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     

Soot differentiation by laser derivatization

Combustion produced soot is highly variable in its composition and nanostructure, both of which are dependent upon combustion conditions. Quantification of high-resolution transmission electron microscopy (HRTEM) images for nanostructure parameters shows that soot nanostructure is dependent upon its source. In principle, this permits identification of the soot and its contribution to any pollution monitoring receptor site. Many structural and chemical aspects are subtle, unaccounted for in direct nanostructure quantification. The process of pulsed laser annealing is demonstrated to enhance slight differences in nanostructure and chemical composition. Chemistry-based limitations imposed due to nanosecond heating and microsecond cooling timescales highlight these initial compositional and structural differences—as dependent upon source-specific formation conditions. This study demonstrates laser-based heating as an analytical tool for soot differentiation by formation conditions/source by identifying operational parameters for optimal derivatization. Nanostructure changes are qualitatively shown using HRTEM and quantified using image-based fringe analysis for real and model soots.

Copyright © 2019 American Association for Aerosol Research     

Influence of waste cooking oil biodiesel on the nanostructure and volatility of particles emitted by a direct-injection diesel engine

To reduce air pollution and the reliance on fossil fuel, biodiesel has been widely investigated as an alternative fuel for diesel engines. The purpose of this study is to investigate the influence of waste cooking oil (WCO) biodiesel on the physical properties and the oxidation reactivity of the particles emitted by a diesel engine operating on WCO biodiesel as the main fuel. Experiments were conducted on a direct-injection diesel engine fueled with biodiesel, B75 (75% biodiesel and 25% diesel on volume basis, v/v), B50, B20, and diesel fuel, at five engine loads and at an engine speed of 1920 rev/min. Particulate samples were collected to analyze the particulate nanostructure, volatility, and oxidation characteristics. Biodiesel or low-load operation leads to smaller primary particles and more disordered nanostructures having shorter and more curved graphene layers. It can be found that particles from biodiesel, blended fuels, or low-load operation have higher volatile mass fractions and faster oxidation reaction rates than particles from diesel or heavy-load operation. The higher oxidation reaction rates are due mainly to the smaller particle size, the more disordered nanostructure, and the higher volatile mass fraction. It is also found that changes in primary particle size and particulate nanostructure are not directly proportional to the biodiesel content, while changes in particulate volatility and particulate oxidation reactivity are proportional to the biodiesel content. The use of biodiesel can enhance particulate oxidation reactivity and the regeneration of soot particles in an after-treatment device.

Copyright © 2016 American Association for Aerosol Research     

Biodiesel combustion in an optical HSDI diesel engine under low load premixed combustion conditions

An optically accessible single-cylinder high-speed direct-injection (HSDI) diesel engine was used to investigate the spray and combustion processes for biodiesel blends under different injection strategies. The experimental results indicated that the heat release rate was dominated by a premixed combustion pattern and the heat release rate peak became smaller with injection timing retardation. The ignition and heat release rate peak occurred later with increasing biodiesel content. Fuel impingement on the wall was observed for all test conditions. The liquid penetration became longer and the fuel impingement was stronger with the increase of biodiesel content. Early and late injection timings result in lower flame luminosity due to improved mixing with longer ignition delay. For all the injection timings, lower soot luminosity was seen for biodiesel blends than pure diesel fuel. Furthermore, NO_x emissions were dramatically reduced for premixed combustion mode with retarded post-TDC injection strategies.     

Biodiesel engine performance and emissions in low temperature combustion

Engine performance and emission comparisons were made between the use of soy, Canola and yellow grease derived B100 biodiesel fuels and an ultra-low sulphur diesel fuel in the high load engine operating conditions. Compared to the diesel fuel engine-out emissions of nitrogen oxides (NO_x), a high-cetane number (CN) biodiesel fuel produced comparable NO_x while the biodiesel with a CN similar to the diesel fuel produced relatively higher NO_x at a fixed start of injection. The soot, carbon monoxide and un-burnt hydrocarbon emissions were generally lower for the biodiesel-fuelled engine. Exhaust gas recirculation (EGR) was then extensively applied to initiate low temperature combustion (LTC) mode at medium and low load conditions. An intake throttling valve was implemented to increase the differential pressure between the intake and exhaust in order to increase and enhance the EGR. Simultaneous reduction of NO_x and soot was achieved when the ignition delay was prolonged by more than 50% from the case with 0% EGR at low load conditions. Furthermore, a preliminary ignition delay correlation under the influence of EGR at steady-state conditions was developed. The correlation considered the fuel CN and oxygen concentrations in the intake air and fuel. The research intends to achieve simultaneous reductions of NO_x and soot emissions in modern production diesel engines when biodiesel is applied.     

