Diesel Engine Exhaust Particles Research Articles

Mechanism underlying the role of integrin α3β1 in adhesive dysfunction between thyroid cells induced by diesel engine exhaust particles

The role and mechanisms of DEP exposure on thyroid injury are not yet clear. This study explores thyroid damage induced by in vivo DEP exposure using a mouse model. This study has observed alterations in thyroid follicular architecture, including rupture, colloid overflow, and the formation of voids. Additionally, there was a significant decrease in the expression levels of proteins involved in thyroid hormone synthesis, such as thyroid peroxidase and thyroglobulin, their trend of change is consistent with the damage to the thyroid structure. Serum levels of triiodothyronine and tetraiodothyronine were raise. However, the decrease in TSH expression suggests that the function of the HPT axis is unaffected. To delve deeper into the intrinsic mechanisms of thyroid injury, we performed KEGG pathway enrichment analysis, which revealed notable alterations in the cell adhesion signaling pathway. Our immunofluorescence results show that DEP exposure impairs thyroid adhesion, and integrin α3β1 plays an important role. CD151 binds to α3β1, promoting multimolecular complex formation and activating adhesion-dependent small GTPases. Our in vitro model has confirmed the pivotal role of integrin α3β1 in thyroid cell adhesion, which may be mediated by the CD151/α3β1/Rac1 pathway. In summary, exposure to DEP disrupts the structure and function of the thyroid, a process that likely involves the regulation of cell adhesion through the CD151/α3β1/Rac1 pathway, leading to glandular damage.

Analysis of the correlation between mechanical and physicochemical properties of particles based on a diesel oxidation catalytic system

The mechanical and physicochemical properties of diesel engine exhaust particles before and after diesel oxidation catalyst (DOC) treatment are analyzed. It is considered important to explore the interrelationships between these attributes in order to understand their relevance. Understanding of these properties provides insights into the deposition characteristics of particles within the system and the evolution of the particles after the DOC treatment, which may help the selection of appropriate aftertreatment strategies. In this paper, particle samples were collected before and after the DOC to explore the variations in the mechanical and physicochemical properties of the particles under different operating conditions. Atomic force microscopy, thermogravimetric analysis, transmission electron microscopy, and Raman spectroscopy were employed to investigate the attraction force, adhesion force, adhesion energy, oxidative reactivity, primary particle size, nanostructure, and graphitization degree of the particles. The results indicated that under post-injection conditions, the attraction force, adhesion force, and adhesion energy of the particles increased significantly. However, when the particles passed through the DOC, these properties decreased to varying degrees. By analyzing the combination of physicochemical properties, it was determined that the attraction force of the particles was primarily influenced by the primary particle size and the particle's graphite structure. The adhesion force was found to be closely related to the content of soluble organic matter. Additionally, the soluble organic matter affected the degree of particle agglomeration by altering the adhesion energy of the particles.

Effects of different national standards and driving conditions on pollutants and persistent free radicals in diesel engine exhaust particles

Exhaust pollutants from diesel vehicles constitute an important portion of air pollution. In addition to conventional pollutants such as carbon and nitrogen oxides, persistent free radicals (PFRs) exist on exhaust particles could also pose a health risk by inducing oxidative stress. However, recently there is a dearth of comprehensive studies addressing this concern. In this study, the exhaust particles emitted by tractors adhering to two prominent emission standards, namely GB III and GB I, that currently hold the largest tractor stocks, were collected under various working conditions. For the first time, this study dynamically monitored the characteristics of PFRs in exhaust particles emitted by internal combustion engines using biodiesel as fuel during driving on rural actual roads. Due to the stricter emission standard of GB III, which resulted in lower particle emissions, the concentration of PFRs emitted under the same fuel consumption was ultimately reduced. Noteworthily, while advancements like fuel atomization under engine electronic control unit (ECU) and the utilization of oxidation catalysts with low ignition temperature successfully decreased polycyclic aromatic hydrocarbons (PAHs) emission by altering combustion in the engine, they also resulted in heightened carbon structure defects, leading to a higher concentration of PFRs emitted per unit mass of particles. Additionally, compared to non-plowing driving conditions, localized hypoxia during plowing that could cause excessive fuel injection and uneven formation of fuel-air mixture resulted in the emission of a significant amount of carbon-containing substances with unstable structures. Consequently, this scenario led to an increased concentration of PFRs during plowing conditions. The results of this study demonstrated that the stricter emission standards and optimized technology could better reduce the concentration and types of PFRs in exhaust particles, reducing the environmental risk of exhaust particle, which is also of great significance for the realization of pollution reduction and carbon reduction goals.

