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Combustion and Flame
Volume 161, Issue 12,
, Pages 3014-3021
Author links open overlay panelWeijingWangSandeepGowdagiriMatthew A.OehlschlaegerPersonEnvelope
Ignition delay time measurements are reported for two reference fatty-acid methyl ester biodiesel fuels, derived from methanol-based transesterification of soybean oil and animal fats, and four primary constituents of all methyl ester biodiesels: methyl palmitate, methyl stearate, methyl oleate, and methyl linoleate. Experiments were carried out behind reflected shock waves for gaseous fuel/air mixtures at temperatures ranging from 900 to 1350K and at pressures around 10 and 20atm. Ignition delay times were determined by monitoring pressure and ultraviolet chemiluminescence from electronically-excited OH radicals. The results show similarity in ignition delay times for all methyl ester fuels considered, irrespective of the variations in organic structure, at the high-temperature conditions studied and also similarity in high-temperature ignition delay times for methyl esters and n-alkanes. Comparisons with recent kinetic model efforts are encouraging, showing deviations of at most a factor of two and in many cases significantly less.
Biodiesel fuels offer reductions in important pollutant emissions (carbon monoxide, unburned hydrocarbons, and particulates) when used as alternatives to petroleum-based fuels in diesel engines and offer a potential pathway to reduced green house gas emissions from the light- and heavy-duty transportation sectors . In order to develop high-efficiency, clean, and robust engines operating on biodiesel, an understanding of biodiesel combustion characteristics is desired, including the fundamental chemical kinetic behaviors of biodiesels. Among macroscopic chemical kinetic properties, the ignition delay time, the time delay prior to ignition for a fuel/oxidizer mixture at specified conditions, has drawn special attention since it describes a process of fundamental importance to diesel engines, autoignition. Autoignition initiates combustion in diesel and other compression-ignition engines; hence, its prediction is important for the design of these engines with optimized performance and minimized pollutant emissions.
There are a variety of experimental methods available to study autoignition, including shock tubes, rapid compression machines, and flow reactors. While each method has its advantages and drawbacks, shock tubes have been widely used for the following reasons. First, the shock tube provides nearly stationary, spatially uniform, and homogeneous conditions behind the reflected shock wave, which are amenable to simplified zero-dimensional modeling. Second, conditions similar to practical combustion systems can be obtained in shock tubes including elevated pressures, a wide range of temperatures, and fuel/oxidizer mixtures. Third, the shock tube provides a relatively simple experimental platform offering highly reproducible experimental conditions for which quantitative measurements of chemical kinetic behaviors can be realized. Here we present a study of biodiesel autoignition using the shock tube technique.
Biodiesels are mixtures of long-chain mono-alkyl esters formed via the transesterification of fatty acids. Methanol is typically used in the transesterification process yielding fatty-acid methyl esters, which when derived from most feedstocks have carbon chains between 14 and 20 carbon atoms with zero to three double bonds found in the carbon chain. See Fig. 1 for the organic structures of several methyl esters found in large quantities in biodiesels and Table 1 for a compositional characterization of methyl ester biodiesels synthesized from different feedstocks . The methyl ester components are described using a standard nomenclature for their organic structure, CXX:Y, where XX represents the length of the carbon chain attached to the methyl ester functionality and Y is the number of double bonds within the carbon chain.
As shown in Table 1, biodiesels synthesized via methanol-based transesterification of vegetable oils (rapeseed, sunflower, safflower, and soybean), animal fats (tallow and lard), and waste grease (yellow and brown grease) contain four predominate methyl esters (structures given in Fig. 1): methyl palmitate (C16:0), methyl stearate (C18:0), methyl oleate (C18:1), and methyl linoleate (C18:2).
