Experimental and Kinetic Study on the Cool Flame Characteristics of

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Experimental and Kinetic Study on the Cool Flame Characteristics of Dimethyl Ether Zijun Wang, Xiao-Long Gou, and Chen Zhong Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.9b01711 • Publication Date (Web): 09 Aug 2019 Downloaded from pubs.acs.org on August 12, 2019

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Experimental and Kinetic Study on the Cool Flame Characteristics of Dimethyl Ether Zijun Wanga,b, Xiaolong Goua,b*, Chen Zhonga,b

*

Corresponding author. E-mail: [email protected]. Tel: 86-23-65103080.

ACS Paragon Plus Environment

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a

Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Chongqing University, Ministry of Education, Chongqing 400044, China b

School of Power Engineering, Chongqing University, Chongqing 400044, China

Abstract As one of the most promising alternative fuel to diesel engines, dimethyl ether plays a significant role in improving combustion efficiency and decreasing emissions, and an in-depth understanding of its combustion characteristics is the basis for efficient use. Although there are several chemical mechanisms which used for kinetic modeling of dimethyl ether to reproduce its detailed information in the combustion process, the mechanism for cool flame is still imperfect and the experimental data for ignition and flame is also very scarce. At the same time, low-temperature combustion associated with cool flame not only affects the safety of the engine but is also critical to the technologically advanced engine. In this work, both experimental and numerical methods are applied to study the cool flame characteristics of dimethyl ether. In a cylindrical reactor, the premixed dimethyl ether/air cool flame under different temperature, pressure and equivalence ratio conditions was studied in detail, and the different ignition zones were obtained. Based on the commonly used dimethyl ether kinetic mechanism, the numerical simulation of the process of cool ignition and extinction limits were carried out. And the species concentration distribution and temperature profile


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were compared and analyzed. Combined with heat release and reaction path analysis, the ability of these mechanisms to describe the characteristics of dimethyl ether cool flame was evaluated, which contributes to the deep understanding of the cool flame process and the improvement of the mechanism in the cool flame zone.

Keywords: cool flame, dimethyl ether, auto-ignition, kinetic mechanism


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1 Introduction Since the first observation about the dimethyl ether (DME) cool flame by Davy in the 19th century 1 , lots of researches have been carried out to study the detail of cool flame including the formation, propagation2, extinction3, stabilization4-5 and application

6-7.

Cool flame exists

in the combustion process of most hydrocarbon fuels and is an important part of lowtemperature combustion 8, and it is related to the engine knock 9-10, the negative temperature coefficient (NTC) phenomenon 11, fuel cell system 8 and fire safety in space 12. Besides, the radicals like HO2 accumulated in the premixed cool flame process significantly affect the second stage ignition [6] and the cool flame reactions do have influences on the harmful species formation 13. Cool flame is generally known as a faint and blue flame by visual observation. Another unique characteristic is that the emission spectrum of cool flame coincides with that of the excited formaldehyde (CH2O*) regardless of the fuel type

14.

It is basically induced by low-

temperature oxidation mechanisms such as the secondary oxidation of hydrocarbon fuels, molecular elimination of HO2 from ROO and the isomerization of hydro-peroxide

15-16,

while

the hot flame is controlled by the production of radical species O and OH in the hightemperature region. Dimethyl ether was one of the most promising alternative fuel to diesel engines due to the low toxicity, better combustion efficiency, and high accessibility. Its high oxygen content and non-C-C bond results in less smoke emission, while its high cetane number makes it a good alternative for auto-ignition. Besides, it can be mixed not only with diesel but also with


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biodiesel, liquefied petroleum gas, palm methyl ester and other fuels17, which will have contrary properties with alcohol/diesel dual fuel. For a deeper understanding of the combustion process of dimethyl ether, lots of effort has been contributed to the development of accurately detailed DME chemistry since the end of last century. In 1996, Pfah et al. 18 investigated the stoichiometric DME/air mixture ignition delay time using high-pressure shock tubes with pressure of 13 and 40 bar, temperature of 650-1300 K. Dagaut et al. 19 firstly measured the species concentration profiles in a jet-stirred reactor over 1-10 atm, 0.2 G equivalence ratio G 2.5, 800-1300 K temperature and a DME kinetics model consist of 43 species and 286 reactions was also developed. Subsequently, Curran et al. 20 established another DME detailed reaction mechanism (78 species and 336 reactions) capable of predicting the above two experiments, of which low-temperature pathways was later abounded by Dagaut P et al. 22-23

21.

After that, Fischer, Dryer, and Curran

carried out a series of experiments based on turbulent flow reactors, covering high (1118

K, 3.5 atm and 1085 K, 1 atm, equivalence ratio of 0.32-3.40, with N2 diluent of about 9899.7%) and low temperature (550-850 K, 12-18 atm, equivalence ratios of 0.7-4.2, with N2 diluent of about 98.5%) conditions, meanwhile a detailed DME reaction mechanism updated from prior Curran’s model 20 was obtained. Recently, benefit by the more reliable molecular simulation and more advanced measuring approach, some improvement have been made about the detailed DME reaction model. Zhao et al. 24 update the decomposition reactions of the Fischer’ model 22 by the new pyrolysis data obtained by Rice Ramsperger Kassel Marcus (RRKM)/master equation


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calculations

25.

The compact kinetics model performed reasonably well in a wide range of

combustion conditions including flow reactors, jet stirred reactors, shock tubes, and burner stabilized flames. Wang et al.

