) effect, equivalence ratio, and hydrogen enrichment in determining ignition time scales in dual-mode ramjet engines. The spray results reveal that the volatile alternative jet fuels have short penetration depths and that the flame of the most chemically divergent fuel (C1) stabilizes relatively close to the spray.

Optimization of a two-step CH4/air reaction mechanism in a CO2-enriched environment for high-fidelity combustion simulations

In the gas turbine framework, the adoption of carbon capture and storage (CCS) systems coupled with strategies to improve the exhaust CO2 content is a promising technology to abate the carbon footprint of such machines. However, any departure of the oxidant from the air can compromise the accuracy of the conventional models to represent the combustion process. In this work, the effect of the CO2 enrichment of the mixture on an atmospheric premixed swirled flame is investigated by means of large eddy simulation (LES), comparing the numerical predictions with the experimental results. The high-fidelity numerical model features a dedicated global reaction mechanism derived through an in-house optimization procedure presented in this study. The chemical scheme is obtained by optimizing a widely used CH4–air two-step mechanism to improve key flame parameters such as the laminar flame speed and thickness and the resistance of the flame to the stretch with moderate CO2 dilution. The numerical results are analyzed in terms of flame shape, heat losses, and pressure fluctuations, showing a promising agreement with the experimental measurements and demonstrating the capabilities of the numerical model for CO2-diluted combustion.

Numerical Modeling of Supersonic Combustion of Hydrogen in the Wake Region of a Strut

Numerical modeling of combustion of a sonic hydrogen stream injected into a supersonic stream of air using a strut is presented. Results are obtained by numerically solving unsteady, compressible, turbulent Navier-Stokes equations, using Unstructured Finite Volume Method (UFVM) incorporating RNG based κ−ε two equation model and time integration using three stage Runge Kutta method. Reaction is modeled using an eight step H2-air chemistry. The developed numerical procedure is based on the implicit treatment of chemical source terms by preconditioning and solved along with unsteady turbulent Navier Stokes equations explicitly. Code is validated against a standard wall jet experimental data and is successfully used to model the reacting flow field resulting due to combustion of hydrogen in the wake region of strut placed in heated supersonic air stream.

Unimolecular Reactions of 2-Methyloxetanyl and 2-Methyloxetanylperoxy Radicals.

Alkyl-substituted cyclic ethers are intermediates formed in abundance during the low-temperature oxidation of hydrocarbons and biofuels via a chain-propagating step with ȮH. Subsequent reactions of cyclic ether radicals involve a competition between ring opening and reaction with O2, the latter of which enables pathways mediated by hydroperoxy-substituted carbon-centered radicals (Q̇OOH). Due to the resultant implications of competing unimolecular and bimolecular reactions on overall populations of ȮH, detailed insight into the chemical kinetics of cyclic ethers remains critical to high-fidelity numerical modeling of combustion. Cl-initiated oxidation experiments were conducted on 2-methyloxetane (an intermediate of n-butane oxidation) using multiplexed photoionization mass spectrometry (MPIMS), in tandem with calculations of stationary point energies on potential energy surfaces for unimolecular reactions of 2-methyloxetanyl and 2-methyloxetanylperoxy isomers. The potential energy surfaces were computed using the KinBot algorithm with stationary points calculated at the CCSD(T)-F12/cc-pVDZ-F12 level of theory. The experiments were conducted at 6 Torr and two temperatures (650 K and 800 K) under pseudo-first-order conditions to facilitate Ṙ + O2 reactions. Photoionization spectra were measured from 8.5 eV to 11.0 eV in 50-meV steps, and relative yields were quantified for species consistent with Ṙ → products and Q̇OOH → products. Species detected in the MPIMS experiments are linked to specific radicals of 2-methyloxetane. Species from Ṙ → products include methyl, ethene, formaldehyde, propene, ketene, 1,3-butadiene, and acrolein. Ion signals consistent with products from alkyl radical oxidation were detected, including for Q̇OOH-mediated species, which are also low-lying channels on their respective potential energy surfaces. In addition to species common to alkyl oxidation pathways, ring-opening reactions of Q̇OOH radicals derived from 2-methyloxetane produced ketohydroperoxide species (performic acid and 2-hydroperoxyacetaldehyde), which may impart additional chain-branching potential, and dicarbonyl species (3-oxobutanal and 2-methylpropanedial), which often serve as proxies for modeling reaction rates of ketohydroperoxides. The experimental and computational results underscore that reactions of cyclic ethers are inherently more complex than currently prescribed in chemical kinetic models utilized for combustion.

