Model For Simulation Of Combustion Research Articles

Comparative study on the molecular evolution of changqing petroleum coke during air and pure oxygen combustion: A ReaxFF method analysis

Based on reactive force field (ReaxFF) simulation, the molecular evolution mechanism of air combustion simulation and pure oxygen combustion simulation of Changqing petroleum coke was studied. On the basis of the original petroleum coke molecular model, N2 and O2 molecules were added to construct the air combustion simulation model and the pure oxygen combustion simulation model respectively. The number of molecules, main products, and typical hydrocarbon gases in the two simulation results were analyzed by setting up the LAMMPS in. file. Finally, the molecular changes of pyrrole and pyridine were described. The results show that the main reaction interval of pure oxygen combustion is earlier than that of air combustion. In the main reaction temperature range, the reaction rate of pure oxygen combustion is higher than that of simulated air combustion. At 170 ps, the two simulations reaction speed is the fastest time point; Pyridine is more stable than pyrrole. The research on the distinction and comparison of two kinds of simulation has certain guiding significance for the clean utilization of petroleum coke combustion process in industry.

Study on the active jet spark induced combustion technology for aviation kerosene piston engine

Aviation kerosene is increasingly being used in aviation piston engines because it is safe for use. However, if the traditional compression ignition (CI) mode is adopted for such engines, the high compression ratio will lead to an increase in the weight of moving parts and a decrease in the engine speed, thereby restricting the improvement of the power–weight ratio. If the traditional spark ignition (SI) mode is adopted, a high-performance output cannot be achieved owing to the restriction of knock. To overcome the abovementioned problems and realize kerosene high efficiency and knock free combustion, in this study, we designed a new combustion mode for active-jet spark-induced (AJSI) compound combustion in aviation kerosene piston engines. In order to verify the feasibility of AJSI combustion, a detailed three-dimensional in cylinder combustion simulation model was established, and the combustion process of AJSI combustion was studied. The results showed that the ignition delay period of kerosene could be reduced by 30% in the AJSI combustion mode. Compared to the ordinary SI combustion, the maximum pressure rise rate reduced by 26%, and knock index reduced by 34%. From the research results, AJSI combustion can effectively suppressing knock. In this paper, the combustion mechanism of AJSI combustion is analyzed in detail. The AJSI combustion process in an engine is divided into five stages, and the combustion characteristics are similar to those of SI in the early stage and similar to those of CI in the later stage. The period of similar–SI lasted for a long time, and the temperature and pressure increased gradually, which was mainly used for preparing for the similar–CI. Combustion during the period of similar–CI was intense. Spontaneous combustion of a large amount of premixed fuel occurred during this period, which lasted for a short time, with a rapid release of large amounts of heat. In this process, owing to the rapid combustion, the knock intensity can be decreased.

The Influence of Design Geometry on the Operational Performance of Helmholtz Pulse Combustor

The objective of this study is to build a pulse combustion simulation model in order to determine the design parameters that influence the pulse combustor’s optimized performance. The Helmholtz valveless pulse combustor type is the simple design of pulse combustors. It has many advantages over conventional combustion, so it has been used in a variety of applications. There are many parameters that need to be studied in order to design this combustor type to achieve optimal performance. This research presents numerical and experimental investigations of pulse combustion. FLUENT software is used to conduct numerical simulations of the design parameters and pulse combustor performance. These simulations are then experimentally validated and confirmed to be accurately optimized in order to be applicable. The performance of the pulse combustor is studied for different inlet and tailpipe length and combustion chamber volume. This research accurately predicts how the frequency and pressure amplitude vary as the lengths of the inlet and tailpipe increase, as well as the combustion chamber volume.

Simulation Research of the n-Butanol Proportion Influence on HCCI Combustion of Free-Piston Diesel Engine Generators

For researching the influence of n-butanol proportion in diesel fuel on homogeneous charge compression ignition (HCCI) combustion of the free-piston diesel engine generator (FPDEG), a three-dimensional (3D) moving mesh computational fluid dynamics (CFD) simulation model of a FPDEG prototype was developed. A detailed chemical reaction mechanism of diesel fuel was selected as the HCCI combustion mechanism and coupled in the established HCCI combustion simulation model of the FPDEG prototype. The validity of the established HCCI combustion simulation model is proved by comparing the simulation and experimental pressure curves under the condition of pure diesel fuel. The simulation results of different n-butanol proportions in diesel fuel showed that as the n-butanol proportion increased from 0 to 60%, the maximum heat release rate decreased to 59.6 J/deg, the calculated indicated thermal efficiency augmented to 4.6%, the calculated indicated mean effective pressure increased to 0.057 MPa, and the final NOx and CO content decreased to 0.239 and 0.57 g/kg fuel, respectively, but the final soot content increased to 0.000562 g/kg fuel. Therefore, the n-butanol proportion of diesel fuel played a vital role in combustion and emission progress of the FPDEG.

