Laminar Burning Velocity of n-Propanol and Air Mixtures at Elevated

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Laminar burning velocity of n-propanol and air mixtures at elevated mixture temperatures Amit Katoch, Ayush Chauhan, and Sudarshan Kumar Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.8b00997 • Publication Date (Web): 27 Apr 2018 Downloaded from http://pubs.acs.org on April 28, 2018

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Energy & Fuels

Laminar burning velocity of n-propanol and air mixtures at elevated mixture temperatures

1 2 3

Authors: Amit Katoch1, *, Ayush Chauhan2, Sudarshan Kumar1

4

1

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Technology, Bombay, Mumbai, Maharashtra, 400076, India

6

2

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Himachal Pradesh, 177005, India

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CORRESPONDING AUTHOR: *Amit Katoch, ([email protected])

Combustion Research Laboratory, Department of Aerospace Engineering, Indian Institute of

Department of Mechanical Engineering, National Institute of Technology Hamirpur,

9 10

Abstract:

11

The present work reports the measurement of laminar burning velocity for n-propanol and air

12

mixtures at 1 atm pressure with unburnt mixture temperature varying up to 620 K using

13

externally heated meso-scale diverging channels. Planar flames were stabilized in quartz

14

channels using externally heated meso scale diverging channel to create a positive

15

temperature gradient along the direction of fluid flow. Laminar burning velocity was

16

extracted using mass conservation principle at the flame surface and channel inlet. The

17

performance of six recent kinetic mechanisms was evaluated through comparison of the

18

predictions with present experimental results. A significant disagreement (≈ 22 %) was

19

observed between different mechanism predictions even at lower mixture temperatures of

20

335 K. The temperature exponent, α was extracted using power-law correlations and

21

observed to follow an inverted parabolic pattern with a minimum at slightly rich equivalence

22

ratio of 1.1, similar to other alcohol fuels.

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Keywords: n-propanol, biofuel, laminar burning velocity, meso-scale channels, temperature

24

exponent

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26

1 ACS Paragon Plus Environment

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1

Nomenclature:

2

Laminar burning velocity (m/s)

3

Temperature exponent

4

Φ

Equivalence ratio

5

,

Reference temperature (K)

6

,

Laminar burning velocity at reference temperature (m/s)

7

Mixture flow velocity at the inlet (m/s)

8

Tinlet

9

Ainlet Channel cross-section area at inlet (m2)

Mixture temperature at the channel inlet (K)

10

Tf

Mixture temperature at the flame stabilization location (K)

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Af

Channel cross-section at flame stabilization location (m2)

12

13

14

15

16

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Energy & Fuels

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1. Introduction:

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Increasing green-house gas emissions and shrinking ice cover is becoming a major global

3

concern which is being directly linked to various combustion processes. The increasing

4

interest of the policy makers in the use of renewable fuels has led to the intensification of

5

research efforts towards understanding the production and combustion processes of biofuels.

6

During the past one decade, the interest in alcohol-based biofuels has increased significantly.

7

More than 90 % of the biofuel market is focused around bioethanol and other higher chain

8

derivatives of alcohols are also being looked upon as potential alternatives. More studies are

9

being conducted to understand the fuel behavior and performance with different types of 1-4

10

engines

. Apart from being renewable fuels, biofuels offer unique advantages in

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combustion linked to the presence of additional oxygen content, which promotes clean

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combustion resulting in less particulate generation, when compared to conventional

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hydrocarbon fuels. In this context, a large number of studies have been reported with a focus

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on assessing the engine performance with methanol, ethanol, butanol and pentanol isomers.

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As compared to its isomer (isopropanol) and other alcohols from C1 to C5 group, n-propanol

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has received little attention as a potential biofuel for combustion studies. Gautam et al.

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investigated combustion characteristics of higher alcohol (n-propanol, n-butanol and n-

18

pentanol) blends with gasoline. They found that increased oxygen content from the alcohol

19

addition provided the blended fuels with improved knock resistance than a pure gasoline fuel.

