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This study concerns a quantitative analysis of late-cycle soot oxidation in diesel engines that focuses on two-dimensional KL factor images obtained by the two-color method. The spatially integrated KL factor was converted into the in-cylinder soot mass using a new formula of diesel soot emissivity. This methodology was applied to two combustion systems: a heavy-duty optical engine which was tuned for a higher fuel–air mixing capability and a rapid compression and expansion machine which had a lower mixing performance. The in-cylinder soot mass history during the last stage of soot oxidation phase was converted into a normalized soot mass history and was used for comparison with simulated soot mass history. A model calculation of in-cylinder soot mass history which was based on oxidation of a primary soot particle was performed with the surface-specific soot oxidation rate as a parameter. A value of the surface-specific soot oxidation rate was specified from the curve fitting approach between the experimental and simulated in-cylinder soot mass traces. The resultant soot oxidation rates plotted on the Arrhenius diagram were found to lie in domains with different oxidation mechanisms. The reason for the scattered plots was discussed referring to model predictions of soot oxidation in the literature, and it was concluded that the higher oxidation rates could be attributed to well-mixed soot oxidizer structure. [ABSTRACT FROM AUTHOR]

Diesel engines have advantages due to their potential for high fuel conversion efficiency. However, it is necessary to reduce pollutant emissions, particularly NOx and soot to meet emission mandates. Many studies have shown that oxygenated fuel additives can effectively reduce soot emissions. In this research, to investigate the effect of oxygenated fuel properties on combustion and soot emission, CFD simulations were carried out using newly developed chemical mechanisms for various oxygenated fuels such as tri-propylene glycol methyl ether, methyl decanoate, and dimethyl ether. The results show that the formation of soot precursors decreases with increased oxygen content and decreased number of C–C bonds in the fuel. The fuel molecular structure strongly affects soot formation in addition to fuel-air mixing. Comparisons of fuel blends (oxygenated fuels with n-hexadecane) including methyl decanoate, which have the same fuel oxygen ratio, show that the effects of the ignition delay and lift-off length control soot formation for fuels with similar fuel oxygen ratio and number of C–C bonds. [ABSTRACT FROM AUTHOR]

We investigate effects of post injection strategies on regular exhaust emissions and soot particulate matters on in-cylinder emission control. A trade-off relation indicates that CO and THC emissions increase as post injection timing delays, but NOx emission significantly decreases when crank angle intervals increase because of cylinder volume expansion and heat transfer. In PM emission, total particle concentration and particle size distributions indicate that, at early post injection timing, SOF emission is relatively low but soot emission is relatively large caused by high temperature and local lean oxygen conditions. As crank angle intervals increasing, soot emission decreases quickly and becomes insensitive to the post injection timing. When SOF emission has an obvious increasing trend, there is a lowest level for the PM emission at intermediate post injection timing. Moreover, variations for total particle concentration are similar with soot emission at different post injection strategies. Particle size distribution result illustrates that PS is insensitive to post injection timing at different post injection strategies. [ABSTRACT FROM AUTHOR]

Industrial Flares are important safety devices to burn off the unwanted gas during process startup, shutdown, or upset. However, flaring, especially the associated smoke, is a symbol of emissions from refineries, oil gas fields, and chemical processing plants. How to simultaneously achieve high combustion efficiency (CE) and low soot emission is an important issue. Soot emissions are influenced by many factors. Flare operators tend to over-steam or over-air to suppress smoke, which results in low CE. How to achieve optimal flare performance remains a question to the industry and the regulatory agencies. In this paper, regulations in the US regarding flaring were reviewed. In order to determine the optimal operating window for the flare, different combustion mechanisms related to soot emissions were summarized. A new combustion mechanism (Vsoot) for predicting soot emissions was developed and validated against experimental data. Computational fluid dynamic (CFD) models combined with Vsoot combustion mechanism were developed to simulate the flaring events. It was observed that simulation results agree well with experimental data. [ABSTRACT FROM AUTHOR]

It is necessary to install a specific burner system to burn out fuel-rich post combustion gas produced from a gas generator in a rocket engine when the performance of gas generator is separately evaluated in a test facility. Because of the fuel-rich reburning conditions, the burner still emits a significant amount of soot and produces thermal radiation. In this study, a laboratory-scale coflow diffusion burner was developed to examine the effects of fuel composition in combustion products on the soot emission and radiation behavior. The post combustion gas was simulated by adding carbon monoxide and carbon dioxide to two different base fuels: kerosene vapor and ethylene. The radiation flux sensor and laser extinction apparatus were used to measure the radiation intensity and soot emission, respectively, within a flame. The flame length and temperature were measured to examine the combustion behavior of each sooting flame having a strong radiation. Finally, the relationship between soot emission and radiation intensity was proposed based on all the experimental data.

