Experimental Study on Premixed Hydrogen-Air and Hydrogene-methaneair Mixtures Explosion in 90 Degree Bend Pipeline-libre

Experimental study on premixed hydrogen/air and

hydrogenemethane/air mixtures explosion in 90

degree bend pipeline

Sina Davazdah Emami a,b,*, Meisam Rajabi b, Che Rosmani Che Hassan a,Mahar Diana A. Hamid a, Rafiziana M. Kasmani b, Mojtaba Mazangi b

aChemical Engineering Department, Faculty of Engineering, University of Malaya, 50603 UM Kuala Lumpur,

Malaysiab Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Malaysia

a r t i c l e i n f o

Article history:

Received 15 May 2013

Received in revised form

27 July 2013

Accepted 12 August 2013

Available online xxx

Keywords:

Flame propagation

Flame speed

Overpressure

a b s t r a c t

Nowadays, hydrogen is being utilized massively in industries as a clean fuel. Displacing of

hydrogen due to unique chemical and physical properties has adversely affect on pipeline

network, hence increases the potential risk of explosion. This study was carried out to

determine the flame propagation of hydrogen/air and hydrogenemethane/air mixtures in

pipeline. A 90 pipeline with L/D ratio of 40 was used. Pure hydrogen/air mixture with

equivalence ratio, 4 0.13, 0.17, 0.2, 0.24, 0.27 and 0.30 were used in this work. Different

composition of hydrogenemethaneeair mixtures were tested in this study i.e. 3%

H2 97CH4, 4%H2 96CH4, 6%H2 94CH4 and 8%H2 92CH4. All mixtures were operated at

ambient condition. The results show that bending is the critical part of pipeline and higher

concentration of hydrogen can affect on maximum overpressure, flame speed and tem-

perature rise of both pure hydrogen/air and methane-hydrogen/air mixtures.

Copyright 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights

reserved.

1. Introduction

Hydrogen-enrichment has been recognized as a useful pattern

to overcome problems associated to turbulent premixed

combustion of natural gas in different systems [1e7] which it

would change the fuel-air combustion behavior, namely

laminar burning velocity and flame stability dramatically [1,8].

Xiao [9] analyzed the premixed hydrogen/air flame propaga-

tion in a horizontal rectangular closed duct. Thework resulted

that the flame speed decreased rapidly, inducing more tur-

bulent combustion when the flame front develops closer to

the side walls. Cammarota et al. [1] studied the explosion

behavior of stoichiometric hydrogen-enriched methane/air

(with 10% of hydrogen molar content in the fuel) and pure

methane/air mixtures in a 5 L closed cylindrical vessel at

different initial pressures. In their study, the low hydrogen

content has negligible effect on the flame reactivity and the

deflagration index as well as the burning velocity on the

overpressure. It is also found that the burning velocity de-

creases with the initial pressure, yet, this effect being less

pronounced in the case of the hydrogen-enriched flame.

On the other hand, studies showed that the effect of

hydrogen substitution to methane in terms of maximum rate

of pressure rise or laminar burning velocity for any initial

* Corresponding author. Chemical Engineering Department, Faculty of Engineering, University of Malaya, 50603 UM Kuala Lumpur,Malaysia. Tel.: 60 166308085.

E-mail addresses: [email protected], [email protected] (S.D. Emami).

Available online at www.sciencedirect.com

journal homepage: www.elsevier .com/locate/he

i n t e rn a t i o n a l j o u rn a l o f h y d r o g e n en e r g y x x x ( 2 0 1 3 ) 1e6

Please cite this article in press as: Emami SD, et al., Experimental study on premixed hydrogen/air and hydrogenemethane/airmixtures explosion in 90 degree bend pipeline, International Journal of Hydrogen Energy (2013), http://dx.doi.org/10.1016/j.ijhydene.2013.08.056

0360-3199/$ e see front matter Copyright 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.ijhydene.2013.08.056

pressure is quite dramatic [10,11]. The addition of hydrogen to

methane gives considerably the flame stability, wide flam-

mable regions and relatively higher burning velocity, thus a

good replacement for hydrocarbon fuels. In addition, the

hydrogen presence affects the flow field in both quantitative

and qualitative terms [11,12]. As the value of hydrogen in-

creases in mixture, the velocity of the toroidal vortex in-

creases [12]. However, the safe use of hydrogenemethane as

alternative fuel on the pipeline is still unclear.

