Soot Oxidation Characteristics Research Articles

Study on soot oxidation activity of ethylene/methane laminar diffusion flame

the soot oxidation characteristics and oxidation mechanism of ethylene flame with different methane mixing ratios were studied by thermogravimetric analyzer and oxidation reaction kinetics analysis. The conclusions are as follows: in the process of programmed temperature rise, there is almost no loss in the quality of soot particles below 450 °C; With the increasing temperature, the mass of soot particles began to decrease when the temperature exceeded 500 °C; When the temperature exceeds 750 °C, the mass of soot particles is close to zero; With the increase of flame height, the thermogravimetric curve of soot first shifts to high temperature and then to low temperature; The activation energy of soot is closely related to its oxidation process, and decreases first and then increases with the deepening of soot oxidation; The mixing of methane promotes the rise of soot ignition temperature and burnout temperature, and the minimum activation energy of soot decreases at low flame height and increases at high flame height.

Investigations on anti-Tampering of diesel particulate filter

Tampering is making inoperable or removing, any device or system, used to control emissions from a vehicle or engine. Tampering may include, but is not limited to: removing the Diesel Particulate Filter (DPF), drilling hole into the DPF, adjusting any functionality of a vehicle’s emission control, which is different from the manufacturer’s specifications, installation of a replacement part that is not certified on vehicle. Experimental investigations were done on tamper detection on a vehicle installed with a diesel particulate filter along with regeneration system. The temperature characteristics and characteristics of soot oxidation were used to indicate tampering. It could be concluded from the experimental investigations that the availability of oxygen and DPF soot loading affects temperature rise during soot oxidation and hence the temperature could be used as an effective method for detecting DPF tampering.

A Role of NO <sub>2</sub> on Soot Oxidation in DPFs and Effect of Soot Cake Thickness in Catalyzed DPFs Using Temperature-Programmed Oxidation and Electron Microscopic Visualization

<div class="section abstract"><div class="htmlview paragraph">Development of the diesel particulate filter (DPF) aims to attain fast oxidation of accumulated soot at low temperature. Numerous researchers have explored the characteristics of soot oxidation under ambient conditions of simulated exhaust gas using thermogravimetric analysis or a flow reactor. In this study, temperature programmed oxidation (TPO) experiments were carried out for soot entrapped in miniaturized DPFs, cut-out from practical particulate filters, yielding wall-flow features typically encountered in real-world DPFs. Furthermore, when using the miniaturized samples, highly accurate lab-scale measurements and investigations can be facilitated. Examining different temperature ramping rates used for the TPO experiments, we propose a rate of 10°C/min as the most effective in analyzing soot oxidation in the practical filter substrates. Then, wash-coated catalyzed filters (CDPFs) were benchmarked with bare-type DPFs to clarify their effects on soot oxidation in a practical wall-flow system. According to the Arrhenius expression, differences in soot cake thickness in CDPFs reflect various values of estimated activation energy. This is due to the soot-catalyst proximity. With presence of 450 ppm nitrogen dioxide (NO<sub>2</sub>) in a reactant gas mixture, the soot oxidation range was extent to a lower temperature. Moreover, a reduction in the estimated activation energy was achieved, even in the case of using bare-type DPFs. The thick soot cake layers in bare-type DPF result in a significant amount of soot mass remaining after treatment at 600°C, a typical active regeneration temperature. Subsequently, soot residuals were traced and characterized after a complete active regeneration process. For these reasons, thickness of a soot cake layer was proposed to be a new factor to define an updated regeneration strategy.</div></div>

Physical properties of exhaust soot from dimethyl carbonate-diesel blends: Characterizations and impact on soot oxidation behavior

