Soot Mass Research Articles

Механохимический синтез пористых кремнийоксиуглеродных композитов

The work is devoted to investigation of the process of mechanochemical synthesis of porous silicon oxycarbide composites. The synthesis was carried out by mechanical treatment of several mixtures of activated carbon and white soot with different mass ratios. Samples were investigated using such methods as X-ray diffraction, infrared spectroscopy, low-temperature nitrogen adsorption/desorption and potentiometric titration. Synchronous thermal analysis including thermogravimetric analysis and differential scanning calorimetry was performed. The results of X-ray diffraction analysis showed that no new phases were formed in the process of mechanochemical synthesis, and the structure of composites obtained can be characterized as highly amorphous. The possibility of activated carbon and white soot to be chemically bonded with the formation of silicon oxycarbides, which act as a binder in the composite structure, during intensive supply of mechanical energy to raw materials was proved. Thermal stability of silicon oxycarbides formed and the amount of free carbon that was not bonded with silicon dioxide were estimated by synchronous thermal analysis. It was established that the initial mixture composition significantly affects the surface chemistry of composites synthesized, which is expressed by a change in concentration of different surface functional groups. A possible mechanism of solid phase interaction between activated carbon and white soot resulting in the formation of Si–O–C bonds was proposed. Investigation of porous structure of composite materials obtained showed that the specific surface area and pore volume become lower with an increase in white soot concentration in the initial mixture. It is possible to adjust the porous structure of composites by changing the activated carbon to white soot mass ratio.

Soot Distribution and Thermal Regeneration of Marine Diesel Particulate Filter

Diesel particulate filter (DPF) is a leading technology reducing particle emissions from marine diesel engines. The removal or regeneration of soot in DPF is an important issue. The purpose of this study is to provide some reference strategies to design the DPF for marine diesel engines. In this paper, a mathematical model of a marine DPF was built up and the particle trap process and the regeneration dynamics were simulated. The results show that the cake soot mass concentrations from 0 to 4.2 g/L during the trap process increase linearly with the increase of the exhaust gas flows while the depth soot mass concentrations from 0 to 2.2 g/L firstly increase linearly and then keep constant. Soot is mainly concentrated in the front and rear portion of the filter and less soot is in the middle. The soot distribution in the cake and depth layers shows the unevenness during the trap and regeneration process. The initial soot loadings have great effects on pressure drops and soot mass concentrations before regeneration, but the little effect after regeneration. The exhaust gas temperature heated to 850 K can achieve 94% efficiency for the DPF regeneration. The heating rate has no effects on the pressure drops and soot mass concentrations, but the heating duration time of exhaust gas has an important impact on them.

Simulation study on the influence of fuel injection strategy on the soot emission of dual-injection engine

A 2.0T gasoline engine was modified to a dual-injection engine. Numerical simulation method is used to study the influence of fuel type and fuel injection strategy on the in-cylinder mixture formation process, combustion process and soot emission of dual-injection gasoline engine. The simulation results show that an appropriate increase in the intake port fuel injection ratio can improve the uniformity of the air-fuel mixture. Increasing the fuel injection ratio in the intake port of the dual-injection system, the proportion of fuel directly injected into the cylinder decreases and the oil film distribution in the cylinder is reduced. Among the three injection schemes, the flame front of the D85 injection scheme reaches the cylinder wall earliest, and the flame spreads faster; the soot mass fraction generation decreases with the decrease of the GDI injection ratio. In particular, the amount of soot generated under the D65GDI injection ratio is significantly reduced.

