Characterization of Submicron Exhaust Particles from Engines Operating Without Load on Diesel and JP-8 Fuels

Diluted exhaust from a selection of Air Force ground support vehicles was subjected to gravimetric, carbon, and size distribution analyses in September 1999. The vehicles operated on diesel and JP-8 fuels. In most cases, the engines involved were similar to civilian counterparts. The tests involved "low" and "high" idle settings but no external loads were imposed. Particle size distribution data, obtained over the 10 to 352 nanometer diameter range using an SMPS instrument, showed that the relative number count of accumulation mode particles increased with respect to nucleation mode particles as the engine rpm increased. The SMPS distributions often explained the main variations in the integrated PM 2.5 gravimetric mass data. Particulate mass derived from the SMPS data and from cascade impactor measurements were well correlated (regression slope 1.02). Empirically determined "elemental" carbon (EC) and "organic" carbon (OC) were the main constituents of the PM 2.5 gravimetric mass (regression slope 0.89). EC contributed less, and OC contributed more to the PM 2.5 mass than was found in some recent studies of exhaust from vehicles operated under external loads. The observed particle nucleation modes were attenuated by coagulation with accumulation mode particles, but it does not appear that artifact particle formation was operative in these experiments. The estimated - 1 σ measurement precisions range from about - 4% for the largest impactor mass concentration determinations to - 24% for some of the SMPS mass concentration estimates.     

Characterization of Soot Particles Produced in a Transparent Research CR DI Diesel Engine Operating with Conventional and Advanced Combustion Strategies

The effect of the combustion mode on particle emission was analyzed both in the cylinder and at the exhaust of a direct injection (DI) Common Rail (CR) transparent research diesel engine by means of spectroscopic and conventional methods. The engine was equipped with a flexible electronic control unit (ECU) capable of operating up to 5 injections per cycle with different start of injection and dwell time allowing performing different combustion modes. The conventional diesel combustion, the homogeneous charge compression ignition (HCCI), and the low temperature combustion (LTC) modes were analyzed. In-cylinder broadband UV–visible scattering and extinction measurements were carried out to follow the particle formation and oxidation processes as well as to have information about their chemical nature and size distribution. The characterization of the particulate emission at the exhaust was performed by means of an electrical low pressure impactor (ELPI), for the counting and the sizing of the particles, and an opacimeter, for measuring the smoke opacity. The in-cylinder measurements highlighted that particles ranged from 3 to 100 nm whatever was the combustion mode. Nevertheless, particles produced by a conventional diesel combustion process principally consist of soot. Whereas particles formed during HCCI and LTC modes are composed mainly of organic compounds. The exhaust particle emissions depend on the combustion mode both in terms of size and number. A larger amount of particles smaller than 100 nm was emitted during HCCI and LTC modes with respect to the conventional one. Moreover, HCCI mode showed a strong accumulation mode.

Copyright 2012 American Association for Aerosol Research     

Prediction of NOx Emissions from a Transiently Operating Diesel Engine Using an Artificial Neural Network

For an adequate control of the reductant flow in selective catalytic reduction of NO_x in diesel exhaust, a tool has to be available to accurately and quickly predict the engine's NO_x emission. For these purposes, elaborate computer models and expensive NO_x analyzers are not feasible. The application of a neural network is proposed instead. Measurements were performed on a transient operating diesel engine. One part of the data was used to train the network for NO_x emission prediction, the other part was used to test. The average absolute deviation between the predicted and measured NO_x emission is 6.7 %. The reductant buffering capacity of the deNOx catalyst will diminish the effect of the deviation on the overall NO_x removal efficiency. The high accuracy of the neural network predictions, combined with the short computation times (0.2 ms/data point), makes the neural network a very promising tool in automotive NO_x control.     

Physico-Chemical Characterization and Oxidative Reactivity Evaluation of Aged Brake Wear Particles

Brake wear dust is a significant component of traffic emissions and has been linked to adverse health effects. Previous research found a strong oxidative stress response in cells exposed to freshly generated brake wear dust. We characterized aged dust collected from passenger vehicles, using microscopy and elemental analyses. Reactive oxygen species (ROS) generation was measured with acellular and cellular assays using 2′7-dichlorodihydrofluorescein dye. Microscopy analyses revealed samples to be heterogeneous particle mixtures with few nanoparticles detected. Several metals, primarily iron and copper, were identified. High oxygen concentrations suggested that the elements were oxidized. ROS were detected in the cell-free fluorescent test, while exposed cells were not dramatically activated by the concentrations used. The fact that aged brake wear samples have lower oxidative stress potential than fresh ones may relate to the highly oxidized or aged state of these particles, as well as their larger size and smaller reactive surface area.