An interesting alternative to fossil fuel for Diesel engines is the use of Diesel-like oil from plastic wastes: such a solution yields the double advantage of recovering the valuable energy content of wastes, as well as of mitigating the disposal problem of the very large amount of plastic wastes produced by both domestic and industrial activities. The present paper describes the experimental campaign carried out on a current production indirect injection, naturally aspirated diesel engine, running on standard Commercial Diesel Oil (CDO) and on a Waste Plastic Oil (WPO) derived from the pyrolysis of plastics. Tests have been carried out at both full and partial load, while in-cylinder pressure traces have been measured in order to analyze the combustion phase. The results of the experimental campaign showed a slight reduction of engine performance for the WPO, basically due to a lower volumetric fuel rating, but better brake specific fuel consumption and brake fuel conversion efficiency (differences up to 8%). In-cylinder pressure traces, measured at the same load, revealed some difference in the first part of the combustion process, in particular at high speeds, where for WPO heat release is smoother. Engine soot emissions are always lower running on WPO, with difference up to 50% at full load. [ABSTRACT FROM AUTHOR]

To investigate the effects of ambient temperature on the combustion characteristics, and soot formation and oxidation, a detailed comparative study between two different volumetric diesel–soybean biodiesel–butanol blended fuels was carried out in an optical constant volume combustion chamber. The volumetric ratios were the 80% diesel/15% soybean biodiesel/5% butanol denoted as S15B5 and 80% diesel/10% soybean biodiesel/10% butanol denoted as S10B10 and were tested in this study with different ambient temperatures (from 800 K to 1200 K) at the start of injection. Experimental results indicated that the ignition delays of the two blended fuels were almost identical, and S15B5 fuel presented higher maximum cumulative heat release, heat release rate and combustion pressure compared to those of S10B10 fuel. With the increase of ambient temperature, the flame propagated downstream of the spray jet and became brighter. The soot distribution was also increased at the downstream of the spray jet with a higher ambient temperature for both blended fuels, and S10B10 had a lower value of normalized time-integrated soot mass (NTISM). Therefore, S10B10 had more advantages to reduce the soot emission compared to S15B5 fuel. Also, increasing the ambient temperature from 800 K to 1200 K led to a rapid decrease in the value of NTISM for both blended fuels. [ABSTRACT FROM AUTHOR]

Based on the design principles of connecting passage, the article first proposed the idea of dual channel insert with expansion angle and designed three solutions which differed in the expansion angle between channel A and B by 0°& 0°, 5°& 10°, and 10°& 5°. Furthermore, the economic and emission characteristics of the swirl chamber were determined by conducting a bench test. Results indicate that the geometry of dual channel can promote the development of swirl, and a proper increase in the expansion angle of the channel has a positive effect on the development of the swirl in the swirl chamber. When the expansion angles of channel A and B are 10° and 5°, respectively, the swirl characteristic is relatively good, but experimental results show that the oil consumption rates of the Scheme at both the low and heavy load being at their least, which, respectively, are 3% and 3.2% lower than that of the original engine; and the corresponding exhaust transmission coefficients are also 72% and 9.7% lower than that of the original engine, respectively. And the economy and emission characteristics of the other two dual-channel schemes are also improved in some degree. The research results provide certain reference for the performance improvement of swirl chamber air-cooled diesel engine and are beneficial to the further design and optimization. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1793-1800, 2016 [ABSTRACT FROM AUTHOR]

Polyoxymethylene dimethyl ethers (PODE) is an emerging biofuel with properties of high cetane number (CN), high oxygen content and no C–C bond, which shows a significant potential to achieve high efficient and clean combustion and to be one of the competitive alternative fuels for diesel engine. In the current study, the effects of diesel/PODE blends on the combustion and emission characteristics with the PODE volume blending ratio of 15% and 25% have been experimentally investigated in a heavy duty diesel engine. Fuel properties optimization coupled with exhaust gas recirculation (EGR) is utilized to achieve high efficient and clean combustion. The combustion and emission characteristics of diesel, PODE15 and PODE25 are compared at low, medium and high loads. The experimental results show that blending PODE can accelerate the combustion rate in the late combustion phase and it is also beneficial for soot emission reduction, especially at low excess air ratio conditions. The HC and CO emissions can be improved by fueling diesel/PODE blends. The NOx emission of diesel/PODE blends can be slightly improved, while the brake thermal efficiency (BTE) is penalized at low and medium loads. As the NOx is further decreased to relatively low values by increasing EGR at high load, the BTE of diesel/PODE blends gradually gets close to that of diesel and shows the capability to improve BTE. The NOx–soot trade off relationship can be dramatically improved by fueling diesel/PODE blends. The weighted results over the World Harmonized Stationary Cycle (WHSC) indicate that the raw soot emission of PODE25 can meet the Euro VI soot emission standard when the weighted NOx is controlled at 2.7 g/kW h, In this case, a selective catalytic reduction (SCR) device with an average conversion efficiency of 85% is adequate to meet the Euro VI NOx emission standards for PODE25, which means that the requirement on aftertreatment device for achieving low emissions can be reduced by fueling diesel/PODE blends. [ABSTRACT FROM AUTHOR]