The number of double bonds in the methyl ester carbon chain, or degree of saturation, influences the ignition quality of neat methyl esters or multi-component methyl ester biodiesel in diesel engines, with more highly saturated methyl esters being more reactive than less saturated methyl esters. The degree of variation in reactivity has been demonstrated through the variation in the cetane number (CN). For example, fully saturated methyl stearate has a CN=76, while methyl oleate (one double bond) and methyl linoleate (two double bonds) have CN=57 and 37, respectively . Cetane numbers ranging from 44 to 70 have been reported for multi-component biodiesels derived from vegetable oils and animal fats .
As shown in Table 1, the compounds found in biodiesels are large in carbon number (C14+), complicating kinetic modeling due to the numerous species and reaction pathways needed to describe their oxidation. The large size of biodiesel compounds also complicates gas-phase experiments, necessary to elucidate the chemical kinetic behaviors unique to biodiesels, due to their low vapor pressures. Therefore, most kinetic investigations performed to date have focused on smaller surrogate compounds containing the chemical functionalities found in biodiesel but without the long carbon chain. For example, methyl butanoate (C4:0) has been the subject of a number of studies (e.g., , ) and a number of recent studies have investigated intermediate-sized methyl ester biodiesel surrogates, including methyl decanoate (C10:0) (e.g., , ).
Fewer studies have focused on the larger compounds found in biodiesel; however, Dagaut et al.  performed jet-stirred reactor oxidation studies on rapeseed biodiesel, Marchese et al.  studied the ignition of methyl oleate and commercial soy biodiesel fuel droplets, and Bax et al.  have studied methyl oleate oxidation in a jet-stirred reactor. Relevant to the present study, Campbell et al.  performed the first shock tube autoignition study of biodiesel compounds, measuring ignition delay times using an aerosol shock tube technique for methyl oleate and methyl linoleate at dilute conditions (4% O2), pressures of 3.5 and 7.0atm, and temperatures from 1100 to 1400K. In a following study Campbell et al.  made measurements of ignition delay times for methyl decanoate, laurate, myristate, and palmitate and a methyl oleate/FAME blend at similar high-temperature (1026–1388K) argon–dilute conditions.
Detailed kinetic models have been developed by several groups for large biodiesel components. Detailed kinetic models containing low- and high-temperature oxidation chemistry for methyl palmitate, stearate, oleate, linoleate, and linolenate (C18:3) have been reported by Westbrook et al. ,  and for methyl palmitate and stearate by Herbinet et al. . Saggese et al.  have reported kinetic models developed using a reaction and species lumping approach for saturated and unsaturated large biodiesel compounds, including methyl palmitate, stearate, oleate, linoleate, and linolenate. When used in combination, models from these authors can describe biodiesels comprised of mixtures of methyl esters (e.g., Table 1). Golovitchev and Yang  have reported a highly reduced kinetic model for rapeseed methyl ester biodiesel and diesel engine simulations performed with their model. See the reviews of Coniglio et al.  and Violi et al.  for details regarding kinetic modeling for biodiesel compounds.
To the authors’ knowledge, there have been no previous fundamental studies of autoignition for multi-component biodiesel fuels, other than those that have been performed in engines, and the only one previous autoignition study for the predominate biodiesel components given in Fig. 1 and Table 1, that of Campbell et al. ,  who investigated methyl oleate and methyl linoleate autoignition at dilute conditions. Here we report shock tube ignition delay time measurements carried out at elevated-pressures and lean to stoichiometric fuel/air conditions for the four biodiesel components shown in Fig. 1, methyl palmitate, stearate, oleate, and linoleate, as well as for two reference multi-component methyl ester biodiesels, derived from soybean oil and animal fats.
Shock tube ignition delay time measurements were performed in the Rensselaer heated high-pressure shock tube (5.7cm inner diameter, 2.59m long driver, 4.11m long driven) . There are five points relating to the shock tube experiments described here: shock tube heating, fuel/air mixture preparation, determination of post-shock conditions, measurement of ignition delay times, and the fuels studied and experimental conditions considered.