Copyright 2015 American Association for Aerosol Research     

Sintering Effect on Material Properties of Electrochemical Reactors Used for Removal of Nitrogen Oxides and Soot Particles Emitted from Diesel Engines

In the present work, 12‐layered electrochemical reactors (comprising five cells) with a novel configuration including supporting layer lanthanum strontium manganate (LSM)‐yttria stabilised zirconia (YSZ), electrode layer LSM‐gadolinia‐doped cerium oxide (CGO) and electrolyte layer CGO were fabricated via the processes of slurry preparation, tape casting and lamination and sintering. The parameters of porosity, pore size, pore size distribution, shrinkage, flow rate of the sintered reactors and the electrical conductivities of the supporting layer and the electrode in the sintered reactors were characterised. The effect of sintering temperature on microstructures and properties of the sintered samples was discussed, and 1,250 °C was determined as the appropriate sintering temperature for reactor production based on the performance requirements for applications. Using the present ceramic processing route, porous, flat and crack‐free electrochemical reactors were successfully achieved. The produced electrochemical reactors have the potential application in the removal of NO_x and soot particles emitted from the diesel engines.     

Hygroscopic Behavior of Aerosol Particles Emitted from Biomass Fired Grate Boilers

This study focuses on the hygroscopic properties of submicrometer aerosol particles emitted from two small-scale district heating combustion plants (1 and 1.5 MW) burning two types of biomass fuels (moist forest residue and pellets). The hygroscopic particle diameter growth factor (Gf) was measured when taken from a dehydrated to a humidified state for particle diameters between 30–350 nm (dry size) using a Hygroscopic Tandem Differential Mobility Analyzer (H-TDMA). Particles of a certain dry size all showed similar diameter growth and the Gf at RH = 90% for 110/100 nm particles was 1.68 in the 1 MW boiler, and 1.5 in the 1.5 MW boiler. These growth factors are considerably higher in comparison to other combustion aerosol particles such as diesel exhaust, and are the result of the efficient combustion and the high concentration of alkali species in the fuel. The observed water uptake could be explained using the Zdanovski-Stokes-Robinson (ZSR) mixing rule and a chemical composition of potassium salts only, taken from ion chromatography analysis of filter and impactor samples (KCl, K₂SO₄, and K₂CO₃). Agglomerated particles collapsed and became more spherical when initially exposed to a moderately high relative humidity. When diluted with hot particle-free air, the fractal-like structures remained intact until humidified in the H-TDMA. A method to estimate the fractal dimension of the agglomerated combustion aerosol and to convert the measured mobility diameter hygroscopic growth to the more useful property volume diameter growth is presented. The fractal dimension was estimated to be ～ 2.5.     

Investigation on Particulate Oxidation from a DI Diesel Engine Fueled with Three Fuels

In this study, particles generated from a direct-injection (DI) diesel engine fueled with biodiesel, ultra-low-sulfur diesel (ULSD, <10 ppm-wt), and low-sulfur diesel (LSD, <500 ppm-wt) were investigated experimentally for their oxidation properties, using the thermogravimetric analysis (TGA), at five engine loads. Kinetic analysis of particulate oxidation was conducted based on the mass loss curves obtained from the TGA. The activation energy was found to be in the range of 142–175, 76–127, and 133–162 kJ/mol for the particulate samples for ULSD, biodiesel, and LSD, respectively. The particulate oxidation rate decreases with the increase of engine load for each fuel, and at each engine load, the oxidation rate decreases in the order of biodiesel, LSD, and ULSD. The primary particle size, nanostructure, and volatile fraction were also investigated for different particulate samples. The results indicate that the higher oxidation rate of biodiesel particles could be related to the smaller primary particle size, the more disordered nanostructure, and the larger volatile fraction, compared with the ULSD and LSD particles. The increase of sulfur content in a diesel fuel has a limited influence on primary particle size and nanostructure, while inducing a larger volatile fraction, which might be one of the reasons for the stronger oxidative reactivity of the LSD particles, compared with the ULSD particles.

