Hybrid Fuels Research Articles

Autoignition of premixed hydrogen/air mixtures with uniformly dispersed carbon particles

The autoignition of a stoichiometric hydrogen/air mixture laden with uniformly distributed coal char particles is simulated with the Eulerian-Lagrangian approach under isochoric conditions. A zero-dimensional model is adopted to assess the effects of gas temperature, pressure, particle diameter, and concentration on ignition dynamics. Increasing the initial temperature reduces the ignition time and maximum heat release rate of the homogeneous reactions, while the parameters for particle reactions stabilize after reaching a critical temperature. Initial pressure exhibits a non-monotonic influence on gas phase ignition, with higher pressures promoting particle autoignition. An increase in particle diameter decreases the ignition time for the homogeneous reaction, approaching that of particle-free conditions. Meanwhile, particle ignition time first decreases and then linearly increases. Increasing particle concentration reduces the interphase disparities of ignition times, while the two-phase ignition times rapidly rise after exceeding the critical concentration. Moreover, pre-ignition temperature equilibrium (PTE) significantly impacts the ignition parameters and processes. PTE results in a minimal ignition time disparity between the gas and particles, with coal char particles markedly influencing hydrogen ignition. Failure to reach PTE leads to significant two-phase ignition time differences, with negligible impact from the solid phase on gas phase ignition. The particle effect ratio, δ, is introduced to evaluate these effects. Notably, the evolution variations in ignition time and heat release rate are determined by the existence of the PTE under corresponding initial conditions. The findings of this study are crucial for developing strategies to mitigate explosion hazards and enhance the performance of detonation propulsion systems using hybrid fuels.

A review of the application development and key technologies of rotary engines under the background of carbon neutrality

Rotary engines possess advantages such as light weight, high power density, and strong fuel adaptability, which are essential for powertrain systems. They hold great potential in the field of power machinery. However, the development of rotary engines has been constrained by increasingly stringent emission regulations. Despite this, numerous scholars and institutions continue to optimize rotary engines, leading to a proliferation of related research. It is necessary to synthesize these findings to guide future promotion and application efforts. This review examines the current applications and development status of rotary engines globally. It summarizes the development of key technologies such as sealing techniques, rotor configurations, and ignition devices, which have achieved lower energy consumption and emissions. The suitability of rotary engines for automotive and unmanned aerial vehicle applications has also been reported. To further reduce carbon emissions, researchers have explored zero-carbon fuel rotary engines. Hydrogen-fueled rotary engines have demonstrated higher combustion efficiency. By integrating EGR, load control strategies, and ignition system layouts, they have addressed issues such as NOx emissions, knock, and leakage. The development of ammonia-hydrogen hybrid fuels is also a potential effective solution. Continuous innovative research indicates that, with their inherent advantages and the integration of alternative fuels and advanced ignition technologies, rotary engines have the potential to meet future energy and environmental requirements. This positions them as strong contenders in future diversified power systems.

Hydro-co-processing Jatropha oil and crude oil blend with Ni-Mo-supported Al2O3 catalyst to produce hybrid fuels: the effect of catalyst particle size

Hydro-co-processing Jatropha oil and crude oil blend with Ni-Mo-supported Al2O3 catalyst to produce hybrid fuels: the effect of catalyst particle size

Biodiesel production from eggshells derived bio-nano CaO catalyst–Microemulsion fuel blends for up-gradation of biodiesel

The utilization of bio-oil derived from biomass presents a promising alternative to fossil fuels, though it faces challenges when directly applied in diesel engines. Microemulsification has emerged as a viable strategy to enhance bio-oil properties, facilitating its use in hybrid fuels. This study explores the microemulsification of Jatropha bio-oil with ethanol, aided by a surfactant, to formulate a hybrid liquid fuel. Additionally, a bio-nano CaO heterogeneous catalyst synthesized from eggshells is employed to catalyse the production of Jatropha biodiesel from the microemulsified fuel using microwave irradiation. The catalyst is characterized through UV–Vis, XRD, and SEM analysis. The investigation reveals a significant reduction in CO, CO2, and NOX emissions with the utilization of microemulsion-based biodiesel blends. Various blends of conventional diesel, Jatropha biodiesel, and ethanol are prepared with different ethanol concentrations (5, 10, and 20 wt%). Engine performance parameters, including fuel consumption, NOX emission, and brake specific fuel consumption, are analyzed. Results indicate that the conventional diesel/Jatropha biodiesel/ethanol (10 wt%) blend exhibits superior performance compared to conventional diesel, Jatropha biodiesel, and other blends.The fuel consumption of the conventional diesel/Jatropha biodiesel/ethanol (10 wt%) blend is measured at 554.6 g/h, surpassing that of conventional diesel and other biodiesel blends. The presence of water (0.14 %) in the blend reduces the heating value, consequently increasing the energy requirement. CO and CO2 emissions for the conventional diesel/Jatropha biodiesel/ethanol (10 wt%) blend are notably lower compared to conventional C-18 hydrocarbons and various biodiesel blends. These findings accentuate the efficacy of the microemulsion process in enhancing fuel characteristics and reducing emissions. Further investigations could explore optimizing the emulsifying agents and their impact on engine performance and emission characteristics, contributing to the advancement of sustainable fuel technologies.