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Fernandez et al. 6, 7 investigated the performance of direct injection CI engine with n-butanol-

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diesel and n-propanol diesel blends. The study revealed that n-propanol can be successfully

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blended up to 25% by volume, without causing any significant change in combustion and

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engine performance. Laminar burning velocity is a fundamental fuel parameter which

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characterizes the reactivity, thermo-diffusivity and exothermic nature of a fuel. It is defined

25

as the steady propagation of a planar, adiabatic and one-dimensional reaction front into a


5

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relatively stationary mixture in a doubly infinite domain 8. It is widely used in the estimation

2

of turbulent burning velocity and validation of chemical kinetic mechanisms. For a particular

3

fuel-oxidizer mixture it’s value depends on initial pressure, unburnt mixture temperature and

4

equivalence ratio. The dependence of laminar burning velocity on initial mixture temperature

5

9

for constant pressure study is described as:

= , /,

6

(1)

7

where is the temperature exponent and a function of mixture type and equivalence ratio.

8

, is the laminar burning velocity at reference temperature , .

9

There are very few studies reported in literature on measurement of laminar burning velocity

10

of n-propanol-air mixtures at atmospheric pressure. Gong et al. 10 used the combustion bomb

11

method to measure atmospheric laminar burning velocities at 343 K and 393 K mixture

12

temperatures for an equivalence ratio range of 0.75 - 1.5. They used the linear extrapolation

13

scheme

14

obtained in the combustion bomb.

15

Veloo et al.

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343 K mixture temperature and atmospheric pressure and used the non-linear stretch

17

extrapolation scheme suggested by Wang et al.

18

velocity. Galmiche et al.

19

using shadowgraphy in a spherical bomb. Non-linear correlations suggested by Kelly and

20

Law

21

values were reported for an unburnt mixture temperature of 423 K at atmospheric pressure.

22

Recently, Capriolo et al.

23

in the temperature range 323 -343 K.

15

11

to extrapolate the results to zero stretch from a spherically expanding flame

12

used the counterflow burner method to measure laminar burning velocities at

and Halter et al.

14

16

17

13

to obtain the unstretched laminar burning

extracted the burning velocities from the flame front evolution

were used for extrapolation of stretch. Laminar burning velocity

used the heat-flux method to measure laminar burning velocities


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Energy & Fuels

Johnson et al.

1

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developed a kinetic model using shock tube ignition delay studies to add

2

reactions pertaining to n-propanol and iso-propanol to the base chemistry of methanol and

3

ethanol. Galmiche et al.

4

experiments. Mann et al.

5

mixtures in argon-diluted oxygen mixtures and developed a new kinetic model based on the

6

mechanism of Johnson et al. 18 . The authors reported a reasonable agreement with measured

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JSR (Jet Stirred Reactor) and laminar burning velocity data. However, they stated that there

8

was a disagreement with ignition delay predictions using Johnson et al. model 18. Togbe et al.

9

20

14

developed a model with species inputs from Jet-Stirred Reactor 19

reported ignition delay data for n-propanol and iso-propanol

and Galmiche et al. 14 reasoned that this could be ascribed to the exclusion of few oxidation

10

paths in their propanol sub-model which manifests due to absence of important oxygenated

11

intermediate species in JSR modelling. Gong et al.10 developed a detailed and reduced model

12

for simulating n-propanol combustion. These models were developed by modifying the

13

kinetics of Man et al.19 model with CHEM-RC software21. Liu et al.22 developed a combined

14

mechanism for C1-C5 alcohols. Frassoldati et al.

15

mechanism for n-propanol and iso-propanol combustion (Polimi CRECK group).

23

also proposed a detailed kinetic

16

To the authors’ knowledge, there are no studies reported in literature, which have reported

17

the variation of the laminar burning velocities at mixture temperature higher than 423 K,

18

variation of temperature exponent with equivalence ratio and comparison of various kinetic

19

models at higher mixture temperatures. Besides, there is no experimental data reported for

20

mixture temperature greater than 423 K to validate various kinetic mechanisms at still higher

21

temperatures. The externally heated diverging channel method has been used in previous

22

works to measure the laminar burning velocities of gaseous

23

mixture temperatures. Therefore, the motivation of the present work is to present the high

24

temperature laminar burning velocity data and associated temperature exponent variation

24-28


and liquid fuels

29

at higher

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with mixture equivalence ratio, which would be invaluable for further development and

2

validation of high temperature kinetic models for this fuel.

