Analysis Of Combustion Process Research Articles

Variation on anthracite combustion efficiency with CeO2 and Fe2O3 addition by Differential Thermal Analysis (DTA)

Effects of CeO2 and Fe2O3 on anthracite combustion efficiency were investigated using differential thermal analysis (DTA). Based on heat release (QD) of anthracite as well as anthracite with CeO2 and anthracite with Fe2O3 additions against α-Al2O3 in DTA experiment, effects of additives CeO2 and Fe2O3 on anthracite combustion efficiency were evaluated. Under the same experimental conditions, heat releases of raw anthracite, anthracite with CeO2 and anthracite with Fe2O3 were 11.04 kJ/g, 11.30 kJ/g and 11.42 kJ/g, respectively, indicating that anthracite combustion efficiency was improved by addition of CeO2 and Fe2O3. To confirm the above results, carbon transfer was monitored using Thermogravimetric analysis Fourier transform infrared (TGA-FTIR) and Carbon-Sulfur analyzer during catalytic combustion process. The results indicated that CO2 emission was increased, whereas CO emission and residual carbon of ash were decreased, being in accordance with the results of DTA. Finally, according to analyses of ignition temperature and catalytic combustion process, the possible mechanism of catalytic combustion of anthracite was proposed.

Analysis of Flame and OH* Natural Emissions of n-Heptane Combustion in a Homogeneous Charge Compression Ignition (HCCI) Engine: Effect of Burnt Gas Dilution

The present study examines the global effect of a laboratory-simulated exhaust gas recirculation (EGR) on the homogeneous charge compression ignition (HCCI) combustion of n-heptane in a transparent monocylinder diesel engine. The investigations were carried out during the engine cycle for two EGR rates, 0 and 30%, at a constant 0.3 equivalence ratio. The analysis is focused on the relation between natural combustion emissions during the cold and main combustion phases and the OH* chemiluminescence and the processes involved inside the combustion chamber of a compression engine. By observing cool and main flame emissions, it was observed that the dilution by burnt gas delays and degrades the combustion phenomenon. For both cases, the natural flame emission is not uniformly distributed, because of the nonhomogeneity of the gas temperature. By coupling kinetic analysis, provided by a zero-dimensional model, it was shown that the natural emissions of combustion are sufficiently sensitive to yield combustion process analysis.

Comprehensive Study of Biomass Particle Combustion

This investigation provides a comprehensive analysis of entrained-flow biomass particle combustion processes. A single-particle reactor provided drying, pyrolysis, and reaction rate data from poplar particle samples with sizes ranging from 3 to 15 mm. A one-dimensional particle model simulates the drying, rapid pyrolysis, gasification, and char oxidation processes of particles with different shapes. The model characterizes particles in three basic shapes (sphere, cylinder, and flat plate). With the particle geometric information (particle aspect ratio, volume, and surface area) included, this model can be modified to simulate the combustion process of biomass particles of any shape. The model also predicts the surrounding flame combustion behaviors of a single particle. Model simulations of the three shapes agree nearly within experimental uncertainty with the data. Investigations show that spherical mathematical approximations for fuels that either originate in or form aspherical shapes during combustion poorly represent combustion behavior when particle size exceeds a few hundred microns. This includes a large fraction of the particles in both biomass and black liquor combustion. In particular, composition and temperature gradients in particles strongly influence the predicted and measured rates of temperature rise and combustion, with large particles reacting more slowly than is predicted from isothermal models.

313 高EGRディーゼル機関の燃焼過程および燃焼生成物の化学動力学に基づく3次元数値解析(OS-4・GS-7 ガス燃料・ディーゼル燃焼)

313 高EGRディーゼル機関の燃焼過程および燃焼生成物の化学動力学に基づく3次元数値解析(OS-4・GS-7 ガス燃料・ディーゼル燃焼)

An experimental study of HCCI-DI combustion and emissions in a diesel engine with dual fuel