Kinetics for the highly selective hybrid and cleaner diesel production by hydro-co-processing of a Jatropha curcas L. oil and gas oil blend using a supported Ni-W/Al-SBA-15 sulfided catalyst

ABSTRACT This work reports the kinetics for the hydro-co-processing of a Jatropha curcas L. oil and gas oil mixture using a sulfided NiO(5.5%)-WO3(25%)/Al(0.05)-SBA-15 catalyst at 360–420°C, 6 MPa of initial H2 pressure, and 4 h of reaction time. It was found that more than 47% of a diesel-like fraction could be obtained due to the HDO of the vegetable oil, and the HDS and HCK of the sulfured and heavier compounds in the gas oil within the mixture. HDO was the most favored reaction, followed by HDS and HCK due to HDO rates were two times higher than those for HDS, demonstrating that oxygen removal was influenced by H2S production during HDS. Accordingly, 96% of the oxygen compounds and 24% of the sulfured compounds were removed during hydro-co-processing. Finally, the intrinsic properties (acidity and metallic character) influenced HCK reactions due to 52.9% of the heavier fraction in the reaction mixture was readily hydroconverted into lighter hydrocarbons. Hence, lighter, cleaner and hybrid fuels can be obtained by hydro-co-processing technologies with the sulfided NiO(5.5%)-WO3(25%)/Al(0.05)-SBA-15 catalyst at reaction temperatures below 400°C to avoid thermal cracking.

Effect of Hybrid Fuels of Aqueous Ammonia, Dimethyl Ether, Biodiesel and Diesel Fuel on Thermal Performance of Diesel Engine

Effect of Hybrid Fuels of Aqueous Ammonia, Dimethyl Ether, Biodiesel and Diesel Fuel on Thermal Performance of Diesel Engine

A Taguchi-based hybrid multi-criteria decision-making approach for optimization of performance characteristics of diesel engine fuelled with blends of biodiesel-diesel and cerium oxide nano-additive

Given the pressing demand and ongoing necessity for fossil fuels, there is an imperative to actively seek alternative resources to replace petroleum-based fuels. The presents study considers a problem of experimentally investigating the effect of varying levels of important input parameters of a diesel engine fuelled with a novel blend of biodiesel-diesel and cerium oxide nano-additive on the sustainable performance characteristics of a diesel engine. Four input parameters, i.e., blend percentage (B in %), nanoparticle concentration (NPC in ppm), engine load (LD in %) and ignition pressure (IP in bar) each at four levels are considered. Experiments are conducted as per the Taguchi’s L16 standard orthogonal array and for each experiment, performance parameters (such as Brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC)), emission measures (Carbon monoxide (CO), oxides of nitrogen (NOx), unburnt hydrocarbons (UBHC) and Vibration level (VL)) of the diesel engine are collected. A hybrid multi-criteria decision-making (MCDM) approach, i.e., integrated MEREC-MARCOS method along with signal-to-noise (S/N) ratio and analysis of mean (ANOM) is employed to determine optimal setting of the input parameters that yield optimal multiple performance characteristics. The results reveal that B at 40%, NPC at 80 ppm, LD at 50% and IP at 200 bar is the optimal setting of the input parameters that produce optimum values of the output responses considered simultaneously. Further, results of the analysis of variance (ANOVA) show that Nanoparticle concentration percentage contribution is the maximum (79.63%) followed by engine load (8.40%), ignition pressure (6.28%), and blend percentage (2.11%). The optimization results are: BTE is 32.87%, BSEC is 0.285, CO is 0.018%, NOx is 559.6 ppm, UBHC is 28.1 ppm and VL= 19.57m2/sec which were validated with a confirmation test. Henceforth, such hybrid fuels provide sustainable energy solutions and environmental conservation simultaneously addressing the current and future demands.