Methodology of diesel particulate filter testing on test bed for non-road engine application

This paper describes the methodology and test results of diesel particulate filter (DPF) functional testing performed on non-road compression ignition engine installed on test bed. The scope of work included testing of various DPF regeneration strategies, backpressure and balance point tests and emission performance evaluation during a legislative test cycles. The aim of this study was to observe and investigate the influence of exhaust gas parameters on DPF functionality in terms of soot loading, type and duration of the regeneration and emission performance. Under investigation was also the capability of soot burning rate. The DPF sample under test was part of the complete exhaust aftertreatment system (ATS) which consisted of: a diesel oxidation catalyst (DOC), a DPF and a selective catalytic reduction system (SCR). Testing was carried out on a heavy-duty diesel engine installed on a test stand with a dynamic dynamometer and equipped with an emission bench. The test program allowed to assess the engine matching to exhaust aftertreatment system with regard to emissions compliance, in-service operation and necessary engine control unit (ECU) calibration works. The results show the influence of the DPF regeneration strategy on its duration and on the soot mass burn rate. Passive DPF regeneration was a favorable mode of DPF cleaning, due to lack of fuel penalty and lower aging impact on the entire ATS. Optimization of soot flow rate, exhaust gas temperature and the chemistry of the DOC/DPF was further recommended to ensure the long-term durability of the entire system.

Effects of ambient CO2 and H2O on soot processes in n-dodecane spray combustion using large eddy simulation

In this study, large eddy simulations, coupled a two-equation soot model, are performed to investigate the effects of ambient carbon dioxide (CO2) and water (H2O) additions on the soot formation and oxidation processes in an n-dodecane spray flame. In the soot model, acetylene (C2H2) is soot precursor and surface growth species, while hydroxyl radical (OH) and oxygen (O2) are soot oxidizers. The effect of ambient CO2 and H2O additions on soot formation/oxidation can be separated into thermal and chemical effects. For the thermal effects, the ambient CO2 and H2O additions increase C2H2 but reduce OH formation by lowering the flame temperature. This leads to a higher soot mass formed. On the contrary to the thermal effects, the ambient CO2 and H2O additions reduce the soot formation due to their chemical effects. The reaction CH2∗+CO2↔CH2O+CO is found to be responsible for reducing C2H2 formation. The ambient H2O addition results in a higher OH but lower the C2H2 mass formed owing to the reverse reactions H2+OH↔H2O+H and OH+OH↔H2O+O. Furthermore, the chemical effects is more significant than the thermal effects under the tested conditions. This leads to a lower soot mass formed when adding ambient CO2 and H2O.

Three-Dimensional Simulation Analysis of the Effect of Hydrous Ethanol and Exhaust Gas Recirculation on Gasoline Direct Injection Engine Combustion and Emissions

Abstract To analyze the influence of hydrous ethanol on the performance of the direct-injection engine, the three-dimensional simulation is carried out by using converge software coupled with the combustion mechanism of hydrous ethanol gasoline and the soot model. The combustion and soot generation characteristics of a direct-injection gasoline engine burning hydrous ethanol gasoline using exhaust gas recirculation (EGR) technology are investigated. It is found that the increase of the blending ratio of the hydrous ethanol can accelerate the flame propagation speed, shorten the combustion duration, and improve the combustion isovolumetric. The nucleation and growth of soot are jointly controlled by polycyclic aromatic hydrocarbons (PAHs) and the small molecular components such as C2H2. The oxygen content properties and high reactive OH of the hydrous ethanol-containing gasoline inhibit soot formation. Compared with pure gasoline, the carbon soot precursor mass is reduced by 60%, 54.5%, 73.3%, and 52.4% for 20% anhydrous ethanol blended with gasoline, A1, A2, A3, and A4, respectively, and the carbon soot mass is reduced by 63.6% and the carbon soot volume density is reduced by 40%. The introduction of EGR exhaust reduces the burning rate and leads to an increase in the production of carbon monoxide, hydrocarbon, and soot. However, the combination of EGR with hydrous ethanol gasoline can significantly improve the engine combustion environment and significantly reduce soot and PAHs concentrations. The impact of EGR also includes the ability to reduce combustion chamber temperatures and reduce NOx emissions from hydrous ethanol gasoline by 75%.