26

measured species profiles of low-pressure laminar burner-

stabilized DME flames by Molecular-beam synchrotron photoionization mass spectrometry and electron-ionization mass spectrometry method. According to the experimental results and theoretical calculations, Wang adjusted the Zhao’s reaction model 24 with the addition of chemically-activated pathway of CH3OCH2 reaction with O2, as well as of the new decomposition chemistry of OCH2OCHO radical. Burke et al. 27 measured the ignition delay time of DME/Air mixture, at T = 600-1600 K, p = 7-41 atm, and equivalence ratios = 0.3, 0.5, 1.0, 2.0, in a rapid compression machine (RCM) and a shock tubes. The low-temperature reactions of DME were firstly treated as pressure-dependent in their detailed chemical kinetic model. Although there are a large number of mechanisms describing the combustion process of dimethyl ether, the low-temperature reactions related to cool flame is still unrevealed. Flow reactor 28-30 and counter-flow apparatus 31-33 are used to study DME laminar cool flame. Most of the cool flame in counter-flow apparatus focused on the premixed cool flame with ozone addition to sustain the cool flame 31-33. Under these experimental circumstances, the flames are visible and the temperature rises are around 200-300K. However, the temperature rises are much lower, around 20-30K in the regularity of periodic oscillation and no luminescence can be captured in flow reactors 28. It is found that a proper residence time corresponding to an appropriate strain rate is essential to a steady state cool flame in premixed DME/N2/O2 mixture in the counter-flow configuration 2. The turbulent cool diffusion flames are also studied


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experimentally with Co-flow Axisymmetric Reactor-Assisted Turbulent (CARAT) burner

34.

Therefore, it is urgent to improve the mechanism for cool flame and enrich the experimental data for ignition and flame structure in the cool flame region. In this paper, the widely used dimethyl ether mechanisms in recent years were used to simulate the cool flame characteristics of dimethyl ether and compared with the experimental results. Then the path analysis and heat release analysis were carried out in the cool flame zone and the decisive path and species were obtained, and the existing problems of the dimethyl ether mechanism in simulating the cool flame are pointed out, which provides a piece of useful information for the future mechanism improving.

2 Non-adiabatic Autoignition Lots of cool flame experiments have been performed, most of which focus on the cool flame structure information through counter-flow configuration. However, the cool flame data of DME under homogeneous conditions are still very scarce. In this study, the constantvolume chamber was used to study the ignition limit of premixed DME/Air cool flame.

2.1 Experimental approach and results

Figure 1 illustrates the experimental apparatus. A cylindrical reaction chamber that can produce a homogeneous condition for DME/Air mixtures at the desired concentration was constructed. The reaction vessel is cylindrical and made of 316 stainless steel with an inner diameter of 4.5 cm, a wall thickness of 0.08 cm and a volume of 450 cm3. More detailed information is illustrated in 35. The chamber will be pre-heated by using a heating tape to the


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of the temperature and pressure at the time of the gas distribution. Therefore, the flammable region of DME/Air in the constant-volume chamber in which the equivalence ratio is the abscissa and the density is the ordinate is given in Fig.2. The flammable region can be divided into cool ignition, hot ignition and non-reaction according to the pressure change.

Fig 2 Flammable region of DME/Air in the constant-volume chamber (black line: polynomial fit)

In the case of a certain equivalence ratio, as the density of the initial mixture increases, it will undergo four stages of no reaction, cool ignition, no reaction and hot ignition. And the lower boundary pressure value of the ignition zone increases with the equivalence ratio. However, it is not enough to distinguish cool ignition and hot ignition based solely on the pressure change. In order to figure out the type of the ignition model and the specific reaction


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taking place under each condition, the numerical simulation is carried out, and the results are shown in the next section.

2.2 Numerical Analysis

To simulate the non-adiabatic ignition process of DME, the constant-volume homogenous reaction kinetics model considering heat exchange with the solid wall has been established. In this numerical model, the temperature distribution inside the steel wall of the reactor is governed by the one-dimensional unsteady transfer equation: d 2Ts 2 s c dx

dTs dt

Qtransfer s

c

(1)

where Ts, Ls ,c is the solid temperature, density and specific heat capacity, respectively,

M is the thermal conductivity and Qtransfer is the rate of heat exchange between the premixed mixture and solid wall per unit time.

With the assumption that the reacting mixture in the vessel is always keeping the homogenous static state, the equations for fluid are given as: Ut

S

(2)

with 0 Qtransfer

f

Ef U

Y

S

f 1

...

1

(T f , p, Y1 ,..., YNS 1 )

... f

YNS

1

,

NS 1

(T f , p, Y1 ,..., YNS 1 )


,

E

p

f

hmix

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in which Lf represents the mixture density, p is the pressure, hmix is the mixture enthalpy per mass, E is the total energy, Yi is the mass fraction of the ith species. In addition, the thermally perfect ideal gas is assumed to give the auxiliary relations as: NS

M mix

[ i 1

NS

Yi 1 ] ,p Mi

RuT / M mix , hmix

(3)

Yi hi i 1

Numerical method solving the heat transfer equation is the standard second-order central difference scheme and the reaction ODEs and thermal psychical property simulated by the open source reaction kinetics solving tools

36.

The mixture temperature is evaluated

with the Newton-Raphson iteration. The detailed mechanisms used in this numerical study are shown in Table 1. Because the cool flame mechanism is still imperfection and the performance of each mechanism is different in the test, all of the mechanisms are used to simulate the experimental conditions in Fig.2.

Table 1 Mechanisms of Dimethyl Ether

No

Mechanism ID

.

Species(Reactio

Mechanism Validation

ns) number Shock

JSR

Tube

Flow

Flame

Flame

Reacto

Speed

Speciatio

r

1

Reference

HPmech-v3.3

130(893)

R

R

R

n

R


R

Reuter et al. 2018 37

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2

AramcoMech3.

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581(3037)

R

R

R

R

R

Zhou et al. 2018 38

0

3

NUI Galway

113(710)

R

-

-

-

-

Burke et al. 2015 39

4

Liu

55(295)

-

-

-

R

R

Liu et al. 2013 40

5

Zhao

55(290)

R

R

R

R

R

Zhao et al. 2008 41

6

LLNL

79(351)

R

R

R

-

R

Fischer

et

al.