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4

2. Details of experimental setup and numerical modeling

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2.1. Experimental setup:

6

In the present work, the externally heated meso-scale diverging channel method is used. The

7

diverging channel is made of quartz material. Figure 1 shows the schematic diagram of the

8

present setup. The channel consists of an initial rectangular part with 25 mm × 2 mm

9

dimensions and 50mm length followed by a diverging section of 50 mm length. The starting

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of the diverging channel is termed as inlet (X=0) and the divergence angle used in this study

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are 10 and 15 degrees. The channel gap between the upper and lower quartz plates is varied

12

as 2 mm and 1.5 mm. The thickness of the channel plates is kept fixed at 2 mm.

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Figure 1. Schematic of the experimental setup

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The channel is heated from the bottom using an infrared heater where the heating rate can be

16

controlled using a voltage controller. The heating rate can be set to a maximum output power


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Energy & Fuels

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of 1200 W to the infra-red heater. The external heating creates a positive and linear

2

temperature gradient along the length of the channel, similar to the principle of micro-flow

3

reactors

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can be varied by altering the heating rate and the horizontal and vertical clearance between

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the channel and the heater. Figure 2 shows the direct measurements of wall temperature

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profile in transverse and axial direction for a flow condition of Uinlet = 0.88 m/s. The

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transverse temperature profile shows a maximum deviation of 3 K amongst all the measured

8

values for a particular axial location. The axial temperature increases linearly along the

9

direction of the fluid flow with a temperature gradient of 2.58 K/mm.

30, 31

and earlier studies on diverging channel method

26-29

. This temperature profile

10 11

(a)

(b)

12

Figure 2. Temperature profile of the diverging channel walls along radial and axial direction

13

with infra-red heater for Uinlet = 0.88 m/s and an external heating rate of 600 W.

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Since n-propanol is in liquid state at ambient conditions, it needs to be vaporized and mixed

15

with air to form a combustible mixture before entering the diverging channel. For this

16

purpose, air is preheated to a certain temperature, and the required mixture ratio is achieved

17

based on the saturation vapor pressure for the liquid fuel at that temperature. The air


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preheater consists of two plate type heaters of 1.5 kW rating each and the heating rate is

2

controlled through a PID temperature controller driven unit attached to an IR heater. The fuel

3

flow rates are very small and hence an infusion pump is used for controlled fuel metering.

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The preheated air is directed into a heated copper tube where the fuel is injected using a

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micro syringe. Due to high temperature of the incoming air, the fuel vaporizes instantly and

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mixes with it to form a uniform combustible mixture. The entire flow path is heated using

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tape heaters and insulated to avoid any chances of fuel condensation along the length of the

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flow circuit. The mixture is ignited at the exit plane of the diverging channel. The domains

9

are studied starting from low inlet velocities to establish the flashback regimes. The flow

10

velocities are slowly increased to obtain stable flames. In the stable flame regimes, initially

11

negatively stretched flames are observed followed by planar flames and on further increasing

12

the inlet velocity positively stretched flames are observed till the flame moves out of the

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channel 29. Figure. 3 shows a typical stabilized planar flame used for laminar burning velocity

14

evaluation of n-propanol-air mixture. This flame is stabilized for a mixture flow velocity of

15

Uinlet = 0.85 m/s and a mixture equivalence ratio of Φ = 0.9.

16 17

Figure 3. Direct photograph of a stabilized planar flame for Uinlet = 0.85 m/s at Φ = 0.9

18

conditions.


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Energy & Fuels

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No cellular flames are observed, since the depth of the channel is very small (1.5 and 2.0

2

mm). The temperature profiles are measured a priori with heated airflow only. Planar flame

3

regimes are used for measuring the laminar burning velocity. At the point of flame

4

stabilization, the mixture temperature is assumed to be equal to the wall temperature and is

5

measured using a 0.25 mm K-type thermocouple of Omega make (accuracy ± 5 K). This is

6

substantiated by the fact that the Peclet number (Pe) corresponding to such low flow rates is

7

small

8

traverse system with an accuracy of 0.25 mm. The location of the stabilized flame is recorded

9

using a digital camera and further image processing is carried out. The burning velocity is

10

calculated using the mass balance relation at the channel inlet and the flame stabilization

11

location:

12

=

13

Where is the mixture flow velocity at the inlet (X = 0), Tinlet is the mixture temperature

14

at the channel inlet (with area, Ainlet), Tf is the mixture temperature at the flame stabilization

15

location (with area Af). The present measurements are accurate to ± 5 %, at all condition of

16

mixture equivalence ratio of temperature as discussed in previous studies 25, 27, 29, 33.