The transportation of the hydrogen frommanufacturing to

end users could affect the integrity or durability of the pipeline

network therefore the existing gas pipeline network are

designed, constructed and operated using natural gas. The

hydrogen would also mix with natural gas once introduced

into the pipeline. Hence, for the safe use of hydrogen fuels, it is

essential to fully characterize and quantify their explosion

behavior. The leakage and failure in the gas pipelines carrying

a massive volume and tremendous pressure of hydrogen

could also become a potential catastrophic incident leading to

severe casualty and cost [2]. The effect of obstruction, junc-

tions and bends that normally integrated in piping design

would create issues associated with reaction location and the

flame stability [1,8].

For authors knowledge, there is sparse experimental

studies have been carried out in micro scales [9,13], particu-

larly in 90 bend [14e17]; hence, this study was carried out

focusing on the flame propagation of hydrogen/air and

hydrogenemethane/air mixtures explosion in 90 pipelines in

order to investigate the physical and dynamic characteristics

(e.g. maximum pressure, rate of pressure rise, temperature

changes and flame speed) of these gas/air mixtures explosion.

2. Methodology

A 90 pipeline, with 3 m long in horizontal, 1 m in vertical and

0.1mdiameter,withL/Dratioof40wasused in this study (Fig. 1).

The pipeline is made up of a number of segments ranging from

0.5 to 1 m in length, bolted together with a gasket seal in-

between the connections and blind flanges at both ends. The

mixtureswere ignitedat thecenterofentrancepointofpipeline.

The flammable mixture was initiated by an electrical spark,

which gives 16 J energies for the gas explosion tests.

The history of flame propagation along the pipeline was

recorded by an axial array of mineral insulated, exposed

junction, type K thermocouples (analogue output) which was

detected via NI CompactDAQ [18]. Flame speeds in the pipe

were measured from the time of arrival of the flame at an

array of thermocouples on the vessel. The average flame

speed between two thermocouples was determined and

ascribed to the mid-point of the distance between the

thermocouples.

The pressure at various points along the length of the pipe

was recorded using piezoelectric pressure transducers (Keller

Series 11). A 14 channels transient data recorder was used to

record and process all the data via LabView (SoftwareNational

Instrument Company). Each explosion was repeated at least 3

times for accuracy and reproducibility.

Only low concentrations of hydrogen and hydrogene-

methane mixtures were utilized in this study. For pure

hydrogen-air mixture, equivalence ratio of 0.13, 0.17, 0.2, 0.24,

0.27 and 0.3 were used. Different concentration of hydro-

genemethaneeair mixtures were prepared in this experiment

i.e. 3%H2 97CH4, 4%H2 96CH4, 6%H2 94CH4 and 8%

H2 92CH4. Moreover, methane, hydrogen and oxygen initially

storedat different storage tank andkept athigherpressure than

mixer vessel to facilitate gas flow from tank into the mixer

vessel.Mixingcellwasusedfor formingthemethane-hydrogen/

air and hydrogen/air mixtures by considering partial pressure

method so a homogeneous composition was achieved.

3. Result and discussion

Fig. 2 shows the pressure profiles against the distance from

ignition in 90 bend pipe. The vertical dotted line on the graph

indicates the bending position. It can be seen that the pressure

increased gradually while approaching the bending before

sharply decreased after the bend due to the flame propagation

obstructed by the closed end as well as heat losses [14]. It was

observed that with enhancement of 8% H2 v/v into meth-

aneeairmixture, themaximumpressureobtainedwas10bars,

about 1.2 bars higher than maximum overpressure of pure

H2eair mixture, as illustrated in Fig. 2. It can be depicted that

themass-burning rate of the flamehas clear effect on pressure

rising due to the larger flame area of the spherical flame for

both mixtures. This would create more turbulence as well as

higher overpressures regarding to the faster flame speeds in

the pipe. On the basis ofmaximumoverpressure of pure H2/air

mixtures, it can be said that the enhancement of H2 concen-

tration into methane-hydrogen/air leads to the dramatic

increasing of maximum overpressure. The closed end pipe-

lines also increase the pressure development at the regimes of

flame propagation because it acts same as same as obstacles.

The reactivity of explosion on methane-hydrogen/air

mixture has been studied in different vessels [1,10,11,19e22].

It was observed that by increasing the percentage of hydrogen

in mixtures, the overpressure values increased slightly. It can

be said that the additional of hydrogen content in meth-

aneeair mixtures could increase the burning velocity and

thus, giving higher overpressure, especially at the bend area.

Even though the result obtained in this study has a good

agreementwith previousworks, yet, the value of overpressure

increased dramatically in 90 bend [14].

