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The combustion process is an indispensable energy conversion step in modern industry and energy production. Especially in high-performance engines and energy conversion systems, understanding and controlling the combustion process is critical to improving efficiency and reducing environmental pollution. As a key component of mechanical systems, the combustion characteristics of lubricants at high temperatures and pressures have a direct impact on system performance and emissions. This study investigated the combustion characteristics of lubricant films in an ammonia-methane premixed environment using Planar Laser-Induced Fluorescence (PLIF) and Planar Laser-Induced Incandescence (PLII). It focused on the effects of varying ammonia concentrations on the emission of soot and polycyclic aromatic hydrocarbons (PAHs) in the constant volume combustion vessel. Experiments varied the ammonia-to-methane molar ratios, initial oil film thickness, and base oil type to study their influence on the lubricant combustion characteristics. Results indicated that ammonia significantly reduced soot formation by altering the dynamics of NH* and OH* and impacting PAH distribution. For the lubricating oil soot formation factors, the increase of the initial mean oil film thickness was more obvious for the promotion of soot formation, the increase of the unsaturated hydrocarbon content in the oil film also promoted the generation of carbon soot to a certain extent, and the initial flame energy ratio had the least influence on the promotion of soot formation. Overall, the study contributed to the understanding of the formation mechanism of soot caused by lubricating oil in zero-carbon and low-carbon blended atmospheres and provided a new insight into the interaction between nitrogen-containing zero-carbon fuels and large-carbon-number hydrocarbons, which is of great significance for controlling soot emissions from engines under zero-carbon fuel blending. • Ammonia alters NH and OH dynamics, reducing PAHs and soot formation. • Film thickness, lubricant type, NH3:CH4 ratio affect pool fire combustion. • New insights for engine soot emission control under zero/low-carbon fuels. [ABSTRACT FROM AUTHOR]

Threshold sooting index (TSI) is one of the critical properties related to the soot emission of diesel. Investigating the effects of TSI on the prediction of soot emission and the response of the soot model to TSI may improve our understanding of the soot formation process and model establishment during the combustion of diesel under engine-like conditions. To meet this need, two different d.iesel surrogates, named S1 and S2 were developed. S1 comprised n-dodecane, iso-octane, methylcyclohexane, and 1-methylnaphthalene, while S2 replaced 1-methylnaphthalene with toluene. Both were adjusted for similar cetane numbers, H/C ratios, and heating values, differing in TSI to analyze sooting tendencies to ensure the S1 and S2 had different soot tendencies but close ignition quality. Then, the skeletal mechanism containing the kinetics of the components in S1 and S2 was developed and validated against ignition delay times, speciation, laminar flame speeds and the 3-D spray combustion with results agreeing well with predictions. Finally, the soot performances of S1 and S2 in different soot models were compared in the constant volume combustion chamber (CVCC). The results showed that the comparison of S1 and S2 in different soot models could promote the understanding of soot models. [ABSTRACT FROM AUTHOR]

New challenges posed to internal combustion engines require a fresh approach and the application of modern simulation methods. This study focuses on the numerical analysis of the co-combustion process of diesel fuel with butyl alcohol in a dual-fuel, self-ignition internal combustion engine based on a three-dimensional engine model developed in AVL Fire software. The influence of butanol content, ranging from 0 to 60 %, on engine performance and emissions was investigated. Increasing the amount of butyl alcohol burned with diesel fuel leads to a delay in ignition, decreases maximum cylinder pressure and temperature, and increases the rate of pressure rise and heat release rate. For alcohol content of 20 % and 40 %, there is an increase in pressure and indicated power compared to diesel fuel alone. The addition of butanol to diesel fuel reduces the specific emissions of nitrogen oxides and Soot in the dual-fuel engine. The most favorable case was with a 40 % butanol content. For DB40, the highest IMEP (0.69 MPa) and Ni (10.37 kW) values were obtained, along with the highest TE efficiency (43.64 %). In comparison to D100, lower NO and Soot emissions were achieved for this case by 35 % and 65 % respectively. [ABSTRACT FROM AUTHOR]