17

2.2

18

Laminar flame speeds were calculated from kinetic mechanisms using PREMIX code 34. It is

19

a FORTRAN code used for modelling 1-D steady premixed freely propagating laminar

20

flames. The governing differential equations for flame dynamics are solved using implicit

21

finite difference schemes along with steady and transient temporal schemes. The schemes

22

employ a coordinate system, which is a fixed point on the flame. In the solution, the flame

23

speed is an Eigen-value of the scheme, wherein, it is the inlet velocity at which flame is

24

stabilized at a fixed location. The steady state solver TWOPNT solves the non-linear

32

. The thermocouple is traversed within the channel with the help of an accurate

(2)

Numerical Simulations


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governing equations using a damped Newton’s method. Soret effect was taken into

2

consideration for all simulations. Mixture-averaged values were used to account for transport

3

parameters. The adaptive grid parameters were set to stiff values with CURV= 0.03 and

4

GRAD= 0.01. Table 1 gives a brief summary of various mechanisms used for simulations.

5

Gong et al. 10 have proposed a detailed and reduced model. Here, only the detailed model has

6

been used for comparison, since the difference between the predictions from the detailed and

7

reduced model is less than 0.4 %. The following models from literature are used for

8

simulating n-propanol combustion.

9

Table 1. Summary of various n-propanol mechanisms Mechanism Johnson et al.-2011-18 Galmiche et al.-2011-14 Polimi CRECK-2011-23 Man et al.-2014-19 Gong et al. (detailed)-2015 10 Gong et al. (reduced)-2015 10 Liu et al.-2016-22

Species 237 93 225 238 260 91 161

Reactions 1415 663 7645 1448 1653 706 622

10 11

3. Results & Discussions

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3.1 Effect of initial mixture temperature on laminar burning velocity

13


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Energy & Fuels

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Figure 4. Comparison of laminar burning velocity with mechanism predictions for the lean

2

case of Φ = 0.7

3

Figure 4 and 5 show the variation of laminar burning velocity with temperature ratio for lean

4

mixtures. The unburnt mixture temperature has been normalized with a reference temperature

5

of 300 K (Tu,0) to obtain the temperature ratio. The present data is fitted with power law

6

correlations to obtain the trends across the complete temperature range investigated in the

7

present experiments studies. For the lean case of Φ = 0.7 shown in Figure 4, the kinetic

8

model predictions of Polimi CRECK

9

mechanism

14

23

gives the highest predictions, whereas the Galmiche

predicts the lowest values. For Φ = 0.7, the trend obtained from experimental 23

and Gong (D) mechanism

10

10

values lies between the predictions of Polimi CRECK

11

predictions. Figure 5 shows the measurements of predictions of laminar burning velocities for

12

Φ = 0.9 conditions. For Φ = 0.9, the trend line is in good agreement with the predictions of

13

various mechanisms ( Johnson 18, Man 19, Gong (D) 10 and Liu 22 ).

14

15 16

Figure 5. Comparison of laminar burning velocity with mechanism predictions for the lean

17

case of Φ = 0.9 11 ACS Paragon Plus Environment

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Figure 6 and Figure 7 show the variation of the laminar burning velocity with temperature

2

ratio for rich mixture conditions with Φ =1.1 and 1.3 respectively. On the richer side, as

3

shown in Figure 6, for Φ = 1.1, the trends are similar to those at Φ = 0.9. However, at Φ = 1.3

4

the predictions from various kinetic models of Johnson et al.

5

CRECK

6

show a good match with a slight over prediction at higher mixture temperatures.

23

18

, Mann et al.

are much higher than present results. Here, Gong (D)

10

and Liu

19

and Polimi

22

mechanisms

7 8

Figure 6. Comparison of laminar burning velocity with mechanism predictions for the rich

9

case of Φ =1.1

10


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Energy & Fuels

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Figure 7. Comparison of laminar burning velocity with mechanism predictions for the rich

2

case of Φ = 1.3

3

4

5

6

7

3.2 Influence of mixture equivalence ratio on temperature exponent

8

The value of the temperature exponent, α is obtained at each mixture equivalence ratio by

9

fitting a power-law correlation to the variation of laminar burning velocity with mixture

10

temperature. Figure 8 shows the variation of temperature exponent, α with equivalence ratio,

11

Φ. Since there is no other data reported in the literature for the variation of temperature

12

exponent, α with equivalence ratio, Φ, only the kinetic model predictions are shown in the

13

figure for comparison purpose. It is to be noted that all the mechanism predictions show a

14

qualitative inverted parabolic variation with a minimum value of temperature exponent, α for

15

slightly rich mixtures.

