Ethanol In Isooctane Research Articles

Effect of Ethanol and Iso-Octane Blends on Isolated Low-Temperature Heat Release in a Spark Ignition Engine

<div>Low-temperature heat release (LTHR) is of interest for its potential to help control autoignition in advanced compression ignition (ACI) engines and mitigate knock in spark ignition (SI) engines. Previous studies have identified and investigated LTHR in both ACI and SI engines before the main high-temperature heat release (HTHR) event and, more recently, LTHR in isolation has been demonstrated in SI engines by appropriately curating the in-cylinder thermal state during compression and disabling the spark discharge. Ethanol is an increasingly common component of market fuel blends, owing to its renewable sources. In this work, the effect of adding ethanol to iso-octane (2,2,4-trimethylpentane) blends on their LTHR behavior is demonstrated. Tests were run on a motored single-cylinder engine elevated inlet air temperatures and pressures were adjusted to realize LTHR from blends of iso-octane and ethanol without entering the HTHR regime. The blends were tested with inlet temperatures of 40°C–140°C at equivalence ratios of 0.5, 0.67, and 1.0 with boosted (1.5 barA) conditions. The measured LTHR decreased with increasing ethanol content for all conditions tested; iso-octane–ethanol blends with above 20% ethanol content (by volume) showed minimal LTHR under engine conditions. These net effects resulted from the combination of thermal effects (charge cooling) and chemical effects (reactivity changes at low temperatures). The effect of temperature, pressure, fuel composition, and equivalence ratio on ignition delay times calculated from chemical kinetic modeling are presented alongside pressure–temperature trajectories of the in-cylinder gases to explain the trends. The underlying cause of the trends is explained by using a sensitivity analysis to determine the contribution of each reaction within the chemical kinetic mechanism to first-stage ignition, revealing the effect of introducing ethanol on the OH radical pool and resulting LTHR intensity.</div>

The role of polar ethanol induction in various iso-octane ethanol fuel blend during single droplet combustion

This study aims to disclose the role of molecular interactions of iso-octane ethanol blend during droplet combustion. The iso-octane ethanol composition which has the potential to form molecular clusters was analyzed using integer interaction modeling with mole ratio. Comparison of mole-based compositions was converted to a volume base to verify empirically using the single droplet burning method. The molecular interaction analysis gave the composition close to the molecular cluster composition was 10, 15, 25, 40, 50, 60, 70, 80, and 90% v/v. Ethanol fractions of 20% and 30% v/v were also tested using the same method as a mixture that do not form the molecular cluster. This study shows that the total molecular interaction forces on molecular clusters are inversely proportional to puffing events during single droplet combustion. The number of free molecules that do not form molecular clusters tends to produce micro-explosions at the final stage of single droplet combustion. The research also revealed that the increasing ethanol fractions in molecular clusters tends to reduce the combustion rate constant exponentially.

Competitive Adsorption of a Multifunctional Amine and Phenol Surfactant with Ethanol on Hematite from Nonaqueous Solution.

Surfactants, which contain phenol and amine groups, are commonly used in industries to protect metallic surfaces, and their efficiency depends strongly on factors such as pressure and temperature, solvent properties, and the presence of other surfactants in the system. In this work, we present a molecular simulation study of the competitive adsorption between a multifunctional phenol and amine surfactant model and ethanol at the oil/solid interface formed between iso-octane and a model hematite (α-Fe2O3) slab. We show that the surfactant strongly adsorbs at the iso-octane/hematite interface in the absence of ethanol at moderate temperatures. As the concentration of ethanol is increased, the ethanol molecules compete effectively for the adsorption sites on the iron oxide surface. This competition drives the surfactant molecules to remain in the bulk solution, while ethanol forms ordered and strongly coordinated layers at the oil/solid interface, despite the well-known complete miscibility of ethanol in iso-octane in bulk under standard conditions. Potential of mean force calculations show that the free energy of adsorption of the surfactant is approximately two times larger than that for a single ethanol molecule, but the simulations also reveal that a single surfactant chain needs to displace up to five ethanol molecules to adsorb onto the surface. The end result is more favorable ethanol adsorption which agrees with the experimental analysis of similar oil/iron oxide systems also reported in this work.

The role of molecule cluster on the azeotrope and boiling points of isooctane-ethanol blend

This study aims to assess the fraction of the isooctane-ethanol blend which has azeotrope condition. Isooctane was selected as a conventional fuel. Isooctane-ethanol blend with various mixture fractions is given the heat to obtain the distillation temperature curve and the fuel vapor. The blended fraction is varied from 0, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100% v/v ethanol to predict the condition (near) azeotrope fuel blend. Molecular analysis was used to verify the predicted azeotrope mixture of isooctane-ethanol. The results show that the isooctane ethanol blend has an azeotrope mixture at exactly on the ethanol fraction of 41.48% v/v. In this fraction blended, two polar molecules of ethanol induce a nonpolar molecule of isooctane to form a molecular cluster.