Quantitative Analysis of Biodiesel Adulterants Using Raman Spectroscopy Combined with Synergy Interval Partial Least Squares (siPLS) Algorithms

Biodiesel has emerged as an alternative to traditional fuels with the aim of reducing the impact on the environment. It is produced by the esterification of oleaginous seeds, animal fats, etc., with short-chain alcohols in an alkaline solution, which is one of the most commonly used methods. This increases the oxygen content (from the fatty acids) and promotes the fuel to burn faster and more efficiently. The accurate quantification of biodiesel is of paramount importance to the fuel market due to the possibility of adulteration, which can result in economic losses, engine performance issues and environmental concerns related to corrosion. In response to achieving this goal, in this work, synergy interval partial least squares (siPLS) algorithms in combination with Raman spectroscopy are used for the quantification of the biodiesel content. Different pretreatment methods are discussed to eliminate a large amount of redundant information of the original spectrum. The siPLS technique for extracting feature variables is then used to optimize the input variables after pretreatment, in order to enhance the predictive performance of the calibration model. Finally, the D1-MSC-siPLS calibration model is constructed based on the preprocessed spectra, the selected input variables and the optimized model parameters. Compared with the feature variable selection methods of interval partial least squares (iPLS) and backward interval partial least squares (biPLS), results elucidate that the D1-MSC-siPLS calibration model is superior to the D1-MSC-biPLS and the D1-MSC-iPLS in the quantitative analysis of adulterated biodiesel. The D1-MSC-siPLS calibration model demonstrates better predictive performance compared to the full spectrum PLS model, with the optimal determination coefficient of prediction (R2P) being 0.9899; the mean relative error of prediction (MREP) decreased from 9.51% to 6.31% and the root--mean-squared error of prediction (RMSEP) decreased from 0.1912% (v/v) to 0.1367% (v/v), respectively. The above results indicate that Raman spectroscopy combined with the D1-MSC-siPLS calibration model is a feasible method for the quantitative analysis of biodiesel in adulterated hybrid fuels.

A comparative study on the effect of nano-additives on performance and emission characteristics of CI engine run on castor biodiesel blended fuel

Biodiesel is a promising alternative fuel because of its renewable status, biodegradability, non-toxicity, and low pollution levels. However, other limitations such as high viscosity, low thermal energy content, poor atomization, greater densities, and higher (NOx) exhaust emissions hinder its adoption as a prospective diesel alternative. The current study focuses on comparing and analyzing the performance and emission effects of introducing single and hybrid cerium oxide (CeO2) and aluminum oxide (Al2O3) nanoparticles to a fuel blend of 20 % castor biodiesel and 80 % diesel (CB20) made from castor seed oil. The pulsed plasma in liquid technique, a straightforward one-step procedure, was used to create cerium oxide (CeO2) nanoparticles. When Al2O3 nanoparticles were added to the CB20, the cylinder pressure and rate of heat release increased. Therefore, in this study single and hybrid cerium oxide (CeO2) and aluminum oxide (Al2O3) nanoparticles are introduced. The tests were conducted on a single cylinder compression ignition engine at varied engine speeds between 1250 and 3200 rpm while keeping a constant engine load. Using a water bath and sonication, two concentrations of the nanoparticles—80 and 100 ppm—were introduced to the fuel blends, along with Tween 80 and span 80 surfactants to improve blend stability. Different tested fuel samples, including pure diesel CB0, CB20, CB20C100, CB20C80, CB20A100, CB20A80, CB20A40C40, and CB20A50C50, were examined for their physiochemical properties, such as density, viscosity, cloud point, pour point, flash point, and fire points, as well as engine performance parameters, including torque, power, fuel consumption, BTE, and EGT. CB20A50C50 and CB20A40C40 both had an average brake power that was higher than diesel fuel by 6.14 % and 1.25 percent, respectively. The average brake-specific fuel consumption decreased by 3.21 % to 8.29 % when using hybrid and single nano-additive blended fuels compared to CB20. CB20A50C50 exhibited a 20.38 % higher brake thermal efficiency than CB20. Notably, CB20C100 showed a 29.52 % reduction in HC and a 38.32 % reduction in CO, while CB20A50C50 demonstrated a 10.24 % decrease in NOx compared to CB20. Overall, the results of this study indicate that the generated fuel blends combining castor biodiesel and aluminum oxide/cerium oxide nanoparticles hold promise as alternate fuels for diesel engines, with positive impacts on engine performance and emissions.

