Experimental and Kinetic Modeling Study on Self-ignition of α

7 modeling of α-methylnaphalene (AMN) are still very insufficient. The ignition ... rapid compression machine (RCM) was measured in this study. The d...
0 downloads 0 Views 2MB Size
Subscriber access provided by UNIVERSITY OF ADELAIDE LIBRARIES

Article

Experimental and Kinetic Modeling Study on Self-ignition of #Methylnaphthalene in a Heated Rapid Compression Machine Shuzhou Sun, Liang Yu, Sixu Wang, Yebing Mao, and Xingcai Lu Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b00987 • Publication Date (Web): 30 Aug 2017 Downloaded from http://pubs.acs.org on August 31, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Energy & Fuels is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 29

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

1

Experimental and Kinetic Modeling Study on Self-ignition of α-Methylnaphthalene in a

2

Heated Rapid Compression Machine

3 4

Shuzhou Sun, Liang Yu, Sixu Wang, Yebing Mao, Xingcai Lu*

5

Key Lab. for Power Machinery and Engineering of M. O. E, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China

6 7

Abstract: As an important component of diesel and kerosene surrogate, the experimental study and chemical kinetic

8

modeling of α-methylnaphalene (AMN) are still very insufficient. The ignition delay of AMN/O2/Ar mixture in a heated

9

rapid compression machine (RCM) was measured in this study. The data was obtained for equivalence ratios of 0.7, 1, 1.2,

10

at pressures of 12bar, 15bar, 20bar, over the temperature range of 860K~1040K. A semi-detailed kinetic mechanism for the

11

oxidation of AMN was established, which consists of 196 species and 1330 reactions. Compared with the different previous

12

mechanism, the new mechanism can more accurately predict the ignition delay of AMN in RCM and shock tube

13

experiments. It can also accurately predict the experimental data obtained in a jet stirred reactor (JSR) from the literature.

14

The ignition delay using adiabatic constant volume simulation (CV simulation) and RCM simulation were compared, which

15

indicated that RCM simulation could better predict the experimental data. Sensitivity and reaction path analysis were also

16

carried out to explore the effect of key reactions and paths on AMN ignition.

17

Keywords: α-methylnaphalene, RCM, ignition delay, kinetic modeling

18

1. Introduction

19

The more and more severe energy crisis and environmental problems make a higher request for the design of internal

20

combustion engines. In order to achieve a precise control of the combustion and emissions in engines, it’s necessary to

21

study the combustion chemical mechanism of the actual fuels. However, the composition of the actual fuels is extremely

22

complex. There are thousands of components in gasoline and diesel. The mechanisms of many components are not clear.

*

Corresponding author: E-mail address: [email protected]. Tel.: +86-21-34206039; Fax: +86-21-34206139. 1

ACS Paragon Plus Environment

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 2 of 29

23

The interaction between the various components is more difficult to study. At present, the common method is to construct

24

the surrogate fuel which can characterize the physical and chemical properties of the actual fuel. The research on the

25

mechanism of gasoline surrogate represented by toluene reference fuel (TRF) has been extensively studied in the past few

26

years [1-4]. Other mixtures related to gasoline like PRF with ethanol [5] and n-heptane/toluene [6] are also studied in

27

mechanism and experiment. The main components of diesel include alkanes, olefins, cycloalkanes, aromatic hydrocarbons,

28

and a small amount of other substances. Compared with gasoline, the diesel consists of larger molecules with more complex

29

structures and lower vapor pressure at room temperature. Higher temperature is needed to obtain the homogeneous mixture.

30

Therefore, the experimental and kinetic modeling of diesel surrogate are very lacking.

31

With the development of chemical kinetics, the mechanisms of ordinary alkanes (n-heptane [7], iso-octane [8] et al. ),

32

cycloalkanes (cyclohexane [9], methyl-cyclohexane [10] et al. ), aromatic hydrocarbons (toluene [11,12] et al. ) have been

33

extensively proposed and validated in different reactors, which makes it possible to construct a more complex diesel

34

surrogate mechanism. As one of the fuels that characterize the cetane number of diesel, α-methylnaphalene is considered to

35

be one of the representatives of polycyclic aromatic hydrocarbons in diesel. Suzuki et al. [13] investigated the ignition and

36

combustion characteristics of the diesel surrogate in a micro flow reactor, which includes n-hexadecane, n-decane,

37

n-heptane, iso-hexadecane, and α-methylnaphthalene. Ramirez et al. [14] used n-decane and α-methylnaphthalene as the

38

diesel surrogate and mixed it with biodiesel as the surrogate fuel of B30, constructing a chemical mechanism involving

39

1964 species and 7748 reactions. Lemaire et al. [15] compared the soot formation of commercial diesel and diesel surrogate

40

components n-decane and α-methylnaphthalene based on the turbulent diffusion flame, and found that the proportion of

41

α-methylnaphthalene has an important effect on soot formation. Barths et al. [16] used 70% n-decane and 30%

42

α-methylnaphthalene as a diesel surrogate.

43

In addition, α-methylnaphthalene is also considered to be one of the components of the kerosene surrogate. Schulz et al.

44

[17] proposed a twelve-component surrogate fuel for kerosene, in which α-methylnaphthalene was a major component.

