Comparison of ignition,injection and micro - Explosion characteristics of RP-3/ ethanol and biodiesel / ethanol mixed drops

The ignition, injection, and micro-explosion characteristics of aviation fuel (RP-3)/ethanol mixed droplets and biodiesel/ethanol mixed droplets at different proportions under high temperature conditions (420 °C) were compared using an experimental setup. A device for measuring small droplet volumes was designed using an infusion set and different types of needles, and a corresponding equation was established. Mixed droplets suspended on high-temperature resistance nichrome wire with a diameter of 0.2 mm were heated by sending them to a position approximately 2 mm from the forklift preheating plug using a moving rail. SLR and high-speed cameras were used to observe the flame structure as well as the injection and micro-explosion of the mixed droplets during combustion, respectively. Expansion, injection, and micro-explosion were observed in the biodiesel/ethanol mixed droplet experiments when the biodiesel content was 60%. Although the micro-explosion of mixed droplets of aviation fuel/ethanol was not observed, expansion and ejection of the droplets were observed. Image Pro-plus software was used to calculate the diameters at different times in the combustion cycle of the droplets. Through this analysis, the occurrence of micro-explosion was described, and a model for the calculation of micro-explosion strength was established.     

Enhancing compression ignition engine performance using biodiesel/diesel blends and HHO gas

The proposed experimental study aims to investigate the effect of adding HHO gas with a constant flowrate (50% of the engine capacity) on the thermal efficiency for six different Biodiesel/diesel blends, which are 0B, 10B, 15%B, 20B, 25B and 30B. For all the studied fuelling scenarios, it was decided to mix HHO gas with the inlet air perpendicularly on the air streamline by a constant flowrate aiming to enhance the thermal efficiency of the engine. The study assumed maintain the rotational speed of the engine is constant (four different speeds) while varying the engine torque. The experimental results were recorded for four different rotational speeds of the engine, which are 1500, 1750, 2000 and 2250 RPM. Obtained results investigated that, increasing biodiesel content resulted in reducing the engine's brake thermal efficiency and increasing its brake specific fuel consumption due to the relatively lower heat content of the biodiesel comparing with conventional diesel. Adding HHO gas to the engine resulted in enhancing the thermal efficiency due to its high heat content and it was observed that; 20B with HHO gas supply provided the highest brake thermal efficiency of the engine as well as reducing its brake specific fuel consumption.     

Combustion characteristics of fuel droplets with addition of nano and micron-sized aluminum particles

The burning characteristics of fuel droplets containing nano and micron-sized aluminum particles were investigated. Particle size, surfactant concentration, and the type of base fluid were varied. In general, nanosuspensions can last much longer than micron suspensions, and ethanol-based fuels were found to achieve much better suspension than n-decane-based fuels. Five distinctive stages (preheating and ignition, classical combustion, microexplosion, surfactant flame, and aluminum droplet flame) were identified for an n-decane/nano-Al droplet, while only the first three stages occurred for an n-decane/micron-Al droplet. For the same solid loading rate and surfactant concentration, the disruption and microexplosion behavior of the micron suspension occurred later with much stronger intensity. The intense droplet fragmentation was accompanied by shell rupture, which caused a massive explosion of particles, and most of them were burned during this event. On the contrary, for the nanosuspension, combustion of the large agglomerate at the later stage requires a longer time and is less complete because of formation of an oxide shell on the surface. This difference is mainly due to the different structure and characteristics of particle agglomerates formed during the early stage, which is a spherical, porous, and more-uniformly distributed aggregate for the nanosuspension, but it is a densely packed and impermeable shell for the micron suspension. A theoretical analysis was then conducted to understand the effect of particle size on particle collision mechanism and aggregation rate. The results show that for nanosuspensions, particle collision and aggregation are dominated by the random Brownian motion. For micron suspensions, however, they are dominated by fluid motion such as droplet surface regression, droplet expansion resulting from bubble formation, and internal circulation. And the Brownian motion is the least important. This theoretical analysis explains the different characteristics of the particle agglomerates, which are responsible for the different microexplosion behaviors that were observed in the experiments.     