A study of diesel and Pongamia Pinnata biodiesel combustion in compression ignition engines using zero-dimensional modelling and experimental methods

ABSTRACT The present study develops a single-zone zero-dimensional progressive combustion simulation model using Python programming language for compression ignition engines. The model is capable of predicting in-cylinder pressure, heat release rate, engine performance, and emissions characteristics. The numerical model is experimentally validated using resuts from engine testing for diesel, Pongamia Pinnata biodiesel and diesel-biodiesel blends. The chemical composition of fuel is identified using Gas Chromatography-Mass Spectrometry. The values of power output, mean effective pressure and exhaust oxygen concentration are independently obtained from the numerical model and from the experiments. The engine performance is not significantly affected for biodiesel to diesel blending ratio of up to 30%. A higher oxygen concentration in the exhaust gas is observed with increase in blending ratio. The developed numerical model would be useful in studying the performance and emission characteristics for any alternative fuel with known calorific value and chemical composition.

Effect of the Plasma Jet Ignition and Flame Kernel Under The Combustion Process in a Constant Volume Combustion Chamber

This work is to study the plasma application using a capacitive discharge ignition capable of using the plasma jet which belongs to the non-thermal plasma physic. A plasma-jet spark plug was designed to combine a discharge chamber including an insulator and expanding the plasma area. The nonresistance was applied to acting the interference suppression of a plasma-jet spark plug to ensure the high energy generated at a DC-DC converter. An ANSYS FLUENT program was used to conduct analyzing combustion progress. The combustion simulation model is composed of configurations of a spark plug, a lambda sensor, and an internal combustion chamber. Resultantly, the minimum value of the combustion pressure is verified at λ = 1.6, and the plasma jet has higher values in the order of 2, 3, and 4 bar than the conventional models due to having a fast reaction. Consequently, the plasma jet has advantageous in combustion diffusivity in comparison to the conventional spark plug since the negative electrode of the cathode is not designed in front of a jet plug.

Low_NOx emission and high efficiency combustion optimization for opposed firing boiler BASED on intelligent algorithm

On the basis of BP-GA algorithm for boiler efficiency and NOx emission concentration, a combustion simulation model was established. By learning the training samples based on low NOx combustion adjustment tests, the combustion simulation model can accurately map the nonlinear relationship between boiler operation parameters and boiler efficiency and NOx emission concentration. Genetic algorithm was used to obtain the optimization strategies to get the best boiler efficiency and NOx emission concentration, which provides guidance for the operation.

An adaptive least-squares global sensitivity method and application to a plasma-coupled combustion prediction with parametric correlation

We introduce an efficient non-intrusive surrogate-based methodology for global sensitivity analysis and uncertainty quantification. Modified covariance-based sensitivity indices (mCov-SI) are defined for outputs that reflect correlated effects. The overall approach is applied to simulations of a complex plasma-coupled combustion system with disparate uncertain parameters in sub-models for chemical kinetics and a laser-induced breakdown ignition seed. The surrogate is based on an Analysis of Variance (ANOVA) expansion, such as widely used in statistics, with orthogonal polynomials representing the ANOVA subspaces and a polynomial dimensional decomposition (PDD) representing its multi-dimensional components. The coefficients of the PDD expansion are obtained using a least-squares regression, which both avoids the direct computation of high-dimensional integrals and affords an attractive flexibility in choosing sampling points. This facilitates importance sampling using a Bayesian calibrated posterior distribution, which is fast and thus particularly advantageous in common practical cases, such as our large-scale demonstration, for which the asymptotic convergence properties of polynomial expansions cannot be realized due to computation expense. Effort, instead, is focused on efficient finite-resolution sampling. Standard covariance-based sensitivity indices (Cov-SI) are employed to account for correlation of the uncertain parameters. Magnitude of Cov-SI is unfortunately unbounded, which can produce extremely large indices that limit their utility. Alternatively, mCov-SI are then proposed in order to bound this magnitude ∈[0,1]. The polynomial expansion is coupled with an adaptive ANOVA strategy to provide an accurate surrogate as the union of several low-dimensional spaces, avoiding the typical computational cost of a high-dimensional expansion. It is also adaptively simplified according to the relative contribution of the different polynomials to the total variance. The approach is demonstrated for a laser-induced turbulent combustion simulation model, which includes parameters with correlated effects.