45

Agosta et al. [18] used n-dodecane and iso-octane to represent the normal and isomeric components of alkanes,

2

ACS Paragon Plus Environment

Page 3 of 29

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

46

methyl-cyclohexane and decalin for cycloalkanes, and α-methylnaphthalene for aromatics to build a five-component

47

kerosene surrogate fuel. α-methylnaphthalene is also an important component in the 5-7 component surrogate fuel proposed

48

by Violi et al. [19]. Slavinskaya et al. [20] used 10% n-propylcyclohexane, 13% iso-octane, 20% n-dodecane, 23%

49

α-methylnaphthalene, 32% n-hexadecane as the surrogate fuel for kerosene. Mensch et al. [21] also considered that

50

α-methylnaphthalene is an important component of the surrogate fuel for JP8 and Jet-A (aviation fuels).

51

The experimental and kinetic modeling study for α-methylnaphthalene is still relatively lacking. Pfahl et al. [22]

52

measured the ignition delay of α-methylnaphthalene in a shock tube and observed two kind of combustion characteristics

53

which were described as mild ignition and strong ignition. The detailed mechanism of α-methylnaphthalene constructed by

54

Pitsch [23] was also verified. Mati et al. [24] conducted a JSR experiment for the oxidation of α-methylnaphthalene at 1-13

55

atm. The concentration profiles of reactants, stabilized intermediates and final products were measured using sonic probe

56

sampling and GC-MS analysis. A detailed kinetic mechanism for the oxidation of α-methylnaphthalene with 146 species

57

and 1041 reactions was constructed. And then a detailed mechanism for diesel surrogate consist of five components

58

including α-methylnaphthalene was proposed [25]. Wang et al. [26] have also measured the ignition delay of

59

α-methylnaphthalene in the shock tube. Based on the mechanism of Mati [24] and Bounaceur [27], a detailed mechanism of

60

α-methylnaphthalene was constructed and verified with various experimental data, showing a good agreement. More

61

recently, Kukkadapu et al. [28] measured the ignition delay of AMN/air mixtures in a RCM at pressure of 15-40 bar,

62

temperature of 837-980 and equivalence ratio of 0.5-1.5. This is the only α-methylnaphthalene experiments in the RCM as

63

is known by the authors. The mechanisms of Wang et al. [26] and Narayanaswamy et al. [29] were used to simulate the

64

experiments. The results show that the mechanism of Wang et al. has an obvious defect in predicting the ignition delay of

65

AMN in the low temperature.

66

Somers et al. [30] measured the pyrolysis products of α-methylnaphthalene in 585 oC, 110 atm, 140s with

67

high-pressure liquid chromatography (HPLC) with ultraviolet-visible (UV) diode-array detection in series with a mass

68

spectrometer. A total of 37 PAHs with 2-7 rings were observed, many of which were not previously observed. The

3

ACS Paragon Plus Environment

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 4 of 29

69

consumption path studies of α-methylnaphthalene by Shaddix et al. [31] show that, in the flow reactor, abstraction of a

70

''benzylic'' hydrogen from the methyl side chain dominates the consumption of α-methylnaphthalene, although O atom

71

addition to the aromatic ring, displacement of the side chain by H atom, and homolytic decay also contribute significantly.

72

Changes in the α-methylnaphthalene decay mechanism under higher temperature combustion environments and the

73

oxidation mechanisms of even larger polycyclic aromatic hydrocarbons are postulated. The study of Yang et al. [32]

74

indicated that in the combustion process, resonance stabilize radicals can result in more soot and PAC (polycyclic aromatic

75

compounds) formation in combustion processes. As the largest single polycyclic aromatic constituent in petroleum fuels, 1-

76

and 2-methylnaphthalenes can readily form resonance-stabilized radicals in combustion, and yet the reaction mechanisms

77

are not well understood. The authors investigated the pyrolysis products of 1- and 2-methylnaphthalene between

78

650-800 °C and the oxidation products of 2-methylnaphthalene between 650-950 °C in a flow reactor. Naphthalene is the

79

most abundant product and is formed from methyl loss by H displacement. Isomerization in pyrolytic conditions results in

80

the second most abundant product. The methyl radicals recombine with the reactants to form ethylnaphthalenes and

81

dimethylnaphthalenes. Experimental results show that the lack of carbon dimerization products in significant quantities may

82

be due to their further growth into soot.

83

In general, the experimental studies of α-methylnaphthalene are still relatively lacking, especially for the study of

84

ignition characteristics in low and moderate temperature. In this study, the ignition delay measurments of

85

α-methylnaphthalene in a heated rapid compression machine was carried out. The data was obtained for equivalence ratios

86

of 0.7, 1, 1.2, at pressures of 12bar, 15bar, 20bar, over the temperature range of 860K~1040K. A semi-detailed kinetic

87

mechanism containing 196 species and 1330 reactions was established and compared with the mechanism of Wang et al. [26]

88

and Narayanaswamy et al. [29]. The mechanism of this study shows a better agreement with the experimental results.