This study presents the physical properties and oxidation reactivity of exhaust soot from a modern direct injection diesel engine fueled with dimethyl carbonate (DMC)-diesel blends and discusses the relationship between physical properties and oxidation reactivity of soot. The soot morphology, size, fractal dimension and nanostructure were analyzed by transmission electron microscopy and Raman scattering spectrometry. The thermogravimetric analysis was carried out to characterize soot oxidation reactivity in the form of apparent activation energy. The results showed that soot aggregates from DMC/diesel blended fuels exhibited fewer and smaller primary particles as well as small-sized clusters than the diesel soot aggregates. Soot primary particles presented shorter fringe length, wider separation distance and greater tortuosity with increasing DMC blending amount, while the degree of graphitization for soot presented an increasing trend. It was also found that soot from DMC/diesel blends, or low loading operation had higher oxidation reactivity than those from pure diesel or heavy loading operation. Among the physical properties, fractal dimension and primary particle size appeared to be insignificant than the nanostructure for governing the soot oxidation reactivity. Further analysis showed the separation distance was more correlated with soot oxidation characteristics than fringe length and tortuosity. These results illustrated that the use of DMC blended diesel fuel affects the physical properties of soot, enhances soot particle oxidation reactivity, which will be significant for improving the regeneration efficiency of after-treatment device.

Experimental Study on Soot Oxidation Characteristics of Diesel Engine with Ce-Based Fuel-Borne Catalyst Fuel

AbstractIn order to investigate the effects of a Ce-based fuel-borne catalyst (FBC) on the catalytic oxidation of soot particles from a diesel engine, a naphthenic acid cerium solution was selected...

Study on oxygen species characteristics of CexMn1-xO2 catalyst for diesel soot oxidation

ABSTRACT 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.

Gasoline direct injection engine soot oxidation: Fundamentals and determination of kinetic parameters

Current emissions legislation for road transport vehicles, including modern gasoline vehicle fleet limits the mass and the number of Particulate Matter (PM) emitted per kilometre. The introduction of a gasoline particulate filter (GPF) is expected to be necessary, as was the case for diesel vehicles, the traditionally recognised source of PM in transportation. Therefore, for the design of efficient GPFs and the regeneration strategies, soot oxidation characteristics in gasoline must be understood.Extensive research has been carried out mainly to investigate the oxidation of diesel soot, however, in the most cases soot were collected on microfiber filters and the activation energy was calculated with the logarithm method assuming mass and oxygen reaction orders equal to one. Identified limitations that lead to inconsistent and inaccurate trends and results are presented in this paper. As a consequence, a novel methodology to accurately obtain the oxidation kinetic parameters for soot emitted from a Gasoline Direct Injection (GDI) engine has been developed and presented in this paper. The particles collected in a silicon carbide wall-flow particulate filter are directly exposed to oxidation conditions in a thermogravimetric analysis (TGA) without the use of microfiber filter.The significance of more accurate and consistent calculations of soot oxidation kinetic parameters as a result of this methodology will aid modelling and experimental work of the aftertreatment systems and will lead in improving the GPF regeneration process in modern GDI vehicles. Avoiding high peak temperatures during regeneration and large thermal stress gradients and thus increasing the operating life of the filters is amongst the benefits can be seen.

Influence of on-board produced hydrogen and three way catalyst on soot nanostructure in Gasoline Direct Injection engines

Effectively controlling carbon soot emission from Gasoline Direct Injection (GDI) engines to achieve legislative emission limits is a challenge for both the vehicle manufacturers and researchers. Transmission electron microscopy is a powerful tool for obtaining morphological and nanostructural parameters of carbon soot in Particulate Matter (PM) emissions. These parameters play a significant role in PM emissions control as are affecting filtration efficiency and soot oxidation characteristics.In this paper, a comprehensive analysis of the interlayer spacing, fringe length and fringe tortuosity (curvature) of primary soot particles from GDI engine has been performed. GDI primary particles showed a core-shell structure, similar to diesel soot, with an inner core diameter between 6 and 16 nm and the outer graphene layer between 6 and 13 nm. The soot nanostructure is not significantly modified by changing the fuel injection timing or by introducing EGR and hydrogen in the combustion process. These results are opposed to those obtained from soot emitted in diesel engines where soot nanostructure is affected with changes in engine operating conditions. Furthermore, the three way catalytic converter does not influence soot nanostructure or the soot oxidation characteristics.