16


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Figure 8. Comparison of temperature exponent variations with equivalence ratio for n-

2

propanol and air mixtures with predictions from detailed mechanisms

3

Prior to 2010, many studies reported linear decrements or constant values of α for different

4

hydrocarbon fuels. Konnov

5

variation of temperature exponent for various hydrocarbon fuels. Similar variation of

6

temperature exponent, α is obtained through a series of experiments at different equivalence

7

ratios as shown in Figure 8. The temperature exponent variation with equivalence ratio can be

8

fitted with a second-order polynomial as: = 2.3688Φ% − 5.2376Φ + 4.5889. The present

9

values are in good agreement with the predictions of Gong et al.

35

discouraged such variations and justified a non-monotonic

10

and Liu et al.

22

10

mechanisms for lean conditions and with a slight under prediction for stoichiometric and rich

11

mixtures. The error bars associated with each equivalence ratio were evaluated using the least

12

squares method proposed by Alekseev et al.

13

from kinetic models is significantly higher than the current measurements indicating a

14

possibility of over prediction of laminar burning velocities at higher mixture temperatures by

15

these kinetic models.

16

3.3

17

Figure 9 and Figure 10 show the comparison between the present results with predications of

18

various kinetic models and available experimental data at different mixture temperatures of

19

343 K and 423 K respectively. It is interesting to note that at both 343 K and 423 K

20

temperatures, Polimi CRECK

21

Galmiche mechanism

22

mechanism follow closely across the complete range of equivalence ratios.

36

. The prediction of temperature exponent, α

Laminar burning velocity at low and elevated temperatures

14

23

mechanism predicts the highest values, whereas the

predicts the lowest values. Predictions using the Gong et al.


10

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Energy & Fuels

1 2

Figure 9. Comparison of laminar burning velocity with experimental data and predictions

3

from mechanisms at 343 K

4

At 343 K, the present data is in good agreement with the data of Veloo et al.

5

equivalence ratios, except at Φ ≥ 1.2. A significant difference of nearly 7 cm/s on the lower

6

side is observed for Φ ≥ 1.2 conditions. It is interesting to see that, for lean and stoichiometric

7

conditions, the heat flux method measurements reported by Capriolo et al.

8

higher than the predictions of all kinetic models.

9


17

12

at all

are relatively

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2


3 4


5


6

At 423 K mixture temperature, it is interesting to note that the measurements of Galmiche et

7

al.

8

predictions of their kinetic model. The measurements reported by Gong et al.

9

using spherical flame method with non-linear extrapolation model are quite close to the

10

measurement of Galmiche et al. 14. There exists very little difference between the two despite

11

a significant difference in the mixture temperature. However, it is to be noted that both these

12

experimental measurements are significantly lower than all other mechanism predictions and

13

present measurements at 423 K mixture temperature.

14

using spherical flame method and linear extrapolations model follow closely with the


10

at 393 K

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Energy & Fuels

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3


4

Figure 11 shows a detailed comparison of present measurements with various kinetic model

5

predictions at 500 K and Figure 12 shows similar comparison at 600 K mixture temperature.

6

The data for comparison was obtained using temperature exponents shown in Fig. 8 through

7

interpolation for specific mixture temperatures at each equivalence ratio. It can be seen that

8

Polimi CRECK mechanism

9

Galmiche mechanism 14 predicts the lowest values across all equivalence ratios, for both 500

10

K and 600 K mixture temperatures. The difference is predictions is as large as 26 % at 600 K.

11

The present data shows a close agreement with Gong et al.

12

difference of about 4 cm/s at 600 K. Various other kinetic models (Johnson 18, Man 19 , Liu 22

13

) predict a close agreement with the present experimental results at different mixture

14

temperatures and equivalence ratios as clear from Figures. 9-12.

15

3.4

16

To present the sensitivity analysis, the model of Gong et al.

17

consistently good agreement with the present experimental results. The objective of the

23

predicts highest values of laminar burning velocity and

10

mechanism with a maximum

Sensitivity Analysis


10

was used as it has shown a

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Page 18 of 25

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present analysis is to identify the key reactions and their influence on the variation of laminar

2

burning velocity with varying mixture temperature and equivalence ratios. The normalized

3

sensitivity coefficient of laminar burning velocity with respect to the reaction rate constant is

4

given by the correlation: ,-./ , 01 =

5

sensitive to laminar burning velocity are plotted in Figure 13. It is well known that the

6

laminar flame speed is directly proportional to the concentrations of H and OH radicals.