Adding hydrogen to methane has gained interest as a means of reducing CO 2 emissions from combustion systems. However, this process can lead to several issues, such as flashback and NOx emissions. Therefore, it is essential to determine the optimal conditions for flame stabilization and emission to design effective hydrogen burners. This study chose a turbulent fuel jet with coaxial air as the basic configuration, and its combustion characteristics were investigated under elevated pressures. Additionally, the depth of the fuel tube in the coaxial air tube was actively controlled to regulate flame stabilization, and its effects were examined for various pressures, velocities, and hydrogen concentrations. Three flame stabilization modes were observed clearly, i.e., inner-attached, outer-attached, and inner-lifted modes. Furthermore, the parameters that influenced the flame modes were identified, and the characteristics of soot and NOx emissions were studied. The inner-lifted mode demonstrated the best combustion performance, and the corresponding conditions were predicted to be extended through hydrogen enrichment and pressure elevation. Therefore, the inner-lifted flame is recommended as the conceptual design goal for hydrogen-enriched high-pressure burners. [Display omitted] • Non-premixed jet flames of hydrogen and methane mixtures were investigated. • Effects of coaxial air and pressure on flame stabilization were explained. • Emission characteristics of soot and NOx were examined. • An optimal condition for flame stabilization and emission was suggested. [ABSTRACT FROM AUTHOR]

In a large-bore marine engine, the larger cylinder diameter and space correspond to more fuel injection in a limited time of each working cycle. The fuel injection of multiple injectors can achieve fast atomization and homogeneous fuel-gas mixing performance, which is liable to cause the spray collision problem, but the twin-spray collision phenomenon is rarely observed and studied. Therefore, this work aims to explore the effect of various collision angles (60°, 90°, 120°, and 150°) and injection pressures (60, 100, 140, and 180 MPa) on the combustion and soot emission of twin-spray collision process. Based on a large-bore constant volume chamber and two optical diagnostic techniques, the ignition delay time, initial ignition location, flame collision structure, and soot emission luminosity are obtained in a reactive atmosphere. The results show that near the collision point, there exists a fan-shaped flame structure. Due to the mutual entrainment from twin sprays, the ignition delay time of twin-spray collision is shorter than that of single free spray. As a result, at the constant diesel injection mass, the soot emission intensity of twin-spray collision becomes higher. With the collision angle increasing, the ignition delay time becomes shorter, and the initial ignition location gradually moves upstream, while the soot emission intensity becomes higher. The time integrated natural luminosity difference between 60 and 180 MPa gradually decreases and then reverses. Moreover, the wider collision angle also makes the ignition delay time less sensitive to the injection pressure. [ABSTRACT FROM AUTHOR]

Abstract Gasoline compression ignition combustion has demonstrated the potential of getting high fuel efficiency. In this work, two engine models are established in the commercial software Converge 2.3 based on the experimental results of an optical engine and a modified metal engine. The effect mechanism of mixture stratification and the influence of compound control strategy on gasoline compression ignition (GCI) combustion and soot emissions under high load condition are investigated. Results show that synergistic effect of physics and chemistry is the dominant control mechanism of GCI combustion. Stronger mixture stratification can effectively reduce the maximum pressure rise rate (MPRR) and improve the indicated thermal efficiency (ITE) and emissions; applying high EGR will significantly reduce OH radical in the cylinder and subsequently weaken the soot oxidation process, resulting in high soot emission; under the premise of reasonable NOx emission and MPRR, the soot emission can be effectively reduced with a proper advanced main injection timing. The effect of temperature on the soot oxidation process is the primary mechanism for the ultimate soot emission at different main injection timings; properly increasing the interval between the pre‐ and main injection can reduce NOx and soot emissions under the premise of ensuring that the MPRR is within the upper limit. However, the effect is not significant because of the small proportion of preinjection fuel.

