The high-temperature autoignition of biodiesels and biodiesel components (2023)

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• Cited by (47)
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Combustion and Flame

Volume 161, Issue 12,

December 2014

, Pages 3014-3021

Author links open overlay panelWeijingWangSandeepGowdagiriMatthew A.OehlschlaegerPersonEnvelope

(Video) How does biodiesel impact engines?

Abstract

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.

Introduction

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 [1]. 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 [2]. 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 [3]. Cetane numbers ranging from 44 to 70 have been reported for multi-component biodiesels derived from vegetable oils and animal fats [4].

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., [5], [6]) and a number of recent studies have investigated intermediate-sized methyl ester biodiesel surrogates, including methyl decanoate (C10:0) (e.g., [7], [8]).

Fewer studies have focused on the larger compounds found in biodiesel; however, Dagaut et al. [9] performed jet-stirred reactor oxidation studies on rapeseed biodiesel, Marchese et al. [10] studied the ignition of methyl oleate and commercial soy biodiesel fuel droplets, and Bax et al. [11] have studied methyl oleate oxidation in a jet-stirred reactor. Relevant to the present study, Campbell et al. [12] 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. [13] 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. [14], [15] and for methyl palmitate and stearate by Herbinet et al. [16]. Saggese et al. [17] 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 [18] 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. [19] and Violi et al. [20] 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. [12], [13] 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.

Experimental method

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) [21]. 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

Summary

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

Acknowledgments

This work was supported by the National Science Foundation under Grant CBET-1032453.

References (30)

• H. Wang et al.

Fuel

(2012)

• C.K. Westbrook et al.

Combust. Flame

(2009)

• H.P.S. Shen et al.

Combust. Flame

(2009)

• J.Y.W. Lai et al.

Prog. Energy Combust. Sci.

(2011)

• L. Coniglio et al.

(Video) Production of Biodiesel From Vegetable Oil

Prog. Energy Combust. Sci.

(2013)

• C. Saggese et al.

Proc. Combust. Inst.

(2013)

• O. Herbinet et al.

Proc. Combust. Inst.

(2011)

• C.K. Westbrook et al.

Proc. Combust. Inst.

(2013)

• C.K. Westbrook et al.

Combust. Flame

(2011)

• M.F. Campbell et al.

Proc. Combust. Inst.

(2013)

• S. Bax et al.

Combust. Flame

(2010)

• A.J. Marchese et al.

Proc. Combust. Inst.

(2011)

• W. Wang et al.
• O. Herbinet et al.

Combust. Flame

(2008)

• S. Dooley et al.

(2008)

• Cited by (47)

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FAQs

What is the temperature of biodiesel? ›

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? ›

MaterialAutoignition Temperature oFNotes
Diesel350-625Laboratory - ASTM
Diesel>1200Heated catalytic converter. No ignition, test stopped at 1200 degrees F
Diesel950-1000Heated pipe
Diesel1010-1125Recessed stainless steel plate
3 more rows

Which fuel has the highest auto ignite temperature? ›

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.

How is autoignition temperature determined? ›

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.

How do you stop autoignition? ›

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 is a renewable, biodegradable fuel manufactured domestically from vegetable oils, animal fats, or recycled restaurant grease.
...
Biodiesel Fuel Basics.
Specific gravity0.88
Kinematic viscosity at 40°C4.0 to 6.0
Cetane number47 to 65
Higher heating value, Btu/gal˜127,960
Lower heating value, Btu/gal˜119,550
9 more rows

What temperature does biodiesel solidify at? ›

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) - YouTube

Can 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? ›

Biodiesel Fuel Basics
Specific gravity0.88
Kinematic viscosity at 40°C4.0 to 6.0
Cetane number47 to 65
Higher heating value, Btu/gal˜127,960
Lower heating value, Btu/gal˜119,550
9 more rows

Which is better biodiesel or diesel? ›

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.

Is biodiesel the same as diesel? ›

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.

Videos

1. Biodiesel Masterclass: Testing Your Oil Beforehand
(Biodiesel Education)
2. CIMAC Tech Talks special 'Engine Components + Basic research'
(CIMAC)
3. Biodiesel
(Stephanie Lansing)
4. Biofuel instead of coal and oil - How promising are these renewable resources? | DW Documentary
(DW Documentary)
5. 1672 Biodiesel 101 - The How And The Why And The Wherefore Of Making It
(Robert Murray-Smith)
6. The Chemistry Of Diesel Fuel - Russell S.
(Science is Life)
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Author: Lakeisha Bayer VM

Last Updated: 02/05/2023

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Name: Lakeisha Bayer VM

Birthday: 1997-10-17