Furthermore, it seems that the addition of hydrogen into

the methane/air mixtures would speed up the reaching time

of the flame to the bending section about 5 ms, as comparedFig. 1 e Scheme of pipeline.

i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n en e r g y x x x ( 2 0 1 3 ) 1e62


with pure hydrogen. However, it is interesting to note that the

time variance to reach the end pipe on either pure hydrogen or

methane-hydrogen is negligible (Fig. 3).

Fig. 4 illustrated the rate of pressure rise as a function of

distance from the ignition, with the reference point at the

bend. The significant profile of dP/dt was observed on 6%

H2 94CH4, 8%H2 92CH4, 8%H2 and 9%H2. This phenomenon

is in good agreement with previous study [14] due to the

release of energy and chaotic combination of reactivity mix-

tures by adding more hydrogen to methaneeair mixtures. On

0

2

4

6

8

10

0 50 100 150 200 250 300 350 400

Pres

sure

(b

ar)

Distance (cm)

3.9% H2

5.1% H2

6.0% H2

7.2% H2

8.1% H2

9.0% H2

bend

0

2

4

68

10

0 50 100 150 200 250 300 350 400

Pres

sure

(b

ar)

Distance (cm)

3%H2+97%CH4

4%H2+96% CH4

6%H2+94%CH4

8%H2+92%CH4

bend

(b)

(a)

Fig. 2 e Pressure Vs. Distance from ignition of (a) hydrogen/air and (b) hydrogenemethane/air mixtures in 90 pipeline.

0

2

4

6

8

10

12

0 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

Pres

sure

(b

ar)

Time (ms)

3.9% H25.1% H26.0% H27.2% H28.1% H29.0% H2bend

0

2

4

6

8

10

12

0 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

Pres

sure

(b

ar)

Time (ms)

3%H2+97%Ch44%H2+96% CH46%H2+94%CH48%H2+92%CH4bend

(b)

(a)

Fig. 3 e Pressure Vs. Time profile of (a) hydrogen/air and (b) hydrogenemethane/air mixtures in 90 pipeline.

i n t e rn a t i o n a l j o u rn a l o f h y d r o g e n en e r g y x x x ( 2 0 1 3 ) 1e6 3


the other hand, rate of pressure rise is experienced a sudden

decrease after the bend. This is due to flame propagation is

obstructed by the closed end, leading to the overpressure to

drop significantly. Furthermore, the explosion severity based

on pressure rise is shown in Table 1. However, it can be

depicted that the KG (deflagration index for gas explosion

severity) values obtained was increasing with the increase of

hydrogen percentage in the mixtures; although it can be

considered as weak severity. Moreover, since KG value

depends on initial condition, mixture concentration and

properties, it is lower than puremethane in Sphere Apparatus

System [23].

Flame speed profile against the distance from ignition

was shown in Fig. 5. A significant rate changes can be seen

in flame acceleration along the centerline of the pipe due to

different fuel concentration [24]. The highest flame speed is

406 m/s on 8%H2 92CH4 mixtures which is observed at the

bend, almost two times higher, as compared to the flame

speed of a very lean concentration of 3%H2 97CH4 i.e.

178 m/s. By taking maximum flame speed for pure hydrogen

as a basis, it can be seen that it is about 1.33 times incre-

ment of flame speed in additional of hydrogen into the

mixtures. This confirms the previous results of Phylaktou

et al. [12] and Zhu et al. [24]. They indicated that higher gas

concentration increase the heat released by the reaction

which it increase flame speed.

In otherwords, addingmore hydrogen tomixtures resulted

in significantly earlier times of flame arrival to 90 pipeline

(Fig. 3), same as rig enclosure [8] and plenum chamber [25],

giving higher flame speeds for both pure hydrogen/air and

methane-hydrogen/air mixture as concluded by Hu et al. [26].

The acquiesced data showed that while the flame speed

reached to the maximum value at the bend, it declined

dramatically after the bend. The flame speed losses suffered

-300-250-200-150-100-50

050

100

0 50 100 150 200 250 300 350 400dP

/dt

Distance (cm)

3.9% H2 5.1% H2 6.0% H2 7.2% H28.1% H2 9.0% H2 bend

-300-250-200-150-100

-500

50100150

0 50 100 150 200 250 300 350 400

dP/d

t

Distance (cm)

3%H2+97%Ch4 4%H2+96% CH4 6%H2+94%CH48%H2+92%CH4 bend

(b)

(a)

50

60

130 140

Fig. 4 e Rate of pressure rise of (a) hydrogen/air and (b) hydrogenemethane/air mixtures in 90 pipeline at different distance

from ignition.