Among the new combustion technologies available for internal combustion engines to enhance performance and reduce exhausted emissions, the homogeneous charge compression ignition method is one of the most effective strategies for the compression-ignition engine. There are some challenges to realize the homogeneous charge compression ignition method in the compression-ignition engine. The use of gasoline–diesel blended fuel has been suggested as an alternative strategy to take advantages of homogeneous charge compression ignition while overcoming its challenges. Gasoline and diesel fuels are reference fuels for the spark-ignition and compression-ignition engines, respectively, both of which are widely used. The application of both these fuels together in the compression-ignition engine has been investigated using a hybrid injection system combining port fuel injection (gasoline) and direct injection (diesel); this strategy is termed reactivity controlled compression ignition. However, the pre-blending of gasoline and diesel fuels for direct injection systems has been rarely studied. For the case of direct injection of pre-blended fuel into the cylinder, various aspects of blended fuels should be investigated, including their spray breakup, fuel/air mixing, combustion development, and emissions. In the present study, the use of gasoline–diesel pre-blended fuel in an optical single-cylinder compression-ignition engine was investigated under various conditions of injection timing and pressure. Furthermore, KIVA-3V release 2 code was employed to model the formation of fuel/air mixtures in the cylinder. Neat diesel fuel was tested, as well as gasoline–diesel blends of 20% and 40% gasoline mass fraction. Experiments on the mixed fuels showed that the inclusion of gasoline fuel improved fuel/air mixing, yielding more homogeneous mixtures over wider cylinder areas. The low cetane index of gasoline fuel induced long ignition delays in the mixed fuels. Compared with neat diesel combustion flame, blended fuel did not produce the soot flame, white-yellow flame. Soot intensity was calculated based on captured flame images, and its variations were investigated as a function of fuel type and injection conditions. [ABSTRACT FROM AUTHOR]

In spite of the relevance of residential heating burners in the global emission of soot particles to the atmosphere, relatively little information on their properties (concentration, size distribution) is available in the literature, and even less regarding the dependence of those properties on the operating conditions. Instead, the usual procedure to characterize those emissions is to measure the smoke opacity by several methods, among which the blackening of a paper after filtering a fixed amount of gas (Bacharach test) is predominant. In this work, the size distributions of the particles generated in the combustion of a variety of gaseous and liquid fuels in a laboratory facility equipped with commercial burners have been measured with a size classifier coupled to a particle counter in a broad range of operating conditions (air excesses), with simultaneous determination of the Bacharach index. The shape and evolution of the distribution with progressively smaller oxygen concentrations depends essentially on the state of the fuel: whereas the combustion of the gases results in monomodal distributions that ‘shift’ towards larger diameters, in the case of the gas-oils an ultrafine mode is always observed, and a secondary mode of coarse particle grows in relevance. In both cases, there is a strong, exponential correlation between the total mass concentration and the Bacharach opacity index, quite similar for both groups of fuels. The empirical expressions proposed may allow other researchers to at least estimate the emissions of numerous combustion facilities routinely characterized by their smoke opacities. [ABSTRACT FROM AUTHOR]

An optically accessible constant volume chamber was adopted to investigate the combustion and soot emission characteristics of soybean biodiesel under 800, 900, 1000, and 1200 K initial ambient temperatures. Results showed that with the decrease of initial ambient temperature ignition delay prolonged and heat release rate transited from mixing controlled combustion to premixed dominate combustion mode. As the initial temperature decreased, natural flame luminosity gradually decayed, which indicated lower soot emission at lower initial ambient temperature. [ABSTRACT FROM PUBLISHER]

The effect of wall parameters on combustion and soot emission characteristics remains to be revealed so far, especially in the case of spray impingement at low temperatures. Therefore, the visualization experiments are carried out in a constant volume combustion chamber using the Mie scattering and direct photography techniques, and the two-color method was used to extract the flame temperature and soot volume. The results show that increased wall distance and wall angle contribute to fast and stable ignition, but result in more soot production. In addition, the lower the ambient temperature, the more prominent the above characteristics are. At T amb = 820 K, as the wall distance increases from 40 mm to 60 mm, the liquid spray impingement changes to the vapor impingement, so the ignition delay shortens, and the flame area and natural luminance increase significantly. At lower T amb = 770 K, a complete misfire is observed at L w = 40 mm but the ignition remains stable at L w = 60 mm. The variation of the ignition characteristic parameters with the wall angle is similar to that of the wall distance. Under P inj = 40 MPa, as the wall angle increases from 0° to 70°, the time to reach luminance saturation advances from 0.60 ms to 0.27 ms. Under higher P inj = 100 MPa, a complete misfire occurs at θ = 0° but bright flames are observed at θ = 30–70°. With the increase of wall distance, the mean flame temperature increases due to reduced wall cooling. Coupled with the expanded flame area and combustion duration, the high-temperature region (>1800K) of soot distribution and KL factor increase significantly, especially in the range of L w = 40–50 mm. [Display omitted] • Impinging combustion and soot emission at different wall parameters are studied. • The effect of wall distance on impinging ignition is strongly temperature dependent. • Increasing wall distance accelerate ignition and ensure stability at low temperature. • Soot increases with wall distance due to reduced cooling and extended combustion. • Increased wall angle contributes to stable ignition but results in more soot product. [ABSTRACT FROM AUTHOR]