Placental-fetal distribution of carbon particles in a pregnant rabbit model after repeated exposure to diluted diesel engine exhaust

BackgroundAirborne pollution particles have been shown to translocate from the mother’s lung to the fetal circulation, but their distribution and internal placental-fetal tissue load remain poorly explored. Here, we investigated the placental-fetal load and distribution of diesel engine exhaust particles during gestation under controlled exposure conditions using a pregnant rabbit model. Pregnant dams were exposed by nose-only inhalation to either clean air (controls) or diluted and filtered diesel engine exhaust (1 mg/m3) for 2 h/day, 5 days/week, from gestational day (GD) 3 to GD27. At GD28, placental and fetal tissues (i.e., heart, kidney, liver, lung and gonads) were collected for biometry and to study the presence of carbon particles (CPs) using white light generation by carbonaceous particles under femtosecond pulsed laser illumination.ResultsCPs were detected in the placenta, fetal heart, kidney, liver, lung and gonads in significantly higher amounts in exposed rabbits compared with controls. Through multiple factor analysis, we were able to discriminate the diesel engine exposed pregnant rabbits from the control group taking all variables related to fetoplacental biometry and CP load into consideration. Our findings did not reveal a sex effect, yet a potential interaction effect might be present between exposure and fetal sex.ConclusionsThe results confirmed the translocation of maternally inhaled CPs from diesel engine exhaust to the placenta which could be detected in fetal organs during late-stage pregnancy. The exposed can be clearly discriminated from the control group with respect to fetoplacental biometry and CP load. The differential particle load in the fetal organs may contribute to the effects on fetoplacental biometry and to the malprogramming of the fetal phenotype with long-term effects later in life.

34 Placental-Fetal Distribution of Carbon Particles in a Pregnant Rabbit Model After Repeated Exposure to Diluted Diesel Engine Exhaust

Abstract Airborne pollution particles have been shown to translocate from the mother’s lung to the fetal circulation but their placental-fetal distribution and internal tissue load remain poorly explored. Here, we investigated the placental-fetal distribution of diesel engine exhaust particles during gestation under controlled exposure conditions using a pregnant rabbit model. Pregnant dams were exposed by nose-only inhalation to either clean air (controls) or diluted and filtered diesel engine exhaust (1 mg/m3) for 2h/day, 5 days/week, from gestational day (GD) 3 to GD27. At GD28, placental and fetal tissues (i.e., heart, kidney, liver, lung and gonads) were collected for biometry and to study the accumulation of carbon particles (CPs) using white light generation by carbon particles under femtosecond pulsed laser illumination. CPs were detected in the placenta, fetal heart, kidney, liver, lung and gonads in significantly higher amounts compared with controls. By using multiple factor analysis, we were able to discriminate the diesel engine-exposed pregnant rabbits from the control group taking all variables related to fetoplacental biometry and CP load into consideration. Although our findings did not reveal a sex effect, a potential interaction effect might be present between exposure and fetal sex. The results confirm the translocation of maternally inhaled CPs from diesel engine exhaust to the placenta and the ability to reach fetal organs during late-stage pregnancy. The differential particle load in the fetal organs may contribute to the disruption of blood flow in the placenta with possible effects on fetoplacental biometry and placental function.