On droplet combustion of biodiesel fuel mixed with diesel/alkanes in microgravity condition

The burning characteristics of a biodiesel droplet mixed with diesel or alkanes such as dodecane and hexadecane were experimentally studied in a reduced-gravity environment so as to create a spherically symmetrical flame without the influence of natural convection due to buoyancy. Small droplets on the order of 500 μm in diameter were initially injected via a piezoelectric technique onto the cross point intersected by two thin carbon fibers; these were prepared inside a combustion chamber that was housed in a drag shield, which was freely dropped onto a foam cushion. It was found that, for single component droplets, the tendency to form a rigid soot shell was relatively small for biodiesel fuel as compared to that exhibited by the other tested fuels. The soot created drifted away readily, showing a puffing phenomenon; this could be related to the distinct molecular structure of biodiesel leading to unique soot layers that were more vulnerable to oxidative reactivity as compared to the soot generated by diesel or alkanes. The addition of biodiesel to these more traditional fuels also presented better performance with respect to annihilating the soot shell, particularly for diesel. The burning rate generally follows that of multi-component fuels, by some means in terms of a lever rule, whereas the mixture of biodiesel and dodecane exhibits a somewhat nonlinear relation with the added fraction of dodecane. This might be related to the formation of a soot shell.     

On the burning and microexplosion of collision-generated two-component droplets: miscible fuels

The combustion and microexplosion of freely falling two-component droplets, generated either independently or through the collision or merging of two droplets of the two fuels have been studied experimentally. The results show that the non-disruptive combustion characteristics, including the ignition delay, the flame shrinkage and the burning rates are largely similar for droplets generated with these two different modes, hence indicating the efficiency of mixing through the internal motion produced when droplets coalesce. Microexplosion induced by internal superheating and hence nucleation, however, was only observed for the collision-generated droplets, and is believed to be initiated by the air bubbles entrained during a collision. The potential importance of bubble entrainment during droplet and spray generation on spray atomization and burnout is emphasized.     

Tribological behavior of diesel/biodiesel blend from waste cooking oil and ethanol

One kind of novel biodiesel waste cooking oil ethyl ester (WCOEE) was prepared via transesterfication reaction between waste cooking oil and ethanol. The tribological behavior of diesel/WCOEE blend was evaluated with a four-ball tribometer. The wear resistance, extreme pressure, and friction reduction of the blend were improved with increasing WCOEE. The optimal content of WCOEE in the blend was 20 vol%. It was also found that free fatty acids (FFAs) had a positive effect on the wear resistance of blend. The lubrication improvement of the blend was ascribed to the formation of polyester film and high polarity of fatty acid ethyl ester.     

Effects of ammonia borane on the combustion of an ethanol droplet at atmospheric pressure

Adding compounds rich in hydrogen to liquid fuels has the potential to change combustion behavior and enhance performance. One potential additive is ammonia borane (AB), which contains 19.6 wt.% hydrogen and can be dissolved in anhydrous ethanol (up to 6.5 wt.%). The particular system studied here would have limited use due to energy density and stability but is studied as a model system. Single droplet combustion experiments were performed with AB concentrations in ethanol varying from 0 to 6 wt.%. Measurements performed using high speed (5 kHz) planar laser-induced fluorescence (PLIF) indicate that hydrogen gas addition from the decomposition of AB continues throughout the droplet burning process. The hydrogen addition leads to an increase in the D² law rate constant, k₀, of up to 16%. While AB (and residual material) participates throughout the combustion process, it dramatically impacts the combustion behavior at the end of the droplet lifetime as the concentration of AB residual grows within the droplet. This results in droplet shattering, causing fine atomization and rapid combustion of the remaining fuel. Boron is also oxidized in this short period of time, increasing the energy released. In combustors, droplet shattering could enhance mixing and increase combustion efficiency. Thus, the approach of adding compounds rich in hydrogen is a promising method to introduce H₂ gas to practical combustion systems, while enhancing performance.     