An experimental study of port injected n-heptane homogeneous charge compression ignition (HCCI) in combination with in-cylinder diesel fuel direct injection (DI) was conducted on a single cylinder diesel engine. By adjusting the quantities of premixed n-heptane as well as the direct injected diesel fuel, different premixed ratios were obtained over a wide range of load conditions while the test engine was kept at a constant speed. The effects of premixed ratio ( r p ) and direct injection timing on HCCI-DI combustion characteristics and emissions were investigated. In order to evaluate the traits of HCCI-DI combustion, the conventional diesel and HCCI engine performances were presented to be compared with their results. Furthermore, special emphasis was put on the combined combustion process analysis. It can be found that the NOx emissions decreased dramatically with partial premixing and it exhibited a descending trend as a function of r p increase when the r p was lower than 0.3, but it showed a great tendency to increase when the premixed ratio was higher. The inherent trade-off of NOx and soot was not obvious since the soot emissions remained at the same level of the prototype diesel engine under the condition of lower r p . Moreover, the influence of r p on the CO and UHC emissions was assessed. The results also revealed that the HCCI-DI combustion could effectively improve the indicated thermal efficiency of diesel engine at low to medium loads.

Characteristics and energy distribution of modulated multi-pulse injection modes based diesel HCCI combustion and their effects on engine thermal efficiency and emissions

Cycle fuel energy distribution and combustion characteristics of early in-cylinder diesel homogenous charge compression ignition (HCCI) combustion organized by modulated multi-pulse injection modes are studied by the engine test. It is found that heat loss due to unburned fuel droplets and CO emission can be decreased effectively by injection mode regulation, and thermal efficiency can be potentially increased by 4%–12%. From the analyses of combustion process, it is also found that diesel HCCI combustion is a process with a finite reaction rate and is very sensitive to injection timing and injection mode. At injection timing of −90°CA ATDC, extra low NOx emissions can be obtained along with high thermal efficiency.

Vibrational nonequilibrium and electronic excitation in the reaction of hydrogen with oxygen behind a shock wave

A theoretical analysis of ignition and combustion processes in a hydrogen-oxygen mixture behind a shock wave is presented (1000 K ≤ T ≤ 2500 K; 2.0 atm ≥ P ≥ 0.3 atm). The experiments performed using stoichiometric mixtures with the detection of OH (2Σ+) and rich mixtures with the detection of OH (2Π) were interpreted in terms of a general kinetic approach. In this case, the apparent rate constant of the chain branching reaction H + O2 → O + OH was the only adjustable parameter. It was found that this rate constant increased with decreasing hydrogen content and exceeded equilibrium values. In this context, the mechanism of chain branching, which occurs through the formation of the vibrationally excited radical HO2(v), and the role of secondary vibrationally nonequilibrium O2 and O2(1Δ) molecules and the reaction H + O2(1Δ) → O + OH are discussed. New mechanisms of the formation and quenching of electronically excited OH(2Σ+) radicals, O(1 D) atoms, and O2(1Δ) molecules are considered. The results of a nonempirical (ab initio) analysis of molecular systems and the corresponding estimations of reaction rate constants were widely used.

Stereo imaging and analysis of combustion process in a gas turbine combustor

Quantitative digital 3D information extraction from a stereo imaging pair of a semi-transparent flame has been attempted in this paper. A semi-automatic image matching methodology has been adopted to overcome the very challenging problem of non-unique matching of semi-transparent flame. It is shown that the tracking of flame features in relation to the 3D position to the combustor wall surface is possible by combining optical 3D visualization and digital image reconstruction. Useful statistics can be obtained. 3D particle tracking has also been demonstrated. The complex 3D trajectory of a residual particle near one of the dilution holes of the combustor has been computed. A time-resolved analysis of flame positions from stable combustion mode to unstable mode has been carried out. The results show that the general flame in depth distribution is different under the stable, transition and unstable combustion modes. The most scattered in depth distribution is observed in the transition combustion mode. The technique is most suitable for practical devices with very limited optical access.

Combustion process analysis

As the limits being placed on emissions grow to be more and more stringent, optimizing the start-up process becomes extremely important. This article by Robert Bosch GmbH, Germany, shows how the analysis of the cylinder pressure measurements and the combustion processes calculated from these can be applied to the highly dynamic start-up process. It is shown that the ability to investigate the thermodynamic processes in a cyclic manner is the key to efficient improvement of the start-up process at all stages of development.

