• Energy Research

Abstract Direct injection spark ignition (DISI) engines have been widely used in passenger cars due to their lower fuel consumption, better controllability, and high efficiency. However, DISI engines are suffering from wall wetting, imperfect mixture formation, excess soot emissions, and cyclic variations. Applying a new fuel atomization technique and using biofuels with their distinctive properties can potentially aid in improving DISI engines. In this research, the effects of isobutanol and 2-butanol and their blends with Toluene Primary Reference Fuel (TPRF) on spray characteristics, DISI engine combustion, and particle number (PN) emissions are investigated for conditions with and without flash boiling of the injected fuel. Spray characteristics are investigated using a constant volume chamber. Then, the combustion, flame propagation, and PN emissions are examined using an optical DISI engine. The fuel temperature is set to 298 K and 453 K for liquid injection and flash boiling injection, respectively. The tested blending ratio is 30 vol% butanol isomers and 70 vol% TPRF. The results of the spray test reveal that liquid fuel plumes are distinctly observed, and butanol blends show a slightly wider spray angle with lower penetration length compared to TPRF. However, under flash boiling injection, the sprays collapse towards the injector axis, forming a more extended single central vapor jet due to the plumes' interaction. Meanwhile, butanol blends yield a narrow spray angle with more extended penetration compared to TPRF. The flame visualization test shows that the flash boiling injection reduced yellow flames compared to liquid fuel injection, reflecting the improvements in mixture formation. Thus, improvements were noted in the heat release and PN emissions. Butanol addition reduced the PN emissions by 43% under regular liquid injection. Flash boiling injection provided an additional 25% reduction in PN emissions.

Abstract Pool fire and fuel-rich combustion have been considered the primary soot/particulate matter sources for gasoline direct injection (GDI) engines, which is a crucial issue for commercial and passenger vehicles. Flash boiling atomization, achieved by heating the fuel before injection, can notably improve spray atomization and reduce the occurrence of pool fire, thus reduce soot emission under extreme conditions. This investigation compared the performance of subcooled spray combustions and flash boiling spray combustions with the use of an optical engine facility. The optical engine was equipped with an optical liner so that side views of the combustion can be captured with a high-speed color camera. The high-speed measurement data from early injection conditions were then analyzed with the HSV color model to investigate the flame characteristics in the premixed, infrared, and diffusion flame regions. Indicated mean effective pressure (IMEP) and particulate number (PN) under different conditions were also analyzed under different conditions. It was found that the combustion performance using flash boiling sprays is superior to that using subcooled sprays, and the difference between the two combustion modes was discussed with the use of the flame model.

AbstractIn this study, an experimental investigation was conducted to assess the combustion and emissions of a single cylinder diesel engine using water injection in the exhaust manifold. Water is injected into the exhaust manifold and by opening the exhaust valve during the intake stroke, the injected water, and exhaust gases are reentered the engine cylinder then mixed during the intake and compression stroke and participated in the combustion process. The purpose of this injection strategy is to utilize the exhaust gases enthalpy to evaporate water before combustion to reduce soot and NOx emissions without decrease combustion temperature. The results show that water injection leads to increase in the cylinder pressure, apparent heat release rate (AHRR) in premixed combustion phase and, the ignition delay comparing with EGR without water injection. The indicated mean effective pressure (IMEP) for EGR without water injection is lower than conventional diesel combustion with 14%. However, with water injection, the IMEP increased with 11% comparing to EGR without water injection. NOx emissions reduced up to 85% comparing to conventional diesel combustion due to the EGR effect. Soot concentration increased dramatically with EGR. However, with water injection, soot emissions reduced by up to 40% but still higher than conventional diesel combustion.

Abstract In current work, ultrasonicator was used to produce Castor Oil Methyl Ester (COME) from raw castor oil to properly reduce the production period. GC-MS and FT-IR analyses were used to confirm the conversion of raw oil into esters. Blended fuel of COME and diesel fuel with blending ratio up to 40% (symbolized as B40) were used to experimentally investigate the influence of COME blending ratio on diesel engine combustion and on engine emissions flow as per ISO 8718 steady state test cycle. The in-cylinder pressure records were applied through zero-dimensional thermodynamic model to compute the variation of heat release rate and accumulated heat released. Results of engine measurements revealed that (i) best effective utilization of fuel energy is attained for B30, (ii) best fuel economy with best brake thermal efficiency was identified for B20, and (iii) lowest emission flow of nitrogen oxides (NOx), carbon monoxide (CO), and unburned hydrocarbons (HC) with lowest calculated particulate matter (PM) were observed for B10 while minimum opacity level in engine exhaust was attained for B30. It can be concluded that, B20 would be recommended to get the best engine mechanical performance and emission characteristics with slight deterioration in the in-cylinder combustion parameters.