The processes of spray penetrations, flame propagation and soot formation and oxidation fueling n-butanol/biodiesel/diesel blends were experimentally investigated in a constant volume combustion chamber with an optical access. B0S20D80 (0% n-butanol, 20% soybean biodiesel, and 80% diesel in volume) was prepared as the base fuel. n-Butanol was added into the base fuel by volumetric percent of 5% and 10%, denoted as B5S15D80 (5% n-butanol/15% soybean biodiesel/80% diesel) and B10S10D80 (10% n-butanol/10% soybean biodiesel/80% diesel). The ambient temperatures at the time of fuel injection were set to 800 K, 900 K, 1000 K, and 1200 K. Results indicate that the penetration length reduces with the increase of n-butanol volumes in blending fuels and ambient temperatures. The spray penetration presents a sudden drop as fueling B10S10D80 at 800 K and 900 K, which might be caused by micro-explosion. A larger premixed combustion process is observed at low ambient temperatures, while the heat release rate of high ambient temperatures presents mixing controlled diffusion combustion. With a lower ambient temperature, the auto-ignition delay becomes longer with increasing of n-butanol volume in blends. However, with increasing of ambient temperatures, the auto-ignition timing between three fuels becomes unperceivable. Generally, low n-butanol addition has a limited or no effect on the auto-ignition timing in the current conditions. Compared with the base fuel of B0S20D80, n-butanol additive with 5% or 10% in volume can reduce soot emissions at the near-wall regions. Compared with lower ambient temperatures, n-butanol additive presents larger soot reduction ability at higher ambient temperatures. [ABSTRACT FROM AUTHOR]

Mathematical simulator results of the influence of effective utilization degree of (a diesel engine) cylinder air charge on soot emission and connected losses of heat are given in this paper. Increase reserve of the indicated efficiency by the reduction of inopportunity of soot burning and radiation heat exchange loss is shown.

A four-cylinder, direct-injection (DI) diesel engine was used to study the effects of altitude on the variations of the exhaust soot emission and engine performance. The experiments were conducted in Mashhad, Iran, at an altitude of 975 m above sea level. A three-lobe rotary blower of Roots type was employed in order to simulate the altitudes down to 350 m by increasing the inlet manifold pressure of the engine. The tests were performed based on the ECE-R49 test cycle, and for each testing point, the experiments were repeated for five boosting pressures which correspond to five different altitudes. Results indicate that with increasing the altitude from 350 m to 975 m, the soot emission increases about 40%. This increase is due to the relatively lower the air density introduced into the cylinders in higher altitudes that leads to the increase of autoignition delay time which could shorten the late combustion phase; hence, the soot burnout process deteriorates. Also it was found that at low engine loads, the Brake-Specific Fuel Consumption (BSFC) increases about 20% with raising the altitude from 350 m to 975 m. At higher loads, the raising rate of fuel consumption is insignificant. The effects of altitude on the other engine parameters such as induced air mass flow rate, volumetric efficiency, equivalence ratio, and exhaust temperature were investigated as well. In addition, a sensitivity analysis was conducted and the results revealed that among the engine parameters, the soot emission alteration has the most sensitivity to the change of the altitude.

Effects of the initial ambient temperature on combustion and soot emission characteristics of diesel fuel were investigated through experiments conducted in an optical constant volume chamber and simulation using a phenomenological soot model. Four different initial ambient temperatures were adopted in this research: 1000, 900, 800 and 700 K. In order to obtain a better prediction of soot behavior, the phenomenological soot model was revised to take into account the feedback of soot oxidation on the soot number density and good agreement was observed in the comparison of soot measurement and prediction. The results indicated that the ignition delay was prolonged with decreasing initial ambient temperature. The heat release rate demonstrated the transition from mixing controlled combustion at high ambient temperatures to the premixed combustion mode at low ambient temperatures. At lower ambient temperatures, soot formation and the oxidation mechanism were both suppressed. However, the soot mass concentration was finally 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 ratios, in which soot usually is rapidly generated. At an initial ambient temperature of 700 K, soot emissions were almost negligible, which indicates that sootless combustion might be achieved under super low initial temperature operation conditions. [ABSTRACT FROM AUTHOR]

As more strict regulations on soot emission with increasing emphasis on the emitted soot particle size have been imposed, diesel engine partially premixed combustion had been proven to achieve ultra-low NO x and soot emissions with high thermal efficiency simultaneously, by synergy control of mixing and chemical parameters. It calls for further study in the effect of combustion boundaries on soot formation. In this study, soot formation characteristic was investigated by CFD code coupled with reduced n-heptane model and improved multistep soot model. History of acetylene, which is taken as the main species of PAH formation and soot surface growth, plays more important roles on soot prediction. The revised parameter of fraction of active sites α was introduced as the indicator of soot surface activity in diesel soot formation. The effects of combustion boundaries on soot surface activity and soot surface growth were explored in this study. When the mixture was quite homogeneous, lowered combustion temperature was the main factor for reduced soot formation due to the lowered specific surface growth rate R, in spite of α increasing slightly due to the slowed decay rate of surface activity. As the inhomogeneity of the mixture was increased, more unburned hydrocarbons were produced, promoting the formation of acetylene and soot surface activity. It was the dominated reason for higher soot surface growth rate, resulted worsened engine-out soot. In addition, residual of CO in later combustion phase impeded the re-oxidation of soot. [ABSTRACT FROM AUTHOR]