Copyright 2012 American Association for Aerosol Research     

Peroxide Oxidative Desulfurization of a Diesel Fuel

Theoretical Foundations of Chemical Engineering - The catalytic activity of transition metal compounds (Mo, V, and W) in the reaction of oxidative desulfurization of straight-run diesel fuel with...     

用氧化脱硫剂脱除柴油中硫的方法

介绍将氧化脱硫剂M102加入含硫柴油中,在一定反应条件下,有效脱硫的过程。本实验所采用的氧化脱硫剂来源广泛,成本相对低廉,可有效降低柴油中的硫含量,从而达到国标要求。该脱硫工艺简便,操作灵活,可满足各种规模炼油企业的要求。     

超声条件下柴油氧化脱硫的研究

采用H2O2-甲酸作为氧化剂将催化裂化柴油中的硫化物（主要为苯并噻吩类）氧化成相应的砜,同时引入超声波为反应提供能量,考察（油/剂）比、氧化温度、反应时间、萃取静置时间、（萃取剂/油）比和萃取次数等因素对脱硫效果的影响。在适宜条件下,脱硫率可达94.2%,收率可达90%以上。     

Drying of Pepper Seed Particles in a Superheated Steam Fluidized Bed Operating at Reduced Pressure

A series of drying experiments was performed in a reduced-pressure superheated steam fluidized bed, employing pepper seed particles and some novel data were obtained. Experiments were carried out using different chamber pressures (40–67 kPa), temperatures (90–122°C), steam velocities (2.35–4.10 m/s), and mass flow rates (0.0049–0.0134 kg/s). In the majority of the experiments, the moisture gain observed in some other studies in the warm-up period of the process was prevented through some supplementary heat provided to the column. The drying rate was found to be increasing by operating temperature; however, it was not affected much by the superficial gas velocity and the operating pressure. Nevertheless, the reduced pressure operation increases the degree of superheating that appears as the most important parameter of the process. The experimental results showed that the equilibrium moisture content decreases by the increasing degree of superheating. On the other hand, the critical moisture content assumes higher values for the greater degrees of superheating. It was concluded that a relatively lower temperature process can be achieved through a reduced-pressure superheated steam fluidized bed.     

Experimental Study on Particulate Emissions of a Methanol Fumigated Diesel Engine Equipped with Diesel Oxidation Catalyst

In this article, the effects of fumigation methanol, diesel oxidation catalyst, and engine operation parameters (engine load and engine speed) on diesel smoke opacity, particulate mass concentration, particulate number concentration and the soluble organic fraction (SOF) in the particulate were investigated at certain selected operation conditions. Experiments were performed on a 4-cylinder direct injection diesel engine operating at three engine speeds and three loads for each engine speed. For each engine speed, there was a decrease of smoke opacity with increase in the level of fumigation methanol. The reduction was particularly obvious at the high engine load but was not significant at the low and medium engine loads. For all test conditions, fumigation methanol could effectively reduce the particulate mass and number concentrations. However, fumigation methanol increased the fraction of SOF in the particles. The DOC could further reduce the particulate mass and number concentrations as well as the fraction of SOF in the particles when the exhaust gas temperature was sufficiently high.     

Effective Density and Volatility of Particles Emitted from Gasoline Direct Injection Vehicles and Implications for Particle Mass Measurement

The effective density and volatility of particulate emissions from five gasoline direct injection (GDI) passenger vehicles were measured using a tandem differential mobility analyzer (DMA) and centrifugal particle mass analyzer (CPMA) system. The measurements were conducted on a chassis dynamometer at three steady-state operating conditions. A thermodenuder was employed to find the volatility and mixing state of the particles as well as the effective density of nascent and non-volatile particles (defined as particle phase remaining after denuding at 200°C). The mass–mobility exponent ranged between 2.4 and 2.7 for nascent (or undenuded) particles and between 2.5 and 2.7 for non-volatile particles; higher than typical diesel soot. The effective density function was 4278d_m^?0.438 ± 76.3 kg/m³ (for mobility diameter, d_m, in nm) for nascent particles and 3215d_m^?0.395 ± 37.9 kg/m³ for non-volatile particles. The effective density functions of the non-volatile particles were fairly similar for the conditions studied. The uncertainty in using the effective density and mixing state data to determine the mass concentration of the aerosol by integrating mobility size distributions was examined. The uncertainty in mass concentration is minimized when only the non-volatile component is measured. However, the uncertainty in the mass concentration increases substantially if nascent particles are measured due to uncertainties in the particle mixing state and their associated effective densities. Furthermore, transient vehicle operation (cold-starts, accelerations, and decelerations) would likely change the mixing state of the exhaust particles suggesting it is difficult to accurately measure the mass concentration of undenuded GDI exhaust particulate using integrated size distribution methods.