Agricultural residues receive significant attention worldwide as a sustainable and green energy source. The accurate assessment of agricultural residues’ energy potential depends on physicochemical properties that change with location and climate. Several studies provide an imprecise estimation of agricultural residues’ energy potential in Egypt based on characteristics in literature from other sites. This study investigates the physicochemical properties, pyrolysis, and kinetics of seven types of agricultural residues, namely corn stalks, switchgrass, okra stems along with ficus, camphor, desert olive, and blueberry tree woodchips sampled from several locations in Egypt. The thermogravimetric, differential thermal, proximate, ultimate, lignocellulosic constituents, kinetics, crystallinity, and microstructure analyses are used to characterize the biomass. Kinetic parameters were determined by applying Coats-Redfern and Direct-Arrhenius approaches. The results revealed that woody residues have higher volatile matters, energy contents, hemicellulose, and lignin with lower ash, moisture, and cellulose than herbaceous residues. The activation energies of woody residues are lower than that of switchgrass and okra stems but higher than Cornstalks. The tested residues are bulk with nonuniform crystal structures, and their usages require further processing. The woody residues have promising properties. This study facilitates the accurate assessment of the agricultural residues’ energy potential in Egypt.

Abstract The effect of ethanol/water blends addition on diesel fuel combustion and emissions is investigated experimentally in this study using optical diagnostics. Basic study is performed using rapid compression machine (RCM) under CI conditions. The tested ethanol energy fractions varied in the range of 10–40% of the total added fuel energy, while water volume ratios varied in the range of 10–40% of the injected ethanol. Ethanol and water were evaporated before entering the combustion chamber to eliminate their endothermic effect. Results reveal that addition of ethanol/water blends to diesel fuel results in longer ignition delay and promote the apparent heat release rate (AHRR) at the premixed combustion phase compared to absolute ethanol addition. Additionally, soot and NOx emissions are reduced with ethanol/water addition compared to absolute ethanol addition and neat diesel combustion. The basic study is then extended to investigate the effect ethanol/water blends addition on diesel fuel combustion using single cylinder diesel engine. Waste heat in exhaust manifold is utilized to vaporize ethanol/water blends before combustion. Results reveal that ethanol/water blends injection leads to increase in peak cylinder pressure, indicated mean effective pressure (IMEP), and AHRR at premixed combustion phase. Additionally, the ignition delay increased with ethanol/water addition. NOx emission is decreased up to 88% along with a reduction in soot by 50%. The lower ethanol to water volume ratios show better combustion efficiency, IMEP, NOx and soot emissions compared to the higher ethanol to water volume ratios. The addition of water to ethanol leads to longer ignition delay and lower soot concentrations compared to absolute ethanol. Additionally, water addition reduces the flame temperature, which leads to NOx reduction.

AbstractDiesel engines play a vital role in the transportation sector. Ternary blends of alcohol, biodiesel, and diesel have the potential to improve diesel engine combustion and emissions. In the current work, three different types of alcohols; n‐butanol, n‐heptanol, and n‐octanol were added to biodiesel/diesel blends to improve diesel engine performance, combustion, and emissions. The biodiesel was produced from used frying oil (UFO) by ultrasonic enhanced transesterification to achieve the highest yield, lowest viscosity, and minimum production time. Three ternary fuels containing 10 vol% (n‐butanol or n‐heptanol or n‐octanol), 10 vol% UFO biodiesel, and 80 vol% diesel were tested using diesel engine at 25%, 50%, and 75% load conditions. Thermogravimetric analysis of the ternary blends proved the enhancement in the vaporization characteristics compared with biodiesel and diesel fuels; the lighter the alcohol, the faster the vaporization rate but with longer ignition delay which enhanced the premixed burning mode. The specific fuel consumption increased by up to 6% with a slight reduction in thermal efficiency (≈1%) when n‐octanol was used while n‐butanol and n‐heptanol showed comparable values to neat diesel. Ternary blends showed a reduction in smoke opacity, NOx, CO, and CO2 by up to 38%, 11%, 35%, and 14% compared with diesel, while the lowest emissions were attained for the addition of n‐heptanol.

Abstract The combination of distinctive physicochemical properties of biofuels and recent engine technologies offer benefits in terms of efficiency improvement and emissions reduction. The recent development in butanol bio-based production pathways encourage researchers to study their combustion characteristics. This paper experimentally evaluates the combustion and emissions of a gasoline direct injection (GDI) engine fueled with the butanol isomer/gasoline surrogate blends, in which primary reference fuel (PRF) and toluene primary reference fuel (TPRF) are selected as the gasoline surrogates, respectively. The flame propagation behaviors, in-cylinder pressure, apparent heat release rate, along with PN emissions from this optical GDI engine are discussed. First, butanol addition to the gasoline surrogates is found to slow down flame propagation, reduce peak cylinder pressure and heat release rate, and extend ignition delay and combustion duration. Further, among the four butanol isomers, n-butanol and tert-butanol are the most and least reactive fuels, respectively, whereas iso-butanol and sec-butanol show reactivities in between, as supported by the measured flame propagation and pressure traces, calculated heat release rates, as well as time scales describing the combustion progress, e.g. ignition delay and combustion duration. Finally, butanol addition reduces the PN emissions from the GDI engine, and the PN emissions reduction capacity of the four butanol isomers ranks as sec-butanol > iso-butanol > n-butanol > tert-butanol. Also, compared to the PRF/butanol blends, the PN emissions are reduced to a less extent when butanol is blended with TPRF.