Study of the influence of methanol/F-T diesel combustion particle materiality parameters on the deposition process in diesel particulate filter trap units

The use of different fuels will change the structural characteristics of the diesel engine exhaust particulates. This paper studies the impact of the particle physical and structural properties on DPF capture, and proposes to measure the particle deposition by particle chain length and particle layer thickness. This study builds a test bench based on a four-cylinder diesel engine, using F-T diesel fuel with 0%, 5%, and 15% methanol mixing ratio to collect particles after running for half an hour under the calibration condition. The physical properties of particles were analyzed by synchrotron radiation small angle scattering. The particle formation rate, friction between particles, particle size, and other parameters of mixed fuel combustion particles were then confirmed. The particle model was developed in EDEM based on the experimental data, and the creation of particle chains was studied. In addition, the impact of collision bounce on the particle deposition was taken into consideration to mimic the process of particle collision deposition on the filter wall. The results show that when the methanol mixing ratio increases, the Particles Number (PN) value of methanol F-T diesel combustion particles increases, the inter-particle friction increases, and the average particle size decreases. During the deposition process, the amount of deposition on the non-windward side of the DPF trap unit sharply increases, and the particle deposition efficiency increases with the increase of the deposition time. The particle deposition increases with the deposition time, and the thickness and length of the particle layer and chain increase with the increase of the particle number, friction, and size.

Plasma-enhanced electrostatic precipitation of diesel exhaust particulates using nanosecond high voltage pulse discharge for mobile source emission control

This study reports enhancement in the electrostatic precipitation (ESP) of diesel engine exhaust particulates using high voltage nanosecond pulse discharge in conjunction with a negative direct current (DC) bias voltage. The high voltage (20 kV) nanosecond pulses produce ion densities that are several orders of magnitude higher than those in the corona produced by a standard DC-only ESP. This plasma-enhanced electrostatic precipitator (PE-ESP) demonstrated 95 % remediation of PM and consumes less than 1 % of the engine power (i.e., 37 kW diesel engine at 75 % load). While the DC-only ESP remediation increases linearly with applied voltage, the plasma-enhanced ESP remains approximately constant over the applied range of negative DC biases. Numerical simulations of the PE-ESP process agree with the DC-only experimental results and enable us to verify the charge-based mechanism of enhancement provided by the nanosecond high voltage pulse plasma. Two different reactor configurations with different flow rates yielded the same remediation values despite one having half the flow rate of the other. This indicates that the reactor can be made even smaller without sacrificing performance. Here, this study finds that the plasma enhancement enables high remediation values at low DC voltages and smaller ESP reactors to be made with high remediation.

A controlled chamber study of effects of exposure to diesel exhaust particles and noise on heart rate variability and endothelial function

Background Adverse cardiovascular effects are associated with both diesel exhaust and road traffic noise, but these exposures are hard to disentangle epidemiologically. We used an experimental setup to evaluate the impact of diesel exhaust particles and traffic noise, alone and combined, on intermediary outcomes related to the autonomic nervous system and increased cardiovascular risk. Methods In a controlled chamber 18 healthy adults were exposed to four scenarios in a randomized cross-over fashion. Each exposure scenario consisted of either filtered (clean) air or diesel engine exhaust (particle mass concentrations around 300 µg/m3), and either low (46 dB(A)) or high (75 dB(A)) levels of traffic noise for 3 h at rest. ECG was recorded for 10-min periods before and during each exposure type, and frequency-domain heart rate variability (HRV) computed. Endothelial dysfunction and arterial stiffness were assessed after each exposure using EndoPAT 2000. Results Compared to control exposure, HRV in the high frequency band decreased during exposure to diesel exhaust, both alone and combined with noise, but not during noise exposure only. These differences were more pronounced in women. We observed no synergistic effects of combined exposure, and no significant differences between exposure scenarios for other HRV indices, endothelial function or arterial stiffness. Conclusion Three-hour exposure to diesel exhaust, but not noise, was associated with decreased HRV in the high frequency band. This indicates activation of irritant receptor-mediated autonomic reflexes, a possible mechanism for the cardiovascular risks of diesel exposure. There was no effect on endothelial dysfunction or arterial stiffness after exposure.