89

2. Experimental

90

2.1 Heated rapid compression machine

91

The experiment in this study is carried out in the heated rapid compression machine of Shanghai Jiao Tong University,

4

ACS Paragon Plus Environment

Page 5 of 29

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

92

which is modified based on the previous one [33,34]. Some major parameters like the diameter of the combustion chamber

93

and the compression ratio have been changed. So the experiment system is been introduced here. The system consists of

94

driving system, braking system, fuel pre-mixing system, heating and temperature control system, combustion test system

95

and data acquisition system, as shown in Fig.1. The pneumatically driven impact piston diameter is 125mm and the

96

combustion chamber diameter is 35mm. Creviced piston is adopted due to its ability to restrain

97

vortex forming at the boundary layer and to ensure the consistency of the temperature during compression and ignition

98

process. The creviced piston design has referred to that of Case Western Reserve University [35] and optimized by

99

FLUENT software subsequently. The piston stroke in the combustion chamber is fixed at 215mm. The compression process

100

of RCM typically takes 30-40ms and 50% pressure rise during the compression occurred in the last 5ms. The length of the

101

connecting rod between the two pistons can be adjusted to change the initial and the end volume so as to alter the

102

compression ratio. The compression ratio can change from 4 to 20. Pressure measurements are taken using a pressure sensor

103

(Kistler 6125B) on the end wall and processed by a charge amplifier (Kistler 5015) and saved to a computer using a data

104

acquisition card. All data acquisition and system operation are controlled by the Labview program.

105

A significant feature of the second-generation RCM is the adding of a high-temperature heating system. The mixing

106

tanks for fuel and inert gas, the intake pipe and the combustion chamber can be heated precisely and controllable. The

107

maximum operating temperature can reach more than 200 °C with a temperature accuracy of ±1 °C. So the large-molecular

108

fuels with high boiling point and low saturation pressure can form homogenous gas mixture. The heating and temperature

109

control system is self-designed, including PT100 thermistor, thermal silicone oil, flexible heating tape and PID temperature

110

controller. In order to avoid the fuel mixture reacting in the preparation and mixing process, a lower temperature is adopted

111

in the prerequisite to ensure that the fuel pressure is much lower than the saturated vapor pressure under that temperature.

112

The compressed temperature Tc is calculated using the adiabatic core assumption:

113



Tc

T0

114

P  dT = ln  c  γ −1 T  P0 

γ

(1)

Where Pc is the compressed pressure; γ is the specific heat ratio, as a function of temperature. The compressed 5

ACS Paragon Plus Environment

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 6 of 29

115

temperature is obtained by solving the integral. Pc and Tc can be controlled by changing the initial fuel temperature (T0), the

116

initial pressure (P0) and the compression ratio.

117

2.2 Mixture preparation

118

The homogeneous mixture of fuel and oxidant was prepared in a 27.68L stainless steel tank which is heated by

119

circulating silicone oil to ensure the uniformity of temperature. Digital pressure gauges (OMEGA DPG4000) and

120

PT100-type thermistor are connected to the top of the fuel tank to real-time monitor the pressure and temperature of the

121

mixture. The fuel tank was maintained at 130 °C and the pressure of AMN is less than 2.5 kPa, which is below the

122

saturation pressure (about 3.37 kPa) of AMN at 130°C. A fuel vaporization experiment was conducted before the formal

123

experiment. Fuel can be vaporized within a few minutes, and vaporization rate is 98% or more. There was no significant

124

change in the pressure of the fuel tank after several hours, demonstrating that the mixture was reliable. The purity of O2, Ar

125

and α-methylnaphthalene in this study was 99.999%, 99.999% and 98%, respectively. The fuel tank is first heated to the

126

specified temperature, and then fuel, Ar, and O2 were injected successively after vacuuming. The mixture preparation

127

process is similar with the literature [36]. Each component was kept for a certain period of time after injection to stabilize

128

the temperature and then inject other components. The mixture is maintained for 2-3 hours after completion of the

129

preparation to ensure adequate gas mixing.

130

2.3 Definition of ignition delay

131

The typical pressure trace and the derivative of pressure obtained in the experiment are shown in Fig.2. It can be seen

132

that the ignition process of α-methylnaphthalene is very intense, and the rate of pressure rise is high. The time of the end of

133

compression with the maximum pressure in the compression process is set to 0. The time when the rate of pressure rise is

134

the highest during the combustion is taken as the ignition time. And the time interval between the end of compression and

135

the ignition time is defined as the ignition delay (τ).

136

2.4 Experimental reproducibility

137

The reproducibility experiments are shown in Fig.3 when the equivalence ratio is 1 and Pc = 15 bar. The slight error of

6

ACS Paragon Plus Environment

Page 7 of 29

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

138

the initial pressure will result in a slight difference in the compressed temperature and pressure. The error of compressed

139

pressure in this experiment is within ± 0.5bar, and the overall reproducibility is good. O2 in the mixture was replaced by N2

140

in the inert run. According to the simulation, such a method will result in a slight increase in the compressed temperature in

141

the inert run under the same initial conditions due to the small difference in heat capacity between O2 and N2. The

142

calculation shows that the inert-run compressed temperature is about 13 °C higher than that of the experiment in this study.

143

Comparing the inert-run heat loss curves under different experimental conditions, it can be found that the heat loss before

144

ignition is more affected by the volume of the combustion chamber (surface-to-volume ratio) rather than the temperature.

145

Therefore, this inert-run experiments are reasonable.

146

2.5 Experimental conditions

147

Pitz et al. [37] noted that α-methylnaphthalene could not ignite at time within the diesel engine's time scale below 860

148

K. In order to reach a higher temperature, Ar was chosen as the dilution gas for all experiments in this study. The molar ratio

149

of O2:Ar was 0.21: 0.79, and the temperature was 860K~1040K. A total of 7 different ignition delay curves of

150

α-methylnaphthalene were measured under different conditions. The specific conditions are shown in Table 1.

151

3. Kinetic Modeling

152

In this paper, a semi-detailed chemical kinetic mechanism of α-methylnaphthalene with 196 species and 1330 reactions

153

was established. The mechanism mainly consists of the toluene sub-mechanism from the literature [12] and the

154

α-methylnaphthalene sub-mechanism from the literature [24]. The mechanism of PAHs formation in these two mechanisms

155

is not considered in this study. The mechanism can be found in Supplementary Materials.