Results and discussion
Measured ignition delay times for methyl palmitate/air mixtures at variable equivalence ratio and pressure are shown in Fig. 4. The measurements demonstrate a reduction in apparent activation energy with decreasing temperature from 1300 to 900K, from a high-temperature value of approximately 170kJ/mol near 1200–1300K. The change in apparent activation energy is consistent with the entrance to the negative-temperature-coefficient (NTC) regime, due to contributions from low-temperature oxidation
Ignition delay time measurements made using a heated shock tube technique are reported for four neat methyl esters found in large quantities in methyl ester biodiesels, methyl palmitate, methyl stearate, methyl oleate, and methyl linoleate, and two reference methyl ester biodiesels, derived from soybean oil and animal fats. Measurements were carried out a range of conditions (fuel/air at ϕ=0.25, 0.5, and 1.0; 10 and 20atm; and 900–1300K) for methyl palmitate allowing the determination power-law
This work was supported by the National Science Foundation under Grant CBET-1032453.
- H. Wang et al.
- C.K. Westbrook et al.
- H.P.S. Shen et al.
- J.Y.W. Lai et al.
Prog. Energy Combust. Sci.
- L. Coniglio et al.(Video) Production of Biodiesel From Vegetable Oil
Prog. Energy Combust. Sci.
- C. Saggese et al.
Proc. Combust. Inst.
- O. Herbinet et al.
Proc. Combust. Inst.
- C.K. Westbrook et al.
Proc. Combust. Inst.
- C.K. Westbrook et al.
- M.F. Campbell et al.
Proc. Combust. Inst.
Proc. Combust. Inst.
- Combustion reaction kinetics of biodiesel/n-butanol blends: Experiments in an ultrahigh-pressure rapid compression machine
2022, Combustion and Flame
Burning oxygenated hydrocarbon biofuels in engines is a viable path for saving energy and reducing carbon emissions. N-butanol and biodiesel are two representative biofuels and have attracted widespread interest. In this study, the blends of n-butanol and biodiesel (a waste cooking oil) with different n-butanol ratios (40%, 60%, 80% by volume) were adopted to study their autoignition characteristics in a newly developed ultrahigh-pressure rapid compression machine. The ignition delay times of the blends were precisely measured under wide pressures of 10/20/40/60bar, equivalence ratios of 0.3/0.5/1.0, and a temperature range of 700–970K. Experimental results show that the ignition delay time decreases with the increase of pressure and equivalence ratio at the investigated conditions regardless the blending ratios. It is also found that the ignition delay time becomes slightly longer with the increasing n-butanol ratio in the blends at temperatures below 820K. However, as the temperature further increases, the ignition delay times of different blends get closer and has a crossover tendency. The composition of the biodiesel was quantitively analyzed and a surrogate fuel was developed. An optimized mechanism was proposed based on a documented detailed mechanism with 461 species and 18,217 reactions. Simulation results show that the optimized mechanism better captures the dependence of the measured ignition delay times on temperature, pressure, and blending ratios over the entire temperature range compared to the original mechanism. In the end, species evolution and sensitivity analysis were performed sequentially with the optimized mechanism to give kinetics insight into the chemical interaction between biodiesel and n-butanol. The experimental data and modeling results reported here provide a basis for understanding the combustion reaction kinetics of biodiesel/n-butanol blending fuels.