Correlation analysis of mechanical and state characteristics of diesel engine exhaust particles

AbstractAiming at the influence of diesel engine exhaust particle mechanical characteristics on the state characteristics, studies were carried out using atomic force microscopy, high‐resolution transmission electron microscopy, and x‐ray small‐angle scattering. The variation rules of cluster‐particle interaction force and state characteristic parameters such as particle morphology and spatial structure were discussed. According to the principle of normalization, the relationship between the mechanical and state characteristics of the particles is analyzed. The results show that as the particle size increases in the exhaust process, the attractive force Fat, adhesion Fad, and adhesion energy Wad increase between the particles, Fat from 1.27 to 1.58 nN, Fad from 3.75 to 4.38 nN, Wad from 2.17 × 10−16 to 2.44 × 10−16 J. The particles are gradually agglomerated, and the cluster size is increased, indicating a certain relationship between the mechanical characteristics of the particles and the morphology. Along the exhaust direction, the particle equivalent diameter increases, and the mechanical characteristics are enhanced, while the organic matter and moisture in the exhaust are continuously adsorbed, aggravating the aggregation and shrinkage between the particles. The scattering characteristic parameters qminand qTdecrease, qminfrom 0.34 to 0.28 and qTfrom 0.72 to 0.63, the pore structure parameters decrease, the pore number concentration decreases, the peak pore size changes from 7–9 nm to 5–6 nm, the agglomerate particle structure defects decrease and the density is increased, indicating that there is a certain relationship between the mechanical characteristics of the particles and the spatial structure.

Environmental persistent free radicals in diesel engine exhaust particles at different altitudes and engine speeds

The occurrence of environmental persistent free radicals (EPFRs) in the environment has attracted a great deal of research attention. Although the major sources of EPFRs in the environment is diesel engine exhaust, the study on the emission characteristics of EPFRs at different working conditions is still very limited. An integrated engine system was adopted to simulate different working conditions of various altitudes and engine speeds, and to examine the emission process of a diesel engine. The results suggested that low engine speed and high altitude are generally associated with high PM10 emission with more stable and ordered structures. Based on the analysis of PAHs on solid and gas phases, PM10 generated from diesel engine at altitude higher than 2000 m may contain substantial amounts of PAHs embedded inside particles, but not adsorbed on the surface. EPFRs signal up to 1.66 × 1020 spins/g were detected in PM10 of the diesel exhaust. Higher engine speed and lower altitude were associated with stronger EPR signals on PM10. However, the accumulated EPR signal intensities after consuming 1 L of diesel were higher at lower engine speed and higher altitude, suggesting higher overall risks. A positive correlation between R value (signal strength ratio of D and G peaks on the Raman spectra) and EPFRs intensity indicated that the EPR signals were associated with the defects of carbon structure. EPFRs intensity in particles showed no significant change in dark, and over 70% of the EPR signals survived under UV light in a one-month aging simulation. The strong persistence of these EPFRs suggested their potential long lasting and widespread risks, which should be investigated extensively.

Study on the purification of diesel engine exhaust particles based on water film adsorption

Given the severe pollution caused by particulate matters in diesel engine exhaust, we discuss herein the problem of exhaust back-pressure and regeneration of commonly used diesel particulate filter treatment technology. This paper proposes a method based on water film adsorption to remove exhaust particles from exhaust gas. Particulates flowing through the purification device are adsorbed by the continuous isobaric water film formed on the wave adsorption plate. The formation process and characteristics of the equal pressure-differential water film are studied through combined theoretical analysis and experimental verification. The regeneration process and influencing factors of the purification system are also analyzed, and the treatment of the device is verified. Experiments show that the device offers a better purification of exhaust particulates with lower exhaust resistance and regeneration of the system during the treatment.

An Exploratory Study of the Relationships Between Diesel Engine Exhaust Particle Inhalation, Pulmonary Inflammation and Anxious Behavior.