This study investigated the combustion characteristics by changing the operating parameters and piston bowl geometries in diesel/gasoline dual-fuel combustion. The experiment was conducted in a light-duty single cylinder diesel engine satisfying the EURO-6 regulation adapted for dual-fuel operation. The engine was operated under a low load condition, which was 1,500 rpm and gross IMEP 5.2 bar, with compression ratio of 14. The effects of the operating parameters, namely, the fuel ratio, diesel injection timing, and pilot duration, were analyzed for three different piston bowl geometries. Based on each result, the optimization experiments were conducted to satisfy the various constraints. The gross indicated specific NOx (gISNOx) was restricted below 0.21 g/kWh, the soot emission was limited to below 0.2 FSN, and the maximum pressure rise rate (mPRR) was confined to below 5 bar/deg. Simultaneously, the gross indicated efficiency (GIE) was controlled over 40 %. As a result, these constraints were completely satisfied in all pistons. [ABSTRACT FROM AUTHOR]

Intake port geometry is the most significant parameter for air supply of engines into combustion space. Especially because only air is supplied into combustion spaces of diesel engines and the fuel is sprayed over the air, intake port geometry should form a specific horizontal turbulence ratio in formation of fuel-air mixture. In this study, the impact of cylinder heads of intake port of a single cylinder compression ignition engine produced with 3 different geometries on performance and emissions of the engine was analysed experimentally. Additionally, the impact of intake port geometry produced with old and new moulds on 3 different geometries was researched. As a result of the study; power, torque, specific fuel consumption, exhaust gas temperatures, intake air flow and soot emission were measured. It was found out that the different intake port designs had impact on performance parameters, specific fuel consumption and soot emission following the study. Moreover, it was shown that the change of intake port didn't have any impact on the flow of the air intake in low speed. It was observed that the cylinder heads produced with old and new mould cores had a significant impact. It is predicted that the main reason for the poor performance of the port geometry, which is called Y-type and creates a wider auger around the intake valve, may be due to the low turbulence intensity it creates in the cylinder. X and Z type ports gave better results by about 15% in power and torque values. Z type intake port gave the best performance in terms of exhaust gas temperature and soot emission. [ABSTRACT FROM AUTHOR]

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Electric fields were proved to affect combustion stability, flame form, and pollutant emissions. The influence of the electric field on soot formation and growth is still an open topic. In this context, the effect of an external electric field on a 67 mm laminar diffusion flame was studied and ethylene was used as well-suited fuel to investigate soot formation and growth. The flame was placed under a uniform high voltage difference and laser Extinction/Scattering techniques were employed to monitor soot volume fraction, particles' diameter and particles' number concentration at different locations in the flame body. Interestingly, when a potential of 8 kV was applied, the flame appeared to be shorter and larger, soot volume fraction diminished whilst the particles' diameter increased under the effect of the electric field. The ionic wind is considered the main cause of the geometrical modifications of the flame due to the increase in the burning rate and the acceleration of charged species. It was, besides the action of the electric field on the growth mechanism, the plausible source for the soot formation variation in the flame. [ABSTRACT FROM AUTHOR]

Gasoline compression ignition combustion has demonstrated the potential of getting high fuel efficiency. In this work, two engine models are established in the commercial software Converge 2.3 based on the experimental results of an optical engine and a modified metal engine. The effect mechanism of mixture stratification and the influence of compound control strategy on gasoline compression ignition (GCI) combustion and soot emissions under high load condition are investigated. Results show that synergistic effect of physics and chemistry is the dominant control mechanism of GCI combustion. Stronger mixture stratification can effectively reduce the maximum pressure rise rate (MPRR) and improve the indicated thermal efficiency (ITE) and emissions; applying high EGR will significantly reduce OH radical in the cylinder and subsequently weaken the soot oxidation process, resulting in high soot emission; under the premise of reasonable NOx emission and MPRR, the soot emission can be effectively reduced with a proper advanced main injection timing. The effect of temperature on the soot oxidation process is the primary mechanism for the ultimate soot emission at different main injection timings; properly increasing the interval between the pre‐ and main injection can reduce NOx and soot emissions under the premise of ensuring that the MPRR is within the upper limit. However, the effect is not significant because of the small proportion of preinjection fuel. [ABSTRACT FROM AUTHOR]