Copyright 2015 American Association for Aerosol Research     

焦化柴油过氧化环己酮氧化脱硫工艺研究

为了满足日趋严格的环保标准及市场对低硫柴油的巨大需求,柴油氧化脱硫技术显得日益重要。实验采用氧化萃取相结合的方法对焦化柴油进行了氧化脱硫实验。以自制过氧化环己酮为脱硫氧化剂,分别考察了氧化剂用量、氧化温度、氧化时间、萃取剂用量和二次萃取对焦化柴油硫含量的影响。结果表明,反应温度为100℃,反应时间3h,氧化剂与柴油的体积比0．04,萃取剂氮一甲基吡咯烷酮与柴油的剂油比为0．5,一级萃取可以脱除焦化柴油中93％的硫化物,柴油回收率达99％。二级萃取,可以脱除焦化柴油中95％的硫化物,柴油回收率为94．5％,硫含量可达到43．6μg·g^-1,小于50μg·g^-1,满足欧Ⅳ标准。     

Particulate Emission Characteristics of a Compression Ignition Engine Fueled with Diesel–DMC Blends

The effect of fuel composition on the combustion characteristics and particulate emissions of a compression-ignition engine fueled with Euro V diesel fuel blended with dimethyl carbonate (DMC) was investigated experimentally. Blended fuels containing 4.48%, 9.07%, 13.78%, and 18.6% by volume of DMC, corresponding to 3%, 6%, 9%, and 12% by mass of oxygen in the blended fuels, were investigated. By analyzing the measured in-cylinder pressure data and the derived heat release rate, it is observed that the addition of DMC increases the ignition delay and the amount of heat release in the premixed combustion duration, but shortens both the diffusive burning duration and the total combustion duration. On the emission side, the smoke opacity, the particulate mass concentration as well as the total number of particulates are all reduced, while the proportion of soluble organic fraction (SOF) in the particulate is increased, by using the blended fuels. The geometric mean diameter of the particles shifts towards smaller size in comparison with that of the diesel fuel. The particulate mass concentration, the total number of particles and SOF can be further reduced by the use of diesel oxidation catalyst (DOC), while the particles shift towards larger geometric mean diameter for each fuel, indicating that the DOC could reduce the finer particles.     

Effect of Waste Cooking Oil Biodiesel on the Properties of Particulate from a DI Diesel Engine

The present work focuses on the effect of waste cooking oil biodiesel on the particulate mass, number concentration, nanostructure, and oxidative reactivity under different engine speeds and engine loads. Particulate samples were collected from the diluted exhaust of a medium-duty direct injection diesel engine and were used to analyze the physico-chemical properties via the transmission electron microscope (TEM) and the thermogravimetric analyzer/differential scanning calorimeter (TGA/DSC). The TEM images reveal that smaller primary particles are formed at higher engine speed, lower engine load, or using biodiesel. Quantitative analysis of the nanostructures indicates more soot with more disordered configuration, in which shorter and more curved graphene layer is prevailing at lower engine load or when using biodiesel. Furthermore, the TGA results infer that the soot oxidative reactivity is closely related to the nanostructure properties and the effect of engine load is more pronounced than the effect of engine speed. Also biodiesel soot has faster oxidative reactivity than diesel soot. Moreover, results obtained for B30 (30% biodiesel and 70% diesel fuel) lie in between those for biodiesel and diesel fuel.