&

Curran et al. 20002223

7

Wang

56(301)

R

R

R

-

-

Wang et al. 2015 42

8

UC-SanDiego

63(284)

R

R

R

R

-

Prince et al. 2015 43

As shown in Fig.3, the numerical pressure is in good agreement with the experimental results. According to the temperature results under these conditions, as shown in Fig.4, the peak temperatures simulated by each mechanism are between 1300-1500K, 2700-2800K and 1800-2000K, respectively. And the ignition models at this time can be identified as cool ignition, hot ignition, and cool ignition according to the temperature, respectively. In addition, the same simulation can be carried out for all the other experimental conditions shown in Fig.2 with different heat dissipation conditions, and the obtained peak temperature is roughly divided into two intervals of 1300-2000K and >2500K, and the corresponding pressure change multiples are 3-5, >5 (cool ignition and hot ignition) respectively, which can be seen


Page 13 of 33

as a pressure criterion for judging the ignition model. The region in Fig.2 was defined according to this criterion. Exp HPmech-v3.3 Zhao Wang LLNL Liu NUI-Galway UC-SanDiego

2.5 2.0

Exp HPmech-v3.3 UC-SanDiego Zhao Wang LLNL Liu NUI-Galway

7

Pressure (MPa)

Pressure (MPa)

3.0

1.5

6 5

Exp HPmech-v3.3 Zhao Wang LLNL Liu NUI-Galway UC-SanDiego

1.6 1.4

Pressure (MPa)

3.5

1.2 1.0

4

0.8

3

1.0

0.6

2 0.4

0.5 1

0.0 100

0.2

150

200

250

300

350

400

450

500

0

550

100

200

300

Time (s)

400

500

600

700

0

800

50

100

150

200

250

300

350

400

450

Time (s)

Time (s)

Fig.3 The comparisons of numerical and experimental pressure profile in constant-volume chamber under (a) P0= 0.68 MPa, T0= 485.98K, equivalence ratio=5 (b) P0=1.0 MPa, T0= 491.28K, equivalence ratio=1 (c) P0= 0.41 MPa, T0= 482.81K, equivalence ratio=0.5

2500

3000

HPmech-v3.3 Wang LLNL Liu NUI-Galway UC-SanDiego

1200

HPmech-v3.3 Zhao Wang LLNL Liu NUI-Galway UC-SanDiego

2500

Temperature (K)

1400

1000

800

2000

HPmech-v3.3 Zhao Wang LLNL Liu NUI-Galway UC-SanDiego

2000

Temperature (K)

1600

Temperature (K)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

1500

1000

600

1500

1000

500

500

400 0

100

200

300

t (s)

400

500

600

0 100

0

150

200

250

300

350

400

450

500

550

t (s)

600

0

50

100

150

200

250

t (s)

Fig.4 The comparisons of numerical temperature profile in constant-volume chamber under (a) P0= 0.68 MPa, T0= 485.98K, equivalence ratio=5 (b) P0=1.0 MPa, T0= 491.28K, equivalence ratio=1 (c) P0= 0.41 MPa, T0= 482.81K, equivalence ratio=0.5

The mass fraction distributions of important intermediate component (CH2O/HO2) under cool ignition model are shown in Fig. 4. It is clear that there is a big difference between the numerical results using different mechanisms. In order to determine which mechanism can correctly characterize the characteristics and the key reaction path of dimethyl ether cool


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flame, some dimethyl ether cool flame experiments performed by other researchers are also summarized and reaction path analysis is carried out in next section.

1.2E-01 1.0E-01 8.0E-02

2.5E-03

HPmech-v3.3 Zhao UC-SanDiego Wang LLNL Liu NUI-Galway

HPmech-v3.3 Zhao UC-SanDiego Wang LLNL Liu NUI-Galway

2.0E-03

Mass Fraction of HO2

1.4E-01

Mass Fraction of CH2O

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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6.0E-02 4.0E-02

1.5E-03

1.0E-03

5.0E-04

2.0E-02 0.0E+00

0.0E+00 150

200

250

300

350

400

450

100

150

Time (s)

200

250

300

350

400

450

500

Time (s)

Fig.5 The numerical species distribution under P0= 0.68 MPa, T0= 485.98K, equivalence ratio=5 (a)Mass fraction of CH2O (b) Mass fraction of HO2

3. Diffusion Counter-flow Cool Flame By far, most studies on low-temperature oxidation of dimethyl ether are carried out with the counter-flow burner. In these counter-flow experiments, the flame is typically ignited by preheating the one side of oxidant and fuel, and different flame states are measured in varying the strain rate, the equivalence ratio, the boundary temperature and so on. In addition, Jian G

29

and Reuter C B 34also

performed cool flame measurements in glass tubes and turbulent coaxial jets, respectively. In summary, the DME counter-flow cool flames structure in different configure showed in Table 2. Among these experiments, No.5 is the only current DME cool flame experiment that does not contain any plasma with a component mole fraction, and temperature distribution information of DME cool flame. Therefore, DME cool flame experiments without O3 under counter-flow conditions of Reuter


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C B44 are selected to validate the performance of kinetic mechanisms. The basic ideas of perfecting the cool flame mechanism are obtained by comparing the numerical and the experimental results.