Table 1 e Index for gas explosion severity at bend fromignition point.

Mixture dP/dtmax(bar/s)

V(1/3)

(m)KG (dP/dt)maxV

(1/3)

(bar.m.s1)

3%H2 97%CH4 51.25 0.09 4.6.125

4%H2 96%CH4 63.55 0.09 5.7195

6%H2 94%CH4 77.85 0.09 7.0065

8%H2 92%CH4 93.16 0.09 8.3844

3.9% H2 40.54 0.09 3.6486

5.1% H2 52.34 0.09 4.7106

6.0% H2 64.53 0.09 5.8077

7.2% H2 76.34 0.09 6.8706

8.1% H2 87.74 0.09 7.8966



at the bend are caused by both friction and momentum ex-

changes resulting from a change in the direction of flow.

Interestingly, the recorded maximum flame speeds in this

study are different in comparison with previous studies for

pure hydrogen in 90 bend [17,27]. This difference can be result

of different experimental rig design.

4. Conclusion

Regarding to importance of hydrogen and hydrogenemethane

mixtures as a fuel carriers, this study was conducted to

determine themaximumpressure, rate of pressure rise, flame

speed and temperature changes of hydrogen/air and

methane-hydrogen/air mixtures in 90 bend pipeline in

ambient pressure and temperature.

The findings showed that:

1. due to intense fluctuation of flame speed and pressure, it is

observed that bending is the critical part in the pipeline.

Accordingly, the potential risk of failure in pipeline be-

comes more probable at this part,

2. higher concentration of hydrogen in both pure hydrogen/

air and methane-hydrogen/air mixtures can affect

dramatically on maximum overpressure and flame speed,

3. higher explosion reactivity can be seen in methane-

hydrogen/air mixture regarding to changes of explosion

mechanism properties of methane/air mixture.

4. the explosion severity based on pressure rise has low sig-

nificant effect on lower concentration of both hydrogen/air

and methane-hydrogen/air mixtures in 90 pipeline.

Acknowledgment

This research paper would not have been possible without the

support of many people. The authors wish to express their

gratitude to all of them.

r e f e r e n c e s

[1] Cammarota F, Di Benedetto A, Di Sarli V, Salzano E, Russo G.Combined effects of initial pressure and turbulence onexplosions of hydrogen-enriched methane/air mixtures. JLoss Prev Process Ind 2009;22(5):607e13.

[2] Bjerketvedt D, Bakke JR, van Wingerden K. Gas explosionhandbook. J Hazard Mater 1997;52(1):1e150.

[3] Griebel P, Boschek E, Jansohn P. Lean blowout limits and NOxemissions of turbulent, lean premixed, hydrogen-enrichedmethane/air flames at high pressure. J Eng Gas Turb Power2007;129(2):404e10.

[4] Nguyen O, Samuelsen G. The effect of discrete pilot hydrogendopant injection on the lean blowout performance of amodel gas turbine combustor. ASME Paper; 1999. p. 359 (99-GT).

0

50

100

150

200

250

300

0 50 100 150 200 250 300 350 400

Sf(m

/s)

Distance (cm)

3.9% H25.1% H26.0% H27.2% H28.1% H29.0% H2bend

050

100150200250300350400

0 50 100 150 200 250 300 350 400

Sf (m

/s)

Distance (cm)

3%H2+97%CH4

4%H2+96% CH4

6%H2+94%CH4

8%H2+92%CH4

bend

(a)

(b)

Fig. 5 e Flame speed Vs. distance from ignition of (a) hydrogen/air and (b) hydrogenemethane mixtures in 90 pipeline.

i n t e rn a t i o n a l j o u rn a l o f h y d r o g e n en e r g y x x x ( 2 0 1 3 ) 1e6 5


[5] Schefer R, Wicksall D, Agrawal A. Combustion of hydrogen-enriched methane in a lean premixed swirl-stabilizedburner. Proc Combust Inst 2002;29(1):843e51.

[6] Bauer C, Forest T. Effect of hydrogen addition on theperformance of methane-fueled vehicles. Part I: effect on SIengine performance. Int J Hydrogen Energy 2001;26(1):55e70.

[7] Sierens R, Rosseel E. Variable composition hydrogen/naturalgas mixtures for increased engine efficiency and decreasedemissions. J Eng Gas Turb Power 2000;122(1):135e40.