Recent technical developments brought negative side effects such as air pollution and large-scale fires, increasingly exposing people to diesel engine exhaust particles (DEP). Testing how DEP inhalation triggers pathophysiology in animal models could be useful in determining how it affects humans. To this end, the aim of this study was to investigate the effects of pulmonary exposure to DEP for seven consecutive days in experimental male C5BL6/N mice. Twenty-four C5BL6/N mice were treated with one of the three test materials: distilled water for control, a low DEP exposure (5 mg/kg), or a high DEP exposure (15 mg/kg). Exposure to DEP induced decreased body weight; however, it gradually increased pulmonary weight in a DEP-dose-dependent manner. DEP exposure significantly elevated soot accumulation in the lungs, with the alteration of pulmonary homeostasis. It also elevated infiltrated immune cells, thus significantly increasing inflammatory cytokine mRNA and protein production in the lungs and broncho-alveolar lavage fluid, respectively. Pulmonary DEP exposure also altered behavioral responses in the open field test (OFT). Low exposure elevated moving distance and speed, while significantly decreasing the number of trials to enter the central zone. Different concentrations of DEP resulted in different behavioral changes; however, while anxiety levels increased, their degree was independent of DEP concentrations. Results suggest that DEP exposure may possess pro-inflammatory responses in the lungs and trigger anxiety.

Study on diesel engine exhaust particle separation based on gas–solid two-phase flow theory

Particulate matter in diesel exhaust is one of the primary sources of environmental pollution. This paper mainly studies the purification treatment of particulate matter in exhaust gas. It also studies the stress conditions and moving process of particulates in straight and elbow pipes respectively and explores their capture efficiency on the basis of that the gas–solid two-phase flow composed of particulates and gas is a basic fluid state. This paper mainly analyzes the influence of straight and elbow pipe on the moving process of particulates. It also discusses the impact of the structure parameters of the elbow on the exhaust pressure of inlet and outlet of pipes to provide basis for its designing. In addition, experiment is carried out to verify the capture efficiency of particulates by elbow pipes under different working conditions of diesel engines. The experiment results show that the capture efficiency is improved and separation of particulates is more effective.

Experimental investigation of acoustic agglomeration of diesel engine exhaust particles using new created acoustic chamber

Many researchers have considered air quality degradation due to the emission of fine particles from industrialized and urban areas during recent decades. Recently, the European Parliament has had concerns about ensuring a healthy human environment. Therefore, the experimental and theoretical investigations of the dynamics of fine particulate matter are for determining efficient monitoring and cleaning air from industrially generated air pollutants. These investigations also imply the use of alternate methods that stimulate fine particle agglomeration. One of the methods is the use of acoustics. Many experimental investigations of particles with a diameter between 1 and 10μm have proven that the use of acoustic agglomeration increases the particle size. Then, conventional air filters can be used to collect the larger particles. This process improves the collection efficiency of the particles. Particulate agglomeration chamber consisting of an acoustic field generator and an inner part was created for the test particles of diesel engines (range from 0.3 to 10μm). Modeling of its elements was performed using Comsol multifunctional software. This sound pressure level is enough [1] to lead the acoustic agglomeration process of particles in the measurable range from 0.3 to 10μm. The sound pressure level reach this value (130–140dB) at the acoustic agglomeration zone.Additionally, the theoretical evaluation of the agglomeration time of two sub-micron particles enabled the estimation of efficient agglomeration of particles with sizes between 0.3 and 10μm during the measurement period. A starting value of 136dB of sound pressure level (SPL) was created in the experimental chamber with the turbulence condition, where SPL values were measured by using the Bruel&Kjaer measurement system “Type 9727” with hydrophone 8104. The observation concentrations of diesel engine exhaust particles in the experimental chamber with and without acoustic influence were performed using Particle Concentration Analyzer 4 APC ErgoTouch Pro 2.The results of experimental research shows that the acoustic agglomeration effect formed the proper conditions for the agglomeration of particles of all diameters (0.3, 0.5, 1.0, 3.0, 5.0 and 10μm).

