Impact of lower and higher alcohols on the physicochemical properties of particulate matter from diesel engines: A review

Does distance from the vehicle headlight change the properties of particulate matter?

Understanding factors affecting particulate matter (PM), particularly light exposure from vehicle headlights, is essential for addressing air quality challenges. However, no comprehensive studies are available. This research, therefore, aims to investigate whether light produced by the vehicle headlight (Halogen type; 12V-55w) at various distances (120 cm, 70 cm, and 20 cm) for 1 hr affects the physical and thermal features of PM obtained from a gasoline vehicle at idle speed. The findings indicate that light can significantly change the properties of PM, especially at a close distance of 20 cm. However, as the distance increases, the effectiveness of light decreases, showing almost no impact at 120 cm. At 20 cm, PM shows higher primary particle diameters (42.1 %), core size/particle size ratio (15.2 %), fringe separation distance (12.4 %), low-volatile substances (9.4 %), non-volatile substances (21.4 %), heat required for 5 %, 50 %, and 95 % reductions in PM mass (14.4 %, 41.7 %, and 13.7 %, respectively), and frequency factor (80.3 %), as well as lower shell size/core size ratio (17.4 %), fringe length (9.9 %), PM mass (21.4 %) and high-volatile substances (8.1 %) compared to no light condition. While, fractal dimension, mean radius of gyration, length/width ratio, roundness, fringe tortuosity, soot ignition temperature, and activation energy are almost identical.

Impact of neem oil biodiesel blends on physical and chemical properties of particulate matter emitted from diesel engines

The global searchlight for sustainable alternative fuels to reduce emissions produced from the combustion of fossil fuels illuminates biofuels owing to their matching properties with fossil fuels. This is the impetus for this study which systematically examines the impact of neem biodiesel (NB) blends with pure diesel on the physical and chemical properties of particulate matter (PM) from diesel engines. Pure diesel (B0) and four fuel blends, namely, B5, B10, B15 and B20 are examined. The impact of NB blends on the physical and chemical properties of PM is studied using a single-cylinder, 4-stroke diesel engine. The PM captured directly from the diesel engine at two standard engine speeds is analyzed by physical microscopy techniques and chemical analyses. Comparing the results of gaseous emissions for B0 with those of B20, it is found that B20 decreases CO by 9.6% and 19.3% at low and high engine speeds, respectively, but increases NOX. Regarding PM emission, in comparison to B0, B20 decreases particle sizes from 59.4 ± 8.5 nm to 42.8 ± 4.2 nm and 63.3 ± 8.1 nm to 43.7 ± 5.2 nm; opacities from 15.9% to 9.3% and 21.1%-11.4%; carbon contents from 66.53% to 44.53% and 72.53%-61.99%; and total carbon concentrations (total organic carbon and total inorganic carbon) from 3.6120 mg/L to 1.8435 mg/L and 2.5970 mg/L to 1.6002 mg/L at low and high engine speeds, respectively. Furthermore, B20 increases the unused oxygen content from 14.07% to 21.47% and 16.82%-18.42%; oxygen reactivity from 1.80 ± 0.08 to 2.75 ± 0.18 and 1.10 ± 0.20 to 1.35 ± 0.06; and volatile substances by 68.4% and 57.1% at low and high engine speeds, respectively. This study demonstrates that NB could be a potential alternative fuel for diesel engines regarding PM emissions, where B20 blend has the highest impact on PM properties, but it needs additional NOx mitigation strategies.