Insights into Stoichiometric and Lean Combustion Phenomena of Gasoline–Butanol, Gasoline–Ethanol, Iso-Octane–Butanol, and Iso-Octane–Ethanol Blends in an Optical Spark-Ignition Engine

ABSTRACTIntroduction of novel fuels, such as mixtures of ethanol or butanol with hydrocarbons, requires new fundamental understanding of in-cylinder combustion properties in modern direct-injection spark-ignition engines since those can be quite sensitive to fuel properties. Gasoline and its blends with 25% ethanol and butanol at 25% and 16% per volume (the latter equivalent to 10% ethanol blending ratio in terms of oxygen content) were studied in comparison to gasoline, ethanol, and butanol combustion. The same alcohol blending ratios were also employed with iso-octane as the base component for direct comparison. Testing was performed at 1500 RPM with 0.5 bar intake plenum pressure using 20°C or 80°C engine coolant temperature. Thermodynamic parameters were derived using in-cylinder pressure analysis for stoichiometric (ϕ = 1.0) and lean (ϕ = 0.83) fueling over a range of spark advances. Additionally, high speed color and greyscale chemiluminescence imaging was conducted at gasoline’s maximum break torque spark timing, calculating flame growth speeds, flame roundness, and centroid motion. Laminar burning velocity data from the literature and in-cylinder flow measurements from the same engine were used for interpretation. Overall, the analysis showed small differences between gasoline and the blends in general, but showed changes for the pure alcohols with typically much faster flame progression for ethanol and issues with the combustion stability of butanol at low engine temperatures. Alcohol blending, particularly with iso-octane, showed some benefits at lean conditions.

Investigation of soot formation of spark-ignited ethanol-blended gasoline sprays with single- and multi-component base fuels

Soot formation in DISI-(direct-injection spark-ignition) sprays is analyzed for ethanol-mixtures under stratified charge conditions. The investigation is conducted in a constant volume chamber (CVC), which is equipped with a spark ignition system. The operating conditions of the chamber are 0.8MPa and 473K. In previous studies, soot luminosity imaging indicated higher sooting tendencies for E20 (20vol.% of ethanol in isooctane) sprays in comparison to pure isooctane and pure ethanol, however, no quantification of the soot distribution was possible. In this study, 2D laser-induced incandescence measurements (LII) in combination with laser extinction measurements (LEM) were performed for measurement of soot volume fraction distribution in the spray flame. The results show that soot is mainly formed in the spray front due to droplet combustion. Furthermore, soot volume fraction results confirm an increased sooting tendency of E20 compared to pure isooctane under the investigated conditions although the chemical properties of ethanol should reduce soot formation. This behavior can be explained by the delayed evaporation of E20 in comparison to isooctane due to physical fuel properties (mainly the enthalpy of evaporation), which are more important for soot formation especially at these short mixing times. Similar trends were found for the more complex multi-component fuel mixture isooctane-toluene (TolIso) and gasoline, both blended with 20vol.% ethanol. Here, single combustion cycles were observed, where E20 exhibits higher soot volume fraction.

Combustion and Sooting Behavior of Spark-Ignited Ethanol–Isooctane Sprays under Stratified Charge Conditions

A spray combustion investigation within an optically accessible high-temperature/high-pressure chamber with ignition was conducted to study soot formation of ethanol blended fuels at cold start conditions. The fuels ethanol, isooctane, and its blends E85 (85 vol% of ethanol in isooctane) and E20 were studied at different temperatures under direct injection spark ignition engine stratified charge conditions. A high-speed camera in combination with an image stereoscope was used in order to visualize the combustion in two different wavelength regions simultaneously to distinguish between premixed and sooting combustion. Additionally, a spectroscopic setup was applied for detailed flame emission analysis on high time-resolved scale. Furthermore, a spray formation investigation was carried out in order to evaluate the fuel evaporation process. The study reveals that depending on the operation conditions either the chemical or the physical processes dominate the combustion and sooting behavior. At low ambient t...