Numerical Modeling of Hydrogen Combustion: Approaches and Benchmarks

The paper is devoted to the analysis of two different approaches for the numerical simulation of gaseous combustion. The first one is based on a full system of Navier-Stokes equations describing the dynamics of the compressible reactive medium, while the second one utilizes low-Mach number approximation. The compressible model is realized by the traditional low-order numerical scheme and the contemporary CABARET method. The low-Mach approach is implemented on the base of a widely known FDS numerical scheme. The benefits and disadvantages of compressible and low-Mach approaches are discussed and demonstrated on a specially developed set of problem setups, applicable for validation and verification of the numerical methods for combustion analysis. In particular, the laminar flame velocity test, spherical bomb test, and multidimensional modeling of combustion development inside the rectangular closed vessel are performed via both techniques that allowed to determine the applicability limits of the low-Mach number approximation.

Study on the Effect of External Air Supply and Temperature Control on Coal Spontaneous Combustion Characteristics

Coal spontaneous combustion in underground mine goaf has a great impact on coal mining. The temperature-programmed experiment is a commonly used and effective method for studying the characteristics of coal spontaneous combustion. Aiming at the problem that the numerical simulation of coal spontaneous combustion characteristics under the condition of external air supply and temperature control in a temperature-programmed experiment is insufficient, a multi-physical field coupling numerical model of coal spontaneous combustion in the temperature-programmed experiment is established. The variation characteristics of coal temperature, oxygen, and oxidation products under external air supply and temperature control were studied. The results show that the numerical simulation results are consistent with the experimental results. With the increase in temperature, the volume fractions of oxygen and carbon dioxide decrease and increase, respectively. As the air supply volume increases, the oxygen volume fraction at the outlet increases, and the peak value of the oxygen volume fraction change rate exhibits a “hysteresis” feature, and the time corresponding to the peak value increases. Moreover, the temperature change rate increases. With the increase in the heating rate, the peak value of the oxygen volume fraction change rate increases and shows an “early appearance” characteristic, at the same time, the maximum coal temperature displays a linear increase trend.

Numerical simulation of microwave-enhanced methane-air flames I: Modeling and one-dimensional premixed laminar flames

This study considers the numerical modeling of sub-breakdown microwave-enhanced combustion in one-dimensional laminar methane-air flames over a range of stoichiometries at standard temperature and pressure. The effect of uniform microwave fields on the laminar flame speed, post-flame temperature and composition is of primary interest here.A model for the non-thermal plasma generated by the microwave field in such flames is constructed based on fitting of electron properties and electron impact reaction rates to pre-computed solutions of the Boltzmann equation, combined with ambipolar diffusion transport for charged species. This model is used with a selection of existing and novel methane-air kinetics schemes to compute laminar flame profiles at a range of microwave field strengths and varying stoichiometry. The trends for laminar flame strength and temperature, peak- and outlet species fractions are compared over this parameter space. While all schemes demonstrate increasing flame speed and temperature with higher field strength and richer flames, significant variations in the form and magnitude of this increase are observed for the various kinetics schemes considered.The laminar flame-speed increase at sub-breakdown electric field strengths is found to be due primarily to electron heating of the gases in both the pre-heat region and across the flame. Analysis of the electron energy transfer shows that the majority of the energy at moderate field strengths is transferred via excitement of vibrational states of nitrogen, followed by water and carbon monoxide. In the pre-heat regime, vibrational excitement of methane is also seen to play an important role for fuel-rich flames. Particular attention is paid to the modification of the flame speed due to the relaxation time of the vibrational N2 states, which is demonstrated to result in a moderate reduction of the flame speed for lean and stoichiometric flames.A driving concern here is the development of models suitable for use within large-scale three-dimensional numerical simulations and the knowledge gained in comparing the existing schemes is used to derive a range of simplified mechanisms more suited for this purpose. The ability of these reduced models to capture the flame enhancement is demonstrated over a range of flame stoichiometries and sub-breakdown field strengths.