Effect of adding dimethyl carbonate and gasoline to diesel fuel + corn oil blend on performance and combustion characteristics of a diesel engine

Diesel fuel and corn oil are mixed in the 80:20 volumetric ratio. Dimethyl carbonate and gasoline are added to diesel fuel + corn oil blend in 4:96, 6:94, 8:92, and 10:90 volumetric ratios to obtain ternary blends. Effects of ternary blends on the performance and combustion characteristics of a diesel engine are investigated under different engine speeds (1000-2500 rpm). 3D Lagrange interpolation method is applied to measured data of dimethyl carbonate blends to predict the engine speed, blending ratio, and crank angle giving maximum peak pressure and peak heat release rate. On average, dimethyl carbonate blends and gasoline blends show 4.3642-12.1578% and 1.0323-8.6843% reduction in effective power, and 1.4938-3.4322% and 4.3357-8.7188% reduction in effective efficiency, respectively, relative to diesel fuel. On average, there is a reduction in cylinder peak pressure (4.6701-7.3418%; 4.0457-6.2025%) and peak heat release rate (0.8020-4.5627%; 0.4-1.2654%) for dimethyl carbonate blends and gasoline blends, respectively, compared to diesel fuel. Because of low relative errors (1.0551% and 1.4553%), 3D Lagrange provides well accuracy in the prediction of maximum peak pressure and peak heat release rate. On average, dimethyl carbonate blends produce less CO (7.4744-17.5424%), HC (15.5410-29.5501%) and smoke (14.1767-25.2834%) emissions, compared with diesel fuel.

Physical properties and structural characteristics of particulate matter emitted from a diesel engine fueled with biodiesel blends

This research explores the influence of renewable fuels, including three kinds of biodiesel along with ethanol on the physical properties and structural characteristics of particulate matter (PM) emitted from a diesel engine in comparison with pure diesel. After adding 10 vol% of grape seed biodiesel, coffee biodiesel and eucalyptus oil into diesel, three biodiesel blended fuels (10% grape seed biodiesel (DGs10), 10% spent coffee ground biodiesel (DC10) and eucalyptus oil biodiesel (DEu10)) were produced and tested in this study. Besides, one ethanol blend containing 9 vol% of ethanol and 1 vol% of biodiesel (blend stabilizer) was also tested to do the comparison. In the present study, scanning transmission electron microscope (STEM) and scanning electron microscope (SEM) were employed for analyzing the microstructure, nanostructure and electron diffraction pattern of PM. Raman spectrometer (RS) was also used for the analysis of structural characterization of PM. In addition, several experimental instruments like microbalance, measuring cup, viscometer, oxygen bomb calorimeter and Gas Chromatography-Mass Spectrometer (GC-MS) were employed to detect the fuel properties, including density, heating value, viscosity, composition and cetane number. A conclusion can be drawn that both biodiesel blends and ethanol blend have a changing effect on the PM properties compared to pure diesel, where biodiesel blends have a slightly weaker influence than ethanol blend. Regarding the biodiesel blends, DGs10 has more impact than DC10 and DEu10 in changes of PM properties, particularly in the reduction of PM mass, making it a good candidate for renewable fuel for diesel engines.

Advances in soot particles from gasoline direct injection engines: A focus on physical and chemical characterisation

With an increasing market share of gasoline direct injection (GDI) vehicles, high particulate emissions of GDI engines are of increasing concern due to their adverse impacts on both human health and the ecological environment. A thorough understanding of GDI nanoparticulate properties is required to develop advanced particulate filters and assess the exhaust toxicity and environmental impacts. To this end, this paper aims to provide a comprehensive review of the physical and chemical characteristics of GDI nanoparticles from a distinctive perspective, including soot oxidation reactivity, morphology, nanostructure, surface chemistry, chemical components, and their correlations. This review begins with a brief description of nanoparticle characterisation methods. Then, the nanoparticle characteristics of GDI engines are reviewed with the following aspects: in-cylinder soot, exhaust particulate features, and a comparison between GDI and diesel nanoparticles. Previous studies showed that exhaust nanoparticle presents a more stable nanostructure and is less prone to oxidation if compared with in-cylinder soot. Additionally, GDI particles are less-ordered, more inorganic and metallic containing, and more reactive than diesel particles. Afterwards, the impacts of engine operating parameters and aftertreatments on GDI soot features are discussed in detail. Finally, the conclusions and future research recommendations are presented.