Numerical analysis of very rich propagating spherical flames: Soot formation and its impact on the determination of laminar flame speed

Fuel-rich combustion is a promising technique to produce hydrogen by reforming hydrocarbons. Predictive modeling of the fuel reforming process needs a reliable chemical mechanism which is usually validated using laminar flame speed (LFS) data. While LFSs have been extensively employed to optimize mechanisms under fuel-lean, stoichiometric, and slightly fuel-rich conditions, it remains a formidable challenge to measure the LFSs of very rich mixtures (e.g., equivalence ratio ϕ≥2) due to significant soot formation in such conditions, which leads to the LFS data under fuel-rich conditions being rather scarce. To overcome the challenge, a clear understanding of soot formation and its impact on LFS measurements is required. In this work, a series of one-dimensional outwardly propagating spherical flames (OPFs) with and without considering soot formation are simulated for rich ethylene/air mixtures (2.0≤ϕ≤3.5), in order to understand soot dynamics and morphology in the OPFs and to quantify the effects of soot formation on the determination of LFS using the OPF method under fuel-rich conditions. To this end, a detailed chemistry accounting for major pathways of PAH formation up to A7 (coronene, C24H12) is employed and coupled with a state-of-the-art soot model considering nucleation, condensation, coagulation, surface growth, oxidation, and fragmentation. It is found that soot dynamics and morphology are very sensitive to the change in equivalence ratio and flame radius. Specifically, surface growth and oxidation play a dominant role in soot formation/evolution and can balance each other at ϕ=2.0, resulting in limited soot formation. However, the PAH-based condensation can dominate over other processes at ϕ≥2.5 and hence a large amount of soot is observed. Moreover, the maximum value of primary particle diameters would tend to a constant as the flame radius increases. The results also show that the ratio between total soot mass and the mass of burned gas, msoot/mburned, follows an exponential law given by msoot/mburned=100.47ϕ−3.76, implying that soot formation can be exponentially enhanced by increasing equivalence ratio. Furthermore, it is found that under very rich conditions, the presence of soot has a significant impact on the determination of LFS, which leads to the measured LFS at ϕ=3.5 being 22% lower than 1D planar adiabatic flame speed. This is mainly attributed to the thermal and flow effects of soot radiation, i.e., the reduction of flame temperature and negative flow speed of the burned gas. The above findings suggest that the impact of soot radiation should be carefully treated when determining the LFSs of rich premixed mixtures at ϕ≥2.0.

Large eddy simulation of soot formation and oxidation for different ambient temperatures and oxygen levels

This paper presents the numerical study of soot formation and oxidation processes across different ambient temperatures (900K, 1000K, and 1100K) and oxygen levels (15% and 21% O2) using large eddy simulation coupled with a two-equation soot model. The predicted ignition delay time, lift-off length and soot distribution show good agreements with the corresponding experimental data. A stronger oxidation of the precursor (C2H2) in the 21% O2 cases results in a lower C2H2 formed, as compared to the 15% O2 cases. The increasing ambient temperature leads to the fuel-richer region (roughly equivalence ratio > 1.6) becoming more favorable for C2H2 formation and, consequently, soot formation. This is more apparent in the 15% O2 cases due to a weaker oxidation of C2H2 via O and OH radicals. As a result, the difference in the soot mass between the 15% and 21% O2 cases becomes larger as the ambient temperature increases. The effects of ambient temperature and O2 level on soot sub-processes are investigated. In addition to the flame temperature, OH mass and soot surface area are the dominant parameters in the oxidation processes via OH and O2 at varying O2 levels, respectively.