The soot surface growth plays significant role on the soot mass accumulation, which starts with H (hydrogen) atom abstraction forming activated soot surface sites, and is followed by the acetylene addition process. In this study, the effect of the mixture inhomogeneity and combustion temperature on the soot surface activity and soot formation was investigated by developing a new multi-step phenomenological (MSP) soot model of diesel engines. A new detailed soot surface growth mechanism was proposed by correlation analysis of combustion parameters with soot formation. The inhomogeneity coefficient of soot surface activity α and the specific rate of soot surface growth R were derived to highlight the effect of inhomogeneity of mixture and combustion temperature on soot formation. The predicted diesel engine-out soot agreed well with experimental findings in wide ranges of combustion conditions. In the case of lower engine load with single fuel injection and higher EGR (exhaust gas recirculation) rate, it had quiet homogeneous mixtures before ignition when the combustion temperature dominated the soot surface activity. At medium engine load with multi-pulse fuel injections, it got mixture slightly stratified before ignition and revealed that the mixture inhomogeneity became more dominated on soot surface activity than the combustion temperature. An increased soot surface activity led to increased soot emission. Under the full engine loads with single fuel injection but quite high boost pressure over 0.4 MPa, it led to the combustion conditions of higher mixture density and higher mixture heat capacity, which benefits the mixture homogeneity. The decay rate of soot surface activity became lower due to the decreased combustion temperature and the soot surface activity decreased due to improved mixture homogeneity. In addition, the lowered intake oxygen concentration due to usage of EGR played a role to lower the specific rate of soot surface growth R, but to increase the soot surface activity α. [ABSTRACT FROM AUTHOR]

Highlights: [•] Fuel oxygen content has a more significant effect on soot emission reduction than the altitude effect. [•] The BED fuel with basically the same oxygen content as the BD fuel can reduce soot emissions more. [•] The BSFC of the BED fuel with basically the same oxygen content as the BD fuel is lower. [ABSTRACT FROM AUTHOR]

Abstract: Nowadays, environmental concerns are posing a great challenge to DI Diesel engines. Increasingly tightening emission limits require a higher attention on combustion efficiency. A high efficiency Diesel engine can be developed only mastering all the parameters that can affect the combustion and, therefore, NOx and soot emissions. In this scenario, computational fluid-dynamics can prove its power guaranteeing a deeper understanding of mixture formation process and combustion. In this work, the development of an engine in order to fulfill Tier 4i emission standard will be presented, the Tier 4i compliance must be reached without an excessive increase of the final cost of the engine. Originally, the engine was a two-valve engine supplied with a DPF, since no SCR aftertreatment is supplied, NOx emission target are achieved through external exhaust gas recirculation and retarding the start of injection. Through combustion process simulations, performed with the CFD code KIVA3D, varying different geometric parameters and the intensity of the swirl ratio, the interaction between the swirl flow field, generated by the intake duct, the reverse squish motion, and motions aerodynamically generated by spray has been investigated leading to a better interaction between the flow field, the fuel spray and the piston bowl geometry and to the definition of a new engine lay-out. The study shows how, given the need of retarded injection for limiting NOx emission, the decrease of swirl ratio, when combined with a proper piston bowl design, allows a significant decrease of soot emissions and the achievement of Tier 4i emission standard. The study has been validated comparing the intake phase simulations, performed with the CFD code Fire v2009 v3, followed by the combustion process performed with the KIVA3D code, with the experimental result obtained from the engine assembled following the developed design. [Copyright &y& Elsevier]

A four-cylinder, direct-injection (DI) diesel engine was used to study the effects of altitude on the variations of the exhaust soot emission and engine performance. The experiments were conducted in Mashhad, Iran, at an altitude of 975 m above sea level. A three-lobe rotary blower of Roots type was employed in order to simulate the altitudes down to 350 m by increasing the inlet manifold pressure of the engine. The tests were performed based on the ECE-R49 test cycle, and for each testing point, the experiments were repeated for five boosting pressures which correspond to five different altitudes. Results indicate that with increasing the altitude from 350 m to 975 m, the soot emission increases about 40%. This increase is due to the relatively lower the air density introduced into the cylinders in higher altitudes that leads to the increase of autoignition delay time which could shorten the late combustion phase; hence, the soot burnout process deteriorates. Also it was found that at low engine loads, the Brake-Specific Fuel Consumption (BSFC) increases about 20% with raising the altitude from 350 m to 975 m. At higher loads, the raising rate of fuel consumption is insignificant. The effects of altitude on the other engine parameters such as induced air mass flow rate, volumetric efficiency, equivalence ratio, and exhaust temperature were investigated as well. In addition, a sensitivity analysis was conducted and the results revealed that among the engine parameters, the soot emission alteration has the most sensitivity to the change of the altitude. [ABSTRACT FROM AUTHOR]