7

Across all the equivalence ratios, the results indicate that the burning velocity is most

8

sensitive to the main chain branching reaction: H + O2O + OH which shows the highest

9

positive contribution. The sensitivity contribution of this reaction increases as the mixture

10

moves from lean to rich equivalence ratios. In the lean regime, this reaction competes with

11

H+O2(+M)HO2(+M) reaction. The negative sensitivity of this reaction decreases as the

12

mixture equivalence ratio changes from lean to stoichiometric regime and becomes almost

13

non-existent at very rich conditions, at Φ=1.3. The next main reaction accelerating the flame

14

speed is the CO oxidation reaction: CO + OHCO2 + H, which contributes primarily in the

15

leaner regime. With an increase in equivalence ratio, the quantity of the hydroxyl radicals

16

decreases, thereby decreasing the sensitivity of this reaction. The water recombination

17

reaction: H+OH+M H2O + M which retards the flame, shows slightly increasing

18

sensitivity as equivalence ratio increases at 335 K. However, at 600 K, the contribution

19

remains identical for compared equivalence ratios.

23 24

4

∗ 3

37, 38

. Sixteen reactions which are most


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Energy & Fuels

1 2

(a)

(b)

3

Figure 13. Normalized sensitivity coefficients for the laminar burning velocity of n-propanol

4

+ air mixtures at (a) 335 K and (b) 600 K.

5

Decomposition reaction of formyl radicals: HCO + M H + CO + M produces flame

6

accelerating radicals H and CO. This reaction shows only slight changes as equivalence ratios

7

increases. In a generic sense, both the negative and positive contributions from the reactions

8

decrease in terms of their sensitivity magnitude with increasing temperature. The only

9

reaction involving the fuel (n-propanol) showing any sensitivity is: NC3H7OH + H

10

C3H6OH-3 + H2, which contributes only for the rich case of Φ = 1.3. As the equivalence

11

ratio increases, the burning velocity becomes sensitive to the methyl recombination reaction:

12

CH3+H(+M)CH4(+M). This is a chain terminating reaction, where methyl radical acts as a

13

sink for the H radical to produce CH4, thus slowing down the rate of flame propagation.

14

Another radical termination reaction: HCO+H CO + H2 shows its presence only for the

15

rich case at 335 K However, as the temperature increases to 600 K, it starts influencing the

16

stoichiometric mixtures as well. Another such temperature bias is observed for the reaction:

17

HO2 + OH H2O + O2. At 335 K, this reaction influences the lean and stoichiometric

18

domains, whereas at 600 K, it affects only the lean regime. The participation of the vinyl 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

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1

radical happens for rich mixtures in a competing manner, where the reaction C2H3 + H

2

C2H2 + H2 slows down the flame and the reaction C2H2+H (+M) C2H3(+M) accelerates

3

it. The contribution from the latter reaction is slightly higher, thus leading to a net production

4

of the vinyl radicals.

5

Conclusions

6

New high temperature laminar burning velocity measurements were carried out using the

7

externally heated meso-scale diverging channel method employing planar flames for n-

8

propanol and air mixtures upto unburnt mixture temperatures of 620 K at atmospheric

9

pressure. The effect of mixture temperature on laminar burning velocity was investigated

10

through power law correlations for experimental measurements. The variation in temperature

11

exponents was studied for lean, stoichiometric and rich mixtures to assess the effects of

12

equivalence ratio. An inverted parabolic variation was observed with a minimum at slightly

13

rich mixture. The detailed mechanism by Gong et al.

14

measured values even for high temperatures across studied equivalence ratios except for

15

slight over-prediction at Φ=1.3. Therefore, the discrepancies in the kinetic parameters of

16

various mechanisms, particularly for rich mixtures need further investigation.

10

was observed to closely predict the

17

18

19

Acknowledgement:

20

The authors would like to acknowledge the financial support for this work from Department

21

of Science and Technology (DST), Govt. of India wide grant no. SB/S3/COMB-001/ (2014).

22 23

References

24


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Laminar Burning Velocity of n-Propanol and Air Mixtures at Elevated

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