156

The sub-mechanism of toluene and styrene in this study is from the literature [12]. This mechanism consists of the

157

mechanism of C0-C4, benzene, toluene, and larger molecular aromatic hydrocarbons. The mechanism provides different

158

Arrhenius coefficients of a number of key reactions at different pressures with PLOG (Pressure Dependence through

159

Logarithmic Interpolation), so that it can be applied to a larger pressure range.

160

The α-methylnaphthalene sub-mechanism is an skeleton mechanism containing 60 reactions, which is from literature

7

ACS Paragon Plus Environment

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 8 of 29

161

[24]. The reactions of α-methylnaphthalene sub-mechanism are mainly concentrated in the methyl, while the reactions on

162

the naphthalene ring are not considered. The main reactions include H-atom abstraction and oxidation at methyl, after that

163

the naphthalene ring opens to form indene and continues to produce styryl. The main reactions classes of

164

α-methylnaphthalene include unimolecular decomposition of methylnaphthalene and H-atom abstraction reactions at methyl

165

radicals by radicals, atoms and molecules.

166 167

The chain initiation reactions of α-methylnaphthalene include unimolecular decomposition reactions and H-atom abstraction reactions. Unimolecular decomposition occurs through the following two reactions:

168

C10H7CH3=C10H7CH2+H

169

and

170

C10H7CH3=C10H7+CH3

171

H-atom abstraction reactions include reactions with O2, HO2, O, OH, H, CH3, C10H7 and C10H7CO. All of the rate

172

constants are also taken from [24].

173

4. Experiment result and mechanism validation

174 175

The ignition delay under different temperatures in seven different conditions were measured. Parts of pressure curves are shown in Fig.4. The detailed ignition delay data can be found in Supplementary Materials.

176

The compressed pressures were controlled within ±0.05bar in the experiments. As we can see from Fig.4, the pressure

177

curve during ignition process does not exhibit the characteristics of two-stage ignition. Single stage ignition is observed and

178

the rate of pressure rise is very high. There is no significant difference in the maximum combustion pressure at different

179

temperatures. The experimental compressed temperature is controlled in 860K-1040K. The minimum measured ignition

180

delay is about 2ms. There is no obvious reaction during compression for the weak low-temperature chemistry of AMN.

181

Fig.5 shows the comparison of the ignition delay obtained in this experiment with the RCM experiments of Kukkadapu

182

et al. [28], the shock tube experiments of Wang et al. [26] and Pfahl et al. [22] in the similar conditions. It can be seen that

183

the ignition delay of AMN of this study is in good agreement with the data of Kukkadapu et al. It should be noted that the

8

ACS Paragon Plus Environment

Page 9 of 29

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

184

facility has a significant effect on the RCM ignition delay [38]. By comparison, the time interval of 50% pressure to the end

185

of compression is 3.8ms [28] and 4.5ms (this work) respectively, which is very close. The heat loss after the end of

186

compression is also similar. So the comparison is reasonable. Furthermore, compared with the data of Kukkadapu et al., The

187

temperature range of this study is wider and the maximum temperature is above 1020K, which can basically connect with

188

the shock tube data. Compared with the shock tube data, the ignition delay obtained under similar pressure in this

189

experiment is slightly larger, which is due to the heat loss after the end of compression in RCM experiment. It can also be

190

seen in Fig.5 (b) that the logarithm of the ignition delay of AMN is linearly related to 1000 / T over a very wide temperature

191

range, with no obvious NTC phenomenon.

192 193

The ignition delay curves under different conditions are shown in Fig.6. The ignition delay of AMN decreases with the increase of temperature, pressure and equivalence ratio.

194

The Wang’s mechanism [26] and the mechanism of this work were used to perform the simulation with CHEMKIN.

195

The 0-D adiabatic constant volume (CV) simulation was adopted in the calculation first. CV simulation is the ideal

196

condition of the RCM experiment and it has the advantage of saving time and computing resource. In order to get closer to

197

the actual experimental condition, full RCM simulation is also used to take the compression and post-compression process

198

into consideration for the new established mechanism. Only CV simulations were carried out for Wang’s mechanism

199

because there are issues with convergence when RCM simulation are used with the this mechanism. It can be seen from

200

Fig.6, the ignition delay curve using Wang's mechanism has obvious difference with the experimental data, specifically as

201

follows:

202

1. The mechanism does not correctly predict the effect of the equivalence ratio on the ignition delay. At the same

203

temperature and pressure in the experiment, the ignition delays decrease with the increase of the equivalence ratio.

204

While the simulation result of Wang’s mechanism is the opposite. Moreover, the ignition delay curves of different

205

equivalence ratios are crossed.

206

2. The activation energy (slope) of the experimental curve and the simulation curve are significantly different. The

9

ACS Paragon Plus Environment

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 10 of 29

207

slope of the simulation curve at the lower temperature is obviously decreased which has not been observed in the

208

experiment.

209

Since the effects of compression and heat loss on the ignition delay are not taken into account, the ignition delay

210

calculated by this mechanism is generally less than the experimental value. And with the increase of ignition delay, the

211

effect of heat loss on the experiment is more and more obvious, leading the error of the experimental ignition delay and the

212

simulation with CV simulation obviously increasing. The effect of the equivalence ratio on the ignition delay can be

213

predicted correctly using the new established mechanism of this work and the calculated activation energy is closer to the

214

experimental result. However, it can be found that the effect of the equivalence ratio on the ignition delay is much greater

215

than that of the simulation.