Effect of Biofuels on Catalyzed Diesel Particulate Filter Regeneration

Under the terms of the Renewable Energy Directive, EU member states are required to use 10 % of transport energy sourced from renewable sources, mainly biofuels, by 2020. The purpose is to reduce greenhouse gas (GHG) emissions from the transport sector. However, biodiesel used as fuel has a significant impact on emissions, as related by most of the literature on the subject. In particular, nitric oxides (NOx) and particulate matter (PM) emissions from current diesel technologies are critical factors because they are already close to the limits permitted by regulations and both limits will be even more stringent in the near future. Soot particles are trapped on a diesel particulate filter (DPF). If the DPF is catalyzed like in this study, the soot is then burned by reaction with NO₂ (CDPF continuous regeneration) which occurs at lower temperatures than reaction with O₂ (active regeneration). Tests of ultra-low sulfur diesel blended with rapeseed-biodiesel at 30 % (B30) and Fischer–Tropsch diesel (FT30) were conducted. The Fischer–Tropsch diesel was chosen to represent a biomass-to-liquid fuel. This work investigated the impact of these two biofuels on engine polluting emissions and the resulting CDPF ability to regenerate. When compared with similar inlet conditions on a synthetic gas bench, an impact of fuel was observed on soot reactivity: the CDPF loaded with FT30 soot regenerated slightly faster. Engine bench tests were also performed to combine the effects of fuel on engine emissions and soot reactivity and to evaluate the CDPF. The increase in NOx and decrease in PM emissions observed for B30 appeared to significantly improve CDPF continuous regeneration by NO₂.     

A Low-Waste Process for the Production of Biodiesel

Abstract

The acceptance of methylesters (biodiesel) as an alternative fuel has rapidly increased in recent years. This development has been followed by increasing research activities in the field of methylester processes. After listing reasons that supporte arguments for biodiesel and a survey of production methods, a low-waste process for biodiesel is introduced.     

Morphology and Raman Spectra of Engine-Emitted Particulates

The morphology and nanostructure of soot from different engines were studied. The soot samples were collected from a 1.9 L Volkswagen light-duty diesel (LDD) engine for two different fuel types [ultralow sulfur diesel (ULSD) and B20] and six speed/load combinations, as well as from a heavy-duty engine using a pilot-ignited high-pressure direct-injection (HPDI) natural-gas combustion system for three different speed/load combinations.

Transmission electron microscopy (TEM) was employed to investigate the soot morphology by using alternative fractal measurement methods. The fractal dimensions (D_f ) were computed from the scaling of the projected aggregate dimensions with the number of primary particles (“LW” method) and two-dimensional pair correlation functions. For the soot collected from the LDD, it was found that the fractal dimensions are independent of fuel type, while a higher engine load slightly decreased D_f . The soot produced by the HPDI exhibited a similar correlation between D_f and engine load. The fractal dimension of the engine-emitted soot was measured in a range of 1.70–1.85 and the fractal prefactor k_fLW of 1.08–1.39.

Raman spectroscopy was used to characterize the soot nanostructure based on the degree of microstructural disorder. The Raman spectral analysis was done using two-band (“G” at ～1578 and “D” at ～1340 cm^?1) and five-band (G, D1, D2, D3, and D4 at about 1580, 1350, 1500, 1620, and 1200 cm^?1 respectively) combinations. For the soot sampled from the LDD, the results from both methods showed that B20 soot exhibited a greater structural disorder. Likewise, the Raman analysis of the soot from both engines also showed that the increase in engine load condition caused increases in the degree of the structural order of soot. The use of either D/G ratio or D1 width cannot distinguish between the HPDI and the LDD soot. However, on a plot of D/G versus D1, the data fall into distinct clusters. This may indicate the importance of using more than two spectral parameters to characterize the soot samples.     

