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Journal of Physics: Conference Series
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Estimation of the electric force effect on dispersed additives in the
heterogenous combustion flame plasma in the electrostatic field
presence
To cite this article: I A Zyryanov et al 2019 J. Phys.: Conf. Ser. 1328 012036
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LTP Coatings 2018
IOP Conf. Series: Journal of Physics: Conf. Series 1328 (2019) 012036
IOP Publishing
doi:10.1088/1742-6596/1328/1/012036
1
Estimation of the electric force effect on dispersed additives in
the heterogenous combustion flame plasma in the electrostatic
field presence
I A Zyryanov1, A G Budin1, A P Pozolotin1, V V Kargapoltsev1
1 Vyatka State University, Department of Engineering Physics , 610000, Kirov,
Moskowskaya Street, 36, Russia
b185@mail.ru
Abstract. In the work, the influence of the electric force from the external electric field on the
charged dispersed particles in the flame was evaluated. It is assumed that changes in the effect
of the field on the combustion rate in the presence of dispersed additives in the gas phase take
place due to the heat flux into the burning polymer condensed phase changes. However, as it
turned out, the flame front moving towards the fuel under the action of field forces does not
allow to fully explain the combustion rate increase.
1. Introduction
The dispersed additives using as fuel combustion process catalysts in power plants is a perspective
method of the combustion parameters influencing. On the one hand, additives provide combustion
quality improvement. On the other hand, the particles presence in flame contributes to the electric
charge accumulation on their surface [1, 2].
In [3], the effect of dispersed additives on the resulting change in the combustion rate under the
electric field influence in a hybrid rocket engine (HRE) is investigated. The combustion rate increase
by 30% in the presence of a dispersed additives and an electric field has been established. This fact
indicates the promise of the field and dispersed particles joint influence on the combustion parameters,
but the mechanism of action needs to be studied.
2. Experiment Procedure
In the experiments model HRE is used, the combustion chamber of which is formed by two coaxially
located fuel blocks: the outer block is a thick-walled tube with an inner diameter of 32 mm and a wall
thickness of 5 mm, the inner block is a cylinder with a diameter of 12 mm. The length of the blocks is
50 mm. In the gap between the blocks, an oxidizing agent (gaseous oxygen) is blown through.
Electrodes for an electric field generating are arranged: the first is outside (around) the external fuel
block, the second (in the form of a metal rod) along the internal block axis. With this configuration,
the internal fuel block acts as an insulator and sacrificial coating for the electrode (Fig. 1) [3].
LTP Coatings 2018
IOP Conf. Series: Journal of Physics: Conf. Series 1328 (2019) 012036
IOP Publishing
doi:10.1088/1742-6596/1328/1/012036
2
Figure 1. Model HRE scheme.
In the experiments, we used fuel blocks of the following compositions: external fuel block is made of
polymethylmethacrylate (PMMA); internal - polyethylene (PE) with a dispersed additives (iron oxide).
The compositions of the internal blocks are the following: PE, PE + 20% dispersed additives, PE +
40% dispersed additives, PE + 60% dispersed additives.
3. Experimental Results
The dispersed additives concentration increasing leads to an increase in the field effect of the on the
combustion rate (Fig. 2a - a solid line).
Figure 2. Combustion rate relative change in the field with the additives presence (a), flame
current–voltage characteristic with dispersed additives (b).
According to the Coulomb's law, the force on the charged particle from the electric field leads to
particle movement, in our case in the radial direction. The particle motion law is determined by (1):
,
2
2
dthd
mQE
(1)
where Q and m are the charge and mass of the particle, E is the field strength, h is the radial
displacement of the particle during the residence time t in the combustion chamber.
Assuming that the particles are at the flame temperature, and the heat transfer layer is displaced by h,
we will estimate the change in the fuel block combustion rate.
Flame conductivity (σ) is directly proportional to the charged particles concentration, consequently,
with the introduction of dispersed additives, the conductivity change is due to the processes of their
charging. It is known that during the hydrocarbons combustion, the charged particles concentration in
a flame can reach about n = 1019 m-3 [4]. Using the current–voltage characteristic (Fig.2.b), assuming
that the particles are spherical, and the entire excess charge is located on the dispersed additives
particles, we obtain (2):
LTP Coatings 2018
IOP Conf. Series: Journal of Physics: Conf. Series 1328 (2019) 012036
IOP Publishing
doi:10.1088/1742-6596/1328/1/012036
3
ee
NVnn
Qd5
10
))/((
(2)
Here n is the charge concentration in the flame, V is the combustion chamber volume, N is the
dispersed particles in the combustion chamber volume number, σd and σ is the flame conductivity with
and without additives, respectively.
To assess the combustion rate change, we consider the solution of the heat equation in a system related
to the fuel surface (Fig. 3.a) (3):
0
2
2
dx
dT
U
dxTd
a
(3)
The boundary conditions on the fuel surface and on the flame border (4):
f
TTx
UQ
dx
dT
x
,
,0
(4)
Here
,,a
is the flame thermal diffusivity, flame thermal conductivity and the fuel density,
respectively,
Q
is the total pyrolysis heat,
U
is the linear combustion rate,
is the flame
displacement.
Figure 3. Mathematical model diagram (a) and simulation results (b).
The flame position is determined by the fuel surface temperature Ts, (according to [5] the PMMA
surface temperature Ts = 700 K) and the linear combustion rate value without field. We estimate the
linear combustion rate change in the field with the dispersed additives presence provided that the
flame front shifts by h. Then while maintaining all thermophysical parameters, the relative combustion
rate (5):
h
UUU
E
E
0
(5)
The evaluation results are shown in Fig. 2.a and 3.b (dashed lines). As can be seen from the
calculation results, the combustion rate relative changes curve form is similar to the experimental
results, however, the calculation gives significantly lower values. This indicates the insufficiency of
the field influence only by the combustion front position shift.
LTP Coatings 2018
IOP Conf. Series: Journal of Physics: Conf. Series 1328 (2019) 012036
IOP Publishing
doi:10.1088/1742-6596/1328/1/012036
4
4. Conclusion
The flame front position displacement under the electric force action from the field does not allow to
fully explain the combustion rate increase. The influence mechanism requires further study.
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