Soot toxification: The increasing chemical activity of the emitted soot particulate produced by modern diesel engines is an unwanted side effect of modification of the motors. This makes Euro IV and VI soots chemically and biologically highly active and hazardous. Taking these factors into consideration, the question arises whether the reduced net mass of diesel soot particulate emitted overcompensates for the induced micro‐ and nanostructure. [ABSTRACT FROM AUTHOR]

Abstract: Recently, the stricter diesel emission standards have been setting and an after-treatment of exhaust gas is needed. In this study, as a potential non-catalytic system, the after-treatment using a carbon-fiber filter was investigated, where soot particulates are burned by an electric heater. In the vehicle tests, the experimental validation for our proposed system was conducted, where the soot volume fraction and particle size distribution in diesel exhaust gas were measured. Since the filter was attached to the exhaust pipe, the filter backpressure increased with higher soot emission. Thus, the performance of the filter was evaluated under the same pressure condition. It is confirmed that, the soot emission is greatly reduced by trapping the diesel soot. In addition, the particle number concentration is smaller, so that most of soot particulates are trapped and burned inside the filter. However, in the after-treatment process, particulates less than 30nm are newly formed. In experiments, the information on the soot oxidation process was limited, and the numerical simulation was performed to investigate temperature field and soot oxidation rate in the filter. It is found that the continuous regeneration is largely promoted by increasing the filter wall temperature. Hence, it is necessary to pay more attention on the effect of filter wall temperature on the particle size for more reduction of smaller particulates. [Copyright &y& Elsevier]

Mathematical simulator results of the influence of effective utilization degree of (a diesel engine) cylinder air charge on soot emission and connected losses of heat are given in this paper. Increase reserve of the indicated efficiency by the reduction of inopportunity of soot burning and radiation heat exchange loss is shown. First Published Online: 27 Oct 2010

Abstract: The water/oil emulsified fuel consists of base fuel oil and water doped with or without a trace content of surface active agents. In this study, the water/oil emulsified fuel was successfully produced without usage of any surface active agents. An experimental study has been implemented in an industrial steam boiler to investigate the combustion characteristics of this emulsified fuel by analyzing the exhaust gas emissions and the thermal efficiency of the boiler. The experiment demonstrated that the water/oil emulsified fuel is effective for NO x and soot emission suppression as well as thermal efficiency improvement. These effects were also demonstrated for the commercially operated water heating boiler. [Copyright &y& Elsevier]

Combustion chamber components (cylinder head, cylinder liner, piston assembly and oil film) are treated as a coupled body. Based on the three-dimensional numerical simulation of heat transfer of the coupled body, a coupled three-dimensional calculation model for the in-cylinder working process and the combustion chamber components was built with domain decomposition and boundary coupling method, in which the coupled three-dimensional simulation of in-cylinder working process and the combustion chamber components was adopted. The simulation was applied in the influence investigation of the space non-uniformity in heat transfer among combustion chamber components on the generation of in-cylinder emissions. The results show that the space non-uniformity in heat transfer among the combustion chamber components has great influence on the generation of in-cylinder NO emissions. The heat transfer space non-uniformity of combustion chamber components has little effect on soot formation, and far less effect on soot formation than on NO. Under two situations of different wall temperature distributions, the soot in cylinder is different by 1.3% when exhaust valves are open. [ABSTRACT FROM AUTHOR]

Combustion chamber components (cylinder head-cylinder liner-piston assembly-oil film) were treated as a coupled body. Based on the three-dimensional numerical simulation of the heat transfer of the coupled body, a coupled three-dimensional calculation model for the in-cylinder working process and the combustion chamber components was built with domain decomposition and boundary coupling method, which adopts the coupled three-dimensional simulation of in-cylinder working process and the combustion chamber components. The model was applied in the investigation of the influence of space non-uniformity in heat transfer among combustion chamber components on in-cylinder heat transfer. The results show that the effect of wall temperature space nonuniform distribution of combustion chamber components on heat transfer happens mainly at the end of the compression stroke and expansion stroke. Therefore, it can be concluded that wall temperature space non-uniform distribution of combustion chamber components would influence heat transfer during the intake and exhaust stroke obviously. [ABSTRACT FROM AUTHOR]

This paper reports on-line analyses of the soot emissions from the Inner Mongolia bituminous coal combustion and pyrolysis processes with a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS). The soot particles are generated by heating a small amount of screened coal powder in synthetic air and nitrogen atmosphere in a tubular oven. The vacuum ultraviolet photoionization time-of-flight (VUV-TOF) mass spectra of the soot particles emitted from combustion and pyrolysis at different oven temperatures and different stages are obtained. The VUV-TOF mass spectra are assigned with the references of the results of the off-line GC/MS analysis. [Copyright &y& Elsevier]