Quality assessments, performance, and emissions evaluation of biodiesel from citrullus lanatus oil seeds and diesel blends in compression ignition engine

AbstractDue to limited stock of levels of fossil fuel resources and ecological issues, biodiesel is becoming an attractive alternative choice for replacing conventional fuels. Biodiesel can be used by mixing with different fuels like citrullus lanatus seeds, camphor, cleaner fuel injector, sunflower, safflower, soybean, cottonseed, rapeseed, palm, Jatropha, and Moringa oil seeds.This paper reviews use of biofuels blended with citrullus lanatus seeds. The citrullus lanatus biodiesel was mixed with diesel in different percentages by volume. Some physico‐chemical characteristics of blends and pure diesel were investigated and it was established that it conforms to the American Society of Testing Materials (ASTM) standards. The exceptions were the viscosity and specific gravity of the pure biodiesel B100 which were 0.09 and 0.018 mm2/s above the ASTM standard, respectively. All blends were run on a stationary 4‐cylinder diesel engine at 70% loading and speeds of 1500, 2000, and 2500 rpm. It was deduced that B10 gave the best brake power, thermal efficiency, and optimum specific fuel consumption at a speed of 2500 rpm. B15 gave the highest brake mean effective pressure. B25 and B100 gave the least values of brake power and brake thermal efficiency across the speeds. B100 gave the highest brake specific fuel consumption. Furthermore, the exhaust emission gases such as CO2, CO, NOx, and HC in different engine conditions stated above were recorded and analyzed. It was found that B25 emitted about 53% lesser CO2 and 37% lesser CO as compared to pure diesel with zero HC at 2500 rpm. The blends were better in terms of engine performance and also in reduction of emissions in most cases, than pure diesel fuel.Problem statement: Various emissions from engines like unburnt hydro carbons, particulate emissions, NOx, and CO have bad effects on ecology. This work presents an overview on use of novel hybrid fuels in compression ignition engines with an aim of mitigating effects of emissions on environment. Biodiesel was blended with Citrullus lanatus oil and pure diesel in different proportions to see effects on performance of diesel engines. The presented work may pave the way for use of alternative cheap and environmentally friendly fuels in automotive systems.

Ignition delay and performance of sorbitol based hypergolic hybrid fuels

The ignition delay of ammonia-borane-doped sorbitol and paraffin-based fuel pellets exposed to white fuming nitric acid is measured in oxidizer drop tests. Various mixtures of sorbitol, paraffin and ammonia-borane are tested to investigate the effect of sorbitol concentration on the ignition behavior of hypergolic hybrid fuels. High-speed visible, Schlieren, and mid-infrared imaging techniques are used to study the ignition behavior in a non-intrusive manner. The experiments demonstrate that the ignition flame appears faster and is larger with fuel pellets made of sorbitol compared to those made of paraffin. Sorbitol pellets containing 10 percent ammonia-borane by mass ignited in 8.20 ms on average, while paraffin pellets containing 10 percent ammonia-borane ignited in 60.25 ms. The average ignition flame intensity was measured to be approximately 6 times greater in sorbitol-based pellets than in paraffin-based ones. Ignition delay and oxygen bomb calorimeter tests are also performed using aged pellets and showed that exposure to ambient air negatively impacts the storage stability of sorbitol-based fuel samples. Theoretical performance calculations revealed that sorbitol-ammonia-borane mixtures can reach density-specific impulses similar to those of paraffin-ammonia-borane mixtures. This makes sorbitol-ammonia-borane a rare hypergolic hybrid fuel that is liquefying while also having high propulsive density and a very short ignition delay.