Effects of Diesel Soot Composition and Accumulated Vehicle Mileage on Soot Oxidation Characteristics

Effects of diesel soot composition and accumulated vehicle mileage on soot oxidation characteristics were examined. Four soot samples were extracted from the crankcase oils of diesel engines that had accumulated different mileages. Carbon black was used as a comparative example. Soot structure was studied in situ using X-ray diffraction as it was oxidized to temperatures as high as 700 °C. The soot from older engines exhibited a higher increase in lattice spacing (d002) with an increase in temperature that resulted in soot samples being at lower temperatures, thereby reducing the oxidation resistance. Composition of the residues after oxidation was studied using X-ray diffraction, energy-dispersive spectroscopy, and X-ray absorption near-edge structure. Oxidation residue of the soot samples is made up of decomposed lubricant additives compounds and debris from wear and tribofilms. XRD phase analysis showed that crystalline compounds in soot are CaSO4, CaZn2(PO4)2, Ca3(PO4)2, Zn3(PO4)2, and ZnO. The turbos...

Oxidation characteristics of gasoline direct-injection (GDI) engine soot: Catalytic effects of ash and modified kinetic correlation

In this paper, experimental analyses are conducted into the GDI soot oxidation characteristics as dependent on engine operating conditions. Soot is sampled at various engine operating conditions of a commercial 2.4L GDI engine with a naturally aspirated, homogeneous, and stoichiometric operation strategy. The oxidation reactivity, ash composition, and carbon nanostructure of the GDI soot samples are analyzed using thermogravimetric analysis (TGA), scanning electron microscope–energy-dispersive spectroscopy (SEM–EDS), high-resolution transmission electron microscopy (HR-TEM), and Raman spectroscopy. Based on the analyses, a global GDI soot oxidation mechanism is proposed which includes the effects of soluble organic fractions (SOF)/weakly bonded carbon (WBC), and three types of ash on GDI soot oxidation. The results show that GDI soot contains an order of magnitude higher ash fraction than does conventional diesel soot, and oxidation reactivity is significantly enhanced by the catalytic effects of ash, as a function of ash content in soot. A modified empirical kinetic correlation for GDI soot oxidation is suggested on the basis of the results, and the modified kinetic correlation predicts the GDI soot oxidation rate accurately for various engine operation points at wide ranges of soot conversion and temperature without modifying kinetic parameters. The kinetic parameters are determined from isothermal and non-isothermal thermogravimetric analysis (TGA) soot oxidation tests; the methods are elucidated in detail.

A Model Development for Evaluating Soot-NOx Interactions in a Blended 2-Way Diesel Particulate Filter/Selective Catalytic Reduction

The 2-way diesel particulate filter/selective catalytic reduction (DPF/SCR) emission reduction system has been considered as a potential candidate for future emission standards owing to its advantages in cost savings and packaging flexibility. For the 2-way device, Cu–zeolite is coated inside the DPF substrate as nitrogen oxide (NOx) reducing (DeNOx) catalytic material. Therefore, when exhaust gas passes through the 2-way device, NOx reduction and soot filtration occur simultaneously. However, the operating characteristics of the combinatorial device might be different from individual DPF and SCR devices. In this work, a previously developed model was improved to include soot filtration and oxidation. The model has been tested and validated with experimental data from a reactor flow bench in a systematic manner and applied to capture the effect of soot deposits on NOx reduction performance in a 2-way DPF/SCR device. Accordingly, the soot oxidation characteristics of a 2-way device are investigated with va...

Measurement of soot oxidation with No2-O2-H2O in a flow reactor simulating diesel engine DPF

Understanding the mechanism of carbon oxidation is important for the successful modeling of diesel particulate filter regeneration. Characteristics of soot oxidation were investigated with carbon black (Printex-U). A flow reactor system that could simulate the condition of a diesel particulate filter and diesel exhaust gas was designed. Kinetic constants were derived and the reaction mechanisms were proposed using the experimental results and a simple reaction scheme, which approximated the overall oxidation process in TPO as well as CTO. From the experiments, the apparent activation energy for carbon oxidation with NO2-O2-H2O was determined to be 40±2 kJ/mol, with the first order of carbon in the range of 10∼90% oxidation and a temperature range of 250∼500°C. This value was exceedingly lower than the activation energy of NO2-O2 oxidation, which was 60±3 kJ/mol. When NO2 exists with O2 and H2O, the reaction rate increases in proportion to NO2. It increases nonlinearly with O2 or H2O concentration when the other two oxidants are fixed.