Optimization of Combustion Performance of Bioethanol (Water Hyacinth) Diesel Blends on Diesel Engine Using Response Surface Methodology

In the current study, an attempt has been made to use water hyacinth plant (Eichhornia crassipes) as a raw material for production of bioethanol which is then blended with diesel to obtain biodiesel. To investigate the combustion performance, combustion simulation model was developed and compared with experimental results. Further, the combustion performance of bioethanol–diesel blends in diesel engine was evaluated using response surface methodology technique. Bioethanol extracted from water hyacinth is blended with commercial diesel fuel (BED) in different proportions (volume by volume (v/v)), i.e., 5, 10, 15, 20 and 25BED. This study illustrates the investigation of various compression ratio, loads and fuel injection pressures with different proportion of diesel bioethanol blends. The results show that single-cylinder diesel engine is capable to run up to 25 % bioethanol mixed with diesel by volume. The in-cylinder combustion pressure (Pmax) reduces while increasing bioethanol–diesel ratio. At higher engine loads, compression ratio and fuel injection pressure, bioethanol blends produce higher combustion pressure in comparison with pure diesel fuel. At lower load, compression ratio and fuel injection pressure, ignition delay increases and Pmax reduces. The 5BED (5 % bioethanol + 95 % diesel) and 10BED (10 % bioethanol + 90 % diesel) gave better combustion performance among all the bioethanol–diesel blends.

Simulation of HCCI Combustion Characteristics for Low RON Gasoline Surrogate Fuels

A reduced chemical kinetic model (103species and 468 reactions) for new low-RON(research octane number) gasoline surrogate fuels has been proposed. Simulations explored for ignition delay time have been compared with experimental data in shock tubes at pressure of 10atm-55 atm and temperatue of 600-1400 K (fuel/air equivalence ratio=0.5,1.0,2.0 and EGR rate=0, 20%). The simulation data presented 15% enlargement compared with experiments showed applicability of the new kinetic mode in this work. A combustion simulation model has been build for HCCI(homogeneous charge compression ignition) engine with Chemkin-pro. The effects of different air inlet temperature, inlet pressure, engine speed and the fuel air equivalence ratio on the combustion characteristics of the fuel were researched. The results indicated the combustion in an HCCI engine worked sufficiently with lean mixtures and low speed. Meanwhile the material strength could be influenced when the inlet conditions changed. This helps to promote the low-RON gasoline surrogate fuel application in the HCCI engine.

Hydrogen non-premixed combustion in enclosure with one vent and sustained release: Numerical experiments

Numerical experiments are performed to understand different regimes of hydrogen non-premixed combustion in an enclosure with passive ventilation through one horizontal or vertical vent located at the top of a wall. The Reynolds averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) model with a reduced chemical reaction mechanism is described in detail. The model is based on the renormalization group (RNG) k-e turbulence model, the eddy dissipation concept (EDC) model for simulation of combustion coupled with the 18-step reduced chemical mechanism (8 species), and the in-situ adaptive tabulation (ISAT) algorithm that accelerates the reacting flow calculations by two to three orders of magnitude. The analysis of temperature and species (hydroxyl, hydrogen, oxygen, water) concentrations in time, as well as the velocity through the vent, shed a light on regimes and dynamics of indoor hydrogen fires. A well-ventilated fire is simulated in the enclosure at a lower release flow rate and complete combustion of hydrogen within the enclosure. Fire becomes under-ventilated at higher release flow rates with two different modes observed. The first mode is the external flame stabilised at the enclosure vent at moderate release rates, and the second mode is the self-extinction of combustion inside and outside the enclosure at higher hydrogen release rates. The simulations demonstrated a complex reacting flow dynamics in the enclosure that leads to formation of the external flame or the self-extinction. The air intake into the enclosure at later stages of the process through the whole vent area is a characteristic feature of the self-extinction regime. This air intake is due to faster cooling of hot combustion products by sustained colder hydrogen leak compared to the generation of hot products by the ceasing chemical reactions inside the enclosure and hydrogen supply. In general, an increase of hydrogen sustained release flow rate will change fire regime from the well-ventilated combustion within the enclosure, through the external flame stabilised at the vent, and finally to the self-extinction of combustion throughout the domain.