- A skeletal mechanism for biodiesel-dimethyl ether combustion in engines
The blending of biodiesel and dimethyl ether (DME) can compensate for the shortcomings of the physicochemical properties of each other, which can be used as an alternative fuel in internal combustion engines. A skeletal mechanism including 255 species and 1253 reactions has been developed herein for further in-depth research on the biodiesel-DME blends combustion in an engine. The mechanism consists of four sub-mechanisms associated with fuels, ester groups, small molecules and emissions. During the hierarchical construction of the mechanism, the methyl esters with long carbon chain and high polyunsaturated degree, including methyl-palmitate, methyl-stearate, methyl-linoleate, methyl-5-decenoate and n-decane were used to represent the biodiesel to accurately reflect the combustion behavior of different types of biodiesel fuels. The mechanism has been widely validated against zero-dimensional ignition delay, one-dimensional laminar flame speed, premixed flame species concentration, three-dimensional in-cylinder pressure, heat release rate and soot emissions. The findings reveal that the combustion and emissions characteristics of biodiesel-DME blends can be accurately reproduced by the mechanism. It has been observed that the increasing DME proportion resulted in the extended ignition delay, increasing in-cylinder pressure peak, NOx emissions, and decreasing soot emissions.(Video) What is BIODIESEL? | Skill-Lync
- Numerical modeling of laminar flame speed and autoignition delay using general fuel-independent function
The impact of the transport sector on climate change and carbon dioxide emissions into the atmosphere can be decreased by the utilization of biofuels and e-fuels. The chemical kinetics for calculating the combustion process of new biofuels and e-fuels is often excessively computationally demanding for numerical simulations, leading to the development and employment of combustion models, such as flamelet models. Such models require precalculated data of laminar flame speed and autoignition timing. The developed procedure in this work scrutinizes available reaction mechanisms of several fuels with the validation against existing experimental data of autoignition and laminar flame velocities, aiming for the generation of lookup databases. The autoignition of fuel/air mixtures for different conditions is pre-tabulated from nondimensional calculations of constant pressure reactor. Simultaneously, the laminar flame speed is pre-tabulated from premixed freely propagating reactors, for which calculation chemical kinetics software are applied. The ignition delay of cold flame and primary ignition was calculated using inflection point criteria implemented in the proposed method. The developed imputations method is based on the lognormal distribution for laminar flame speed in equivalence ratio direction and exponential functions for pressure, temperature, and exhaust gas recirculation directions. The laminar flame speed and autoignition databases generation procedure was demonstrated on prospective e-fuel three-oxyethylene dimethyl ether (OME-3) fuel by validating the available mechanism against the experimental data. Finally, the generated databases are implemented into the computational fluid dynamics software and verified with the detailed chemical mechanism of OME-3 fuel.
- Unraveling the low-temperature oxidation mechanism between methyl crotonate radicals and O<inf>2</inf>
2021, Combustion and Flame
In this paper, chemical reaction kinetics at low temperatures on three different methyl crotonate (MC, C5H8O2) radicals with O2 were conducted via quantum chemical methods. The potential energy surfaces (PESs) for these reactions were investigated by M062x/6-311++G(d,p) and CBS-QB3 methods. The related rate coefficients also have been solved by master equations based on Rice-Ramsperger-Kassel-Marcus theory, predicting the competitive relationships over 300 to 1500K and 0.001 to 100 atm. The calculated results indicated that the rate constants of O2 addition reaction at ester methylic site were higher than those at allylic sites, which showed that the conjugation effect caused by the C=C double bond has a crucial effect on the reaction process. Formation of initial adducts and intramolecular H-transfer reactions play a great role in the low temperature oxidation of MC. Furthermore, the mechanism of O2 addition to MC radicals was verified by the previous combustion model. The updated model did a good job to replicate the previous experimental results. This work not only provides the necessary rate constants for the reaction mechanism of MC combustion but also serves as a solid starting point for the further understanding of combustion kinetics of large molecule unsaturated biodiesels.