Table 2. Experiments on DME counter-flow cool flames

Pressur No

ID

Type

Upper nozzle

Lower nozzle

Data

Ref

e

300K DME/N2 1

Deng-2014

Diffusion

Heated Air

HCHO mole fraction;

ignition temperature

(3/7 to 55/45 mole ratio)

Heated O2/N2 2

Deng-2017

16

1 atm

300K DME/N2

Diffusion

ignition and 3

2/3 atm (21/79&25/75 mole ratio)

extinction behavior

(1:1 mole ratio)

flame regime 300K DME/O2/O3

Reuter3

Premixed

600K N2

2016

1 atm

diagram; CH2O

31

(V =0.086 to 0.21,with 3% O3) profile

300K DME/O2/O3 Reuter-

Partially

4

(V = 0.08 to 0.11,with 3.5% 2017

premixed

flame regime

550K DME/N2 1 atm

diagram; CH2O

33

(XF=0.35,0.44,0.48) O3)

profile

extinction limits; 300K O2/O3

Reuter5

Diffusion 2018

1 atm temperature/DME/O

550K DME/CH4/N2 (with 0 to 3.7% O3)

2 profiles


37, 44

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3.1 Extinction Limit

Recently, to clarify the most important exothermic reactions in the cool flames, Reuter et al.37 measured the DME/CH4/O3 cool flames extinction. The critical global extinction strain rate for fuel stream of DME/N2 at 550K and oxidant of oxygen at room temperature are selected as the verification in this section. The one-dimensional simulations are performed using CHEMKIN-PRO software package with the extinction of diffusion counter-flow flame model and the results are shown in Fig.6. 500

EXP HPmech-V3.3 Zhao-Vr-500 LLNL-Vr-290 Wang Liu-Vr-430 UC-SanDiego

450 Extinction Strain Rate (s-1)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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400 350 300 250 200 150 100 50 0.32

0.36

0.40 0.44 0.48 Fuel Mole Fraction

0.52

0.56

Fig.6 Comparison of the simulated and experimental results37 on the extinction limit of DME cool flame (Fuel: DME/N2, 550K Oxide: O2, 300k, L=2.25cm, Zhao-Vr-590: The results obtained from Zhao is shifted down 590)

Figure 6 shows the extinction strain rate calculated from six mechanisms at different fuel mole fraction. It can be obtained that the mechanisms can be divided into two groups according to their derivative. The slope and value of extinction strain rate obtained from


Page 17 of 33

HPmech-V3.3, Wang and UC-SanDiego are closer to the experimental value. On the contrary, the others show a much higher extinction strain rate and the curves are steeper.

3.2 Flame Structure

To further understand which mechanism can describe the cool flame process of dimethyl ether more accurately and illustrate the reaction path in cool flame region, several mechanisms mentioned above were used to describe the cool flame and the results are compared with experimental data 37, shown in Fig.7.

a=60-1

750 700

EXP EXP-shift

650

1.0 0.6 HPmech-v3.3 LLNL NUI-Galway Liu Zhao UC-SanDiego Wang AramcoMech3.0 EXP

0.5 0.4 0.3

0.8

0.6

0.4

0.2

600

0.1

0.2

550

0.0 500 0.6

0.8

1.0

1.2

1.4

0.0 0.6

0.8

Distance (cm)

(a) Temperature

1.0

1.2

Distance (cm)

(b) DME and O2 mole fraction


1.4

O2 Mole Fraction

800

HPmech-v3.3 LLNL NUI-Galway Liu Zhao UC-SanDiego Wang AramcoMech3.0

DME/N2 VS O2 Xf=0.59 Tf=550k

DME Mole Fraction

850

Temperature (K)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Energy & Fuels

0.05 0.04

0.0030

HPmech-v3.3 LLNL NUI-Galway Liu Zhao UC-SanDiego Wang AramcoMech3.0 EXP-shift

DME/N2 VS O2 Xf=0.59 Tf=550k a=60 s

-1

0.0025

CH3OCHO Mole Fraction

CH2O Mole Fraction

0.06

0.03 0.02 0.01 0.00 0.4

0.0020


0.0005

0.0000

0.6

0.8

1.0

1.2

1.4

1.6

1.8

0.4

0.6

0.8

0.004

1.0

1.2

1.4

1.6

1.8

Distance (cm)

(d) CH3OCHO mole fraction

0.025


DME/N2 VS O2 Xf=0.59 Tf=550k -1

a=60

0.020

CO Mole Fraction

0.005

a=60-1

0.0010

(c) CH2O mole fraction

0.006

DME/N2 VS O2 Xf=0.59 Tf=550k

0.0015

Distance (cm)

H2 Mole Fraction

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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0.003 0.002

0.015


DME/N2 VS O2 Xf=0.59 Tf=550k a=60-1

0.010

0.005

0.001 0.000 0.4

0.000

0.6

0.8

1.0

1.2

1.4

1.6

1.8

0.4

0.6

Distance (cm)

0.8

1.0

1.2

1.4

1.6

1.8

Distance (cm)

(e) H2 mole fraction

(f) CO mole fraction

Fig. 7. Measured and computed profiles for DME cool flames without ozone. For easier comparison, the experimental points 37 have been shifted right by 0.2 cm (Fuel: DME/N2=0.59/0.41, 550K Oxide: O2, 300k, a= 60 s-1, L=2.25cm)

Figure 7(a) shows that the temperature peaks appear at similar locations but different values. Compared to the experiment results, Wang’s model has the best performance in temperature prediction while LLNL has the maximum deviation. All the mechanisms can reproduce the consumption of the reactants quite well. But there are some differences in the


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simulation of the generation of intermediate components. All the mechanisms have overpredicted the mole fraction of CH2O and CO, as shown in Fig.7(c) and Fig.7(f). It is indicated in Fig.7(d-e) that the HPmech-v3.3 has under-predicted the mole fraction of CH3OCHO and H2, while others all over-predicted them. And the AramcoMech3.0 has a better performance in predicting CH3OCHO and H2 than others.