The paper presents research results of the AVL diesel engine powered with microemulsion fuels. In particular the emission of soot particles from the engine operated at stationary conditions was investigated. Necessary tests were carried out for two microemulsions containing 3.5 and 7 % by volume of distilled water dispersed in diesel fuel with necessary surfactants/cosurfactants, i.e. Crillet-6/Span-20. Both tested microemulsions contained similar water micelles size distribution with average dimension of 18 nm. Results of investigation confirmed that combustion of tested water – fuel microemulsion in the AVL research engine reduces emission of soot particles even by 50% in comparison with diesel fuel.

Castor oil is an alternative fuel as a substitute for diesel fuel. The property that approaches diesel fuel makes jatropha oil help reduce fossil fuel dependence. Abundant raw materials and high cetane properties make castor oil widely used as fuel in diesel engines. This study aims to observe the consumption of fuel and soot emissions produced by diesel engines using a mixture of diesel fuel with castor oil content of 30%. Based on the results of experiments that have been carried out, fuel consumption and soot emissions have increased. The highest increase occurred in SJ30 fuel at 25% loading. Low heating value is a major cause of increased consumption and soot emissions.

Biofuels are made from vegetable oils and animal fats, which have great potential as an alternative to traditional fuels to reduce environmental pollution. In addition to functioning as an oxygen booster for combustion, biofuels are renewable. Moreover, another advantageous characteristic of biofuels is the ease of mixing them with traditional fuel, without any need for complicated equipment. However, there are many factors affecting the application of biofuel to engines such as the geography of each country or region, its climate, and ingredients to serve human needs for food, while biofuels are developed from many different sources of raw materials. Vietnam is a country located in the tropical monsoon region, thus having great potential in developing raw materials for biofuel production. The main raw material sources, for now, are fish fat, jatropha oil, and coconut oil. Among them, coconut oil is considered one of the abundant raw materials, because the natural and social conditions in Vietnam are suitable and favorable for the growth of coconut trees. In this paper, the development of coconut oil production will be presented, as well as the method of using coconut oil (C10) as fuel for diesel engines of fishing vessels. The experimental research results show that the amount of soot emission from diesel engines using C10 fuel is lower compared to that of engines using traditional fuel (DO).

This article presents a novel triple-pressure combined cycle power plant (CCPP) with a heat recovery steam generator (HRSG) configured with heat exchangers of multiple pressure levels, same as the real case. In addition, combustion chamber steam injection is added to the top cycle in order to reduce hazardous emissions. The research investigates energy, exergy, economic, and environmental aspects of the system to initiate sustainable development in said areas. A thorough parametric study is carried out to evaluate the effects of steam injection and other decision variable on emissions and system performance. Then, the total cost rate and the CO2 index are minimized while maximizing the second law efficiency via a tri-objective optimization using the genetic algorithm. The outcome of the economic analysis is that the HRSG has the maximum total cost rate among all the components, namely 0.1673 $/s. The environmental impact assessments indicate that the CO2 and NO emission has considerable molar fractions of 0.035 and 6.88 × 10−4, respectively. As a result of the tri-objective optimization, a 3D Pareto Frontier is presented, which pointed out the maximum attainable exergy efficiency is 50.32%, as well as the minimum total cost rates of 8.04 $/s and CO2 index of 0.34 kg/kWh. Finally, the scatter distribution of major decision variables revealed the optimum range of decision variables in which the optimum points of the Pareto Frontier are obtained. Accordingly, the scatter distribution showed that 46 kg s−1 is the optimum value for steam injection flow rate in terms of efficiency, cost and emission optimization. [ABSTRACT FROM AUTHOR]