- Oxidation kinetics of methyl crotonate: A comprehensive modeling and experimental study
2021, Combustion and Flame
The current study explores the combustion behavior of methyl crotonate (CHCH=CHC(=O)OCH), which is a short ester representative of large unsaturated methyl esters. Starting with a detailed kinetic model for methyl butanoate (CHCHCHC(=O)OCH) oxidation, revisions are introduced to the C-C chemistry based on the recent Aramco mechanism 3.0. The resulting mechanism is combined with a short model for methyl crotonate, derived from a suitable reference mechanism. Several new classes of reactions are included and the rate constants of the existing reactions are revised based on various theoretical studies and analogies to reactions of similar species. Furthermore, the low-temperature chemistry of methyl crotonate has been implemented in the current study to extend the validity of the mechanism to lower temperatures. The resulting methyl crotonate combustion mechanism has been comprehensively validated using various experiments in the literature. In addition, experiments are performed using a heat flux burner at atmospheric conditions to measure the laminar burning velocities of methyl crotonate at different unburnt mixture temperatures (318, 338, and 358K). The mechanism is found to reproduce the experimental data for high-temperature combustion of methyl crotonate satisfactorily. The mechanism is also found to predict the low-temperature ignition delays accurately. Sensitivity and path flux analysis are performed to delineate the importance of the different reaction classes in methyl crotonate chemistry. The current study presents a comprehensive mechanism for methyl crotonate combustion, along with a new set of experimental results complementing the existing experimental database in the literature.
- Development of a skeletal mechanism for four-component biodiesel surrogate fuel with PAH
2021, Renewable Energy
A four-component skeletal mechanism consisting of 1,4-hexadiene, methyl decanoate, methyl trans-3-hexenoate, n-hexadecane was developed to represent biodiesel fuel from various sources. The methyl decanoate and n-hexadecane were selected to represent saturated fatty acid methyl esters, and trans-3-hexenoate and 1,4-hexadiene were applied to adjust degree of unsaturation. A skeletal mechanism for this four-component biodiesel surrogate fuel with PAH was first formulated based on decoupling methodology, which contained a detailed C1 mechanism, a reduced C2–C3 mechanism, PAH mechanism and sub-mechanisms of four surrogate fuels, including 314 reactions and 98 species. After that, the skeletal mechanism was widely verified against various fundamental combustion experiments for each pure component and their mixtures. Furthermore, the experimental results of biodiesel soot volume fractions from biodiesel spray combustion in a constant-volume combustion vessel were used to verify the accuracy of the mechanism, and the skeletal mechanism was also coupled into the CFD-software to simulate the combustion characteristics of a diesel engine. Results showed that the calculated results agreed well with the experimental data including ignition delay times (IDTs), primary species concentrations, laminar flame speed, soot prediction and in-cylinder pressure of the engine. Overall, the developed compact skeletal mechanism was suitable for the combustion simulation of biodiesel fuel.
Research articleSkeletal reaction model generation, uncertainty quantification and minimization: Combustion of butane
Combustion and Flame, Volume 161, Issue 12, 2014, pp. 3031-3039
Skeletal reaction models for n-butane and iso-butane combustion are derived from a detailed chemistry model through directed relation graph (DRG) and DRG-aided sensitivity analysis (DRGASA) methods. It is shown that the accuracy of the reduced models can be improved by optimization through the method of uncertainty minimization by polynomial chaos expansion (MUM-PCE). The dependence of model uncertainty on the model size is also investigated by exploring skeletal models containing different number of species. It is shown that the dependence of model uncertainty is subject to the completeness of the model. In principle, for a specific simulation the uncertainty of a complete model, which includes all reactions important to its prediction, is convergent with respect to the model size, while the uncertainty calculated with an incomplete model may display unpredictable correlation with the model size.
Research articleAutoignition delay times of propane mixtures under MILD conditions at atmospheric pressure
Combustion and Flame, Volume 161, Issue 12, 2014, pp. 3022-3030(Video) Introduction to Diesel Fuel Analysis
The aim of the present work was to obtain experimental reference data in controlled, simple systems collected under MILD combustion. The combustion processes evolving under such conditions show behaviors specific to unique ranges of operating conditions that are not predictable using the available kinetic mechanisms.
Experimental tests were conducted in a tubular flow reactor for propane/oxygen mixtures diluted in nitrogen under MILD combustion conditions by varying the mixture composition (from fuel-lean to fuel-rich conditions) and the dilution level over a wide range of temperatures (850-1250K) at atmospheric pressure. Several combustion regimes were identified as a function of these external parameters. Auto-ignition delay times were evaluated, and they showed different levels of dependence on the system inlet temperature for intermediate to high temperatures.