Fig 8. The main reaction path of DME Vs O2 diffusion cool flame at 10% of DME consumption under counter-flow conditions. (Fuel: DME/N2=0.59/0.41, 550K Oxide: O2, 300k, a= 60 s-1; L=2.25cm The arrow with a solid line represent shared reaction paths, and the arrow with a dashed line of different colors represent separate paths for each mechanism)

To analyze the detailed information of cool flame and explain why each mechanism produces different results for cool flame simulation, the main reaction path analysis starting from CH3OCH3, illustrated in Fig 8, was taken at the position of 10% DME molar concentration consumption where the combustion totally controlled by the low-temperature reactions and


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Page 20 of 33

the species is relatively simple. The percentages aside the arrow correspond to this path as a percentage of total consumption and each color represents for a different mechanism (e.g.: 38.6% in blue color, on the right side of Fig 8, means that 38.6% of CH3OCH2O2 was consumed to generate O2+CH2O+CH3O in the simulation with the UC-SanDiego mechanism). It can be seen from the path analysis that there are many common paths in different mechanisms, such as the H-atom abstraction of DME, the oxidation/decomposition reaction of CH2OCH2O2H, and so on. However, the proportion of the same reactions in these mechanisms is quietly different. Meanwhile, each mechanism shows lots of unique reactions and even the different primary productions at the position illustrated in Fig 8, only CH2O in the UC-SanDiego model but CH3OCHO and CH2O in others. More specifically, the US-C model shows great differences in the consumption of CH3OCH2O2 (RO2) and CH2OCH2O2H (R’OOH). On one hand, UC-SanDiego's unique cleavage reaction 2CH3OCH2O2 =O2+CH3O+CH2O consumes up to 38.6% of CH3OCH2O2, which seems like a substitute for the CH3OCH2O2

CH3OCH2O

CH2O, CH3O, CH3OCHO,

CH3OCHO pathways in other kinetics models. Moreover, it lacks the reaction from CH3OCH2O2 to CH3OCHO and CH3OCH2OH. The same phenomenon occurs in the NUIGalway model. On the other hand, the decomposition reaction CH2OCH2O2H = HO2CH2OCHO+OH consumed more than 60% of CH2OCH2O2H, which demonstrates that the secondary alkyl+O2 reactions played a dominant role in other mechanisms is neglected.


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Energy & Fuels

The NUI-Galway mechanism has a more complex path of the CH3OCH2O (R

)

consumption and a unique reaction trend of CH3OCH2O2 (RO2). On one hand, there are three type oxidation reactions of CH3OCH2O, among which CH3OCH2 unique to the NUI-Galway model, and CH3OCH2O Galway and HPmech-v3.3 models. CH3OCH2

HO2+CH3OCHO is

CH2O+CH3O is included both in the NUIHO2+CH3OCHO is one of the important

sources of CH3OCHO in the NUI-Galway model since there are no CH3OCHO directly produced from CH3OCH2. On the other hand, the reaction CH3OCH2O2 compensates the relatively low ratio (15.8%) of CH2OCH2O2H

OH+CH2O

OH+CH2O, which are the

same in AramcoMech3.0 model. The HPmech-v3.3 mechanism reaction path shows that H abstraction from CH3OCH3 caused by radical H is lacking. And more than 90% of CH3OCH2O (R

) is decomposed into

CH2O and CH3O, which leads to a higher production of HCO in consequence. The LLNL, Liu and Zhao mechanism have the most simplified reaction structure. Nearly 100% of CH3OCH2 in these three mechanisms went to the road of addition to O2, while others will decompose into OH and CH2O.Especially for the Liu mechanism, the OH abstraction from O2CH2OCH2O2H was also neglected. As for the Wang mechanism, which has the best performance in predicting the temperature, nearly 20% of CH3OCH2 will be oxidized into OH and CH2O through O2 addition, higher than other mechanisms. Besides, the decomposition of HO2CH2OCHO is also emphasized. In general, each mechanism has its own different description for the initial lowtemperature consumption of DME including the reaction path and species. Combined with


Energy & Fuels

the profiles of DME mole fraction and temperature shown in Fig.7, the different initial reaction paths of DME in these reaction kinetics models resulted in different heat release rates, which can be concluded from the temperature distribution, but there is no big difference of DME consumption rates between them according to the slope of the curve. CH3OCH2O+O2CH3OCHO+HO2 CH3OH+HCOCH3O+CH2O CH3O+O2CH2O+HO2 CH3OCH2O2+CH3OCH2O2=O2+2CH3O+2CH2O CH3O+MCH2O+H+M HCO2+HO2=HCO2H+O2 CH3O+CH2OCH3OCH2O

6E+05

Heat Production (J/m3-sec)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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5E+05

CH3OCH2+O2=OH+CH2O+CH2O CH2OCH2O2H+O2HO2CH2OCHO+OH HCO+O2=CO+HO2 CH3OCH3+H=CH3OCH2+H2 H2O2+O2=HO2+HO2 CH2OCH2O2H=OH+CH2O+CH2O CH3OCH2O2+CH3OCH2O2=CH3OCHO+CH3OCH2OH+O2 CH3OCH3+OH=CH3OCH2+H2O O2CH2OCH2O2H=CH2OCH2O2H+O2 O2CH2OCH2O2H=HO2CH2OCHO+OH CH3OCH2+O2=CH3OCH2O2 CH3OCH2O2=CH2OCH2O2H

4E+05 3E+05 2E+05 1E+05 0E+00 LLNL

Zhao

Liu

NUI

Ara3.0

UC-S HP-v3.3 Wang

Mechanism ID Fig 9 The heat production of selected reactions of DME Vs O2 diffusion cool flame at 10% of DME consumption under diffusion counter-flow conditions (Fuel: DME/N2=0.59/0.41, 550K Oxide: O2, 300k, a= 60 s-1, L=2.25cm)

From the results of the path analysis in Fig.8, it can be seen that the reaction path of the UC-SanDiego mechanism is quite different from that of other mechanisms. However, the heat production results are similar to those of the mechanism simulations such as Wang, and the temperature results are relatively close to that obtained by experiments. The results of the heat release analysis of UC-SanDiego indicate that although the intermediate component of