Assessing idling effects on a compression ignition engine fueled with Jatropha and Palm biodiesel blends

In this study, performance of a diesel engine operated with Jatropha and Palm biodiesel blends at high idling conditions has been evaluated. The result obtained from experiment elucidate that, at all idling modes HC and CO emissions of both blends decreases, however, NO_x emissions increases compared to pure diesel fuel. Jatropha biodiesel has higher viscosity compared to Palm biodiesel, which might have degraded the spray characteristics and caused slightly improper mixing which might have led to slightly incomplete combustion, thus at both idling conditions, Jatropha blends emitted higher CO and HC compared to Palm biodiesels. Compared to diesel fuel, CO emissions were 5.9–9.7%, 17.6–22.6%, 23.5–29%, 2.9–6.4%, 5.9–14.5% and 11.8–17.74% less, HC emissions were 10.3–11.5%, 24.13–30.76%, 34.5–39%, 6.9–7.7%, 26–27% and 31–35% less and NO_x emissions were 8.3–9.5%, 14–15%, 22–25%, 5–7.14%, 10–11.3% and 17–18% more respectively for 5, 10 and 20% blends of Palm and Jatropha biodiesel. Compared to diesel fuel, at high idling conditions brake specific fuel consumption all Palm and Jatropha biodiesel–diesel blends increased. Compared to diesel fuel, BSFC were 1.14–1.35%, 2.28–2.96%, 7.1–8.35%, 2.28–2.69%, 3.98–5.39% and 8.83–9.29% more respectively for 5, 10 and 20% blends of Palm and Jatropha biodiesel.     

Investigation on performance,combustion and emission characteristics of biodiesel - Ethanol blends with hydrogen in CI engine

The current research work focus on the utilization of hydrogen as a fuel in CI engine has been increased tremendously, since it is a zero-emission fuel. But higher self-ignition temperature than conventional fuel, makes to operate in dual fuel mode condition in CI engine. The diesel or biodiesel along with hydrogen in a CI engine results in the improvement in the performance but increase of NO. In order to minimize the NO emission, addition of ethanol with jamun B20 biodiesel blend (biodiesel-diesel-ethanol) and two ternary blends such as B20E05 and B20E10 are formed. In the present study, biodiesel along with H₂ is admitted in the CI engine. Ethanol addition reduces combustion temperature and act as cetane improver for the biodiesel. This induces better combustion of the fuel and reduce NO. The biodiesel production from jamun seed is carried out through transesterification process. H₂ of 4 lpm is allowed at the air inlet and jamun B20 blend is injected through the fuel injector. Improvement of brake thermal efficiency and increase in the NO are observed for the hydrogen with biodiesel operated CI engine. The performance and emission behaviors of CI engine done for the test samples. At full load condition (ternary blend) B20E05 assisted H₂ shows the drastic reduction of NO emission of 8.2% than B20 assist H₂ blend. In other hand emission like hydrocarbon, carbon monoxide and smoke opacity show a notable reduction for B20E05 blend assist H₂ than other test sample fuel. The thermal efficiency is 30.98% for B20E05 assist H₂ and it is 7.55% and 4.7% higher than B20 and B20E05 assist H₂ blend respectively.     

Ignition and combustion of n-heptane droplets in carbon dioxide enriched environments

The ignition process and burning characteristics of fiber-supported n-heptane fuel droplets in carbon dioxide enriched and varying pressure environments have been studied under normal gravity. Measured values of droplet burning rates, flame dimensions, broad-band radiant emission, and ignition times were compared to droplets burning in standard air conditions. The burning rate constants increased with increasing carbon dioxide concentration or pressure. For 21% ambient oxygen concentration ignition was achieved for carbon dioxide concentrations up to 46% with the remaining being nitrogen. The experimental burning rates were compared to existing theoretical models. A flammability map for n-heptane burning under normal gravity as a function of carbon dioxide concentration and pressure was also developed using these results.     

生物柴油和乙醇混合燃料的微爆特性实验研究

为了探究乙醇和生物柴油混合燃料的液滴微爆特性,设计并建立了悬挂液滴燃烧的实验装置和实验系统,在管式加热炉内用高速摄影拍摄并记录液滴的变化过程,以此得到了液滴的直径变化和微爆延迟,实验结果表明燃料的组分变化对液滴的微爆表现和性质有显著的影响,在混合燃料中乙醇和生物柴油的含量接近相等时液滴的微爆表现最好。     

Study on combustion and emissions of a turbocharged compression ignition engine fueled with dimethyl ether and biodiesel blends

In this study, combustion and emissions characteristics of a turbocharged compression ignition engine fueled with dimethyl ether (DME) and biodiesel blends are experimentally investigated. The effects of nozzle parameter on combustion and emissions are evaluated. The result shows that with the increase of DME proportion, ignition delay, the peak in-cylinder pressure, peak heat-release rate, peak in-cylinder temperature decrease, and their phases retard. Compared to the nozzle 6 × 0.40 mm, the peak cylinder pressure and peak heat-release rate are higher with nozzle 6 × 0.35 mm, and their phases are advanced. Increased DME proportion in fuel blends causes greater differences. Compared to biodiesel, NO_x emissions of blends significantly decrease; HC emissions and CO emissions increase slightly. DME–biodiesel blends can be used as an alternative in a turbocharged CI engine. To obtain low NO_x emissions and a soft engine operation, for high DME proportion blended fuels, nozzle of 6 × 0.40 mm adopted.     