216

Afterwards, the RCM simulation in [39] is adopted in this work. According to the adiabatic core assumption, the heat

217

loss before ignition is converted to volume expansion, and the compression process is also considered. The changes of the

218

inert-run pressure at Φ = 1 are transformed into the volume changes by formula (2). The volume history can be found in

219

Supplementary Materials. The compressed temperature and pressure calculated by CHEMKIN when introduced the

220

volume-time-dependent relationship is slightly different from the experiment. While compared with the adiabatic constant

221

volume method, this method can significantly reduce the simulation error. Fig.7 shows the comparison of simulated

222

pressure trace obtained by this method with the experimental one. It can be seen that there is a significant exothermic

223

phenomenon during the induction period in the simulation. The pressure before ignition shows a significantly increase

224

compared with the inert run, which is not observed in the experiment. In the experiment, the experimental pressure and the

225

inert run pressure are consistent between the end of compression and ignition without exothermic phenomenon, which is

226

consistent with the experimental phenomenon of Kukkadapu et al. [28] That means the current mechanism is still somehow

227

insufficient. 1

228

 P (t ) γ V (t ) = V0    P0 

229

Fig.8 compares the ignition delay using the CV simulation and the RCM simulation with the mechanism of this work.

(2)

10

ACS Paragon Plus Environment

Page 11 of 29

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

230

The simulated ignition delay is the same definition as the experiment. The compression process is more important than the

231

heat loss process when the temperature is high and the ignition delay is small. The low-temperature reaction during the

232

compression process results in the ignition delay of the RCM simulation being less than that of the CV simulation. Case is

233

the opposite while the temperature is low and the ignition delay is long. Obviously, the ignition delay with RCM simulation

234

is closer to the experimental result. Especially in the case of low temperature and long ignition delay, the RCM simulation

235

considers the effect of heat loss on the ignition delay. The simulated ignition delay is very close to the experimental result.

236

At higher temperatures, the simulated ignition delay is less than the experimental value. The maximum error is about -60%.

237

Since there were convergence problems in RCM simulations using CHEMKIN with the mechanism of Wang et al. [26],

238

the mechanism of Narayanaswamy et al. [29] was adopted in RCM simulations, as is shown in Fig.9. The results of the two

239

are similar in about 1000K, but Narayanaswamy's mechanism underestimate the ignition delay of AMN near the low and

240

moderate temperature.

241

In addition, the simulation results of current mechanism are also compared with the measures of shock tube of Wang et

242

al. [26] and JSR of Mati et al. [24]. The ignition delay of α-methylnaphthalene/air mixtures at equivalence ratios of 0.5, 1,

243

1.5, pressure of 10 bar, 40 bar, and temperature of 1032K~1445K were measured by Wang et al. The experimental data and

244

simulation results with different mechanisms are shown in Fig.10. In the experiments, the ignition point was defined by

245

extrapolating the peak in the slope of the OH signal to the baseline value. The time interval between the ignition point and

246

the arrival of reflected shock at the end wall is defined as the ignition delay. The same definition is adopted in the simulation.

247

The measured ignition delay times have been scaled using τ ∝ P −0.90 . It can be seen from the figure that the simulated

248

ignition delay is slightly longer than the experimental value in rich mixture. But in general, the simulation results are in

249

good agreement with the shock tube experiment. The mechanism of Wang erroneously predicts the effect of equivalence on

250

ignition delay. The mechanism of Narayanaswamy et al. overestimates the ignition delay of AMN, especially at high

251

pressure. And at low pressure, the ignition delay curves of different equivalence ratios are crossed.

252

The species concentration profiles of the reactants, products, and various stable intermediates of α-methylnaphthalene

11

ACS Paragon Plus Environment

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 12 of 29

253

oxidation in JSR were measured by Mati et al. The simulated and experimental results of α-methylnaphthalene, O2, CO,

254

CO2, CH4, C2H2, C2H4, C6H6 in 10atm, Φ = 1 were compared in this study, as shown in Fig.11. The results show that the

255

prediction of a variety of reactants, products and intermediates are in good agreement with the experimental data. The

256

predictions of C2H2, C2H4, and C6H6 are slightly error compared with the experiment, but the general trend is consistent.

257

5. Kinetic Analysis

258

The main reaction path of α-methylnaphthalene under the conditions of initial temperature of 900K, pressure of 15bar

259

and Φ = 1 is shown in Fig.12. The reaction path analysis was carried out at 29.2 ms, when the consumption of

260

α-methylnaphthalene was 19.78%, and the temperature was 968 K. The main reaction path is highlighted in bold arrow. It

261

can be seen from the figure that the initial reaction of α-methylnaphthalene includes the H-atom abstraction reaction of

262

methyl yielding naphthylmethyl radical and the C-C bond cleavage yielding naphthalene, in which the path yielding

263

naphthalenemethyl

264

α-methylnaphthalene and the rest yields naphthaldehyde and naphthyl radical. The naphthyl radical is oxidized to the

265

naphthoxy radical and then undergoes a decomposition reaction to produce the indenyl. The indenyl ring is then opened to

266

form C6H5CCH2, which will be oxidized to benzaldehyde by O2. The benzaldehyde breaks down into phenyl and CO. The

267

phenyl can be oxidized in a variety of different ways, but mainly yields phenoxy. The phenoxy continues to be oxidized by

268

the O atom, producing various small molecules

radical

occupies

an

absolute

advantage.