308 化学動力学を考慮したガソリンHCCI機関の着火・燃焼過程の三次元数値解析(OS-1 着火・燃焼解析,噴流解析,研究発表講演)

308 化学動力学を考慮したガソリンHCCI機関の着火・燃焼過程の三次元数値解析(OS-1 着火・燃焼解析,噴流解析,研究発表講演)

Analysis of Combustion Processes by Stochastic Reaction Diffusion Systems and Simulation Studies

Analysis of Combustion Processes by Stochastic Reaction Diffusion Systems and Simulation Studies

320 ジメチルエーテル噴射ディーゼル機関における着火・燃焼過程の数値解析(OS-2 代替燃料の燃焼)

320 ジメチルエーテル噴射ディーゼル機関における着火・燃焼過程の数値解析(OS-2 代替燃料の燃焼)

360 ガス燃料筒内噴射 2 サイクル機関における燃焼過程の数値解析

360 ガス燃料筒内噴射 2 サイクル機関における燃焼過程の数値解析

Gas sampling analysis of combustion processes in a homogeneous charge compression ignition engine

In-cylinder gas sampling experiments were conducted to clarify the chemical reaction processes of homogeneous charge compression ignition (HCCI) combustion. To study the differences in ignition processes by the ignitability of fuels, three kinds of straight-chain saturated hydrocarbons, such as n-pentane, n-hexane and n-heptane, were used as the fuels. Also, to study specific differences in the ignition processes between a single-component fuel and a dual-component fuel, n-pentane was used as the single-component fuel and n-hexane and ethylene, with compositions adjusted in order to have the same ignitability as n-pentane, were used as the dual-component fuel. The results show that the chemical processes in the low-temperature oxidation range, from 700 to 900 K, need to be controlled for the ignition timing control of HCCI combustion. Controlling ignition timing by dual fuel means controlling the oxidation starting time by the ignitability of a high cetane number fuel and controlling the low-temperature oxidation rate by varying the composition of the high and low cetane number fuels.

THE ESTIMATION PROBLEMS OF THE FIRE HAZARD FOR VERTICALLY ORIENTED BUILDING PRODUCTS/VERTIKALIAI ORIENTUOTŲ STATYBINIŲ GAMINIŲ GAISRINIO PAVOJINGUMO ĮVERTINIMO PROBLEMOS

The Directive of new approach 89/106/EEC, which was prepared by Directorate General of the European Commission (DG III), defines the guidelines for development of fire protection in building construction. Six main directions for development of fire protection are defined in this Directive as well. Solid materials are most numerous among building products. Therefore a brief analysis of combustion process of these materials is presented in this article. F.Williams developed the theoretical principles of combustion. Phase transitions in the zone of combustion are analyzed in the theory. Formulas 1–4 describe this process. The process of combustion of solid materials is heterogeneous; therefore the model of pyrolysis is presented by 5 formulas. An intricate energy exchange takes place in real fires. The heat is being transferred in different ways. The most acceptable description of heat transfer is by means of radiation. Description of this process is presented in formulas 6–7. The heat transfer by means of radiation can be modelled and used for environment testing. The combustibility of building products can be examined by means of reaction of fire tests. In recent years tests for different building products were carried out according to ISO 5657 test methodology in the Fire Research Centre. Test results indicate that the time to sustained surface ignition for building products is inversely proportional to heat flux. This logarithmic dependence is presented in 8 formulas. Establishment of parameters of this logarithmic flow for different building products can prove this. This work was carried out during the process of verification of this hypothesis. Analysis of fire testing practice of vertically oriented building products in different countries shows that harmonized fire test methods for these products do not exist. Most of these test methods are based on presumption that the flame spread is possible only inside the building not considering the behaviour of facade in fire. The main idea of fire test method for element of vertically oriented building construction together with the principal scheme of test equipment are presented in the article as well. Further development of this idea leads to five questions, which should be answered to solve the problem. After the completion of this task and analysis of test results, all the information is to be submitted for further consideration.