Decrease in Epoxy Composition Combustibility After Laser Treatment

Abstract

The influence of a preliminary CO₂?laser radiation treatment on the epoxy composition combustibility has been studied. This method of polymer surface modification is shown to provide a considerable decrease in polymer combustibility. The maximum effect is observed when an aromatic hardener is used.     

Dependence of biodiesel fuel properties on the structure of fatty acid alkyl esters

Biodiesel, defined as the mono-alkyl esters of vegetable oils or animal fats, is an “alternative” diesel fuel that is becoming accepted in a steadily growing number of countries around the world. Since the source of biodiesel varies with the location and other sources such as recycled oils are continuously gaining interest, it is important to possess data on how the various fatty acid profiles of the different sources can influence biodiesel fuel properties. The properties of the various individual fatty esters that comprise biodiesel determine the overall fuel properties of the biodiesel fuel. In turn, the properties of the various fatty esters are determined by the structural features of the fatty acid and the alcohol moieties that comprise a fatty ester. Structural features that influence the physical and fuel properties of a fatty ester molecule are chain length, degree of unsaturation, and branching of the chain. Important fuel properties of biodiesel that are influenced by the fatty acid profile and, in turn, by the structural features of the various fatty esters are cetane number and ultimately exhaust emissions, heat of combustion, cold flow, oxidative stability, viscosity, and lubricity.     

A comprehensive experimental investigation of combustion and heat release characteristics of a biodiesel (hazelnut kernel oil methyl ester) fueled direct injection compression ignition engine

In the present study, hazelnut (Corylus avellana L.) kernel oil was transesterified with methanol using potassium hydroxide as catalyst to obtain biodiesel and a comprehensive experimental investigation of combustion (cylinder gas pressure, rate of pressure rise, ignition delay) and heat release (rate of heat release, cumulative heat release, combustion duration and center of heat release) parameters of a direct injection compression ignition engine running with biodiesel and its blends with diesel fuel was carried out. Experiment parameters included the percentage of biodiesel in the blend, engine load, injection timing, injection pressure, and compression ratio. Results showed that hazelnut kernel oil methyl ester and its blends with diesel fuel can be used in the engine without any modification and undesirable combustion and heat release characteristics were not observed. The modifications such as increasing of injection timing, compression ratio, and injection pressure provided significant improvement in combustion and heat release characteristics.     

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     

Effect of EGR and injection timing on combustion and emission characteristics of split injection strategy DI-diesel engine fueled with biodiesel

In this study, the effect of injection timing and EGR rate on the combustion and emissions of a Ford Lion V6 split injection strategy direct injection diesel engine has been experimentally investigated by using neat biodiesel produced from soybean oil. The results showed that, with the increasing of EGR rate, the brake specific fuel combustion (BSFC) and soot emission were slightly increased, and nitrogen oxide (NO_x) emission was evidently decreased. Under higher EGR rate, the peak pressure was slightly lower, and the peak heat release rate kept almost identical at lower engine load, and was higher at higher engine load. With the main injection timing retarded, BSFC was slightly increased, NO_x emission was evidently decreased, and soot emission hardly varied. The second peak pressure was evidently decreased and the heat release rate was slightly increased.     

Characterization of Soot Aerosol Produced from Combustion of Propane in a Shock Tube

The knowledge of yields and properties of soot from combustion of hydrocarbon fuels is crucial for accurate evaluation of the impacts of primary aerosols on air quality and climate. This study presents measurements of soot generated from combustion of propane in a shock tube, using independently adjustable fuel equivalence ratio (φ), temperature, and pressure. The characterization of soot yields inside the shock tube by in situ laser extinction is complemented with a set of comprehensive measurements of soot transferred into a fluoropolymer chamber, including particle size distributions, elemental carbon (EC) mass fraction, effective density, mass fractal dimension (Dfm), dynamic shape factor (χ), and optical properties. The properties of soot particles and the soot yield are sensitive to combustion conditions and the duration of the combustion experiment. High-temperature combustion with φ = 2.5 produces small fractal (Dfm = 2) soot particles composed mainly of EC (up to 90%), at a low mass yield. Particles from lower temperature combustion contain a significant fraction of organic material (～50%). Using rich fuel mixtures (φ = 4.0 and 8.0) significantly increases particle size and soot mass yield. At lower temperatures, compact (Dfm = 3) and nearly spherical (χ = 1.1) aggregates with high organic content are formed, whereas at higher temperatures, the particles are fractal and closely resemble those obtained using φ = 2.5. Single scattering albedo (SSA) varies from 0.15 for fractal particles to 0.75 for compact particles. For soot generated at high equivalence ratios, SSA can be used as a proxy for particle morphology and EC content.