Large-Eddy Simulation of Laser-Ignited Direct Injection Gasoline Spray for Emission Control

Large-Eddy Simulations (LES) of a gasoline spray, where the mixture was ignited rapidly during or after injection, were performed in comparison to a previous experimental study with quantitative flame motion and soot formation data [SAE 2020-01-0291] and an accompanying Reynolds-Averaged Navier–Stokes (RANS) simulation at the same conditions. The present study reveals major shortcomings in common RANS combustion modeling practices that are significantly improved using LES at the conditions of the study, specifically for the phenomenon of rapid ignition in the highly turbulent, stratified mixture. At different ignition timings, benchmarks for the study include spray mixing and evaporation, flame propagation after ignition, and soot formation in rich mixtures. A comparison of the simulations and the experiments showed that the LES with Dynamic Structure turbulence were able to capture correctly the liquid penetration length, and to some extent, spray collapse demonstrated in the experiments. For early and intermediate ignition timings, the LES showed excellent agreement to the measurements in terms of flame structure, extent of flame penetration, and heat-release rate. However, RANS simulations (employing the common G-equation or well-stirred reactor) showed much too rapid flame spread and heat release, with connections to the predicted turbulent kinetic energy. With confidence in the LES for predicted mixture and flame motion, the predicted soot formation/oxidation was also compared to the experiments. The soot location was well captured in the LES, but the soot mass was largely underestimated using the empirical Hiroyasu model. An analysis of the predicted fuel–air mixture was used to explain different flame propagation speeds and soot production tendencies when varying ignition timing.

Measurement of soot mass and PAHs during the pyrolysis of C2[sbnd]C4 alcohols at high temperatures

Particulate matter (PM) is emitted from a range of combustion sources, can vary greatly in properties, and is able to penetrate deep into the human lungs, conveying carcinogenic PAHs present on the particle surface. Alcohol based biofuels have been shown to potentially reduce PM emissions when displacing fossil fuels. To improve understanding of the influence of fuel bound oxygen on and the relative toxicity of PM, this paper investigates quantitatively the soot mass and PAHs produced from the pyrolysis of ethanol, 1-propanol, 2-propanol,1-butanol, and 2-butanol in a laminar flow reactor. The pyrolysis of alcohol fuels and collection of soot-bound and gas-phase PAH was carried out between 1323 and 1623 K at a fixed carbon atom concentration in nitrogen. Accelerated solvent extraction (ASE) was used to extract soot bound PAH and gaseous species captured on XAD resin, with speciation and quantification of PAHs undertaken using GCMS. Of the primary alcohols, the highest and lowest masses of soot were observed for 1-butanol and ethanol respectively, while secondary alcohols generated more soot mass than corresponding primary alcohols. An effect of hydroxyl group position on the total PAH distribution in the gas and particulate-bound phases was observed within the temperature range of 1323 to 1423 K. At 1323 K, 1-propanol produced approximately three times more particle phase (PP) PAH concentration than 2-propanol. Amongst the fuels tested, 1-propanol produced the highest level of carcinogenic PAHs at 1323 K, while for all C3 and C4 fuels the toxicity equivalence factor decreased with increasing pyrolysis temperature.

Numerical study of spray combustion and soot emission of gasoline–biodiesel fuel under gasoline compression ignition-relevant conditions

A blend of biodiesel and gasoline fuel has been proposed for powering gasoline compression ignition (GCI) engines to improve overall reactivity, which is essential for the auto-ignition quality of GCI engines. Previous studies emphasized the differences in the physicochemical properties of hydrogenated catalytic biodiesel (HCB) and gasoline, which significantly altered the combustion characteristics. This study is a further step in this direction to gain a deeper understanding on the spray combustion and emission behavior of this promising fuel based on computational fluid dynamic simulation in a constant volume chamber. N-Hexadecane and toluene reference fuel were selected as surrogates for HCB and gasoline fuel, respectively. A reduced kinetic mechanism for HCB-gasoline surrogate was developed and combined with a reduced PAH mechanism to simulate HCB-gasoline spray combustion and soot formation. Liquid penetration length, ignition delay, lift-off length, and soot formation for HCB and HCB/gasoline surrogates were validated against available experimental data in the literature. The proposed mechanism along with a multi-step phenomenological soot model could capture the spray characteristics and soot formation of the tested fuels with acceptable accuracy under GCI engine combustion conditions. The numerical results showed larger spray/flame development for HCB fuel as compared with that of HCB/gasoline blend prior to ignition and at ignition stage, which was mainly due to the less fuel spray mixing with the surrounding fresh air. Furthermore, the outer diffusion flames for HCB and HCB/gasoline blend were identical and existed on the stoichiometric region (at ϕ ∼ 1), while the rich pre-mixed core of HCB was located at higher equivalence ratio, which was more favorable for precursors formation. HCB/gasoline fuel had a lower soot mass yield compared with HCB because of its lower C2H2 concentration, which slowed down the surface growth step. In addition, the effects of ambient oxygen level and ambient temperature on flame structure and soot formation were also investigated. The current study provides a useful information about spray combustion and soot formation of HCB–gasoline blend, which has practical applications in GCI engines.