35.6%

naphthalenemethyl

radical

re-generate

269

Fig.13 shows the sensitivity analysis of OH at P = 15 bar, Φ = 1 and initial temperatures of 900 K and 1300 K,

270

respectively. The negative sensitivity coefficient indicates that the reaction can promote the formation of OH and reduce the

271

ignition delay.

272

The sensitivity analysis shows that there are no significant differences in the main reactions affecting the ignition of

273

α-methylnaphthalene at 900K and 1300K. The H-atom abstraction reaction of α-methylnaphthalene with O2 have the

274

greatest enhancement on the ignition. In the reaction path analysis, 62.1% of the naphthoxy radical yields the stable

275

naphthol via the chain termination reaction R44.C10H7O + H = C10H7OH, which in turn reacts with OH and O to form

12

ACS Paragon Plus Environment

Page 13 of 29

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

276

naphthyloxy. Therefore, R44 has the greatest inhibition on ignition. R43 produces indenyl and CO in the opposite direction.

277

This reaction also has a significant promotion on ignition by producing a relatively active indenyl and competing with R44.

278

R15.C10H7CH3+C10H7=C10H7CH2+C10H8 consumes the active naphthalene and produces a relatively stable naphthalene. So

279

it also has a greater inhibition on the ignition. In the reaction of small molecules, R1308. H+2O2=HO2+O2 and R1321.

280

H+O2=O+OH have obvious promoting effect on ignition at low temperature and high temperature, respectively. In general,

281

the initial reaction of α-methylnaphthalene, the reactions in the path of naphthyl radical → naphthoxy radical → indenyl

282

play the most important role in the oxidation of α-methylnaphthalene.

283

6. Summary

284

In this study, the ignition delay of α-methylnaphthalene on the rapid compression machine was measured. Inert run

285

experiments were carried out on three different pressures with equivalence ratio of 1. A new semi-detailed chemical kinetic

286

mechanism of α-methylnaphthalene was established. The calculation was carried out using the current mechanism, Wang’s

287

mechanism and Narayanaswamy's mechanism with CV simulation and RCM simulation. Comparing the different

288

mechanisms and different simulation methods, the mechanism of this study with the RCM simulation can predict the

289

experimental data well. In this work, the data of shock tube and JSR from literature is also compared with the simulation,

290

which indicates that this mechanism has wide applicability in different reactors. According to the reaction path analysis and

291

sensitivity analysis, α-methylnaphthalene → naphthyl radical → naphthoxy radical → indenyl is the main path of the

292

consumption of α-methylnaphthalene, of which the main reactions play a great role in promoting the ignition of

293

α-methylnaphthalene.

294

Acknowledgements

295

This work was supported by the Nature Science Foundation of China (Grant No. 91641202, 51425602).

296

References

297 298 299 300 301

[1] Andrae JCG, Björnbom P, Cracknell RF, Kalghatgi GT. Autoignition of toluene reference fuels at high pressures modeled with detailed chemical kinetics. Combustion and Flame. 2007;149:2-24. [2] Andrae JCG, Brinck T, Kalghatgi GT. HCCI experiments with toluene reference fuels modeled by a semidetailed chemical kinetic model. Combustion and Flame. 2008;155:696-712. [3] Sakai Y, Miyoshi A, Koshi M, Pitz WJ. A kinetic modeling study on the oxidation of primary reference fuel–toluene 13