The effect of ethanol blending on mixture formation, combustion and soot emission studied in an optical DISI engine

Abstract In various research studies, ethanol blended fuels have shown reduced particulate matter (PM) emissions in comparison to gasoline and its surrogate fuels in direct-injection spark-ignition (DISI) engines. However, there are also studies reporting increased particulate concentration for fuels with low ethanol content. In this work the mixture formation and sooting combustion behavior of isooctane and the mixture E20 (20 vol% of ethanol in isooctane) is analyzed for catalyst heating operation. These operating conditions are critical as they strongly contribute to overall soot emissions in driving cycles. Simultaneous high speed imaging of OH ∗ –chemiluminescence and natural soot luminosity measurements are performed in combination with primary particle concentration measurements using a laser induced incandescence (LII) sensor in the engine exhaust duct. At these operating conditions E20 exhibits a higher sooting tendency as compared to isooctane. In order to identify the reason for increased soot formation, the mixture formation process is analyzed by planar laser induced fluorescence (LIF) measurements. The results show that soot was formed in fuel rich regions with incomplete evaporated fuel droplets remaining from the injection event. A different evaporation process of E20 fuel spray and mixing behavior is indicated showing a more compact rich mixture cloud with surrounding lean areas near the spark plug region. This mixture stratification is characterized by higher cyclic variations and constitutes a significant source of soot formation.

Immobilization of Candida rugosa lipase on MSU-H type mesoporous silica for selective esterification of conjugated linoleic acid isomers with ethanol

Candida rugosa lipases (CRLs) immobilized on MSU-H type mesoporous silicas with different pore sizes (6.0, 7.2 and 13.3nm) through physical adsorption and a cross-linking method were examined as biocatalysts for esterification of conjugated linoleic acid (CLA) isomers with ethanol in isooctane. N2 adsorption–desorption isotherms indicated that the MSU-H silicas and the immobilized CRL derivatives had mesoporous structure. Introduction of CRL molecules onto MSU-H was confirmed by Fourier transform infrared (FT-IR) spectra. The optimum conditions of the immobilization process (pH of CRL solution, 7.0; initial concentration of CRL solution, 1.6mg/ml; contact time, 8–10h) and the esterification reaction (temperature, 45°C; molar ratio of CLA to ethanol, 1:1; biocatalyst, 6% by weight of CLA) were determined. The MSU-H material with pore size of 13.3nm proved to be more suitable to immobilize CRL onto it than others. The CRL immobilized on MSU-H (pore size, 13.3nm) by cross-linking gave a loading amount 48.2mg CRL/g-dry support and a maximal hydrolytic activity of 3418.2U/g-catalyst. It also exhibited high synthetic activity and operational stability and remained 43.2–67.8% of total esterification in 48h consecutive six runs under the optimized reaction conditions. Moreover, the immobilized CRLs catalyzed 2.0–3.1 times of esterification of cis-(c)9, trans-(t)11-CLA faster than that t10, c12-CLA. The formation of ethyl esters of CLA isomers was identified by GC–MS analysis.

A comparison of the performance analysis of the spark ignition engine fuelled with ethanol–iso-octane and methanol–iso-octane fuel blends

In this research, the effects of unleaded iso-octane (base fuel), iso-octane–ethanol blend (E20) and iso-octane–methanol blend (M20) on engine performance were investigated experimentally in a single-cylinder four-stroke spark-ignition engine. The tests were performed by varying the throttle position and engine speed at a constant load of 8 kg. The engine speed was varied from 1200 to 1750 rpm, with changing the throttle position. The results showed that ethanol and methanol addition to unleaded iso-octane increases the engine torque, power and brake-specific fuel consumption (BSFC) in comparison to base fuel. The results also showed that exhaust temperature increases with the increase in engine speed. The thermal efficiency varies from 14.3% to 35.9% for iso-octane, 20.1–30.59% for E20 and (17.64–27.46%) for M20 fuel. It was also found that the volumetric efficiency of M20 and E20 fuels was higher than that of iso-octane in all speed ranges.

A Study of Spark Ignition Engine Fueled with Methanol and Ethanol Fuel Blends with Iso-Octane

Alternative fuels are derived from resources other than petroleum. The benefit of these fuels is that they emit less air pollutant compare to gasoline and most of them are more economically beneficial compared to oil and they are renewable. In addition, ethanol has higher evaporation heat, octane number and flammability temperature therefore it has positive influence on engine performance and reduces exhaust emissions. In this study, the effects of unleaded iso-octane, unleaded isooctane–ethanol blend (E5) and iso-octane-methanol (M5) blends on engine performance are investigated experimentally in a single cylinder fourstroke spark-ignition engine at a constant 8 Kg load. The engine speed was changed from 1100 to 1800 rpm. The results of the engine test showed that ethanol addition to unleaded iso-octane increases the value of IP, FP and IMEP with E5 fuel. The results also showed that the indicated power, brake power, friction power, indicated mean effective pressure, torque, exhaust temperature, and thermal efficiency increases with the increase in engine speed at a constant load of 8 Kg for E5, M5 and isooctane fuels. Thermal efficiency was maximum for E5 fuel (38.13%) at a speed of 1750 rpm.