Analysis of the Numerical Modeling Results of the Associated Petroleum Gas Combustion in the Convertible Chamber in a Micro Gas TPP

When developing prospective gas turbine plants or converting existing ones for burning nonstandard fuel gases, one of the main tasks is creation of low-emission combustion chambers with stable combustion. At the stage of sketch design, the parameters of recycling chambers are usually determined using engineering calculation methods. Methods of numerical modeling of the working process allow to clarify the obtained parameters and significantly reduce the costs of creating a combustion chamber thanks to the numerical experiment. The purpose of this work is to develop recommendations for converting existing combustion chambers of microgas-turbine power plants to utilize nonstandard fuel gases. To achieve the goal, the problem of numerical modeling of the working process with and without a stepwise air supply to the combustion zone was solved. The most significant result of the conducted studies is provision of stable combustion due to the change in the medium speed along the combustion zone with stepwise air supply and due to intensification of the reverse currents zone from the swirler with continuous air supply. The significance of the obtained results is that the proposed recommendations for converting a low-emission combustion chamber from components (kerosene+air) to components (combined petroleum gas+air) while keeping the diameter and length of the chamber unchanged, with changing the location of only the side holes. In this work, a three-dimensional numerical model of turbulent combustion for utilizing associated petroleum gases was developed to take into account the real operational conditions in a two-zone combustion chamber and analyze the performance characteristics.

Evolutions in Gaseous and Liquid Fuel Cook-Stove Technologies

The rapidly growing global demand for pollutant-free cooking energy has proliferated the research and development of energy efficient and clean cook-stoves. This paper presents a comprehensive review on the gradual improvements in cook-stove designs, focusing on gaseous and liquid fuel-operated cook-stoves around the world. Various literatures concerning the technical aspects such as design and testing, are brought together to provide an insight into the present status of developments in cook-stoves. This review of cook-stove performance covers topics such as stable operating conditions, flame propagation aspects, heat transfer and temperature distribution within the burner, fuel consumption, thermal efficiency, and emissions. Covering both laboratory-scale and field studies, the various cook-stove technologies reported so far are summarized with relevant comments regarding their commercial viabilities. The numerical modeling of combustion in cook-stoves; human health and the environmental impacts of unclean cooking technologies; and various schemes, strategies, and governmental initiatives for the promotion of cleaner cooking practices are also presented, with suggestions for future work.

Effects of EGR on combustion and emission characteristics of PODE/methanol RCCI mode at high load