The objective of this study is to investigate the effect of CO2 mole fraction by simulated‐exhaust gas recirculation (EGR) on the simultaneous reduction of exhaust emission in CI engine, and to find the optimal operating conditions.For the better expression of the actual EGR, the different CO2 mole fractions from 0% to 20% were applied for the simulated‐EGR. The CO2 mole fraction by simulated‐EGR was changed in the initial air in steps of 5% from 0% to 20% in the cylinder. The N2 mole fraction in the initial air was also changed according to the CO2 mole fraction, and the O2 mole fraction was fixed by 16.2% due to the same overall equivalence ratio.When the CO2 mole fraction by simulated‐EGR increased by 5%, the peak cylinder pressure was decreased by about −1.5% and the indicated specific nitrogen oxide value was also reduced from −4.9% to −48.8% because the ignition delay was longer by the higher specific heat of CO2 than N2, it induced to suppress the rise of cylinder temperature. In addition, when the start of energizing timing was advanced until BTDC 23 deg, the ISSoot value was decreased because the proportion of premixed combustion was increased. [ABSTRACT FROM AUTHOR]

CexMn1-xO2 series catalysts were prepared with the sol–gel method. The catalytic activity for soot oxidation was investigated by thermogravimetric analysis(TGA). All catalysts were elevated by X-ray diffraction (XRD), nitrogen adsorption techniques, temperature programmed desorption (TPD), Raman spectroscopy, temperature programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). The influence of the catalysts on soot oxidation characteristics and the relationship between the catalytic oxygen species and the combustion of soot were mainly discussed. The results revealed that the crystal structure of the catalyst did not change after Mn doped CeO2. Mn inhibited the growth of CeO2 cell and promoted the formation of oxygen vacancies on the catalyst surface, which was conducive to the activation and migration of oxygen species. Ce0.5Mn0.5O2 had the most absorptive atomic oxygen O−, and the ignition temperature and peak temperature of Ce0.5Mn0.5O2 were decreased by 37 and 50°C compared to CeO2, respectively. [ABSTRACT FROM AUTHOR]

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.

In this study, firstly, the turbocharged, compression-ignition, light duty vehicle engine was loaded with a DC dynamometer. The real test engine was run at partial load (90%) and at different engine speeds with normal diesel fuel. In the second stage, a model engine was created and verified with the mixing control combustion (MCC) module suitable for hydrogen combustion using AVL BOOST simulation software with real test parameters such as engine performance and cylinder pressure values. At the last stage, multiple hydrogen injection strategies were applied in the simulation program using pure hydrogen as pilot and post fuel and diesel as the main fuel, and were examined numerically in terms of performance and emissions. The results showed that 2 pilot injections and 1 post-injection strategy reduced soot emissions more than 1 pilot injection strategy. However, NOx increased slightly in all three injection applications. In addition, a significant increase in engine power was observed. • Pilot and post injections of hydrogen were investigated in the diesel engine.. • Soot emissions reduced when post-pilot injections hydrogen were applied togethe. • NOx emissions decreased slightly with pilot injection at mean engine speeds. [ABSTRACT FROM AUTHOR]

The paper presents the research results of the AVL diesel engine powered with microemulsion fuels. In particular the emission of soot particles from the engine operated under stationary conditions was investigated. The necessary tests were carried out for two microemulsions containing 3.5 and 7% by volume of distilled water dispersed in diesel fuel with necessary surfactants/cosurfactants, i.e. Crillet-6/Span-20. Both tested microemulsions contained similar water micelles size distribution with average dimension of 18 nm. The results of the investigation confirmed that the combustion of tested water - fuel microemulsion in the AVL research engine reduces the emission of soot particles even by 50% in comparison with the diesel fuel. [ABSTRACT FROM AUTHOR]