Distinguishing fuel and lubricating oil combustion products in diesel engine exhaust particles

The main sources of particulate emissions from engines are fuel and lubricating oil. In this study, particles emitted by a medium speed diesel engine for locomotive use were characterized chemicall...

Differential toxicities of fine particulate matters from various sources

Fine particulate matters less than 2.5 µm (PM2.5) in the ambient atmosphere are strongly associated with adverse health effects. However, it is unlikely that all fine particles are equally toxic in view of their different sizes and chemical components. Toxicity of fine particles produced from various combustion sources (diesel engine, gasoline engine, biomass burning (rice straw and pine stem burning), and coal combustion) and non-combustion sources (road dust including sea spray aerosols, ammonium sulfate, ammonium nitrate, and secondary organic aerosols (SOA)), which are known major sources of PM2.5, was determined. Multiple biological and chemical endpoints were integrated for various source-specific aerosols to derive toxicity scores for particles originating from different sources. The highest toxicity score was obtained for diesel engine exhaust particles, followed by gasoline engine exhaust particles, biomass burning particles, coal combustion particles, and road dust, suggesting that traffic plays the most critical role in enhancing the toxic effects of fine particles. The toxicity ranking of fine particles produced from various sources can be used to better understand the adverse health effects caused by different fine particle types in the ambient atmosphere, and to provide practical management of fine particles beyond what can be achieved only using PM mass which is the current regulation standard.

Analysis on the morphology and mechanical characteristics of agglomerated particles emitted from the diesel exhaust process

The diesel engine particulate which is one of the major sources of PM, affects the development of human health and production activities seriously. With the continuous strict of emission regulations, the diesel engine particles are subject to strict restriction in terms of quality and quantity. At present, the diesel particulate filter technology is an important technical measure to reduce the exhaust particulate matter of the diesel engine. And the efficient capture of particles is one of the key technologies for the diesel particulate filter. Diesel engine exhaust particles undergo nucleation, surface growth, agglomeration and other processes, in which the degree of agglomeration of exhaust particles will directly affect its number density, scale and the trapping efficiency of the filter and so on. The reason why particles can be agglomerated is mainly due to the interaction between the particles. Therefore, to explore the relationship between the force and the effect of particle agglomeration, it is necessary to carry out the study on the interaction between the exhaust particles of diesel engines. The interaction between particles will affect the process of particle agglomeration and related parameters significantly. The main forces include van der Waals force, electrostatic force and liquid bridge force. In this paper, theoretical models of Hamaker and some others are used to analyze the force between particles in the ideal state. The test methods of atomic force microscopy (AFM) and transmission electron microscopy (TEM) are used to investigate the total attraction force, adhesion force and adhesion energy between diesel exhaust particulates in dry environment (relative humidity RH≤20%), and measure the total attraction force, adhesion force and adhesion between particles, and explore the relationship between particle size and particle size. The results show that the particle size increases from 25 to 45 nm, the Van der Waals force increases about 4.6 times, the electrostatic force increases about 9.9 times, and the electrostatic force is smaller than the electrostatic force. The adhesion between particles and adhesion energy both increased about 1.8 times. The particles with the average particle size of 30, 37 and 46 nm are measured by AFM. With the increase of the particle size, the total attraction F at between the particle and the probe increases gradually, which is 1.04–1.38 nN. Van der Waals force F vdw is the main force of the F at, and Coulomb force is smaller. The attraction force F at and the adhesion energy W ad increase with the increase of particle size, F at increases from 3.21–3.75 nN, about 16.8%, while W ad increases from 2.03×10−16 J to 2.20×10−16 J, about 8.4%. The increase of F ad and W ad indicate that the adhesion as well as the energy barrier between the particles is increased, and the particle agglomeration is stable. With the increase of the average particle size, the particles agglomerate gradually and change from branch to cluster, showing a hill-like accumulation, and the particle density as well as the cluster size are increased, which indicates that there was a certain influence between the change of particle force and particle morphology.