This experimental study was conducted to investigate the effects of different opening ranges of waste-gate of a turbo-charged DI diesel engine on improving the exhaust soot emission. Different opening ranges of waste-gate were supplied using an adjustable spring to load the actuating rod of the waste-gate in which, increasing the opening range of the waste-gate decreases the inlet manifold pressure. In this study, the maximum inlet manifold pressures which were supplied by changing the opening range of waste-gate were 0.1bar, 0.23bar, 0.26bar and 0.52bar over atmosphere and experiments were conducted under the ECE-R49, 13 mode standard test. At each mode of the test, soot emission was recorded and then brake specific soot emission was calculated. Results indicate that, soot emission decreases with increasing the maximum inlet manifold pressure from 0.1bar to 0.23bar. This reduction may be due to increasing the intake-air temperature which results in reduction of ignition delay that prolongs the late combustion phase. This improves the soot burnout process because enough time and sufficient in-cylinder temperature are available at the late combustion phase prior to exhaust valve opening. While for the higher maximum inlet manifold pressures from 0.23bar to 0.52bar, although there are enough time at the late combustion phase, but the soot emission increases which could be due to more reduction of the in-cylinder gas temperature at the end of combustion before EVO. [Copyright &y& Elsevier]

Recently, oxy-combustion cycles with CO 2 dilution have been of interest to eliminate NOx emission and to facilitate CO 2 capture. Theoretically, they are operated in an overall stoichiometric condition. In addition, high pressure is preferred not only for better thermal efficiency but also for easier CO 2 capture and storage. In this study, a triple-coaxial-tube was selected as the simplest conceptual design for an oxy-combustion burner at elevated pressure. Flame stabilization, soot emissions, and combustion efficiencies were investigated in relation to variation of the tube size, CO 2 dilution ratio, and pressure. As a result, a jet Reynolds number and CO 2 diffusion could explain the flame stabilization limits. Soot emission could be reduced at atmospheric pressure when the fuel-tube tip was moved into the middle oxidant tube, which also improved the combustion efficiency. Nevertheless, serious soot emissions recurred at excessive fuel flow rates and at elevated pressures. In such conditions, a lifted flame detached from the fuel-tube tip could be employed by increasing the flow rate or enhancing the CO 2 dilution, and the soot emission was reduced again without losing combustion efficiency. Finally, the flame-stabilization mechanisms of the attached flame and of the lifted flame were discussed and optimized designs and operating conditions were proposed for less soot emission and better combustion efficiency at higher pressures. [ABSTRACT FROM AUTHOR]

An extended investigation on the application of blends between diesel oil and used cooking oil methyl esters (UCOME) was developed on an automotive turbocharged diesel engine. Two commercial diesel oils were considered as reference fuels, the first with the conventional content of biodiesel (7%), the second with an amount of 15%. Then, increasing levels of UCOME were added, on a volumetric basis (20%, 40%, 55 or 60%), to analyse the influence of biodiesel content on engine behaviour. Three part load engine operating conditions were selected for tests, measuring average engine parameters and indicated pressure diagrams. Their processing allowed to calculate the most important operating, energy and environmental engine quantities, rate of heat release and related combustion parameters. A proper management of the exhaust gas recirculation circuit, variable nozzle turbine and injection system was applied thanks to the availability of an open electronic control unit. An optimal UCOME content (40%) was identified, leading to highest values of brake thermal efficiency (with maximum increase around 5% referring to baseline fuels) and lowest levels of NO X emissions. For this blend, the analysis of combustion parameters outlined that the use of the renewable fuel corresponded to an enhanced premixed combustion phase, while reducing combustion duration. Lower local temperature levels, related to the decrease of Lower Heating Value, other local effects and biodiesel degree of unsaturation justify NO X reduction. Furthermore, soot emissions were always reduced when increasing biodiesel content, while combustion stability was not affected. All these outcomes were observed with and without EGR. • Tests of blends with high content of UCOME in three part load engine conditions. • Proper control of injection parameters and turbocharger to limit their influence. • Identification of an optimal UCOME content for bte increase and bsNO X reduction. • Assessment of the interactions between tested blends and EGR control variables. • Analysis of the influence of biodiesel on heat release and combustion parameters. [ABSTRACT FROM AUTHOR]

• The in-flame soot formation and soot emission is studied for gasoline/HCB blends. • The soot formation decreases with increasing the gasoline ratio in blends. • There is a little relationship between the particle size distribution and in-flame soot formation. • Increasing proportion of HCB increases the total number of soot particle emission. Gasoline compression ignition engine is one of the most promising low-temperature combustion strategies using gasoline as fuel due to its high thermal efficiency and low emission characteristics. While the ignition difficulty under low loads and knocking combustion under high loads limit its practical applications. To solve these problems low reactive gasoline fuel blending with high reactive hydrogenated catalytic biodiesel was proposed. However, soot characteristics of large hydrocarbons are not yet known. In order to understand the relationship between the in-flame soot formation and soot emission for these blending fuels and to find an optimum ratio for GCI engines. Fundamental study on in-flame soot formation in a constant volume combustion chamber is studied using a diffused background-illumination extinction method. The results show that the in-flame soot mass and soot combustion duration was found to be reduced with increasing the ratio of gasoline. Lower ratios of hydrogenated catalytic biodiesel blends are tested in a gasoline compression ignition engine and the experimental results reveal that the increase of hydrogenated catalytic biodiesel ratio increased the total number of soot particle emission. The total number of particle emission showed a positive relationship with soot formation. But there is a weak relationship between the particle size distribution and in-flame soot formation under the same working loads. The results also demonstrated that the particle diameter was mainly depending on working conditions rather than soot formation. The blend ratio of hydrogenated catalytic biodiesel and the injection strategies were mainly contributed to the concentration of particle size. [ABSTRACT FROM AUTHOR]