The main objective of this study is to provide insights on the modelling of soot emission Turbulence Radiation Interaction (TRI) through a detailed analysis of the joint SVF/temperature statistics in turbulent non-premixed flames. The analysis relies on RANS/Transported Probability Density Function (TPDF) simulation of the Sandia ethylene jet turbulent non-premixed flame. RANS/TPDF predictions reproduce with fidelity the exhaustive set of experimental data, namely the flame structure, the soot and temperature statistics including the soot intermittency, and the radiative outputs. The marginal PDF of SVF exhibits the typical shape of an intermittent process and can be decomposed into a non-sooting mode and a sooting mode, with this latter being reasonably represented by a truncated Gaussian PDF. As expected, the marginal PDF of temperature can be reasonably represented by a clipped Gaussian PDF whereas that of the soot temperature follows a significantly narrower PDF as soot is fully oxidized in the fuel rich side of the flame. Analysis of the joint SVF/temperature PDF shows that both SVF/temperature and SVF/soot temperature first-order cross correlations are positive in the soot formation region and becomes strongly negative in the region of strong soot emission. The TPDF predictions are analysed a priori to design a new joint presumed PDF (PPDF) of SVF and temperature through the Gaussian copula. The Gaussian copula-based PPDF depends on six parameters, namely the five related to the marginal PDFs of SVF and temperature added to the first-order cross-correlation coefficient of SVF and temperature. Mean soot emission term computed with the copula-based PPDF agrees very well with the reference TPDF solution over the entire flame and improves significantly the solutions obtained by neglecting either TRI or the correlation between SVF and temperature. These results indicate that the Gaussian copula-based joint PPDF model is a good candidate to interpret soot emission-related experimental data in turbulent non-premixed flames. • RANS/transported PDF simulation of the Sandia ethylene jet turbulent diffusion flame. • Detailed analysis of the joint SVF/temperature statistics. • New Gaussian copula-based joint presumed PDF of SVF and temperature is proposed. • Copula-based presumed PDF provides good predictions for mean soot emission. [ABSTRACT FROM AUTHOR]

Biodiesel is a promising alternative fuel because of its renewability and extensive source of raw materials. Butanol can be blended in biodiesel to reduce the kinematic viscosity and promote the fuel atomization. In this respect, biodiesel was blended with 10% and 20% n-butanol, and the combustion characteristics and particulate emissions of the fuel blends were tested in a turbocharged, 6-cylinder, common rail diesel engine at a constant speed of 1400 rpm under seven engine loads. The experimental results show that under various engine loads, all of the butanol and biodiesel fuel blends provide faster combustion than diesel due to the higher oxygen content of n-butanol and the lower cetane number of butanol which results in stronger premixed combustion. The addition of butanol is beneficial to concentrating the heat release and thus shorten the combustion duration. With an increased proportion of butanol, soot emissions of butanol and biodiesel fuel blends decrease, the number concentration and volume concentration of ultrafine particles (UFPs) reduce noticeably. Meanwhile, the geometric mean diameters of UFPs decrease with an increase in butanol. With an increase of the engine loads, the number concentration peaks of UFPs gradually transfer from the size range of nucleation mode particles (NMPs) to the size range of accumulation mode particles (AMPs) due to the elevated combustion temperatures and high equivalence ratios. Moreover, biodiesel and fuel blends exhibit a higher percentage of NMPs as compared to diesel because of the fuel-bound oxygen, zero aromatics, and low sulfides. • PM emissions of butanol/biodiesel blends were studied on a common rail diesel engine. • Butanol contributed to concentrate heat release and shorten combustion duration. • The number concentrations of UFPs reduce with an increased proportion of butanol. • Butanol/biodiesel fuel blends exhibit higher percentage of NMPs as compared to diesel. • Number concentration peaks of UFPs transfer from NMPs to AMPs as increasing engine loads. [ABSTRACT FROM AUTHOR]