Page 23 of 33

the path CH2OCH2O2H

O2CH2OCH2O2H

HO2CH2OCHO is omitted, the heat of the path

is not neglected, and the heat of the direct reaction (4.00E+05 erg/cm3-s ) is similar to the result of superimposing the heat of the two-step reaction (4.52E+05 erg/cm3-s). On the other hand, at this position, there is an additional reaction of CH3O+O2=CH2O+HO2 and two endothermic

reactions

CH3O+M=CH2O+H+M

and

CH3OCH2O2+CH3OCH2O2=O2+2CH3O+2CH2O in the mechanism of UC-SanDiego. Finally, the total heat release from the UC-SanDiego mechanism simulation is similar to that of the Wang and other mechanisms, which is one reason why the final simulated temperature is also close to the experimental value. 6E8

Net Heat Production from Reactions (erg/cm3-sec)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

6E8

zhao 5E8

5E8

nui

ara 3.0

liu llnl

4E8

uc-s

4E8

hp 3E8

3E8

wang 2E8

2E8

1E8

1E8

0.95

1.00

1.05

1.10

1.15

1.20

0.95

Distance (cm)

1.00

1.05

1.10

1.15

1.20

Distance (cm)

Fig.10 The net heat production from reactions simulated by different mechanisms under diffusion counter-flow conditions (Fuel: DME/N2=0.59/0.41, 550K Oxide: O2, 300k, a= 60 s-1, L=2.25cm The mechanisms framed represent the higher temperature results in Fig.6.)

In addition to the difference in the magnitude of the heat release at the initial stage of the reaction given in the Fig.9, the total amount of heat release along the distance distribution is also very different, as shown in Fig. 10. It can be seen that the heat release distribution


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presents two types of results, in which the results of the HPmech-v3.3 and AramcoMech3.0 mechanisms are single peak, and the heat release values obtained by other mechanism simulations distribute two peaks of the heat releases along the distance.

Net heat production from reactions

Temperature

5E8

1

4E8 600 3E8 500 2E8 400

0.01

P=1 atm

1E-3

1E-4

300

0 0.8

0.1

700

1E8

HPMECHNEW LLNL CURRAN LIU ZHAO UCSANDIEGO WANG ARAMCO3.0

800

Temperature (K)

6E8

Ignition_delay time (s)

Net heat production from reactions (erg/cm3-sec)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 33

0.9

1.0

1.1

1.2

1.3

1.4

1E-5 0.6

Distance (cm)

0.8

1.0

1.2

1.4

1.6

1.8

1000/T (1/K)

Fig.11 (a) The temperature and net heat production from reactions distribution information of Zhao’s model. (b) The

ignition delay time of DME/O2 calculated by each mechanism.

The essential cause of two peaks in heat release is the NTC characteristics of the fuel. Taking the Zhao mechanism as an example, its temperature and heat distribution is shown in Fig. 11. It can be seen that: (1) the temperature at the position of the two heat release peaks is the same (about 760k), and coincides with the initial temperature of the NTC region expressed by the Zhao mechanism; (2) the heat release curve trough position is at the same position as the temperature peak. This means that once the temperature in the cool flame reaches the NTC region, the activity of the reaction system begins to decrease, causing the temperature to rise to slow down or even decrease. Therefore, the lower limit temperature of the NTC zone has a decisive influence on the width of the high-temperature zone of the hedged cool flame. Moreover, the degree of NTC behavior pronounced by the model is also closely related to the heat release profile. As shown in Fig.11, it is indicated that Zhao's


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Energy & Fuels

ignition delay is most negatively correlated with temperature, and the heat release curve is the lowest. In conclusion, all the mechanisms can reproduce the cool flame phenomenon of DME and share a common reaction path: RH

FY

RO2

QOOH, which is recognized as an

important part of low-temperature oxidation of hydrocarbon fuels. And the difference between them is that the way they produce aldehydes and radicals, which results in the different expression of temperature, extinction limit and other species. For extinction limit and temperature, HPmech-v3.3, Wang and UC-SanDiego have better results than others. For CH2O and CO, the results of all the mechanisms are much larger than the experimental values, and the AramcoMech3.0 and HPmech-v3.3 mechanism has the minimum value, respectively. For CH3OCHO, the AramcoMech3.0 and NUI-Galway mechanism have better results than others. For H2, the AramcoMech3.0 and Wang mechanism have better results than others. Considering the simulated results of extinction limit, temperature and the distribution, we recommend the reaction path in Fig.12 as a basic construction of the mechanism for the cool flame. There are also some other reaction paths from RO2 are not shown in Fig.12 because they are optional, which can be seen in Fig.8 that NUI-Galway has a different reaction path from other mechanisms, but this mechanism still can have a good prediction of the distribution of species.


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Fig.12 The basic reaction pathway in the cool flame region concluded from the mechanisms used in this study

4 Conclusions The DME/air mixtures combustion behavior measurements under the homogeneous conditions were carried out and a series of numerical simulations using different reaction kinetics models were conducted, respectively. In this study, the DME flammable region, the difference between several widely accepted mechanisms for DME and the reaction path for cool flame were obtained. According to experimental data, the flammable region of DME/air under non-adiabatic constant-volume spontaneous combustion conditions is divided into two parts, cool ignition and hot ignition. Under the heat dissipation conditions of the experiment, the flammable range of the cool ignition increases with the increase of the equivalent ratio. As the initial gas density increases, the DME/air mixture is in the hot ignition zone over the entire equivalent ratio range (0.2-5).