THE ESTIMATION PROBLEMS OF THE FIRE HAZARD FOR VERTICALLY ORIENTED BUILDING PRODUCTS

Summary The Directive of new approach 89/106/EEC, which was prepared by Directorate General of the European Commission (DG III), defines the guidelines for development of fire protection in building construction. Six main directions for development of fire protection are defined in this Directive as well. Solid materials are most numerous among building products. Therefore a brief analysis of combustion process of these materials is presented in this article. F.Williams developed the theoretical principles of combustion. Phase transitions in the zone of combustion are analyzed in the theory. Formulas 1–4 describe this process. The process of combustion of solid materials is heterogeneous; therefore the model of pyrolysis is presented by 5 formulas. An intricate energy exchange takes place in real fires. The heat is being transferred in different ways. The most acceptable description of heat transfer is by means of radiation. Description of this process is presented in formulas 6–7. The heat transfer by me...

Fluctuation Analysis of Diesel Combustion Process by means of the Optical Fiber Thermometer. Comparison of Combustion Fluctuation between Conventional Injection and Pilot Injection.

In order to clarify the characteristics of combustion fluctuation in diesel engines quantitatively, the fluctuations of pressure and flame temperature were measured, and the root mean square value, the autocorrelation coefficient and the power spectrum density of the measured fluctuations were analyzed by comparing the cases with and without pilot injection. The following concluding remarks are obtained. (1) The frequency power spectrum of the in-cylinder pressure history is reduced markedly by pilot injection in two frequency ranges from 0.2 to 2.0 kHz and from 2 to 5 kHz. (2) The fluctuation of combustion pressure is dependent on the maximum rate of pressure rise, which is dependent on the ignition delay. (3) The maximum rms of the flame temperature fluctuation during diffusion combustion has a clear correlation with that of the pressure fluctuation in the initial combustion. (4) The fluctuation of the flame temperature during diffusion combustion has the characteristics of isotropic turbulence.

Production and Destruction of Nitrogen Oxides in the Dilution Process of Fuel-Rich Burnt Gases.

Production and destruction of nitrogen oxides in the dilution process of fuel-rich burnt gases are investigated based on detailed chemical kinetics. From the analysis of combustion processes with mixing of methane-air fuel-rich burnt gas and air, it is shown that fast mixing due to strong turbulence enables a great deal reduction in NOx concentration, and that a further reduction cannot be achieved for a rich mixture of equivalence ratio higher than 1.2. The NO production rates of elementary reactions indicate that NO is formed by the destruction of HNO at low NO concentration and is deoxidized into HNO at high NO concentration. It is also shown that NOx concentration can be halved if the temperature decreases with the volume expansion in a high-speed piston-engine motion prior to the heat release due to dilution. Furthermore, the effect of temperature fluctuation on the dilution path is discussed from the practical point of view for reducing NOx in two-stage combustion.

Combustion processes in CSTR. Bifurcation analysis of the H2–O2system

A method for the analysis of combustion processes in continuous stirred tank reactors is described. The method, based on the results of the bifurcation theory, appears to be efficient and fast and allows the ignition diagram in the plane temperature–pressure to be plotted. This diagram presents much more information than the traditional one obtained by analysis in the time domain. Moreover, the map can give suggestions on the experimental strategy to be followed in the search for interesting dynamic behaviour. The method is applied to the analysis of the H2–O2 system for a stoichiometric mixture at 4 and 6 s residence times, in the pressure range 0.05–0.20 atm and for temperatures between 600 and 900 K. The results provided by the developed method and some literature experimental data are compared.

Numerical analysis of droplet combustion process: Heating, evaporation, ignition and burning

Abstract Droplet combustion processes of benzene and n‐heptane liquid fuels, including heating, evaporation, ignition and burning, are numerically investigated and compared with the available measured results found in the literature. Investigation shows that the consideration of thermal radiation effect does not introduce too many differences of ignition‐time predictions in the modeling compared to that obtained without thermal radiation effect. However, the predicted ignition times associated with the assumption of semitransparent droplets are mostly in agreement with the measured ones. In contrast, the difference between the predictions of the burned‐out time with and without thermal radiation effect are significant. Finally, the assumption of constant thermophysical properties in the modeling leads to some prediction errors, in comparison with the model associated with the variable thermophysical properties, but this is relatively minor.