Combustion enhancement and soot reduction of kerosene-based fuel under engine-relevant conditions enabled by fuel reactivity modulation

Liquid fuels incorporating biomass components (e.g., bio-alcohols) offer a great potential for improving combustion performance and energy efficiency. However, the insufficient reactivity and Leidenfrost effect of these fuels are two long-standing challenges for its stable combustion under wide engine-relevant conditions. Herein, the effect of methoxydiethylborane (MDEB) on the spray combustion characteristics promotion of kerosene and binary kerosene/ethanol-based fuels is reported, where the suppression of Leidenfrost effect under air conditions is demonstrated. The synergistic effect of MDEB on oxidation heat release and active radical formation not only enable the resultant kerosene/ethanol-based suspended droplets to present high evaporation rate (∼44 % reduction in evaporation time), excellent ignition performance, e.g., elevating ignition reliability and ignition delay time dropping to 1051 ms (∼67 % reduction) at an ambient temperature of 820 °C, and soot reduction property (few residual black particles displayed in suspension unit) compared to neat fuel droplet, but also make single kerosene-based hybrid fuels exhibit improved atomization and jet combustion characteristics. Notably, the negative growth behavior of evaporation time associated with the Leidenfrost effect that is dominated by low thermal conductivity air and local fuel vapor layer can be eliminated by introducing MDEB. Further, the jet dynamic reflects the improvement of gas phase diffusion and fuel–air mixing in jet and radial directions, and the increased flame propagation rate and heat transfer efficiency, which highlights the applicability of fuel reactivity modulation strategy for the enhancement of combustion stability under wider engine-relevant conditions. The findings thus provide a promising way to engineering scalable liquid fuels for advanced aviation engines, and realizing pollutants control for efficient energy conversion and management.

Carbon footprint prediction considering the evolution of alternative fuels and cargo: A case study of Yangtze river ships

For reducing carbon emissions in the shipping sector, application of alternative low-carbon and zero-carbon fuels is the consensus. However, requirements of economic development cannot be ignored while focusing on emission reduction. Cargo development is an important prerequisite. Considering the cargo growth as a novelty, a method to calculate the annual carbon emissions of different alternative fuel-powered ships in different cargo growth prospects and power scenarios is proposed. With respect to the time dimension, the relationship between alternative fuels, cargo, and carbon reduction is revealed. The Yangtze River bulk carrier case was studied and the life cycle carbon emission analysis of diesel, LNG hybrid, LNG, hydrogen, methanol, and ammonia were carried out. The annual carbon curves of the high, steady, and low cargo growth prospects were obtained for different scenarios of the power system structure. The results show that LNG hybrid, LNG and methanol fuels are currently the suitable choices. Their life cycle carbon emissions were reduced by 31.5–38.1% compared with those of diesel power. The carbon emissions of green hydrogen and green ammonia were reduced by 78.8% and 91.3%, respectively, compared with those of hydrogen and ammonia. The carbon reduction results of green fuels in their initial application were explored which are at 0.6–10.8%. In addition, there is a balanced annual growth rate, whose annual carbon curve will be steady under its corresponding scenario of power system structure, which could help the ship owners plan their future.

Analysis of thermal stability and characterization of paraffin-blended hybrid fuels

PurposeThe purpose of this study is to investigate the physical, chemical and thermal characteristics of paraffin-blended fuels to determine their suitability as fuel in hybrid rockets.Design/methodology/approachWax fuels are viable and efficient alternatives to conventional rocket fuels, having excellent structural strength and thermal and mechanical properties. The authors report a study of the morphological, chemical and thermal properties of paraffin wax with and without additives for use as fuels in hybrid rockets. Scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy were used for the morphological and chemical characterizations of the fuel blends. The thermal stability and combustion characteristics were assessed under an atmosphere of nitrogen by the simultaneous application of thermogravimetry and differential scanning calorimetry techniques.FindingsThe melting temperatures for pure paraffin and other formulations were around 61°C as seen in differential scanning calorimetry experiments. Variations in the compositions of monoesters, n-alkanes, fatty acids, carboxylic acids methyl and hydroxyl esters in the fuel samples were assessed using Fourier transform infrared spectroscopy. The assessment criterion was chosen as the relative content of carbonyl groups, and the ratio of the stretching vibration of the C–C bonds to the deformation vibration of the aliphatic carbon–hydrogen bonds was taken as the basis for the quantitative calibration. The crystal phases identified by X-ray diffraction were used to identify nonlinear chemicals and alkane lengths. Scanning electron microscopy validated homogeneity in the paraffin-blended samples.Originality/valueThis study presents the thermal stability and other relevant characteristics of fuel formulations comprising unconventional blends.