In-Cylinder Validation of a Method of Moments-Based Soot Model for Diesel Engines

<div class="section abstract"><div class="htmlview paragraph">Detailed soot models based on method of moments have been reported for combustion engines for more than twenty years. However, these models have always been validated against soot measured at exhaust and none of the modeling works have validated the spatial and temporal evolution of modeled soot with in-cylinder data. In this article a soot model based on method of moments has been evaluated by comparing simulations with the published experimental data for varying operating conditions of the heavy-duty optical engine at Sandia National Laboratories. Closed cycle combustion simulations have been performed using CONVERGE, a computational fluid dynamics solver for reacting multiphase flows. Before modeling soot, confidence in non-reactive modeling has been ensured by validating spray and equivalence ratio distributions from simulations with experimental optical images at different crank angles for each operating condition. Reduced kinetic schemes available in the literature for diesel engines have been assessed to identify the most promising one based on its performance across all operating conditions. The soot mass modeled by the method of moments has shown less sensitivity to the involved soot model constants, and a good agreement for temporal evolution and spatial soot distribution for the considered cases.</div></div>

The effect of fire location and the reverse stack on fire smoke transport in high-rise buildings

In this paper, smoke transport in high-rise buildings through elevator shafts and stairwells is investigated for various fire location and stack effect conditions. For this purpose, a transient network model, Fire-STORM, is upgraded and used. The results are benchmarked by using a computational fluid dynamics (CFD) model. Six scenarios are tested, which are 1st floor, mid-floor, and top-most floor fires under normal stack (cold environment) and reverse stack (hot environment) conditions. For each scenario, the time history of pressures, temperatures, and soot mass fractions in the fire floors, elevator shafts, and stairwells and the average soot mass fraction in all stories of the building are presented. Overall, Fire-STORM has reasonably good accuracy compared to CFD with significantly faster computation times (90 s on a single core vs. 4 days on 32 cores in parallel). One of the intended uses of this fast low-order model is a data generation engine for neural network modeling of high-rise building fires. As such, one of the unique features of this work is the development of a realistic random heat release rate (HRR) modeling approach created using a Gaussian process.

Effects of ammonia addition on soot formation in ethylene laminar premixed flames

This paper presents particle size distributions and chemical compositions of soot measured using a Scanning Mobility Particle Sizer (SMPS) and a Fourier-Transform Ion Cyclotron Resonance Mass Spectrometer (FT-ICR-MS), respectively, in flames of ethylene-oxygen and ethylene-oxygen doped with ammonia. The inhibitory effect of ammonia addition on soot formation in ethylene flames, as well as the influence on soot particle size are discussed. The results of particle size distributions showed that doping with ammonia decreases soot particle size and the volume fraction of soot particles. In this work, the flames were carefully studied under similar temperature conditions, so all observed changes could be attributed to chemical effects. The results of FTICR-MS analysis showed that polycyclic aromatic hydrocarbons (PAHs) were the main compositions in both pure ethylene and ammonia doped ethylene flames. Nitrogen-containing PAHs (N-PAHs) did not contribute significantly to soot nucleation or mass growth processes. Chemical kinetic analysis revealed that CN species generated in ethylene-ammonia flames removed carbon from participating in soot precursor formation, thereby reducing soot formation.