Bioconversion of residual glycerol from biodiesel synthesis into 1,3-propanediol and ethanol by isolated bacteria from environmental consortia

Residual (raw) glycerol originated from biodiesel synthesis is becoming of great environmental and economical concern due to its ever-growing surplus. In the present study, several bacterial strains were isolated and characterized for their ability to convert this raw glycerol into 1,3-propanediol (1,3-PD) and ethanol. The best producers of both 1,3-PD and ethanol were identified by 16S rDNA sequences to be Klebsiella pneumoniae and Pantoea agglomerans strains. Batch bioreactor cultivations under anaerobic and aerobic conditions were carried out in order to access the kinetics of glycerol consumption and product formation. Results showed that one isolated, K. pneumoniae BLh-1, was able to simultaneously produce up to 9.4 g/L of 1,3-PD with yields of 0.41 mol product mol⁻¹ glycerol, and 6.1 g/L of ethanol with yields of 0.14 mol product mol⁻¹ glycerol under anaerobic conditions, showing great potential for bioprocesses.     

Oxidative steam reforming of ethanol for hydrogen production on M/Al2O3

In this work, we investigate oxidative steam reforming (OSR) of ethanol on a series of metals under various catalytic conditions (H₂O/ethanol and O₂/ethanol ratios) to understand the reaction mechanism and to optimize the catalytic conditions for optimal hydrogen production. There are three reaction pathways for OSR using these metals. Ethanol can be oxidized to acetaldehyde on Cu, Ag and Au, and it can be dehydrated to form ethylene on Co, Ni, Pd and Pt. Ethylene can form coke and degrade catalysts after the long-term OSR. In the third pathway, ethanol preferentially breaks its C–C bond and is further oxidized to CO or CO₂ on Ru, Rh and Ir, providing optimal hydrogen production. In addition, increasing H₂O/ethanol and O₂/ethanol ratios can improve catalytic activity, attributable to atomic oxygen from H₂O and O₂ efficiently rupturing the C–C bond of ethanol. This concept explains the improved performance of OSR on the CeO₂-modified catalyst, which shows better oxygen storage capability.     

The use of biodiesel blends in domestic vaporising oil burners

Biodiesel is receiving increasing attention as a partial substitute for home heating oil. The properties that make it a suitable fuel for use in diesel engines also make it suitable for heating systems using pressure jet burner technology. In the UK, however, there are a significant number of vaporising burners whose suitability for operation with biodiesel has not been properly studied. The purpose of this study was therefore to investigate the use of different blends of biodiesel and kerosene in a production Aga that employed a sleeve-type vaporising burner. It was found that significant fouling of the burner well would occur within a short period of time, even with a blend as low as 5% by volume of biodiesel in kerosene. Further investigation revealed the build-up to consist of polymerised biodiesel, most likely triggered by heat. Factors contributing to the rate and extent of fouling are thought to include the type of vegetable oil used as feedstock for the biodiesel, as well as the degree of prior utilisation of the feedstock oil. Further investigation is warranted, possibly with the use of suitable fuel additives to inhibit the polymerisation process.     