Integration of stabilized bio-oil in light cycle oil hydrotreatment unit targeting hybrid fuels

Fast pyrolysis bio-oil requires upgrading in order to be used as an intermediate refinery stream as it contains various acids, oxygenates, heavy compounds and water. This work examines the potential of integrating the organic phase (called BioMates) of a hydrotreated pyrolysis bio-oil as a reliable intermediate refinery stream to be co-processed with a light cycle oil (LCO) towards the production of hybrid fuels. Three blends of BioMates with LCO were fed in a hydroprocessing pilot plant (10/90, 20/80 and 30/70 v/v BioMates/LCO). The dedicated tests aimed to study the BioMates effect on the LCO hydrodesulphurization performance, hydrogen consumption, product quality and catalyst life. The results have confirmed that over 85% per weight of the final product is between 60 and 360 °C boiling range and exhibit favorable fuel properties. The technology can process up to 30% per volume BioMates in LCO without any significant technical limitation, while reducing the hydrogen consumption up to 8.9%. Finally, based on the findings, no clogging or permanent loss of catalyst effectiveness was observed after 37 days on stream.

SIMULATION STUDY OF BREAKUP AND ATOMIZATION CHARACTERISTICS OF GASOLINE-ETHANOL (GASHOLS) FUEL BLENDS

To meet the increasingly stringent constraints on mobile and point emissions in the wake of the dwindling fortunes of fossil fuels, evaluation of hybrid fuels for application in combustion engines has become an imperative, especially in the third world countries. This paper presents, modeling of atomization characteristics of gasoline-ethanol fuel blends. Fuel breakup models and correlations between flow patterns and droplet characteristics were adopted and implemented in OpenFOAM Computational Fluid Dynamics (CFD) modeling suite for direct gasoline injector using a simple cylindrical mesh structure at constant volume. The Rosin Rammler distribution model was used to generate the number of spray particles injected into the cylinder. The spray modeling and atomization employed the use of blob sheet model and Kelvin-Helmholtz-Rayleigh-Taylor (KH-RT) model while the numerical technique for simulating atomization process by CFD included the use of governing equations such as Eulerian for gas phase, Lagrangian for disperse phase and turbulence modeling. The effects of fuel blends, injection pressure, ambient gas pressure and spray cone angle were evaluated on the axial spray tip penetration, spray width, and overall Sauter Mean Diameter (SMD). The SMD was seen to be affected by varying the degree of injection cone angle. The spray tip penetration lengths were larger for higher injection cone angles while higher penetration lengths were obtained at higher injection pressures. One salient conclusion drawn from the modeling is that as the number of particle increased, the density of clusters became smaller.

On promoted combustion stability of kerosene/ethanol blends at wide low temperatures: Fuel reactivity improvement and Leidenfrost effect suppression

Despite the progress in interpretation of Leidenfrost effect suppression for heat transfer enhancement, a knowledge gap still exists in explaining its effects on low-temperature combustion of practical fuels that is heat-related. Here, the effect of the enhancer methoxydiethylborane (MDEB) on the combustion promotion of kerosene/ethanol-based fuels at low temperatures was investigated, where a strategy combining combustion pathway regulation and heat release enhancement is proposed. The deformation of MDEB/kerosene/ethanol droplets induced by vigorous boiling helps destroy the stable indirect thermal contact and thus, decrease the evaporation time (∼49% maximum reduction) and shortens the ignition delay time (IDT), compared with neat kerosene/ethanol. The two-stage negative temperature coefficient behavior of IDT is effectively controlled and ultimately eliminated with the ascending of the MDEB proportion. This is due to a new channel driven by the formation of alkoxy (RO) radicals, which promotes the oxidation of MDEB/kerosene/ethanol hybrid fuels and the accompanying oxidation heat release, and subsequently, boosts the yield of active radicals, involving peroxy (ROO), hydroperoxyalkyl (QOOH) and hydroxyl (OH) radicals. The flammable temperature limit and IDT decrease from 580 °C and 1330 ms for pure 85% RP-3 kerosene/15% ethanol (K85/E15) to 115 °C and ∼ 25 ms for MDEB/K85/E15, respectively, which fulfills the low-temperature reliable and rapid start-up regardless of Leidenfrost effect. Further, the combustion behavior shows that MDEB/K85/E15 combusts completely with blue flame instead of numerous soot, which should be dominated by the self-supplying oxygen or easy oxidation characteristics of the enhancer. The findings therefore open up a new way for promoting combustion stability of kerosene/ethanol blends for aviation engines, and for pollutants control at lower temperatures.