Under MILD combustion conditions, numerical simulations based on several available kinetic models predicted results with weak correlations to the experimental data, especially under fuel-rich, highly diluted conditions.
To identify the controlling reaction pathways that should be tuned to extend the validity of models to wider operating conditions, sensitivity and reaction flux analyses were used. However, this topic is outside of the scope of the present work. This study provides reproducible experimental data for a reference system under novel conditions.
Research articleThe effect of methyl pentanoate addition on the structure of premixed fuel-rich n-heptane/toluene flame at atmospheric pressure
Combustion and Flame, Volume 162, Issue 5, 2015, pp. 1964-1975
The effect of adding methyl pentanoate (MP) on the species pool in a rich premixed flame fueled by n-heptane/toluene blend (7/3 by volume of liquids) at atmospheric pressure is investigated. The emphasis of this work is on the effect of MP on the concentrations of intermediates, which are precursors of polycyclic aromatic hydrocarbons (PAH), in order to understand the processes responsible for reduction of concentration of PAH when biodiesel is added to diesel fuel in combustion devices. Two premixed fuel-rich n-heptane/toluene/О2/Ar (2.29/1.36/21.36/75%) and n-heptane/toluene/MP/О2/Ar (1.26/0.75/2.00/21.355/75%, 50% of liquid MP in liquid fuel mixture of n-heptane and toluene) fuel-rich flames with the same equivalence ratio φ=1.75 were stabilized on a flat burner at 1atm. Molecular beam mass spectrometric measurements of mole fraction profiles of reactants, the major products and many intermediate species were performed. The experimental profiles were compared with those calculated using a detailed chemical kinetic mechanism, which was a combination of two detailed mechanisms proposed earlier in the literature for combustion of n-heptane/iso-octane/toluene mixture and for MP oxidation, respectively. Addition of MP was found to reduce mole fractions of many intermediates, which play an important role in formation of PAH, specifically, benzene, cyclopentadienyl, acetylene, propargyl, and vinylacetylene. Analysis of the reaction pathways responsible for formation of naphthalene, a typical representative of small PAH, was performed in order to elucidate the chemical effect of MP addition on its formation. To ascertain the effect of MP addition on the primary reactions of consumption of n-heptane and toluene, the analysis of the relative contributions of these reactions to the total rate of consumption of the fuels was carried out.
Research articleA skeletal mechanism for biodiesel blend surrogates combustion
Energy Conversion and Management, Volume 81, 2014, pp. 51-59
A tri-component skeletal reaction mechanism consisting of methyl decanoate, methyl-9-decenoate, and n-heptane was developed for biodiesel combustion in diesel engine. It comprises 112 species participating in 498 reactions with the CO, NOx and soot formation mechanisms embedded. In this study, a detailed tri-component biodiesel mechanism was used as the start of mechanism reduction and the reduced mechanism was combined with a previously developed skeletal reaction mechanism for n-heptane to integrate the soot formation kinetics. A combined mechanism reduction strategy including the directed relation graph with error propagation and sensitivity analysis (DRGEPSA), peak concentration analysis, isomer lumping, unimportant reactions elimination and reaction rate adjustment methods was employed. The reduction process for biodiesel was performed over a range of initial conditions covering the pressures from 1 to 100atm, equivalence ratios from 0.5 to 2.0 and temperatures from 700 to 1800K, whereas for n-heptane, ignition delay predictions were compared against 17 shock tube experimental conditions. Extensive validations were performed for the developed skeletal reaction mechanism with 0-D ignition delay testing and 3-D engine simulations. The results indicated that the developed mechanism was able to accurately predict the ignition delay timings of n-heptane and biodiesel, and it could be integrated into 3-D engine simulations to predict the combustion characteristics of biodiesel. As such, the developed 112-species skeletal mechanism can accurately mimic the significant reaction pathways of the detailed reaction mechanism, and it is suitable to be used for diesel engine combustion simulations fueled by biodiesel, diesel and their blend fuels.