Page 26 of 33

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The simulated diffusion opposed-flow DME cool flames are compared to the experimental results. The flame structure comparisons indicate that all of the eight mechanisms could reproduce the temperature and the distributions of initial species (DME/O2) well. However, the prediction of CH2O and H2 obtained by all the mechanisms are in bad agreement with the experiment data. In summary, the HpMech-v3.3 has the best performance of extinction strain rate related to the heat release, Wang has the most accurate temperature profile and AramcoMech3.0 have a better prediction of intermediate species. Moreover, it’s found that the heat release curve of the cool flame is highly related to the NTC related reactions. The heat release curve with two heat release peaks, which leads to the wider high-temperature district of the cool flame and the higher flame temperature peak, would be produced in the simulations employing the mechanisms in which the NTC behavior is overpredicted. At last, a basic reaction path in the cool flame region is recommended. The path from FY and RO2 directly to OH and aldehydes and the path from QOOH to OH and OQ’O are also indispensable in addition to the widely accepted path: RH

FY

RO2

QOOH.

Acknowledgments This work was supported by the National Natural Science Foundation of China (No. 51776023 and 91441112). We thank helpful discussion with Prof. Yiguang Ju at Princeton University.


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

References 1.

Davy, H., Some researches on flame. Philosophical Transactions of the Royal Society of London 1817,

107, 45-76.

2.

Zhao, P.; Liang, W.; Deng, S.; Law, C. K., Initiation and propagation of laminar premixed cool flames. Fuel

2016, 166, 477-487.

3.

Deng, S.; Han, D.; Law, C. K., Ignition and extinction of strained nonpremixed cool flames at elevated

pressures. Combust Flame 2017, 176, 143-150.

4.

Fenske, E. R. HYDROCARBON ANALYZER COMPRISING STABILIZED COOL FLAME GENERATOR

WITH SERVO-POSITIONED FLAME FRONT. 1969-8-26, 1969.

5.

Won, S. H.; Jiang, B.; Diévart, P.; Sohn, C. H.; Ju, Y., Self-sustaining n-heptane cool diffusion flames

activated by ozone. P Combust Inst 2014.

6.

Romano, M. P.; Radulescu, M. I.; Higgins, A. J.; Lee, J. H. S., Sensitization of pentane-oxygen mixtures to

DDT via cool flame oxidation. Combust Flame 2003, 132 (3), 387-394.

7.

Kolaitis, D. I.; Founti, M. A., A tabulated chemistry approach for numerical modeling of diesel spray

evaporation in a "stabilized cool flame" environment. Combust Flame 2006, 145 (1-2), 259-271.

8.

Naidja, A.; Krishna, C. R.; Butcher, T.; Mahajan, D., Cool flame partial oxidation and its role in combustion

and reforming of fuels for fuel cell systems. Prog Energ Combust 2003, 29 (2), 155-191.

9.

Edenhofer, R.; Lucka, K.; Köhne, H., Low temperature oxidation of diesel–air mixtures at atmospheric

pressure. P Combust Inst 2007, 31 (2), 2947-2954.


Page 28 of 33

Page 29 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

10. Lee, K.; Lee, C.; Ryu, J.; Kim, H., An experimental study on the two-stage combustion characteristics of a direct-injection-type HCCI engine. Energ Fuel 2005, 19 (2), 393-402.

11. Cong, S.; McTaggart-Cowan, G. P.; Garner, C. P.; Wahab, E.; Peckham, M., Experimental Investigation of Low Temperature Diesel Combustion Processes. Combust Sci Technol 2011, 183 (12), 1376-1400.

12. Farouk, T. I.; Dryer, F. L., Isolated n-heptane droplet combustion in microgravity: "Cool Flames" - Twostage combustion. Combust Flame 2014, 161 (2), 565-581.

13. Pekalski, A. A.; Pasman, H. J., Distinction between the upper explosion limit and the lower cool flame limit in determination of flammability limit at elevated conditions. Process Saf Environ 2009, 87 (1), 47-52.

14. Sheinson, R. S.; Williams, F. W., Chemiluminescence spectra from cool and blue flames: electronically excited formaldehyde. Combust Flame 1973, 21 (2), 221-230.

15. Burgess, A.; Laughlin, R., The role of hydroperoxides as chain-branching agents in the cool-flame oxidation of n-heptane. Chemical Communications (London) 1967, (15), 769-770.

16. Deng, S.; Zhao, P.; Zhu, D.; Law, C. K. In NTC-affected ignition of DME by heated counterflowing air, 8th US National Combustion Meeting, Utah, USA, 2013.

17. Geng, P.; Cao, E.; Tan, Q.; Wei, L., Effects of alternative fuels on the combustion characteristics and emission products from diesel engines: A review. Renewable and Sustainable Energy Reviews 2017, 71, 523534.

18. Pfahl, U.; Fieweger, K.; Adomeit, G. In Self-ignition of diesel-relevant hydrocarbon-air mixtures under

engine conditions, Symposium (International) on Combustion, Elsevier: 1996; pp 781-789.


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 33

19. Dagaut, P.; Boettner, J.-C.; Cathonnet, M. In Chemical kinetic study of dimethylether oxidation in a jet

stirred reactor from 1 to 10 ATM: Experiments and kinetic modeling, Symposium (International) on Combustion, Elsevier: 1996; pp 627-632.

20. Curran, H.; Pitz, W.; Westbrook, C.; Dagaut, P.; Boettner, J. C.; Cathonnet, M., A wide range modeling study of dimethyl ether oxidation. Int J Chem Kinet 1998, 30 (3), 229-241.

21. Dagaut, P.; Daly, C.; Simmie, J. M.; Cathonnet, M. In The oxidation and ignition of dimethylether from low

to high temperature (500–1600 K): Experiments and kinetic modeling, Symposium (International) on Combustion, Elsevier: 1998; pp 361-369.

22. Fischer, S.; Dryer, F.; Curran, H., The reaction kinetics of dimethyl ether. I: High

temperature pyrolysis

and oxidation in flow reactors. Int J Chem Kinet 2000, 32 (12), 713-740.

23. Curran, H.; Fischer, S.; Dryer, F., The reaction kinetics of dimethyl ether. II: Low

temperature oxidation

in flow reactors. Int J Chem Kinet 2000, 32 (12), 741-759.