Enhanced low-temperature stable combustion of hydrocarbon with suppressing the Leidenfrost effect

Low-temperature stable combustion of liquid hydrocarbons helps improve energy efficiency and alleviate environmental pollution. However, when hydrocarbons (mainly saturated ones) are used as aircraft fuel, they show a long ignition delay time (IDT) and high ignition temperature as a result of Leidenfrost effect and chemical inertness of the CH bond. In especial, the insulated fuel vapor film due to the Leidenfrost effect that inhibits the heat transfer efficiency in the wide Leidenfrost region is unfavorable. Herein, we first propose a strategy that combines low-temperature self-oxidation and enhanced heat conduction to achieve low-temperature stable combustion of hydrocarbon while suppressing the Leidenfrost effect. Specifically, moderately reactive organometallic compound methoxydiethylborane (MDEB) with special radicals and silver nanoparticles (Ag NPs) with high thermal conductivity are preferred as fuel modifiers. By thermodynamic calculation, the heat released by the self-oxidation of MDEB is two orders of magnitude higher than the evaporation latent heat of n-decane, suggesting the applicability of energy conversion supported by enhancing fuel reactivity in suppressing the Leidenfrost effect. Ignition experiment results show that the negative temperature dependence associated with the Leidenfrost effect is eliminated under the specific fuel composition. Encouragingly, compared with n-decane, the IDT of MDEB/Ag/n-decane hybrid fuel is reduced from 4027 to ∼10 ms at a surface temperature of 600 °C. Comparing the ignition of MDEB/Ag/n-decane and MDEB/n-decane hybrid fuels at same temperatures, the influence of Ag NPs on IDT is highlighted by its significant decrease (∼28%). The minimum ignition temperature of n-decane-based hybrid fuel decreases to 112 °C, which is 508 °C lower than that of n-decane. These two ignition characteristic values are the low limit of saturated hydrocarbons to date. Our results thus provide a promising tool for enhancing the low-temperature ignition reliability and combustion stability of liquid hydrocarbons, which potentially decreases the pollution from the low temperature combustion.

Producing hybrid fuels by hydrotreating Jatropha curcas L. and gasoil mixtures in a batch reactor

The co-processing of Jatropha curcas L oil (JC) and gasoil in mixtures of 20:80 and 50:50 volume percentages, respectively, was carried out in a batch reactor by using a commercial NiMo/Al2O3 (5wt%) catalyst at 750 rpm, 70 bar of initial pressure and 80/100 mesh particle size. The effect of temperature (370-390 °C) at fixed reaction time of 4 h in the oxygen and sulfur removals were followed with Fourier Transform Infrared Spectroscopy, Proton Nuclear Magnetic Resonance and Energy Dispersive X-ray Fluorescence Spectroscopy. Also we use simulated distillation to determine the boiling point distributions. It was found that 98 and 99 % conversions of vegetable oils were obtained for 20 and 50 vol% JC feedstocks and similar ∼ 83 and 87 % hydrodesulfuration (HDS) conversions for both fossil-vegetable mixtures at 380 and 390 °C. However at 370 °C the attained HDS conversion was more than 10% lower in mixture with 50 vol% JC. Regarding boiling point distributions, yields averaging 58 vol% and 70 vol% of cut with boiling range 157-343 °C, were obtained with 20 vol% and 50 vol% JC feed mixtures, respectively.

Combustion and exergy investigation of a compression ignition engine fueled with ethanol and methanol blends

Today, the use of hybrid fuels in internal combustion engines has been considered to decrease the level of environmental pollutants. Among the various additives used to increase the efficiency and decrease pollution of Compression Ignition (CI) engines, alcohols especially methanol and ethanol have a special place. In this work, a one-dimensional, thermodynamic and two-zone model was used to evaluate the performance and emission of a compression ignition engine using ethanol and methanol in two volumes of 5% and 10% with diesel fuel by using engineering software such as GT-Power. Also, an exergy assessment is performed to study the exergy efficiency and exergy destruction of the engine for desired cases. The results show that the use of diesel fuel with alcoholic compounds reduces the heating value of the fuel compared to the D100 as well as the maximum brake torque and power and significantly reduces the engine exhaust emissions. This reduction is at most equal to 15%, which is of particular importance with respect to pollutants such as and CO. The exergy analysis shows that addition of alcoholic compounds such as ethanol and methanol by 5% and 10% to diesel fuel reduces braking power, it also reduces input exergy, which decreases exergy destruction and decreases the exergy efficiency by a maximum of 1.1%.