Research articleIgnition delay times of very-low-vapor-pressure biodiesel surrogates behind reflected shock waves
Fuel, Volume 126, 2014, pp. 271-281
Ignition delay times for a variety of low-vapor-pressure biodiesel surrogates were measured behind reflected shock waves, using an aerosol shock tube. These fuels included methyl decanoate (C11H22O2), methyl laurate (C13H26O2), methyl myristate (C15H30O2), methyl palmitate (C17H34O2), and a methyl oleate (C19H36O2)/Fatty Acid Methyl Ester (FAME) blend. Experiments were conducted in 4% oxygen/argon mixtures with the exception of methyl decanoate which was studied in 1% and 21% oxygen/argon blends. Reflected shock conditions covered initial temperatures from 1026 to 1388K, pressures of 3.5 and 7.0atm, and equivalence ratios from 0.3 to 1.4. Arrhenius expressions describing the experimental ignition delay time data are given and compared to those derived from applicable mechanisms available in the literature. Graphical comparisons between experimental data and mechanism predictions are also provided. Experiments of methyl laurate, methyl myristate, and methyl palmitate represent the first shock tube ignition delay time measurements for these fuels. Finally, experiments with methyl palmitate represent, to the authors’ knowledge, the first neat fuel/oxidizer/diluent gas-phase shock tube experiments involving a fuel which is a waxy solid at room temperature.
Research articleDevelopment of a reduced biodiesel combustion kinetics mechanism for CFD modelling of a light-duty diesel engine
Fuel, Volume 106, 2013, pp. 388-400
A reduced chemical kinetics mechanism has been developed and validated under zero-dimension and multi-dimensional engine simulations for a range of engine operating conditions and types of biodiesel fuel. The mechanism is first constructed by reducing a detailed MB/MB2D mechanism consisting of 301 species and 1516 reactions to 77 species and 212 reactions. The ignition delay periods and temporal evolutions of important species are in good agreement with those produced using detailed kinetics. The reduced mechanism is then combined with a skeletal modified n-heptane mechanism to account for actual biodiesel energy content and molecular structure when fuel blends are introduced. Two additional global reactions are also included to cater for the change in ratio between saturated and unsaturated methyl esters in the fuels. The combined mechanism (BOS-V2) consists of 113 species and 399 reactions with integrated nitrogen oxides (NOx) reaction kinetics. This mechanism is then further validated using OpenFOAM® for the computational fluid dynamics (CFD) engine simulations. Here, neat and B50 blends of coconut, palm and soy methyl esters are used. Good agreements in ignition delay, peak pressure, pressure trace, heat-release profile and emission trends are achieved between experimental and predicted data for all the tested fuels and engine operating conditions. The results show that the proposed mechanism gives reliable predictions of in-cylinder combustion and emission processes.(Video) How We Make Biodiesel (2018)
Copyright © 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
Table 2 shows the studies results of various lipases on the production of biodiesel from different substrates. From Table 2, it can be seen that the optimum temperature varies between 30-60 °C which means that the optimum temperature is specific for each type of enzyme and substrate.What is the autoignition temperature of diesel? ›
|Material||Autoignition Temperature oF||Notes|
|Diesel||350-625||Laboratory - ASTM|
|Diesel||>1200||Heated catalytic converter. No ignition, test stopped at 1200 degrees F|
|Diesel||1010-1125||Recessed stainless steel plate|
Methane has the highest auto-ignition temperature.What should be the maximum acid value of a biodiesel used in automobiles? ›
The determined acid number of the biodiesel sample is 0.202 mg KOH/g (Table 2). This value complies with the requirements of ASTM D 6751 and EN 14214, which both stipulate a maximum acid number of 0.5 mg KOH/g.What happens to biodiesel at cold temperature? ›
In cold climates, it can be a challenge to fuel vehicles with high blends of biodiesel because biodiesel tends to gel (freeze) at higher temperatures than does conventional diesel. The actual temperature at which biodiesel freezes depends on the type of oil or fat from which it is made.What is biodiesel fuel used for? ›
Biodiesel is a domestically produced, clean-burning, renewable substitute for petroleum diesel. Using biodiesel as a vehicle fuel increases energy security, improves air quality and the environment, and provides safety benefits.What is the autoignition temperature of a fuel? ›
Autoignition Temperature oF
For example, some researchers reported that gasoline would not ignite up to 1200 degrees F., while others had ignition at 1100 degrees F.