Experimental Study of Coflow Propane—Air Laminar Diffusion Flames at Subatmospheric Pressures

The effect of pressure on the flame’s physical structure and soot formation of the coflow propane—air laminar diffusion flames was studied experimentally at subatmospheric pressures from 30 to 101 kPa. Flames with a constant fuel mass flow rate combined with two different coflow air mass flow rates were investigated at different pressures. The spatially resolved relative soot volume fraction was measured using the laser-induced incandescence (LII) method. The height of the visible flame decreased moderately as the pressure (p) reduced from 101 to 30 kPa. The maximum flame diameter increased proportionally to pn, where the exponent changed from −0.4 to −0.52 as the air-to-fuel velocity ratio decreased from 1.0 to 0.5. Strong pressure dependence of the maximum relative soot volume fraction and the normalized maximum soot mass flow were observed and could be described by a power law relationship. However, a nonmonotonic dependence of soot formation on the air-to-fuel velocity ratio was observed at all the considered pressures.

Comparison of emissions from steam- and water-assisted lab-scale flames

Steam-assisted flares are often used in the downstream oil and gas industries as a strategy to produce “smokeless” combustion. The addition of liquid water to flames is also known to suppress soot formation but is rarely done in industrial flares. Since utilizing liquid water saves the energy required to convert water to steam, it was useful to investigate the extent to which liquid water and steam individually affect soot formation and NOx emissions during flaring. The three fuels used in this study were pure propane, pure methane, and a mixture of 90% methane and 10% propane, the latter approximating the typical volumetric higher heating value of Alberta flare gas. The fuel flow rates were fixed at 20 standard L/min in all cases, and liquid water and steam were introduced into the fuel's combustion zone, while their flow rates varied from 0 to 30 g/min. The results show that both liquid water and steam reduce NOx and soot mass emissions; however, liquid water reduces NOx and soot emissions more than steam. Likewise, the total particle number concentration and the particle sizes decrease with an increase in liquid water and steam. Simultaneously, liquid water reduces the total particle number concentration more than steam at the same assist flow rate, but a slight difference in their particle sizes. The thermodynamic mechanism appears to play the major role in controlling emissions. These results suggest that water-assisted flares in the oil and gas industries would likely produce lower emissions with a lower operating cost than steam-assisted flares.

CFD analysis of combustion and emission characteristics of primary reference fuels: from transient Diesel spray to heavy-duty engine

The pre-blending of low- and high-reactivity fuels for a single direct injection system has been proven to be an effective way to control the reactivity of mixtures in compression ignition engines, having the potential to simultaneously reduce fuel consumption and pollutant emissions. However, there is not much knowledge about the complex physical–chemical phenomena in the turbulent sprays with fuels having widely different auto-ignition qualities, although this information is critical for the design and development of cleaner combustion systems based on this concept. For this reason, a computational analysis of ignition behavior, flame structure, and soot production for reacting sprays with five primary reference fuels (PRFs), from PRF0 (n–heptane) to PRF80 (20% n–heptane, 80% iso-octane) with 20% increment in iso-octane mass fraction, was first performed using the Tabulated Flamelet Progress Variable (TFPV) approach based on the tabulation of diffusion flamelets for different scalar dissipation rates. The temporal and spatial features of the flame structure and soot formation for different fuels were investigated with the so-called intensity-axial distance-time (IXT) plots. Then, ten PRFs, from RRF0 to PRF90 with 10% increment in iso-octane mass fraction, were investigated and compared in a heavy-duty Diesel engine operating at the conventional high-temperature, short-ignition delay (HTSID) condition. The injection timing was altered from −5 to −13 ° ATDC to optimize the combustion phase and engine performance for different fuels. The results showed that PRF70 exhibited the best performance at the tested condition, which reduced the soot mass to 5% of the baseline value without sacrificing fuel efficiency.

