22P028-P
Enhancement of Combustion Reaction by Radical Injection
using Dielectric Barrier Discharges
誘電体バリア放電を用いたラジカル注入による燃焼促進効果
Yujiro Sumiishi, Kohei Nosaka, Yoshihiko Uesugi and Yasunori Tanaka
住石裕次郎, 野阪幸平，上杉喜彦，田中康規
Division of Electrical Engineering and Computer Science, Kanazawa University
Kakuma, kanazawa, Ishikawa 920-1192, Japan
金沢大学自然科学研究科電子情報工学専攻 〒920-1192 石川県金沢市角間町
Through the experiments, we have found that increasing the generation of the important radicals (OH, CH,C2) in the hydro carbon combustion is strongly enhanced and the combustion speed is increased by ~ 20 %when DBD is applied to oxygen gas. The enhancement of the combustion reaction comes from the ozone
production by oxygen DBD. On the other hand, DBD of fuel gas(butane, C4H10)does not improve thecombustion reaction as much as that in oxygen.

1. Introduction
Nowadays, the interaction of plasmas withcombustion flame is getting much attention fromthe view point of effective combustion. The
technology that reactive plasmas are superimposedto the combustion field is called plasma-assistedcombustion. The plasma-assisted combustion
technique has various advantages, such aspromotion of the ignition and the combustion
reaction. Other expected effect is suppression theemission of harmful gases by the electricaldischarges. Because non-equilibrium plasmas havea lot of activated species which promote
combustion reactions, significant synergy effects
are expected. In this report, we investigated theinfluence of radical injection to hydrocarbon
combustion experimentally from the viewpoint of
the enhancement of activated species relating to theignition and improvement of the combustion speed.
2. Experimental Setup and Condition
The experimental setup is shown in Fig. 1. We
used coaxial cylindrical reactor to discharge supply
gases of butane (C4H10) and oxygen (O2). Materialof inside electrode is stainless steel and outside iscopper line. Dielectric material between theelectrodes is quartz. C4H10 and O2 are added todielectric barrier discharges separately. Premixed
combustion is one of the combustion methods thatthe fuel and oxidizer are premixed. Opticalemission from the combustion flame is measured byspectrometer and UV-CCD camera withinterference filter. The combustion radicals are alsomeasured by mass spectrometer working at theatmospheric pressure. C4H10 and O2 gas rate are 0.1
slpm and 0.65 slpm, respectively. A high voltage
power supply for barrier discharges generates Vp-pof 15 kV at a frequency of 15 kHz. The time
averaged discharge power is about ~ P≦40 W in

DBD reactor Flame

Interference filter
ikega SKC161
miCCD camera

C4H10O2~16 kVp-p，15kHzFig. 1 Experimental setup(a) w/o discharge(b) w/ discharge
Fig. 2 Plasma emission that applying discharge to C4H10and O2 separately

the experiment. Combustion power of premixed
flame is about 200 W, so discharge power is muchless than the combustion power.
3. Results and Discussion
Fig. 3 shows the enhancement of the hydro-carbon combustion reaction measured by massspectrometer. When DBD is applied to oxygen,ozone is mainly generated. In the case of butane
DBD decomposed particles, such as H2, C2, CHfrom butane gas are generated. The increase ofhydrogen molecule is most significant. Theemission intensity distributions of OH(λ= 308.48nm) from the flame measured by UV-CCD camera
are shown in Figs. 4(a)~(c) in the different DBD
conditions. The intensity distribution shown inFigs. 4(a)~(c) is obtained from the Abel inversionof the measured profiles. The combustion zone
with a triangle shape is clearly seen. The increaseIncreasing rasio ofion current peak [a.u.]

O3w/ discharge
w/o discharge

14[mm]5128OO24(a) C4H10 and O2 DBD

20[mm] 5 w/o dis
0102030(a) O2 DBD[mm]5 w/o dis

3025C CH106.6 W

41.8 W

43210201540.5 W(b) C4H10 DBDH2C25(c) O2 DBD

005101520253035Discharge Power [W]4045(b) C4H10 DBDFig. 3 Increasing ratio of ion current
by results of mass analysisof the OH emission is larger in O2 DBD case. In
addition to the increase of OH radical emission,
the contraction of the flame is also significant.
Since OH radical is a key particle in the hydro-carbon combustion the enhancement of butane
combustion is related to the ozone production byO2 DBD.
We calculated the combustion speed. Without
radical injection, combustion speed is about 2.5m/s. Combustion speed is enhanced by 20 % in O2
DBD case. On the other hand, they are about 15 %and 14 % in the cases of C4H10 DBD, and O2 andC4H10 individual DBD.
In this experiment, O2 DBD is most effective for
combustion reaction. This is because that O3 withhigh oxidizability reacts with C4H10 to produce Oand OH radicals. These radicals make thecombustion reaction active. In the case of C4H10 andO2 individual DBD, O3 reacted with H2 to produce
H2O. It is possible to cool the temperature incombustion field, and reaction speed reduces that ofO2 DBD. C4H10 DBD produces the resolved
particles such as H2, CH and C2 and assisted thecombustion reaction. When direct electrostatic
discharge applied with the combustion flame,combustion speed increases by 40 % than that ofwithout discharges. This is because that directdischarge is efficient for carrying radicals to theFig. 4 OH radical emission intensity distribution
3.4

Combustion speed [m/s]Increasing ratioof ion current peak [a.u.]

w/ discharge
w/o discharge

358.6 W

4321040

Discharge Power [W]4076 W

15.9 W

432
10106w/o dis

3.2
3.0

Direct discharge
O2DBD(C4H10+O2) DBD

2.8

C4H10DBD
w/o discharge

2.6
2.4
0.1

1

10100

Discharge Power [W]

Fig. 5 Dependence of combustion speed todischarge power
combustion flame before radical deactivated.
5. Conclusion
In summary, our investigations allow one toconclude the following.
1) By radical injection using DBD, radical (OH,CH, C2) emission intensity and combustion
speed is increases. These results demonstratethat radical injection promoted combustion
reaction.
2) In the case of O2 DBD, combustion reaction
becomes effective. According to theseresults, O and OH radical are important todevelop combustion.
References[1] S M Starikovskaia: “Plasma assisted ignition andcombustion”, J. Phys. D, Appl. Phys., Vol.39, no.16,
pp.265-270 (2006)