24. Zhao, Z.; Chaos, M.; Kazakov, A.; Dryer, F. L., Thermal decomposition reaction and a comprehensive kinetic model of dimethyl ether. Int J Chem Kinet 2008, 40 (1), 1-18.

25. Gilbert, R. G.; Smith, S. C., Theory of unimolecular and recombination reactions. 1990.

26. Wang, J.; Chaos, M.; Yang, B.; Cool, T. A.; Dryer, F. L.; Kasper, T.; Hansen, N.; Oßwald, P.; KohseHöinghaus, K.; Westmoreland, P. R., Composition of reaction intermediates for stoichiometric and fuel-rich dimethyl ether flames: flame-sampling mass spectrometry and modeling studies. Phys Chem Chem Phys 2009,

11 (9), 1328-1339.


Page 31 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

27. Burke, U.; Somers, K. P.; O’Toole, P.; Zinner, C. M.; Marquet, N.; Bourque, G.; Petersen, E. L.; Metcalfe, W. K.; Serinyel, Z.; Curran, H. J., An ignition delay and kinetic modeling study of methane, dimethyl ether, and their mixtures at high pressures. Combust Flame 2015, 162 (2), 315-330.

28. Gao, J.; Nakamura, Y., Low-temperature ignition of dimethyl ether: transition from cool flame to hot flame promoted by decomposition of HPMF (HO 2 CH 2 OCHO). Combust Flame 2016, 165, 68-82.

29. Gao, J.; Nakamura, Y., Two-stage ignition of DME/air mixture at low-temperature (< 500 K) under atmospheric pressure. Fuel 2013, 106, 241-248.

30. Shimizu, T.; Nakamura, H.; Tezuka, T.; Hasegawa, S.; Maruta, K., OH and CH2O Laser-Induced Fluorescence Measurements for Hydrogen Flames and Methane, n-Butane, and Dimethyl Ether Weak Flames in a Micro Flow Reactor with a Controlled Temperature Profile. Energ Fuel 2017, 31 (3), 2298-2307.

31. Reuter, C. B.; Won, S. H.; Ju, Y., Experimental study of the dynamics and structure of self-sustaining premixed cool flames using a counterflow burner. Combust Flame 2016, 166, 125-132.

32. Reuter, C. B.; Won, S. H.; Ju, Y., Flame Dynamics and Structures of Partially Premixed Cool Flames. Fuel 2016, 2, O3.

33. Reuter, C. B.; Won, S. H.; Ju, Y., Flame structure and ignition limit of partially premixed cool flames in a counterflow burner. P Combust Inst 2017, 36 (1), 1513-1522.

34. Reuter, C. B.; Yehia, O.; Won, S. H.; Fu, M.; Kokmanian, K.; Hultmark, M.; Ju, Y. In Experimental

Investigation of the Stabilization and Structure of Turbulent Cool Diffusion Flames, 2018 AIAA Aerospace Sciences Meeting, 2018; p 0678.


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

35. Wang, Z.; Gou, X., Cool flame characteristics of methane/oxygen mixtures. Journal of the Energy Institute 2018.

36. Goodwin, D. G.; Moffat, H. K.; Speth, R. L., Cantera: An object-oriented software toolkit for chemical kinetics, thermodynamics, and transport processes. Caltech, Pasadena, CA 2009.

37. Reuter, C. B.; Zhang, R.; Yehia, O. R.; Rezgui, Y.; Ju, Y., Counterflow flame experiments and chemical kinetic modeling of dimethyl ether/methane mixtures. Combust Flame 2018, 196, 1-10.

38. Zhou, C.-W.; Li, Y.; Burke, U.; Banyon, C.; Somers, K. P.; Ding, S.; Khan, S.; Hargis, J. W.; Sikes, T.; Mathieu, O., An experimental and chemical kinetic modeling study of 1, 3-butadiene combustion: Ignition delay time and laminar flame speed measurements. Combust Flame 2018, 197, 423-438.

39. Burke, U.; Somers, K. P.; O’Toole, P.; Zinner, C. M.; Marquet, N.; Bourque, G.; Petersen, E. L.; Metcalfe, W. K.; Serinyel, Z.; Curran, H. J., An ignition delay and kinetic modeling study of methane, dimethyl ether, and their mixtures at high pressures. Combustion & Flame 2015, 162 (2), 315-330.

40. Liu, D.; Santner, J.; Togbé, C.; Felsmann, D.; Koppmann, J.; Lackner, A.; Yang, X.; Shen, X.; Ju, Y.; KohseHöinghaus, K., Flame structure and kinetic studies of carbon dioxide-diluted dimethyl ether flames at reduced and elevated pressures. Combustion & Flame 2013, 160 (12), 2654-2668.

41. Zhao, Z.; Chaos, M.; Kazakov, A.; Dryer, F. L., Thermal decomposition reaction and a comprehensive kinetic model of dimethyl ether. Int J Chem Kinet 2008, 40 (1), 1–18.

42. Wang, Z.; Zhang, X.; Xing, L.; Zhang, L.; Herrmann, F.; Moshammer, K.; Qi, F.; Kohse-Höinghaus, K., Experimental and kinetic modeling study of the low-and intermediate-temperature oxidation of dimethyl ether.

Combust Flame 2015, 162 (4), 1113-1125.


Page 32 of 33

Page 33 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

43. Prince, J. C.; Williams, F. A., A short reaction mechanism for the combustion of dimethyl-ether. Combust

Flame 2015, 162 (10), 3589-3595.

44. Reuter, C. B.; Zhang, R.; Yehia, O.; Ju, Y. In Counterflow Experiments and Kinetic Modeling of Dimethyl

Ether/Methane Cool Diffusion Flames, 2018 AIAA Aerospace Sciences Meeting, 2018; p 2184.


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