[8] Di Sarli V, Benedetto AD. Laminar burning velocity ofhydrogenemethane/air premixed flames. Int J HydrogenEnergy 2007;32(5):637e46.

[9] Xiao H, Wang Q, He X, Sun J, Yao L. Experimental andnumerical study on premixed hydrogen/air flamepropagation in a horizontal rectangular closed duct. Int JHydrogen Energy 2010;35(3):1367e76.

[10] Salzano E, Cammarota F, Di Benedetto A, Di Sarli V.Explosion behavior of hydrogenemethane/air mixtures. JLoss Prev Process Ind 2012;25(3):443e7.

[11] Ilbas M, Crayford AP, Ylmaz I, Bowen PJ, Syred N. Laminar-burning velocities of hydrogeneair andhydrogenemethaneeair mixtures: an experimental study.Int J Hydrogen Energy 2006;31(12):1768e79.

[12] Di Sarli V, Di Benedetto A, Long EJ, Hargrave GK. Time-Resolved Particle Image Velocimetry of dynamic interactionsbetween hydrogen-enriched methane/air premixed flamesand toroidal vortex structures. Int J Hydrogen Energy2012;37(21):16201e13.

[13] Zhian H, Zhigang L, Shengguo C, Yansong Z, Yinghua Z.Numerical simulation and study on the transmission law offlame and pressure wave of pipeline gas explosion. Safety Sci2012;50(4):806e10.

[14] Phylaktou H, Foley M, Andrews G. Explosion enhancementthrough a 90 curved bend. J Loss Prev Process Ind1993;6(1):21e9.

[15] Guo C, Wang C, Xu S, Zhang H. Cellular pattern evolution ingaseous detonation diffraction in a 90-branched channel.Combust Flame 2007;148(3):89e99.

[16] Thomas G, Oakley G, Bambrey R. An experimental study offlame acceleration and deflagration to detonation transitionin representative process piping. Process Saf Environ Prot2010;88(2):75e90.

[17] Blanchard R, Arndt D, Gratz R, Poli M, Scheider S. Explosionsin closed pipes containing baffles and 90 degree bends. J LossPrev Process Ind 2010;23(2):253e9.

[18] Wen-Bin W, Jang-Yuan L, Qi-Jun W. The design of a chemicalvirtual instrument based on labview for determiningtemperatures and pressures. J Autom Methods Manag Chem2007:2007.

[19] Lowesmith BJ, Mumby C, Hankinson G, Puttock JS. Ventedconfined explosions involving methane/hydrogen mixtures.International Int J Hydrogen Energy 2011;36(3):2337e43.

[20] Lowesmith BJ, Hankinson G, Johnson DM. Vapour cloudexplosions in a long congested region involving methane/hydrogen mixtures. Process Saf Environ Prot2011;89(4):234e47.

[21] Wooley RM, Fairweather M, Falle SAEG, Giddings JR.Predictions of the consequences of natural gas-hydrogenexplosions using a novel CFD approach. In: Bertrand B,Xavier J, editors. Computer aided chemical engineering.Elsevier; 2008. p. 919e24.

[22] Lowesmith BJ, Hankinson G, Spataru C, Stobbart M. Gasbuild-up in a domestic property following releases ofmethane/hydrogen mixtures. Int J Hydrogen Energy2009;34(14):5932e9.

[23] Garcia-Agreda A, Di Benedetto A, Salzano E, Sanchirico R.The role of ignition delay time on the deflagration index in a20l bomb. In: Sixth fire and explosion hazards seminar (FEH6)2010.

[24] Zhu C, Lu Z, Lin B, Jiang B. Effect of variation in gasdistribution on explosion propagation characteristics in coalmines. Min Sci Technol (China) 2010;20(4):516e9.

[25] Coppens FHV, Konnov AA. The effects of enrichment by H2on propagation speeds in adiabatic flat and cellularpremixed flames of CH4+O2+CO2. Fuel 2008;87(13e14):2866e70.

[26] Hu E, Huang Z, He J, Jin C, Zheng J. Experimental andnumerical study on laminar burning characteristics ofpremixed methaneehydrogeneair flames. Int J HydrogenEnergy 2009;34(11):4876e88.

[27] Uchida M, Suda T, Fujimori T, Fujii T, Inagaki T. Pressureloading of detonation waves through 90-degree bend in highpressure H2eO2eN2 mixtures. Proc Combust Inst2011;33(2):2327e33.



Documents

Experimental Study on Premixed Hydrogen-Air and Hydrogene-methaneair Mixtures Explosion in 90 Degree Bend Pipeline-libre