Copyright 2015 American Association for Aerosol Research     

Fluid Dynamics of Fluidized and Vibrofluidized Beds Operating with Geldart C Particles

The fluid dynamic behavior of a vibrofluidized bed operating with Geldart C particles was studied. The experiments were conducted in order to observe the influence of amplitude, frequency, and dimensionless vibration number on the minimum fluidization velocity, pressure drop, and standard deviation obtained. It was noted that the dimensionless vibration number should be used very carefully if it is to be the unique parameter to set the vibrational effect of the bed fluid dynamics. The results clearly indicate that the fluid dynamic behavior of the bed is very dependent on the different combinations of amplitude and frequency for the same dimensionless vibration number. Therefore, the use of the amplitude or frequency of vibration and the dimensionless vibration number is recommended for a better characterization of the vibrational effects on the fluid dynamic behavior of the particle bed.     

Laboratory Evaluation of a Microfluidic Electrochemical Sensor for Aerosol Oxidative Load

Human exposure to particulate matter (PM) air pollution is associated with human morbidity and mortality. The mechanisms by which PM impacts human health are unresolved, but evidence suggests that PM intake leads to cellular oxidative stress through the generation of reactive oxygen species (ROS). Therefore, reliable tools are needed for estimating the oxidant generating capacity, or oxidative load, of PM at high temporal resolution (minutes to hours). One of the most widely reported methods for assessing PM oxidative load is the dithiothreitol (DTT) assay. The traditional DTT assay utilizes filter-based PM collection in conjunction with chemical analysis to determine the oxidation rate of reduced DTT in solution with PM. However, the traditional DTT assay suffers from poor time resolution, loss of reactive species during sampling, and high limit of detection. Recently, a new DTT assay was developed that couples a particle-into-liquid-sampler with microfluidic-electrochemical detection. This “on-line” system allows high temporal resolution monitoring of PM reactivity with improved detection limits. This study reports on a laboratory comparison of the traditional and on-line DTT approaches. An urban dust sample was aerosolized in a laboratory test chamber at three atmospherically relevant concentrations. The on-line system gave a stronger correlation between DTT consumption rate and PM mass (R ² = 0.69) than the traditional method (R ² = 0.40) and increased precision at high temporal resolution, compared to the traditional method.

Copyright 2014 American Association for Aerosol Research     

Temperature Dependence of Gas–Particle Partitioning of Primary Organic Aerosol Emissions from a Small Diesel Engine

A new experimental technique has been developed to study the gas–particle partitioning behavior of primary organic aerosol (POA) emissions from combustion sources at atmospherically relevant concentrations. The technique involves slowly filling a Teflon chamber with a constant emission source. As aerosol concentrations increase inside the chamber, the gas–particle partitioning of semivolatile organics shifts to the particle phase, thus increasing the fuel-based POA emission factor. The technique allows characterization of partitioning under isothermal conditions and atmospherically relevant concentrations. The technique was evaluated using emissions from a small diesel engine; the measured changes in gas–particle partitioning agreed well with previously published data for this engine measured with a dilution sampler. The temperature dependence of the gas–particle partitioning was investigated by conducting experiments at three different temperatures (15°C, 26°C, and 33°C). Increasing organic aerosol concentration and decreasing temperature increased the fuel-based POA emission factor. The gas–particle partitioning data were fit using absorptive partitioning theory to determine the volatility distribution and enthalpy of vaporization (ΔH _v) of the emissions. We have derived two fits; one using the volatility basis set approach and a second using a two-product model. Both fits are suitable for use in chemical transport models. These fits were tested using previously published thermodenuder data. Partitioning calculations predict that the gas–particle partitioning from POA emissions from this engine vary by about a factor of 4 across the atmospherically relevant range of temperature and organic aerosol concentrations. This underscores the semivolatile nature of POA emissions.

Copyright 2012 American Association for Aerosol Research     

Development and Evaluation of On-Board Measurement System for Nanoparticle Emissions from Diesel Engine

This work has focused on the development and evaluation of an experimental set-up to measure in real time and with on-board equipments the particle emissions of diesel vehicle minimizing the uncertainties associated to dilution ratio, the length of the transfer line and the sampling point in the engine exhaust pipe. Its suitability has been verified by ensuring the repeatability of the results in dynamometer tests reproducing standard circuits, as well as in closed circuits and in real urban traffic in Madrid, Spain. The experience derived from this work has been very useful, contributing to the advance in the measurement of particle number and size distribution in real time using on-board equipment and bringing us closer to understanding the relationship between the physical characteristics of the particles emitted by a diesel engine and its operation in real urban traffic conditions. The proposed on-board system has provided very satisfactory results.