The aim of present work is to bridge the gap of knowledge concerning crystallite size, graphene layers curvature and inter-layer distance as nanostructure characteristics of soot primary particles, and also to comprehensively characterize the morphology of soot emission in a light hydrocarbon premixed charge compression ignition (PCCI) engine. In this study, the chemical composition, morphology and nano-structure of particulate emissions between conventional diesel and light hydrocarbon PCCI engine were performed with thermogravimetric analysis, gas chromatography mass spectrometry, and high-resolution transmission electron microscopy technology. The results show that the volatile matter content of light hydrocarbon is much higher than that of diesel, and thermogravimetry and differential thermogravimetry curves of light hydrocarbon shift to low temperature regions. The total organic components of particulate matter of light hydrocarbon PCCI engine are less, and the corresponding separation time is shorter. The structure of particles produced in light hydrocarbon PCCI engine is more open, and the size of aggregates is smaller. Fractal dimensions of 1.774 and 1.691 are obtained for soot particles in light hydrocarbon PCCI engine, compared to that of 1.81 and 1.785 in conventional diesel engine. Compared to conventional diesel engine, fringe separation distance and fringe tortuosity in light hydrocarbon PCCI engine are smaller while fringe length is larger. The primary particle nanostructures of light hydrocarbon PCCI engine incline to graphitize and change into the orderly structure. Compared with conventional diesel combustion, the average primary particle diameter of light hydrocarbon PCCI approximately reduces 2.0% at 75% load and 18.2% at 100% load, respectively. Unlabelled Image • Chemical composition, morphology and nano-structure of particles in light hydrocarbon PCCI are studied. • The structure of particles produced in light hydrocarbon PCCI is more open and the sizes of aggregates are smaller. • Fractal dimensions of soot aggregates in light hydrocarbon PCCI are lower. • Fringe separation distance and fringe tortuosity in light hydrocarbon PCCI are smaller while fringe length is larger. [ABSTRACT FROM AUTHOR]

• Inversed-delta injection increases fuel consumption rate versus rectangular profile. • Inversed-delta injection also shortens late combustion period. • Integrated KL factor rapidly decreases after inversed-delta injection. The aim of this study is to clarify the effect of an inversed-delta injection rate, which is a ramp-down injection rate achieved with a tandem injector, on the late combustion period, which affects thermal efficiency and soot emissions. Diesel combustion was simulated in a constant-volume chamber combined with a rapid compression machine. Two types of injection rate profile, namely rectangular and ramp-down, were tested in our experimental trials. To eliminate the significant effect of the maximum injection rate on mixture formation, we compared the results for the two types of injection rate profile under a given rail pressure. The time histories of the heat release rate demonstrated that the ramp-down fuel injection profile shortened the late combustion period by 0.2 ms. As a result, combustion was maintained despite the longer injection duration. The non-dimensional fuel consumption rate, defined in terms of the heat release rate and the fuel injection rate, revealed that high fuel consumption in the injection period reduced the quantity of fuel carried over to the late combustion period, resulting in a short duration of late combustion. When the ramp-down injection profile was employed, the temporal variation of total soot (spatially integrated KL factor) exhibited a rapid decrease after the end of injection. This is due to the abundant oxygen in soot regions that originated from the significant quantity of ambient air entrained into the spray during the injection period. This result indicates that ramp-down injection may reduce engine-out soot emissions. [ABSTRACT FROM AUTHOR]

Injector deposits, which deteriorate the combustion and emissions, are frequent in gasoline direction injection (GDI) engines. An objective of this paper was to investigate the effects of the GDI injector deposits on the spray and combustion characteristics in a constant volume chamber (CVC) and an optical GDI engine, respectively, using different fuel temperature, injection pressure, and injection strategies. The spray and tail droplet characteristics were analyzed by using high-speed imaging. The combustion characteristics involving flame propagation, diffusion flame, and particle emissions were studied in a single-cylinder optical GDI engine. The results showed that the deposits slightly increased the spray penetration at 30 °C, and the deposits enhanced the flash-boiling process at the fuel temperatures of 60 °C and 90 °C. The influence of the deposits on flash-boiling was weakened at 20 MPa injection pressure. Compared with the clean injector, the fouled injector had smaller and lower speed tail droplets, slightly lower combustion flame speed, and slightly smaller peak in-cylinder pressure. Moreover, the fouled injector had much more tip diffusion flame compared with the clean injector. The split injection strategy increased the tip diffusion flame and soot emission for both injectors at a fuel temperature of 90 °C. The diffusion flame luminance was linear with the number concentration of accumulation mode particles, and the luminance of the diffusion flame can characterize the soot concentration. The tip diffusion flame caused by the deposits is the primary source of soot emission at a fuel temperature of 90 °C. [ABSTRACT FROM AUTHOR]