In order to extend the high-load operation range of polyoxymethylene dimethyl ethers (PODE)/methanol dual-fuel reactivity controlled compression ignition (RCCI) combustion mode, a numerical model of in-cylinder combustion was established by coupling PODE/methanol chemical reaction kinetics with CONVERGE software. And then the influence mechanism of exhaust gas recirculation (EGR) addition on in-cylinder combustion process, combustion stability and pollutant formation of the RCCI engine under high load and pilot injection strategy were investigated. The results show that with the increase of EGR ratio, the peak values of the first heat release formed by PODE pilot injection combustion and in-cylinder pressure decrease, the combustion start timing and CA50 phase are gradually delayed. While the peak value of the second heat release formed by PODE main injection combustion at low EGR ratio and the combustion duration remain unchanged. Meanwhile, as the EGR ratio increases from 0 to 30 %, the brake thermal efficiency (BTE) decreases from 46.54 % to 44.40 %. And the in-cylinder equivalent ratio and temperature field distributions become uniform, and both high-temperature region (above 1800 K) and NOx generation area are reduced, which decreases NOx emissions by 42.6 % without increasing soot emissions. The methanol mixture at squish zone is subjected to the high-temperature and high-pressure of pilot injection combustion, resulting in obvious pressure oscillation. While EGR addition decreases the generation of HCO and OH active radicals, ignition points and reaction rate, which effectively inhibits methanol spontaneous combustion and knock phenomenon, and decreases the ringing intensity from 2.82 MW/m2 to 1.50 MW/m2. The pilot injection strategy coupled with 18 % EGR can extend the indicated mean effective pressure to 1.22 MPa. However, the load further extension is mainly limited by the sharp decline of BTE.

Study on the formation mechanism of a radon source during coal spontaneous combustion in a goaf

Surface isotope radon detection technology (SIRDT) is an effective physical exploration technology that provides a solution for detecting hidden underground fire sources. However, because of the inaccessibility of deep underground spaces, current research on the formation mechanism of radon sources during coal spontaneous combustion in a goaf is insufficient, which severely restricts the use of SIRDT to detect such fires. In this study, the quantitative relationship between the coal temperature and radon exhalation rate was revealed through radon exhalation experiments during the low-temperature oxidation of coal, which provides measurement data for the radon source term of coal spontaneous combustion in a goaf. A multi-physical, coupled numerical model of coal spontaneous combustion in a goaf was constructed, and the intrinsic dynamics of radon migration and the formation mechanism of the radon source in the process of coal oxidation were thoroughly investigated. The results show that the radon distribution in a goaf is because of the competition between air leakage and the “porous chimney effect.” When the temperature of the coal was low, air leakage dominated the radon transportation in the goaf, causing radon to accumulate in the area close to the air-return side. When the temperature of the coal increased, the thermal buoyancy and vortex phenomena appeared in the high-temperature area of the goaf, at this point, the “porous chimney effect” took the leading role. The updraft generated by the thermal buoyancy effect rapidly carried the radon to the top of the goaf. The vortex promoted airflow from the surrounding area of coal spontaneous combustion into the interior of the “porous chimney,” which accelerated the process of coal spontaneous combustion and increased the amount of radon transported upward; thus, further intensifying the accumulation of radon at the top of the goaf. This accumulation becomes a source of radon that continues to migrate toward the surface.

Improving the thermophotovoltaic performance of a hydrogen-fueled planar combustor with four-corner inlets via partially inserting porous medium

Micro thermophotovoltaic (TPV) generator is a potentially efficient approach to achieve microscale fuel-to-electricity conversion with high-energy–density, high-efficiency, and small-scale portability, where micro combustor provides the high-temperature continuous combustion process as well as a heat source of thermal radiation. In this study, a hydrogen-fueled planar combustor with four-corner inlets by partially inserting porous medium is proposed and investigated by a three-dimensional numerical model of porous medium combustion with detailed reaction mechanism and local thermal non-equilibrium. The combustor performance with and without partially inserting porous medium under various inlet velocities Vin and equivalence ratios ϕ are compared and analyzed to reveal the inherent strengthening mechanism. Moreover, the effects of various porous parameters on the energy conversion performance are examined: the porosity ɛ, thermal conductivity ks, and porous medium filled volume. The results demonstrate that the inserted porous medium can significantly enhance combustion efficiency, combustor wall temperature and its uniformity, and the largest increase in mean wall temperature reaches 79.7 K at Vin = 9 m/s, resulting in a 35.8 % increase in micro-TPV system efficiency. As ɛ and ks decrease, the combustor energy conversion performance increases while the temperature uniformity decreases. A moderate channel width L = 2.0 mm is good for further improving temperature uniformity and energy conversion efficiency. This study paves the way for the improvement of efficient, practical, and portable microscale generators.