A two-equation soot-in-flamelet modeling approach applied under Spray A conditions

Soot production (including formation and oxidation) is studied in the transient, high-pressure and turbulent n-dodecane Spray A flames from the Engine Combustion Network (ECN) using computational fluid dynamics (CFD) simulations. A two-equation soot-in-flamelet modeling approach is applied within the framework of the Unsteady Flamelet Progress Variable (UFPV) model and results are validated against experimental data. Equations for soot mass fraction and soot number density derived in the mixture fraction space are solved in the context of detailed flamelet calculations. Source terms for the different steps in the soot chemistry are tabulated and incorporated in the flamelet manifold. For the reference condition, the modeling approach based on the tabulated flamelet manifold reduces the computational cost of a CFD calculation by approximately 40 times compared to a non-tabulated well-mixed (WM) modeling approach. The soot-in-flamelet approach is then extended to study the effect of ambient oxygen concentration, ambient mixture composition and ambient temperature on soot production. Results show that the modeling approach is able to capture the experimental trends for the soot volume fraction (SVF) with good quantitative agreement, especially in the soot ramp-up region.

Development of a compact and robust kinetic mechanism for furan group biofuels combustion in internal combustion engines

A compact kinetic reaction mechanism for simulating the oxidation of the unsaturated furanic fuels including furan, 2-methylfuran (MF2) and 2,5-dimethylfuran (DMF) is proposed in this work. The mechanism is developed by integrating the major reaction pathways for the three furanic fuel components into a toluene reference fuel reaction mechanism. The sub-mechanism describing the formation and growth of polycyclic aromatic hydrocarbons up to pyrene is also incorporated so that the prediction of soot formation is enabled. The major reaction pathways for these furanic fuels are derived from the detailed furanic fuel reaction mechanism in the literature via a systematic selection and extraction procedure. An advanced genetic algorithm is applied to automatically optimize the rate parameters for the major furanic fuel reaction pathways. In addition, a simplified empirical soot model is embedded in the mechanism for simulating the soot formation process in the oxidation of the furanic fuels. The resulting mechanism, consisting of 145 species and 643 reactions, has been evaluated against the ignition delays, speciation profiles, laminar flame speeds as well as the soot mass measured from the combustion of the furanic fuels in the literature. The simulation results in general match satisfactorily well with the experimental data, suggesting the high performance of the proposed mechanism. The performance of the reaction mechanism for engine combustion simulation is also tested. A four-cylinder compression ignition engine is simulated using a coupled KIVA4-CHEMKIN code package. The influences of DMF on the engine combustion characteristics and soot emissions are investigated.

CFD Modelling of Soot Formation and Entrainment Processes in Diesel Engine Combustion of Soy, Palm and Coconut Methyl Esters

The aim of this work is to employ computational fluid dynamics (CFD) modelling to elucidate the soot formation and entrainment processes when diesel as well as soy, palm and coconut methyl esters (biodiesel) are used in a light-duty diesel engine under varying operating conditions. ANSYS FLUENT 13, which is linked to a chemical kinetic model via CHEMKIN-CFD, a plug-in chemistry solver, is utilised. The soot entrainment focuses on thermophoretic soot deposition on the cylinder liner and soot transport into the crevice region via blowby. During the closed cycle combustion process, the mass of soot deposited on liner via thermophoresis is more significant than that transported into the crevice region through blowby, representing at least 95% of the total soot entrained. The percentage of entrained soot from the net amount of exhaust soot is dependent on the methyl ester type. Diesel results in the maximum soot entrainment with the largest averaged diameter while coconut methyl esters with short hydrocarbon chain length produces the smallest amount and size of entrained soot. Different saturation levels give rise to different soot entrainment processes under varying operating conditions. Overall, this work provides detailed insights into the main in-cylinder processes controlling soot entrainment for biodiesels.