Improvement of the combustion, emission, and stability features of diesel-methanol blends using n-decanol as cosolvent

This research endeavored to boost the applicability of methanol in CI engines utilizing n-decanol as cosolvents. The work was split into binary phases. Firstly, the stabilities of pure methanol (M100) and hydrous-methanol (MH10), with diesel as a reference fuel, were examined applying various temperatures: 10 °C, 20 °C, and 30 °C. The findings showed that the M100-diesel and MH10-diesel combinations were unstable. Thus, n-decanol was utilized as a cosolvent. Following by the engine combustion and emissions characteristics were evaluated by manipulating three proportions of M100-diesel mixtures with n-decanol. Three mixtures comprised of 5, 10, and 15% M100 with 20% n-decanol, which are denoted as M5, M10, and M15, correspondingly. These combinations were assessed via thermogravimetric assessment, and their physicochemical properties were assessed corresponding to the ASTM. The maximum in-cylinder pressure, heat release rate, and pressure rise rate diminished by 10, 11, and 10%, respectively, for the M100/diesel/n-decanol combinations compared with the diesel oil. The brake thermal efficiency lowered by 10%, whereas the brake specific fuel consumption enlarged by 10% for the combinations compared with the diesel. NO_x and smoke opacity levels diminished by about 30 and 50%, respectively, whereas the CO and UHC enlarged by about 50 and 60% for the blends compared with the diesel oil.

Advanced Biofuels from ABE (Acetone/Butanol/Ethanol) and Vegetable Oils (Castor or Sunflower Oil) for Using in Triple Blends with Diesel: Evaluation on a Diesel Engine

From a technical and economic point of view, our aim is to provide viable solutions for the replacement of fossil fuels which are currently used in internal combustion diesel engines. In this research, two new biofuels composed of second-generation vegetable oils (SVO),used oil sunflower (SO) or castor oil (CO), and the ABE blend (acetone/butanol/ethanol) were evaluated. ABE is an intermediate product from the fermentation of carbohydrates to obtain bio-butanol. Besides, the ABE blend exhibits suitable properties as biofuel, such asvery low kinematic viscosity, reasonable energy density, low autoignition temperature, and broad flammability limits. Diesel/ABE/SVO triple blends were prepared, characterized and then, tested on a diesel engine, evaluating power output, consumption, and exhaust emissions. The power output was slightly reduced due to the low heating values of ABE blend. Also, engine consumed more fuel with the triple blends than with diesel under low engine loads whereas, at medium and high loads, the fuel consumption was very similar to that of diesel. Regarding exhaust gas emissions, soot wasnotably reduced, and nitrogen oxides (NO_x) and carbon monoxide (CO₂) emissions were lower or comparable to that of diesel, while the CO emissions increased. The use of these biofuels allows the replacement of high percentagesof diesel without compromising engine power and achievinga significant reduction in pollution emissions. Furthermore, a notable improvement in cold flow properties of the fuel blends is obtained, in comparison with diesel.

Physical, chemical, and cell toxicity properties of mature/aged particulate matter (PM) trapped in a diesel particulate filter (DPF) along with the results from freshly produced PM of a diesel engine

The lifetime and efficiency of diesel particulate filters (DPFs) strongly depend on the proper and periodic cleaning and servicing. Unfortunately, in some cases, inappropriate methods are applied to clean the DPFs, e.g., using air compressors without proper disposal procedures which can have negative impacts on human health, the environment, and DPF's efficiency. However, there is no information available about the properties of this kind of PM. This research is therefore presented to explore the physicochemical and toxicity properties of aged PM trapped in a DPF (using compressed air for PM sampling) employing STEM, SEM, EDS, Organic Carbon Analyzer, TGA/DSC, and Raman Spectrometer for investigating the physicochemical properties, and assays of cell viability, cellular reactive oxygen species (ROS), interleukin-6, and tumor necrosis factor-alpha (TNF-α) for investigating the toxicity properties. Also, analyses from fresh PM samples from the diesel vehicle at two engine speeds are presented. It is found that at a certain/fixed PM number/mass for all three samples tested, the PM from DPF compared with the fresh PM can have both positive (particularly having the lowest water-soluble total carbon ratio) and negative impacts on human health (particularly having the highest cell death rate of 13.4%, ROS, and TNF-α) and the environment.