ACS Paragon Plus Environment

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

302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348

Page 14 of 29

mixtures including cross reactions between aromatics and aliphatics. Proceedings of the Combustion Institute. 2009;32:411-8. [4] Li H, Yu L, Lu X, Ouyang L, Sun S, Huang Z. Autoignition of ternary blends for gasoline surrogate at wide temperature ranges and at elevated pressure: Shock tube measurements and detailed kinetic modeling. Fuel. 2016;181:916-25. [5] Zhong B J, Zheng D. Chemical kinetic mechanism of a three-component fuel composed of iso-octane/n-heptane/ethanol. Combustion Science and Technology, 2013, 185(4): 627-644. [6] Di Sante R. Measurements of the auto-ignition of n-heptane/toluene mixtures using a rapid compression machine. Combustion and flame, 2012, 159(1): 55-63. [7] Curran HJ, Gaffuri P, Pitz WJ, Westbrook CK. A Comprehensive Modeling Study of n-Heptane Oxidation. Combustion and Flame. 1998;114:149-77. [8] Curran HJ, Gaffuri P, Pitz WJ, Westbrook CK. A comprehensive modeling study of iso-octane oxidation. Combustion and Flame. 2002;129:253-80. [9] Silke EJ, Pitz WJ, Westbrook CK, Ribaucour M. Detailed Chemical Kinetic Modeling of Cyclohexane Oxidation†. The Journal of Physical Chemistry A. 2007;111:3761-75. [10] Pitz WJ, Naik CV, Mhaoldúin TN, Westbrook CK, Curran HJ, Orme JP, et al. Modeling and experimental investigation of methylcyclohexane ignition in a rapid compression machine. Proceedings of the Combustion Institute. 2007;31:267-75. [11] Dagaut P, Pengloan G, Ristori A. Oxidation, ignition and combustion of toluene: Experimental and detailed chemical kinetic modeling. Physical Chemistry Chemical Physics. 2002;4:1846-54. [12] Yuan W, Li Y, Dagaut P, Yang J, Qi F. Investigation on the pyrolysis and oxidation of toluene over a wide range conditions. I. Flow reactor pyrolysis and jet stirred reactor oxidation. Combustion and Flame. 2015;162:3-21. [13] Suzuki S, Hori M, Nakamura H, Tezuka T, Hasegawa S, Maruta K. Study on cetane number dependence of diesel surrogates/air weak flames in a micro flow reactor with a controlled temperature profile. Proceedings of the Combustion Institute. 2013;34:3411-7. [14] Ramirez HP, Hadj-Ali K, Diévart P, Dayma G, Togbé C, Moréac G, et al. Oxidation of commercial and surrogate bio-Diesel fuels (B30) in a jet-stirred reactor at elevated pressure: Experimental and modeling kinetic study. Proceedings of the Combustion Institute. 2011;33:375-82. [15] Lemaire R, Faccinetto A, Therssen E, Ziskind M, Focsa C, Desgroux P. Experimental comparison of soot formation in turbulent flames of Diesel and surrogate Diesel fuels. Proceedings of the Combustion Institute. 2009;32:737-44. [16] Barths H, Hasse C, Bikas G, Peters N. Simulation of combustion in direct injection diesel engines using a eulerian particle flamelet model. Proceedings of the Combustion Institute. 2000;28:1161-8. [17] Schulz W D. Oxidation products of a surrogate JP-8 fuel. Preprints - American Chemical Society. Division of Petroleum Chemistry, 1992.. [18] Agosta A. Development of a chemical surrogate for JP-8 aviation fuel using a pressurized flow reactor. Drexel University. 2002. [19] Violi A, Yan S, Eddings EG, Sarofim AF, Granata S, Faravelli T, et al. Experimental formulation and kinetic model for JP-8 surrogate mixtures. Combustion Science and Technology. 2002;174:399-417. [20] Slavinskaya N A, Zizin A, Riedel U. Towards surrogate reaction model development. ASME Turbo Expo 2011, Power for Land, Sea and Air. DLR, 2011:203-214. [21] Mensch A, Santoro RJ, Litzinger TA, Lee SY. Sooting characteristics of surrogates for jet fuels. Combustion and Flame. 2010;157:1097-105. [22] Pfahl U, Fieweger K, Adomeit G. Self-ignition of diesel-relevant hydrocarbon-air mixtures under engine conditions. Symposium (International) on Combustion. 1996;26:781-9. [23] Pitsch H. Detailed kinetic reaction mechanism for ignition and oxidation of α-methylnaphthalene. Symposium (International) on Combustion. 1996;26:721-8. [24] Mati K, Ristori A, Pengloan G, Dagaut P. Oxidation of 1-methylnaphthalene at 1-13 atm: experimental study in a JSR and detailed chemical kinetic modeling. Combustion Science and Technology. 2007;179:1261-85. [25] Mati K, Ristori A, Gaïl S, Pengloan G, Dagaut P. The oxidation of a diesel fuel at 1–10 atm: Experimental study in a 14

ACS Paragon Plus Environment

Page 15 of 29

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

349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378

Energy & Fuels

JSR and detailed chemical kinetic modeling. Proceedings of the Combustion Institute. 2007;31:2939-46. [26] Wang H, Warner SJ, Oehlschlaeger MA, Bounaceur R, Biet J, Glaude P-A, et al. An experimental and kinetic modeling study of the autoignition of α-methylnaphthalene/air and α-methylnaphthalene/n-decane/air mixtures at elevated pressures. Combustion and Flame. 2010;157:1976-88. [27] Bounaceur R, Glaude PA, Fournet R, Battinleclerc F, Jay S, Cruz APD. Kinetic modelling of a surrogate diesel fuel applied to 3D auto-ignition in HCCI engines. International Journal of Vehicle Design. 2007;44:124-42. [28] Kukkadapu G, Sung C-J. Autoignition Study of 1-Methylnaphthalene in a Rapid Compression Machine. Energy & Fuels. 2017;31:854-66. [29] Narayanaswamy K, Blanquart G, Pitsch H. A consistent chemical mechanism for oxidation of substituted aromatic species. Combustion and Flame. 2010;157:1879-98. [30] Somers ML, McClaine JW, Wornat MJ. The formation of polycyclic aromatic hydrocarbons from the supercritical pyrolysis of 1-methylnaphthalene. Proceedings of the Combustion Institute. 2007;31:501-9. [31] Shaddix CR, Brezinsky K, Glassman I. Analysis of fuel decay routes in the high-temperature oxidation of 1-methylnaphthalene. Combustion and Flame. 1997;108:139-57. [32] Yang J, Lu M. Thermal growth and decomposition of methylnaphthalenes. Environmental Science & Technology. 2005;39:3077-82. [33] Guang H, Yang Z, Huang Z, Lu X. Experimental study of n-heptane ignition delay with carbon dioxide addition in a rapid compression machine under low-temperature conditions. Chinese Science Bulletin. 2012;57:3953-60. [34] Yang Z, Wang Y, Yang X, Qian Y, Lu X, Huang Z. Autoignition of butanol isomers/n-heptane blend fuels on a rapid compression machine in N2/O2/Ar mixtures. Science China Technological Sciences. 2014;57:461-70. [35] Mittal G, Sung* C-J. A rapid compression machine for chemical kinetics studies at elevated pressures and temperatures. Combustion Science and Technology. 2007;179:497-530. [36] Kukkadapu G, Kumar K, Sung C J, et al. Experimental and surrogate modeling study of gasoline ignition in a rapid compression machine. Combustion and Flame, 2012, 159(10): 3066-3078. [37] Pitz WJ, Mueller CJ. Recent progress in the development of diesel surrogate fuels. Progress in Energy and Combustion Science. 2011;37:330-50. [38] Darcy D, Nakamura H, Tobin C J, et al. An experimental and modeling study of surrogate mixtures of n-propyl-and n-butylbenzene in n-heptane to simulate n-decylbenzene ignition. Combustion and Flame, 2014, 161(6): 1460-1473. [39] Sung C-J, Curran HJ. Using rapid compression machines for chemical kinetics studies. Progress in Energy and Combustion Science. 2014;44:1-18.