Copyright 2012 American Association for Aerosol Research     

Potential for reducing emissions in a diesel engine by fuelling with conventional biodiesel and Fischer-Tropsch diesel

A gas-to-liquid (GTL) fuel derived from Low Temperature Fischer-Tropsch process has been tested in an automotive diesel engine fulfilling Euro 4 emissions regulations. Both regulated and non-regulated emissions have been compared with those of a commercial diesel fuel, a commercial biodiesel fuel and a GTL-biodiesel fuel (30% and 70% v/v, respectively) in order to check blending properties, synergistic effects and compatibility between first and second generation production technologies for biofuel consumption in current diesel engines. After presenting a detailed literature review, and confirming that similar efficiencies are attained with the four tested fuels under identical road-like operating conditions (this meaning fuel consumption is inversely proportional to their heating values), significant reductions in smoke opacity, particulate matter emissions and particle number concentration were observed with both GTL and biodiesel fuels, with small changes in NO_x emissions. Compared with the reductions in PM emissions derived from the use of biodiesel fuels, those derived from using GTL fuels were quite similar, despite its lower soot emissions reductions. This can be explained by the lower volatile organic fraction of the PM in the case of GTL. By adequately blending both fuels, a considerable potential to optimise the engine emissions trade-off is foreseen.     

Crystallisation kinetics of hydroxyapatite thin films prepared by sol-gel process

Abstract

Abstract

In this study, the crystallisation of nano hydroxyapatite (HA) films on stainless steel 316L was studied. The film was prepared by sol-gel technique. The process was started with preparation of an HA sol. After aging of the sol at room temperature, a stainless steel 316L substrate was dip coated and then was heat treated from 350 to 450°C at different periods of time in air. The crystallisation behaviour and the transformation-temperature-time diagram of HA films were achieved and analysed using the avrami equation. The results showed that the crystallisation of HA began at 250°C and was increased up to 450°C. The obtained HA film showed a nanostructure character with a suitable crystalinity after heat treatment.     

Analysis of oxidized biodiesel by 1H‐NMR and effect of contact area with air

Biodiesel is continuously gaining attention and significance as an alternative diesel fuel. An important issue facing biodiesel is fuel stability upon exposure to air due to its content of unsaturated fatty acids. Numerous factors influence the oxidative stability of biodiesel, and several methods for its assessment have been developed. In the present work, a defined amount of biodiesel (methyl soyate) was heated in open beakers, with the only difference being the size of the beaker, i.e. the surface area of the biodiesel exposed to air. Biodiesel oxidized in this fashion was analyzed by ¹H‐NMR, kinematic viscosity and acid value. Acid values and kinematic viscosity increased with time and surface area. A previously developed ¹H‐NMR procedure was used to evaluate the unsaturation and “residual” fatty acid composition. The amounts of saturated fatty acids determined by this method increased, with monounsaturated and diunsaturated species increasing and then decreasing with time. After “flash” (3 h, 165 °C) oxidation, NMR shows the greatest effect on saturates and compounds with two double bonds, the former increasing and the latter decreasing. The double bond originally located at δ15 in 18:3 is largely retained, showing that other double bond positions in 18:3 are initially affected by oxidation. The methyl ester signal decreases, coinciding with the increase in acid value. An increasingly strong absorption was observed in the UV‐VIS spectra. Increasing surface area accelerated oxidation and affected fatty acid composition.     

