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.

 

 

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