Autoignition temperature tests are measured by placing the substance in a half-litre vessel and inside a temperature-controlled oven. As mentioned the current standard procedures for such tests are outlined in ASTM E659.What will happen if the temperature of a fuel is raised to its ignition temperature? ›
This temperature is sometimes referred to as the kindling point of the fuel. Raising the temperature of a fuel to its auto-ignition point provides the energy required to initiate the chemical reaction needed for combustion.Why auto-ignition temperature of petrol is higher than diesel? ›
The calorific value of petrol is greater than diesel engine so that pre ignition temp of petrol is less than diesel. In a petrol engine, it is imperative that the autoignition temperature (the temperature at which the fuel will ignite itself) of the fuel stays high enough.
Get rid of any dust or sawdust as quickly as possible to prevent fire. If you're storing oil-soaked or flammable products indoors, make sure you don't pile too many items together or place them in a confined space. Keep any flammable items away from sources of heat, including radiators and windows.What is the difference between flash point and autoignition temperature? ›
While the flash point is the ambient temperature at which the chemical can spark or ignite (if it meets an ignition source), the auto-ignition temperature is the lowest ambient temperature at which the chemical will spontaneously combust (without an ignition source).How long is biodiesel good for? ›
Use It or Lose It: Biodiesel has a shelf life of about six months; sealed opaque containers with minimal head space (to prevent water condensation) are best for storage.What is the composition of biodiesel? ›
Biodiesel is a renewable transportation fuel consisting of fatty acid methyl esters (FAME), generally produced by transesterification of vegetable oils and animal fats.What are properties of biodiesel? ›
Biodiesel Fuel Basics.
|Kinematic viscosity at 40°C||4.0 to 6.0|
|Cetane number||47 to 65|
|Higher heating value, Btu/gal||˜127,960|
|Lower heating value, Btu/gal||˜119,550|
Some people find their WVO biodiesel starts to gel at around 4-5 deg C (40 deg F). This is because any saturated fats/oils in the WVO will crystallise (solidify) at higher temperatures than unsaturated fats and oils, and separate out, clogging the filter.How do you make biodiesel? ›
How We Make Biodiesel (2018) - YouTubeCan biodiesel be used in cold weather? ›
Low blends of biodiesel (i.e. B5) tend to perform more like conventional diesel fuel in cold weather (i.e. regular No. 2 diesel). Both have some compounds that can crystalize in extreme cold. Additionally, a lower saturated fat content generally creates a better cold weather biodiesel.What are the properties of biodiesel? ›
|Kinematic viscosity at 40°C||4.0 to 6.0|
|Cetane number||47 to 65|
|Higher heating value, Btu/gal||˜127,960|
|Lower heating value, Btu/gal||˜119,550|
Superior performance: Biodiesel offers superior performance over petrodiesel since it has a higher cetane rating and added lubricity. Biodiesel's superior cetane rating means an easier engine startup. Higher lubricity means less wear and tear on your engine over time.
Summary. Biodiesel and petroleum diesel are very similar fuels, but they are not identical. However, the differences are remarkably small when we consider the radically different procedure for making biodiesel as compared to petroleum diesel.Can biodiesel be used in cars? ›
Although all diesel vehicles can operate using biodiesel, some original equipment manufacturers (OEMs) do not approve the use of higher-level blends of biodiesel. Before using biodiesel, be sure to check your OEM engine warranty to ensure that higher-level blends of this alternative fuel are approved.