A novel miniature inverted-flame burner for the generation of soot nanoparticles

Lab-scale soot nanoparticle generators are used by the aerosol research community to study the properties of soot over a broad range of particle size distributions, and number and mass concentrations. In this study, a novel miniature inverted-flame burner is presented and its emitted soot particles were characterized. The burner consisted of two co-annular tubes for fuel and co-flow air and the flame was enclosed by the latter. The fuel used was ethylene. A scanning mobility particle sizer (SMPS) and an aerodynamic aerosol classifier (AAC) were used to measure mobility and aerodynamic size distribution of soot particles, respectively. Particle morphology was studied using transmission electron microscopy (TEM). The elemental carbon (EC) and organic carbon (OC) content of the soot were measured using thermal-optical analysis (TOA). The burner produced soot particles with mobility diameter range of 66–270?nm, aerodynamic diameter range of 56–140?nm, and total concentration range of 2?×?10⁵–1?×?10⁷?cm^?3. TEM images showed that most soot particles were sub-micron soot aggregates. Some soot superaggregates, typically larger than 2?µm in length, were observed and their abundance increased with ethylene flow rate. TOA showed that the concentration of EC in the generated soot increased with ethylene flow rate, and the soot was observed to have high EC fraction at high ethylene flow rates. The miniature inverted-flame burner was demonstrated to produce soot nanoparticles over a range of concentrations and sizes with high EC content, making it a practical device to study soot nanoparticle properties in different applications.

Copyright © 2019 American Association for Aerosol Research     

Impact of Fe Content in Laboratory-Produced Soot Aerosol on its Composition,Structure, and Thermo-Chemical Properties

Soot aerosol, which is a major pollutant in the atmosphere of urban areas, often contains not only carbonaceous matter but also inorganic material. These species, for example, iron compounds, originated from impurities in fuel or lubricating oil, additives or engine wear may change the physico-chemical characteristics of soot and hence its environmental impact. We studied the change of composition, structure, and oxidation reactivity of laboratory-produced soot aerosol with varying iron content. Soot types of various iron contents were generated in a propane/air diffusion flame by adjusting the doping amount of iron pentacarbonyl Fe(CO)₅ to the flame. Scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX) was combined with cluster analysis (CA) to separate individual particles into definable groups of similar chemical composition representing the particle types in dependence of the iron content in soot. Raman microspectroscopy (RM) and infrared spectroscopy were applied for the characterization of the graphitic soot structure, hydrocarbons, and iron species. For the analysis of soot reactivity, temperature-programmed oxidation (TPO) was used. It is demonstrated that iron is most dominantly present in the form of amorphous Fe (III) oxide crystallizing to hematite α-Fe₂O₃ upon thermal treatment. Iron contaminations do not change the soot microstructure crucially, but Fe(CO)₅ doping of the flame impacts hydrocarbon composition. Soot oxidation reactivity strongly depends on the iron content, as the temperature of maximum carbon (di)oxide emission T _max follows an exponential decay with increasing iron content in soot. Based on the results of the thermo-chemical characterization of laboratory-produced internally mixed iron-containing soot, we can conclude that iron-containing combustion aerosol samples cannot be characterized unambiguously by current thermo-optical analysis protocols.

Copyright 2012 American Association for Aerosol Research     

Experimental investigation of laminar LPG–H2 jet diffusion flame with preheated reactants

This paper presents an experimental investigation of the effect of H₂ addition on flame length, soot free length fraction (SFLF), flame radiant fraction, gas temperature and emission level in LPG–H₂ composite fuel jet diffusion flame for two preheated cases namely, (i) preheated air and (ii) preheated air and fuel. Results show that the H₂ addition leads to a reduction in flame length which may be caused due to an increased gas temperature. Besides this, the flame length is also observed to be reduced with increasing reactants temperature. The soot free length fraction (SFLF) increases as H₂ is added to fuel stream. This might have been caused by decrease in the C/H ratio in the flame and is favorable to attenuate PAH formation rate. Interestingly, the SFLF is observed to be reduced with increasing reactants temperature that may be due to reduction in induction period of soot formation caused by enhanced flame temperature. Moreover, the decreased radiant heat fraction with hydrogen addition is pertinent with the reduction in soot concentration level. The reduction in NO_x emission level with H₂ addition to the fuel stream is also observed. On the contrary, NO_x emission level is found to be enhanced significantly with reactant temperature that can be attributed to the increase in thermal NO_x through Zeldovich mechanism.