Abstract We studied engine-out soot samples collected from a heavy-duty direct-injection diesel engine and port-fuel injection gasoline spark-ignition engine. The two types of soot samples were characterized using Raman spectroscopy with different laser powers. A Matlab program using least-square-method with trust-region-reflective algorithm was developed for curve fitting. A DOE (design of experiments) method was used to avoid local convergence. The method was used for two-band fitting and three-band fitting. The fitting results were used to determine the intensity ratio of D (for "Defect" or "Disorder") and G (for "Graphite") Raman bands. It is found that high laser power may cause oxidation of soot sample, which gives higher D/G intensity ratio. Diesel soot has consistently higher amorphous/graphitic carbon ratio, and thus higher oxidation reactivity, compared to gasoline soot, which is reflected by the higher D/G intensity ratio in Raman spectra measured under the same laser power. Graphical abstract Comparison of Raman spectra of the soot samples from a diesel engine and a gasoline spark-ignition engine shows that the diesel soot has higher oxidation reactivities than the gasoline soot. Unlabelled Image [ABSTRACT FROM AUTHOR]

• The TSDWSC grows naturally from the protrusion at the outlet of the nozzle without external influence, resulting in a stable structure. • Interestingly, the soot is completely oxidized, and no soot is emission when the TSDWSC is generated. • The large dimensional carbon material with fine structure from acetylene diffusion flame is rarely reported. • The structure of the TSDWSC is similar to that of the flame damper installed at the muzzle. This paper reports the formation of a self-formed three-stage dual-wing-shaped carbon (TSDWSC) from acetylene diffusion flame for the first time. The TSDWSC grows naturally from the protrusion at the outlet of the nozzle, while the emission of soot can be greatly reduced. The evolution of the TSDWSC involves three stages: the first unclosed dual-wing, the second unclosed dual-wing and the unmatured third dual-wing. The effects of protrusion, the flow rate of acetylene and various burner nozzle diameters on the formation of the TSDWSC are investigated. The experimental results show that with the increase of the protrusion height, the time when the first stage begins to appear decreases. With the increase of the acetylene flow rate, the stage number of the final dual-wing-shaped carbon increases. The TSDWSC can only be generated when the nozzle inner diameter is 2 or 3 mm. Using a two-color thermometer, the flame temperature distribution along the flame centerline is measured after the complete growth of the TSDWSC. The results show that the temperature of the TSDWSC area in the lower part is remarkably lower than that of the flame area in the upper part. The efficiency of reducing soot emission increases gradually with the evolution of the TSDWSC and reaches 100%, while the temperature of the flame area in the upper also rises gradually. X-ray diffraction (XRD) result indicates the formation of carbon crystals. [ABSTRACT FROM AUTHOR]

Due to good combustion properties of hydrogen comparative to diesel fuel, it can be used at the automotive Diesel engine for improvement of the energy performance and for reduction of the pollutants emissions level. The use of small hydrogen quantities which can be produced on the vehicle board represents another advantage. The paper presents some comparative results of the experimental investigations carried on a truck Diesel engine of 10.34 L displacement fuelled with diesel fuel and hydrogen at engine middle loads. The hydrogen was injected in the engine intake manifold at different volume flow rates from 9 L/min to 40 L/min. The general objective of the research is the analysis of the effects of the hydrogen use at the Diesel engines on the energy performance and on the pollutant emissions. The engine energy performance, pollutant emissions level and combustion parameters at the hydrogen Diesel engine fuelled were analysed and compared with diesel fuel operation. The researches established the favourable influences of the hydrogen use on the Diesel engine operating. The obtained results of the experimental investigations highlight the improving of engine performance at fuelling with hydrogen as addition in air. [ABSTRACT FROM AUTHOR]

To elucidate the relationship between physicochemical properties, spray characteristics, and combustion performance, a series of experiments have been conducted in a constant volume vessel with injection of hydrous ethanol diesel emulsion and regular diesel. HE30 (emulsion with 30% volume fraction of 20% water-containing ethanol and 70% volume fraction of 0# diesel) is developed using Shah's technique and regular diesel is also employed for comparison. Firstly, the physicochemical properties of two kinds of fuels are investigated. Then, the non-evaporating and evaporating spray characteristics are examined through the high-speed shadowgraphs. Finally, spray combustion experiments under different ambient oxygen concentrations are carried out, and color-ratio pyrometry (CRP) is applied to measure the flame temperature and soot concentration (KL) distributions. The results indicate that the physicochemical properties, such as density, surface tension, kinematic viscosity, cetane number, and oxygen content, have significant impact on the spray mixture formation and combustion performance. HE30 exhibits lower soot emissions than that of regular diesel. Further analysis supports the standpoint that the hydrous ethanol diesel emulsion can suppress the soot and NOx simultaneously. Therefore, the hydrous ethanol diesel emulsion has great potential to be an alternative clean energy resource. [ABSTRACT FROM AUTHOR]