Effects of exhaust gas recirculation at various loads on diesel engine performance and exhaust particle size distribution using four blends with a research octane number of 70 and diesel

Partially premixed combustion using gasoline-like fuels on compression ignition engines shows great potentials to break the soot-nitrogen oxides trade off and reduce both emissions simultaneously. By simply adjusting the dilution strategies and injection events, the control of partially premixed combustion is relatively easier compared to other low-temperature combustion concepts. However despite these advantages, recent research shows this concept tends to emit ultra-fine particles. Most previous work on partially premixed combustion only focuses on the soot emissions while the particulate matter in terms of number concentration and size distribution are not well investigated. Ultra-fine particles are dangerous to human health and are getting increasing attentions. Thus the detailed particulate matter emission from partially premixed combustion needs to be further investigated. In this work four gasoline-like ternary fuel blends are designed and experimentally tested under partially premixed combustion. The test blends all share the same two base fuels and blended with different additives. The fuel composition is varied to have the same research octane number. Tests are conducted under different engine loads and dilution strategies since the temperature and oxygen concentration are the key factors in the formation and oxidation of soot. Standard diesel is also tested under the same conditions as a comparison. It is found that these blends are capable of running under partially premixed combustion at low and medium loads and they produce near zero soot emissions when using high exhaust gas recirculation rate. However, these blends do emit smaller particles than diesel under all test loads. Besides, blends with oxygen content yield less soot emissions and smaller particles compared to non-oxygen blends.

Influence of biodiesel fuel composition on the morphology and microstructure of particles emitted from diesel engines

This study investigates the morphology, microstructure and surface composition of Diesel engine exhaust particles. The state of agglomeration, the primary particle size and the fractal dimension of exhaust particles from petroleum Diesel (petrodiesel) and biodiesel blends from microalgae, cotton seed and waste cooking oil were investigated by means of high resolution transmission electron microscopy. With primary particle diameters between 12 and 19 nm, biodiesel blend primary particles are found to be smaller than petrodiesel ones (21 ± 2 nm). Also it was found that soot agglomerates from biodiesels are more compact and spherical, as their fractal dimensions are higher, e.g. 2.2 ± 0.1 for 50% algae biodiesel compared to 1.7 ± 0.1 for petrodiesel. In addition, analysis of the chemical composition by means of x-ray photoelectron spectroscopy revealed an up to a factor of two increased oxygen content on the primary particle surface for biodiesel. The length, curvature and distance of graphene layers were measured showing a greater structural disorder for biodiesel with shorter fringes of higher tortuosity. This change in carbon chemistry may reflect the higher oxygen content of biofuels. Overall, it seems that the oxygen content in the fuels is the underlying reason for the observed morphological change in the resulting soot particles.

Effect of multiple-injection strategies on diesel engine exhaust particle size and nanostructure

Multiple-injection has been widely investigated to simultaneously reduce diesel NOx and soot emissions. While the comprehensive understanding of the effects of multiple injection on exhaust PM physical characteristics is still lacking. Three injection modes, single main, pilot-main and main-post injections, were compared in this work. The main objective is to better understand the influence of pilot and post injections on particle size and nanostructure characteristics in diesel exhaust. Experimental tests have shown that, for the pilot-main injection case, less premixed combustion and more diffusion combustion occur compared with the single main injection, which promotes formation of soot nuclei and results in a significant increase of number and mass of particles with the diameter above 100nm. On the contrary, soot oxidation later in the combustion is improved due to the enhancement of gas mean temperature (GMT) and air/fuel mixing for the main-post injection case, which favors soot oxidation and leads to the decrease of particle number and diameter. A comparison of particle nanostructures for the pilot-main injection case and main-post injection case has been conducted, which indicates that both low in-cylinder temperature and relative short carbonization time lead to the particles of less carbonization level (short fringe length and large fringe tortuosity) for the pilot-main injection case. Particles exhibit highly ordered graphitic structure for the main-post injection case due to the increase of combustion duration and the enhancement of in-cylinder temperature during the later stage of combustion derived by post combustion, which presents potential negative effect on diesel particle filters (DPF) regeneration efficiency.