Prediction of SOx and NOx emissions from a medium size biomass boiler

While small and medium size biomass combined heat and power (CHP) plants (i.e., up to 5 MW of electrical rated power) represent an attractive option to exploit locally available biomass resources at low cost, the corresponding investment per unit of rated power significantly rises when the installed power decreases. In these cases, secondary pollutant emissions control measures are most of the time not economically viable and primary emissions control must be used alone to avoid the formation of undesired compounds such as NOx and SOx. Primary control measures require the careful optimization of fuel quality and combustion process. For plant operators, being able to accommodate biomass quality changes in order to minimize the fuel cost can be of great importance in order to guarantee the profitability of the plant. This contribution is dedicated to the development of a zero-dimensional (input–output) combustion simulation model able to predict the pollutants emissions resulting from complete and incomplete combustion with respect to varying combustion operation (ambient temperature, humidity, fumes recirculation, …). This tool is intended to be integrated in a global simulation model of the CHP plant and the attached district heating network installed on the University campus in Liège. Doing so, the plant operation can be optimized with respect to economic as well as environmental and energetic aspects (3E approach) thus ensuring the sustainability of the approach.

Simulation of Combustion Field with Lattice Boltzmann Method

Turbulent combustion is ubiquitously used in practical combustion devices. However, even chemically non-reacting turbulent flows are complex phenomena, and chemical reactions make the problem even more complicated. Due to the limitation of the computational costs, conventional numerical methods are impractical in carrying out direct 3D numerical simulations at high Reynolds numbers with detailed chemistry. Recently, the lattice Boltzmann method has emerged as an efficient alternative for numerical simulation of complex flows. Compared with conventional methods, the lattice Boltzmann scheme is simple and easy for parallel computing. In this study, we present a lattice Boltzmann model for simulation of combustion, which includes reaction, diffusion, and convection. We assume the chemical reaction does not affect the flow field. Flow, temperature, and concentration fields are decoupled and solved separately. As a preliminary simulation, we study the so-called “counter-flow” laminar flame. The particular flow geometry has two opposed uniform combustible jets which form a stagnation flow. The results are compared with those obtained from solving Navier–Stokes equations.

舶用ディーゼル機関の故障診断，運転条件決定のための燃焼シミュレーション 第二報 燃焼シミュレーション

Up to now pollutant emissions was not considered a problem in the field of marine engines. However, the International Maritime Organization (IMO) is agreed with the legislation that the NO emission of the marine engine produced from 2000 will be reduced to the present level of 70 percent. In this paper, the combustion simulation model, initially developed for high-speed, direct injection diesel engines, is used for studying the performance and emission characteristics of the 2-cycle, slow speed diesel engines are presented. In the simulative calculation by which we can able to calculate subsequent spatial and temporal history of most of the parameters, such as burning rate, local temperature, NO emission and soot etc, and according to this information, distribution of liquid fuel's temperature and burning area in the combustion chamber can be described three dimensionally using a 3-D volume rendering application.

Percolation model for simulation of coal combustion process

A pulverized coal combustion simulation model applying a percolation theory based on a Monte Carlo method has been developed to predict swelling and fragmentation behaviors during a coal combustion process. The shape of pulverized coal particles before reaction was assumed as a three-dimensional cube arranged in large number of small lattices. These lattices were classified into char, volatile, ash, or macropore, depending on the coal's industrial analysis value, and they were arranged randomly in the cubic. The coal combustion processes were classified as devolatilization and char combustion, and they were assumed to occur simultaneously. In the devolatilization process, the dual-competing reaction model determined the devolatilization time of a volatile lattice. With coal devolatilization, the coal particles swelled due to increase in internal pressure. With char combustion, O 2 lattices were arranged around a coal particle and the random walk model was applied to represent the O 2 diffusion behavior. Furthermore, the char reaction model was applied to determine the char reaction time. Thus, a char lattice was lost when its total reaction time was longer than the O 2 diffusion time and the reaction time. With char combustion, ash agglomeration occured. Char combustion finished when all of char lattices were burned out or the char lattices were completely surrounded by ash lattices, preventing oxygen lattices from coming into contact with the char lattices. It was shown that this model well represents the difficulty of char burnout caused by increase in diffusion resistance in the latter period of the reaction. A particle temperature profile was determined by a model calculation in an environment in which atmospheric temperature was 1500 K. Using only the industrial coal properties, this model predicts detailed variations of reaction rate, porosity, and maximum relative particle diameter with particle conversion in the pulverized coal combustion process.