15

ACS Paragon Plus Environment

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 16 of 29

Table 1 The experimental conditions and mixture composition in this study (mol%). No.

Pc (Bar)

Φ

Fuel

O2

Ar

1

12

1

1.53%

20.68%

77.79%

2

12

1.2

1.83%

20.62%

77.55%

3

15

0.7

1.08%

20.77%

78.15%

4

15

1

1.53%

20.68%

77.79%

5

15

1.2

1.83%

20.62%

77.55%

6

20

0.7

1.08%

20.77%

78.15%

7

20

1

1.53%

20.68%

77.79%

16

ACS Paragon Plus Environment

Page 17 of 29

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

Fig.1. Heated rapid compression machine

17

ACS Paragon Plus Environment

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.2. Definition of ignition delay

18

ACS Paragon Plus Environment

Page 18 of 29

Page 19 of 29

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

Fig.3. Experiment reproducibility

19

ACS Paragon Plus Environment

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

(a) Pc=15bar Φ=1 (b) Pc=15bar Φ=0.7 Fig.4. Typical pressure trace at various temperatures

20

ACS Paragon Plus Environment

Page 20 of 29

Page 21 of 29

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

(a) RCM data comparison Φ=1 (b) Shock tube data comparison Φ=1 Fig.5. Comparison of ignition delays of AMN with the experimental data obtained by Kukkadapu et al. [28], Wang et al. [26] and Pfahl et al. [22]

21

ACS Paragon Plus Environment

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

(a) Pc=12bar Φ=1, 1.2

Page 22 of 29

(b) Pc=15bar Φ=0.7, 1, 1.2

(c) Pc=20bar Φ=0.7,1 (d) Φ=1, Pc=12bar, 15bar, 20bar Fig.6. Comparisons of experimental and simulated ignition delay with adiabatic constant-volume model; symbols: experiment data; dash lines: Wang’s model [26]; solid lines: model of this study

22

ACS Paragon Plus Environment

Page 23 of 29

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

Fig.7. Comparison of experimental and RCM simulated pressure trace, Pc=15bar, Tc=905K, Φ=1

23

ACS Paragon Plus Environment

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 24 of 29

Fig.8. Comparison of experimental and simulated ignition delay at different pressures; symbols: experiment data; dash lines: constant volume simulation; solid lines: RCM simulation

24

ACS Paragon Plus Environment

Page 25 of 29

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

Fig.9. Comparison of experimental and RCM simulated ignition delay at different pressures; symbols: experiment data; dash lines: Narayanaswamy's model; solid lines: current model

25

ACS Paragon Plus Environment

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

(a) Comparison with Wang’s model, P=10bar

Page 26 of 29

(b) Comparison with Wang’s model, P=40bar

(c) Comparison with Narayanaswamy's model, P=10bar (d) Comparison with Narayanaswamy's model, P=40bar Fig.10. Comparison of simulated ignition delay with experiment data of Wang et al. [26] in a shock tube. P=10bar, 40bar, Φ=0.5,1,1.5 Model of Wang et al. [26] and Narayanaswamy et al. [29] were compared with the current model.

26

ACS Paragon Plus Environment

Page 27 of 29

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

Fig.11. Comparison of simulations with measurements of Mati et al. [24] in a JSR. P=10atm Φ=1; symbols: experiment data; lines: simulation

27

ACS Paragon Plus Environment

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. Reaction pathways of AMN with initial temperature of 900K, Φ=1 P=15bar, 20% AMN consumption

28

ACS Paragon Plus Environment

Page 28 of 29

Page 29 of 29

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 1300K 900K

R44.C10H7O+H=C10H7OH R15.C10H7CH3+C10H7=C10H7CH2+C10H8 R45.C10H7OH+OH=C10H7O+H2O R16.C10H7CH2+O=C10H7HCO+H R12.C10H7CH3+H=C10H7CH2+H2 R11.C10H7CH3+OH=C10H7CH2+H2O R1321.H+O2=O+OH R20.C10H7CH2+HO2=C10H7+CH2O+OH R59.Indenoxy=C6H5CCH2+CO R1248.CH2O+OH=HCO+H2O R35.C10H7HCO+C10H7CH2=C10H7CO+C10H7CH3 R50.Indenyl+O=C6H5CCH2+CO R1308.H+2O2=HO2+O2 R42.C10H7+O2=C10H7O+O R43.Indenyl+CO=C10H7O R1312.H+O2+AR=HO2+AR R5.C10H7CH3+O2=C10H7CH2+HO2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

Normalized Sensitivity Coefficient

Fig.13. Normalized sensitivity coefficients of OH radical. P=15bar, Φ=1, T=900K,1300K

29

ACS Paragon Plus Environment