Physicochemical and cell toxicity properties of particulate matter (PM) from a diesel vehicle fueled with diesel, spent coffee ground biodiesel, and ethanol

The literature shows that information about the physical, chemical, and cell toxicity properties of particulate matter (PM) from diesel vehicles is not rich as the existence of a remarkable number of studies about the combustion, performance, and emissions of diesel vehicles using renewable liquid fuels, particularly biodiesels and alcohols. Also, the PM analyses from combustion of spent coffee ground biodiesel have not been comprehensively explored. Therefore, this research is presented. Pure diesel, 90% diesel + 10% biodiesel, and 90% diesel + 9% ethanol + 1% biodiesel, volume bases, were tested under a fast idle condition. STEM, SEM, EDS, Organic Carbon Analyzer, TGA/DSC, and Raman Spectrometer were employed for investigating the PM physical and chemical properties, and assays of cell viability, cellular reactive oxygen species, interleukin-6, and tumor necrosis factor-alpha were examined for investigating the PM cell toxicity properties. It is found that the application of both biodiesel and ethanol has the potential to change the PM properties, while the impact of ethanol is more than biodiesel on the changes. Regarding the important aspects, biodiesel can be effective for better human health (due to a decrease in cell death (-60.8%)) as well as good diesel particulate filter efficiency (due to lower activation energy (-7.6%) and frequency factor (-83.2%)). However, despite a higher impact of ethanol on the reductions in activation energy (-24.8%) and frequency factor (-99.0%), this fuel causes an increase in cell death (84.1%). Therefore, biodiesel can be an appropriate fuel to have a positive impact on human health, the environment, and emissions catalysts performance, simultaneously.

Effects of Propanol on the Performance and Emissions of a Dual-Fuel Industrial Diesel Engine

The search for alternative fuels that can limit the use of traditional fossil fuels to power internal combustion engines is one of the main tasks faced by both the modern automotive industry and the modern energy industry. This paper presents experimental tests of a compression ignition engine, in which the conventional fuel, i.e., diesel, was partially replaced with propyl alcohol, i.e., a renewable biofuel. Studies on the co-combustion of diesel fuel with propanol were carried out, in which the energy share of alcohol varied from 0 to 65%. The research showed that an increase in the proportion of propanol, up to 30%, resulted in a significant increase in the rate of heat release and the rate of pressure increase in the cylinder of a compression-ignition engine. Increasing the alcohol content to 65% resulted in an increase in the ignition delay time and significantly shortened the duration of combustion. During the combustion of diesel fuel with a 50% propanol share, the engine was characterized by maximum efficiency, higher than diesel fuel combustion by 5.5%. The addition of propanol caused a slight deterioration of the combustion stability determined by the coefficient of variation for IMEP. The study of engine exhaust emissions has shown that the combustion of diesel fuel with a small proportion of propanol, up to 30%, causes an increase in nitrogen oxide emissions, while up to 50% contributes to a decrease in HC emissions. The increased share of alcohol contributed to a significant decrease in the emissions of both carbon monoxide and carbon dioxide, and caused a significant reduction in the concentration of soot in the exhaust of the compression-ignition engine.

Experimental and Kinetic Studies of Ethylene Glycol Autoignition at High Temperatures

As one of the simplest polyols with chemical properties of alcohol, ethylene glycol is considered as a renewable energy source and a model fuel for pyrolysis oil. In this work, autoignition characteristics of ethylene glycol have been investigated behind reflected shock waves. Experiments were conducted at pressures of 2, 5, and 10 atm, equivalence ratios of 0.5, 1.0, and 2.0, and temperatures ranging from approximately 1200 to 1600 K. The fuel concentration was also varied. Results show that the ignition delay time increases with decreasing the pressure or fuel concentration. A strong positive dependence upon the equivalence ratio was found. A quantitative relationship has been yielded by the regression analysis of the experimental data. Simulations were carried out using chemical kinetic mechanisms available in the literature to assess the reliability of mechanism. Reaction pathway and sensitivity analysis confirmed the importance of H-abstraction reactions in ethylene glycol oxidation process. Finally, a comparison between ethylene glycol and ethanol ignition was conducted. Ethylene glycol ignites faster than ethanol because of the early accumulation of H and OH radicals in the oxidation of ethylene glycol.