Pressure effects on laminar burning velocities and Markstein lengths for Isooctane–Ethanol–Air mixtures

A new method for extracting the laminar burning velocity from the difference between the flame speed and the local fresh gas velocity at the entrance of the flame front is used for ethanol/isooctane/air mixtures. This approach gives additional information in terms of flame sensitivity to flame stretch represented by the Markstein length relative to the fresh gases Lu and a direct measurement of the unstretched laminar burning velocity without any assumptions on adiabaticity and on the fuel mixture properties. The overall accuracy of the measurements obtained from the repeatability of the experiments is less than ±1.5cm/s at P=0.1MPa and increases with pressure to reach ±3cm/s at P=1MPa. Measurements of the unstretched laminar burning velocities and Markstein lengths of ethanol/isooctane/air flames in the range of initial pressure from 0.1 to 1MPa and for various ethanol mole fractions, ϵ, are presented. A globally good agreement is obtained with literature data for pure fuels, and with both mechanisms of Marinov and of Saxena for pure ethanol/air mixtures (except for rich ethanol/air flames in the case of Marinov mechanism) and with Jerzembeck mechanism for pure isooctane/air flames. The effect of pressure on the burning velocity of pure fuel is interpreted using the correlation un0(P)=un0(P0)(P/P0)β. Particular attention has been paid to the effect of equivalence ratio and fuel blending on the power exponent β. Both experimental and numerical data show the existence of a minimum in β for stoichiometric mixtures and a globally quadratic approximation with ϕ. From our results, we demonstrate also the quasi insensitivity of β with fuel blending. A general correlation is then proposed to express the effect of pressure, equivalence ratio and ethanol mole fraction in isooctane at a constant temperature of 373K. The accuracy of this correlation and the ranges of validity are also provided.

In situ monitoring of turbid immobilized lipase-catalyzed esterification of oleic acid using fiber-optic Raman spectroscopy

Raman spectroscopy with a fiber-optic probe was used to monitor the immobilized Candida antarctica lipase B (Novozym 435)-catalyzed esterification of oleic acid with ethanol in iso-octane as an organic solvent. The effects of reaction temperature and molar ratio of substrates were studied. An optimal reaction rate was found at 60 °C, beyond which deactivation due to denaturing of the lipase was observed. The variation in molar ratio of substrates suggests that the esterification of oleic acid and ethanol proceeds via a Ping-Pong Bi-Bi mechanism with ethanol exhibiting an inhibitory effect. A good fit was obtained between the experimental results and the best-fit Ping-Pong Bi-Bi mechanism. This current work shows that fiber-optic Raman spectroscopy is indeed a suitable instrument to monitor immobilized lipase-catalyzed reaction in turbid organic systems in situ. Since this approach is reliable, simple to use, allows automatic data acquisition, and accurate, it should be applicable to the detailed kinetic analysis on other immobilized enzymatic reactions as well.

Effects of water activity and alcohol concentration on the kinetic resolution of lipase-catalyzed acyl transfer in organic solvents

A lipase-catalyzed enantioselective thiotransesterification between ( R, S)-naproxen 2,2,2-trifluoroethyl thioester (STF S ) and 4-morpholine ethanol in isooctane was employed to produce ( S)-naproxen ester prodrug by controlling the initial water activity and considering the hydrolysis and esterification side-reactions. Good enzyme enantioselectivity with more than 90% of enantiomeric excess for the desired product was obtained when initial water activity and alcohol concentration were controlled at 0.113 and 10 mM, respectively. A detailed analysis of the apparent equilibrium constant and ratio of initial rates of thiotransesterification and hydrolysis varied with the water activity and alcohol concentration indicated that water and alcohol might act as modifiers in manipulating the enzyme active center aside from their conventional roles as acyl acceptor and enzyme inhibitor.

Semi-Preparative High Performance Liquid Chromatographic Separation of Carbon-14 Labeled Avermectin B1afrom a Mixture of Avermectins

Abstract A semi-preparative high performance liquid chromatographic method has been developed to separate carbon-14 labeled avermectin B1a from a fermentation mixture of carbon-14 labeled avermectins, i. e., avermectins A1a, A1b, A2a, A2b, B1a, B1b, B2a, and B2b. Two HPLC systems were employed for the separation: I. A Whatman M20, Partisil 10, normal phase column and a solvent system of 10% ethanol in isooctane (v/v), and II. A Whatman M20, Partisil 10, ODS-3, reverse phase column and a solvent system of acetonitrile/methanol/water (56:18:26, v/v/v); the flow rate was 18 ml/ min. Avermectin separations were monitored using ultraviolet detection (254 nm). Further analyses of avermectin B1a were done using analytical HPLC and TLC/radioassay to check compound purity and identity.