Effects of initial ambient temperatures on combustion and soot emission characteristics of diesel fuel were investigated through experiment conducted in optical constant volume chamber and simulation using phenomenological soot model. There are four difference initial ambient temperatures adopted in our research: 1000 K, 900 K, 800 K and 700 K. In order to obtain a better prediction of soot behavior, phenomenological soot model was revised to take into account the soot oxidation feedback on soot number density and good agreement was observed in the comparison of soot measurement and prediction. Results indicated that ignition delay prolonged with the decrease of initial ambient temperature. The heat release rate demonstrated the transition from mixing controlled combustion at high ambient temperature to premixed combustion mode at low ambient temperature. At lower ambient temperature, soot formation and oxidation mechanism were both suppressed. But finally soot mass concentration reduced with decreasing initial ambient temperature. Although the drop in ambient temperature did not cool the mean in-cylinder temperature during the combustion, it did shrink the total area of local high equivalence ratio, in which soot usually generated fast. At 700 K initial ambient temperature, soot emissions were almost negligible, which indicates that sootless combustion might be achieved at super low initial temperature operation conditions.

An awareness of increasing climate and health problems has driven the development of new functional and affordable soot-oxidation catalysts for stationary sources, such as fireplaces. In this study, Al(OH)3, water glass and acidic aluminium phosphate binder materials were mixed with soot-oxidation catalysts. The effect of the binder on the performance of the Ag/La-Al2O3 catalyst was examined, while the Pt/La-Al2O3 catalyst bound with Al(OH)3 was used as a reference. Soot was oxidised above 340 °C on the Ag/La-Al2O3 catalyst, but at 310 °C with same catalyst bound with Al(OH)3. The addition of water glass decreased the catalytic performance because large silver crystals and agglomeration resulted in a blockage of the support material’s pores. Pt/La-Al2O3 bound with Al(OH)3 was ineffective in a fireplace environment. We believe that AgOx is the active form of silver in the catalyst. Hence, Ag/La-Al2O3 was shown to be compatible with the Al(OH)3 binder as an effective catalyst for fireplace soot oxidation.

The improved nine-step phenomenological soot model of diesel and ten-step phenomenological soot model of ABE (Acetone-Butanol-Ethanol) which had been confirmed in previous studies were implemented into KIVA-3V Release 2 code, and then multi-dimensional computational fluid dynamics (CFD) simulations were conducted to investigate the combustion characteristics and soot formation process of diesel and ABE in constant volume chamber at different temperatures (800 K and 1000 K) and oxygen concentrations (21% and 16%). The comparative results of their soot formation processes and intermediate products indicate that, in the combustion process, the soot mass of ABE and diesel presents in the form of parabolic curve with time change, the soot generation tendency of ABE is lower than diesel, and the initial temperature and oxygen concentration have little effect on the relative relations of their soot and intermediate products mass. At the oxygen concentration of 21%, when initial temperature decreases from 1000 K to 800 K, the soot mass peak values of diesel and ABE reduce by 40% and 83%, respectively. At the initial temperature of 800 K, the relative relations of their soot number and OH free radical keep unchanged; nevertheless, the mass of ABE’s C 2 H 2 and precursor exceeds that of diesel’s in the early stage of combustion. At the initial temperature of 1000 K, when oxygen concentration decreases from 21% to 16%, the soot mass peak values of diesel and ABE increase by 20% and 25%, respectively. At the same time, the C 2 H 2 , precursor and soot number increase in diesel but decrease in ABE. [ABSTRACT FROM AUTHOR]