(632h) Field Switching of Monopropellant Burning Rate: Dielectrophoretic Control of Nitromethane Thermal Conductivity Using Field Aligned Carbon Nanomaterials

Field Switching of Monopropellant
Burning Rate:

Dielectrophoretic Control of
Nitromethane Thermal Conductivity Using Field Aligned Carbon Nanomaterials

A. R. Lawrence, T. R.
Sippel

Department
of Mechanical Engineering

Iowa
State University, Ames IA

Submission
to AIChE Fall Meeting

Session:
Energetic Materials

October
29 - November 3, 2017, Minneapolis MN

Abstract

Control of propellant burn rates is vital to optimizing energetic
material utility. Single-walled carbon nanotubes (SWCNT’s) have a uniquely
high, anisotropic thermal conductivity in the axial direction, and recent nanofluids
research has shown that the addition of carbon nanotubes to liquids can increase
the thermal conductivity of the mixtures by 300%.[1]
When a non-uniform electric field is applied, CNTs will align due to dielectric
forces (i.e. dielectrophoresis). Aligning the CNT’s creates a thermally and
electrically conductive path through the mixture, and can be affected in a
highly efficient manner using low duty cycle fields, as typical alignment times
in water are 100 times shorter than Brownian motion unalignment.[2]
In separate energetic material research, it has been found that the addition of
other nanostructured additives, such as fuctionalized graphene sheets,
increased the burning rates by more than 200%.[3]

Taken together, these two bodies of research suggest that
this alignment method could be utilized to obtain efficient, high-speed
switching of the deflagration of liquid propellants--aligning the SWCNT’s
perpendicular to the burning surface would illicit a high speed burning mode,
while a parallel alignment would result in near-normal combustion. We explore
dielectrophoretic switching of burning rate in liquid nitromethane doped with
single-walled carbon nanotubes burning at motor pressures under the influence
of kHz-rate modulation of 300 kV/m static fields aligned both parallel and transverse
to the burning surface. Burning rates are measured using high speed video and thermal
conductivity will be measured using hot wire technique. The effects of dopant
type, concentration, pressure, and alignment direction are explored.

Bibliography

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H. Gnewuch, M. Hempstead, J. Hammer, and M. L. H. Green, Appl. Phys. Lett. 71,
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Sabourin, D. M. Dabbs, R. A. Yetter, F. L. Dryer, and I. A. Aksay, 3,
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