On the role of transverse detonation waves in the re-establishment of attenuated detonations in methane–oxygen

This investigation concerns the problem of detonation attenuation in stoichiometric methane-oxygen and its re-establishment following its interaction with obstacles, using high resolution numerical simulation. The main focus was on the role of the transverse detonation on the re-establishment of the detonation wave, and the importance of applying a numerical combustion model that responds appropriately to the thermodynamic state behind the complex shock wave dynamics. We applied an efficient thermochemically derived four-step global combustion model using an Euler simulation framework to investigate the critical regimes present. While past attempts at using one- or two- step models have failed to capture transverse detonations, for this scenario, our simulations have demonstrated that the four-step combustion model is able to capture this feature. We thus suggest that to correctly model detonation re-initiation in characteristically unstable mixtures, an applied combustion model should contain at least an adequate description to permit the correct ignition and state variable response when changes in temperature and pressure occur, i.e., behind shocks. Our simulations reveal that (1) there is a relationship between the critical outcomes possible and the mixture cell size, and (2) while pockets of unburned gas may exist when a detonation re-initiates, it is not the direct rapid consumption of these pockets that gives rise to transverse detonations. Instead, the transverse detonations are initiated through pressure amplification of reaction zones at burned/unburned gas interfaces whose combustion rates have been enhanced through Richtmyer–Meshkov instabilities associated with the passing of transverse shock waves, or by spontaneous ignition of hot spots, which can form into detonations through the Zeldovich gradient mechanism. In both situations, non-uniform ignition delay times are found to play a role. Finally, we found that the transverse detonations are in fact Chapman–Jouguet detonations, but whose presence contributes to overdriving the re-initiated detonation along the Mach stem.

Simulation of Combustion Performance of High Salinity Organic Waste Liquid Incinerator

High-salinity organic waste liquid is one of the important industrial pollution sources and the main by-product of petrochemical enterprises in China. Incineration is the mainstream technology for treating this kind of waste liquid. A three-dimensional numerical simulation of a practical 18t/h waste liquid incinerator was carried out using Fluent. The velocity, temperature, component concentration and particle trajectory distribution in the incinerator were obtained, proposing a corresponding incinerator performance optimization scheme according to the simulation results. The results demonstrate that the numerical combustion model established in this paper can accurately simulate the distribution of flow, combustion and heat transfer in the incinerator, verifying the reliability of the numerical model; The overall temperature and flow field organization of this type of waste liquid incinerator is relatively reasonable, with heat exchange reported only in the flue corner and some heat exchange surfaces. The flow field and temperature field distribution in the incinerator can be effectively modified so as to improve the boiler operation and maintenance cycle by optimizing the corner flow line and furnace structure.

Numerical modeling of filtration gas combustion in a cylindrical radiation burner for contactless heating of materials

• A new configuration of radiant burner is considered. • The study of the effect of heat loss on the stability of the filtration combustion in a porous medium is carried out • Numerical modelling of the combustion inside a burner with axial fuel supply has shown the possibility of stable operation at high temperature levels. • There is a range of pressure drops at which the process of contactless heating of the material to high temperature levels can be carried out. The filtration gas combustion in a porous cylindrical tube with axial injection of combustible mixture is numerically investigated. This configuration can be potentially used as new type of heater for the contactless heating of materials in industrial processes. The material under treatment is placed inside the cylindrical porous tube and is heating by radiative flux from the cylindrical tube wall. The simulation of the filtration gas combustion in porous burner was carried out within the framework of the two-temperature thermal-diffusion model. Conducted numerical modeling yields qualitative description of the effects of heat removal from the burner on the limits of a stable combustion regime. The data about range of the gas flow rates and the intensity of the heat losses on the burner's inner surface corresponding to the stable combustion were obtained. The temperature distributions in the gas and the porous burner were as well gas flow field were obtained in general case, without addresing to the details of the material processing.