Bi-metallic and tri-metallic Pt-Sn/C, Pt-Ir/C, Pt-Ir-Sn/C catalysts for electro-oxidation of ethanol in direct ethanol fuel cell

In the present work, combination of bi-metallic and tri-metallic Pt, Ir, Sn electro-catalysts was prepared by impregnation reduction method on carbon Vulcan XC-72 to improve upon electro-oxidation of ethanol in direct ethanol fuel cell. The prepared electro-catalysts were characterized by means of scanning electron microscope (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analyses. XRD and TEM analyses reveal that the prepared catalysts are of nano size (6-10 nm) range. It is shown that Pt lattice parameter decreases with the addition of Ir, and increases with the addition of Sn in Pt-Ir-Sn/C catalyst. The electro-catalytic activities characterized by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry (CA) techniques reveal that the addition of small amount of Ir in Pt-Sn/C electro-catalyst exhibits higher activity towards ethanol oxidation than the Pt-Sn/C (20% Pt and 20% Sn by wt) electro-catalyst. The single direct ethanol fuel cell (DEFC) test at 90 °C, 1 bar with catalyst loading of 1 mg/cm² and 2 M ethanol as anode feed showed an enhancement of catalytic activity in following order: Pt-Ir-Sn/C (20% Pt, 5% Ir and 15% Sn by wt) > Pt-Ir-Sn/C (20% Pt, 10% Ir and 10% Sn by wt) > Pt-Sn/C (20% Pt and 20% Sn by wt) > Pt-Ir-Sn/C (10% Pt, 15% Ir and 15% Sn by wt) > Pt-Ir/C (20% Pt and 20% Ir by wt) >    Pt/C (40% Pt by wt). Pt-Ir-Sn/C (20% Pt, 5% Ir and 15% Sn by wt) exhibited highest performance among all the catalysts prepared with power density of 29 mW/cm² in DEFC operating at 90 °C.     

Role of hydrogen in improving performance and emission characteristics of homogeneous charge compression ignition engine fueled with graphite oxide nanoparticle-added microalgae biodiesel/diesel blends

The development of low-temperature combustion models combined with the use of biofuels has been considered as an efficient strategy to reduce pollutant emissions like CO, HC. NO_x, and smoke. Indeed, Homogeneous Charge Compression Ignition (HCCI) is the new approach to drastically minimize NO_x emissions and smoke owing to the lower cylinder temperature and a higher rate of homogeneous A/F mixture as compared to compression ignition (CI) engines. The present research deal with the behavior analysis of a CI engine powered by diesel, Euglena Sanguinea (ES), and their blends (ES20D80, ES40D60, ES60D40, ES80D20). The experimental results revealed the highest brake thermal efficiency for ES20D80 although it decreased by 4.1% compared to diesel at normal mode. The average drop in HC, CO, and smoke was 2.1, 2.3, and 5.7% for ES20D80 as opposed to diesel fuel. Therefore, in the next stage, ES20D80 with various concentrations of graphite oxide (GO) nanoparticle (20, 40, 60, and 80 ppm) was chosen to carry out experiments in the HCCI mode, in which hydrogen gas was induced along with air through the intake pipe at a fixed flow rate of 3 lpm for the enrichment of the air-fuel mixture. As a result, the combination of hydrogen-enriched gas and GO-added ES20D80 in the HCCI mode showed similar performance to the CI engine but registered a major reduction of NO_x and smoke emissions, corresponding to 75.24% and 53.07% respectively, as compared to diesel fuel at normal mode.     

The role of viscosity in the fluorescence behavior of the diesel/biodiesel blends

Recently, the potentiality of fluorescence spectroscopy to be used in the quantification of biodiesel content in diesel/biodiesel blends (DBB) was demonstrated. However, the source of the fluorescence dependence of the DBB with biodiesel concentration remains unanswered. In the present paper, a close analysis of the optical properties of the DBB was performed over a wide composition range. The findings suggest that the alterations in the fluorescence intensity can be accounted for only after taking into account changes in viscosity as well as absorbance, in a model where the fluorophores were considered as molecular rotors.     

Laminar mass burning and entrainment velocities and flame instabilities of i-octane,ethanol and hydrous ethanol/air aerosols

The paper reports experiments employing the cloud chamber technique for creating fuel aerosols, in studies of premixed laminar flames. Spherical explosion flames were initiated at different times after the start of expansion of the original gaseous mixture to lower pressure. Flame speeds were measured close to atmospheric pressure, over a range of equivalence ratios of iso-octane, ethanol and hydrous ethanol with air. A methodology was developed for deriving mass burning velocities and entrainment velocities, as well as mass burning fluxes, from the measurements of aerosol number densities, droplet sizes and flame speeds. It was vital to estimate whether droplet evaporation was completed in the flame preheat zone. This was done by calculating the spatial progress of droplet evaporation for the different aerosols from values of the evaporation rate constants of the different fuels.