Impact of carbon chain length of alcohols on the physicochemical properties and reactivity of exhaust soot

Particle is the main pollutant in diesel engine exhaust, which seriously endangers human health and the atmospheric environment. The use of alcohol fuels in diesel engines can effectively reduce particle emissions, but alcohol fuels with different carbon chain lengths will affect the generation process of particles, which in turn changes the physicochemical properties and oxidation characteristics of the particles. Therefore, it is particularly important to study the properties of particle emitted by diesel engines fueling alcohol fuels with different carbon chain lengths. The physicochemical properties of soot emitted from commercial diesel engines were studied by thermogravimetric analyzer, HRTEM (high-resolution transmission electron microscopy), and XPS (X-ray photoelectron spectroscopy) in this paper, respectively. The diesel engine used alcohol-diesel blends of different carbon chain lengths with the same oxygen content as fuels, such as methanol/diesel blend (M10), n-butanol/diesel blend (NB25), and n-octanol/diesel blend (NO45), and pure diesel fuel was used as a reference. The results showed that the use of alcohols reduced the fractal dimension (D_f) of particles, and the NB25 particles had the smallest D_f. Moreover, the particles of blended fuels had smaller primary particle diameter (d_p) compared to pure diesel. However, with the use of short-chain to long-chain alcohols, an increasing tendency of d_p was observed. In terms of the nanostructure, as the use of short-chain to long-chain alcohols, the L_a (fringe length) increased, both the d (fringe separation distance) and T_f (fringe tortuosity) reduced, which was not favorable for the oxidation of the particles. In addition, in terms of oxygenated surface functional groups (SFGs), the CO group occupied a higher proportion in most working conditions relative to the groups of CO and COO. Further analysis showed that the d_p and nanostructure had more influence on the oxidation behavior of soot than D_f and oxygenated SFGs.

Why is the world not yet ready to use alternative fuel vehicles?

Despite the improvement in technologies for the production of alternative fuels (AFs), and the needs for using more AFs for motor vehicles for the reductions in air pollution and greenhouse gases, the number of alternative fuel vehicles (AFVs) in the global transportation sector has not been increasing significantly (there are even small drops for adapting some AFs through the projections) in recent years and even in the near future with projections to 2050. And gasoline and diesel fuels will remain as the main energy sources for motor vehicles. After reviewing the latest advantages and disadvantages of AFVs, including flexible-fuel, gas, electric, hybrid electric, and fuel cell electric vehicles, it is found that the higher price of AFVs, compared to that of gasoline and diesel vehicles, might be one of the main barriers for their wider adoption. But on the other hand, there is the "chicken and egg" problem. Because people mostly do not select AFVs due to their higher price and sometimes their less infrastructure availability compared to those of gasoline and diesel vehicles, however, governments and AFVs manufacturers claim that the insignificant demand volume and less interest by people to purchase them, is one of the main reasons for a higher price and less infrastructure availability of AFVs. So, what should we do for adopting AFVs? This review shows that there are two very important and fundamental points that might cause a rise in the demand and usage of AFVs, rather than waiting for the reduction in AFVs prices. Those points are car salespeople's and people's knowledge about AFVs and the environmental issues, and their encouragement to accept and use AFVs. Although the AFVs are available on the market for many years, many people around the world have no/less/old/wrong knowledge about the current AFVs. Thus, most of these people reject these vehicles for usage, even when their important parameters such as purchase price, operating cost, driving range, and fuel availability be the same (or close) as those of gasoline or diesel vehicles. Detailed information, examples, and recommendations to the increases in people's knowledge and encouragement are presented in this review.