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International Journal of Energetic Materials and Chemical Propulsion
ESCI SJR: 0.142 SNIP: 0.16 CiteScore™: 0.29

ISSN Print: 2150-766X
ISSN Online: 2150-7678

International Journal of Energetic Materials and Chemical Propulsion

DOI: 10.1615/IntJEnergeticMaterialsChemProp.v1.i1-6.50
pages 43-61

Ignition and Combustion Behavior of MTV Igniter Materials for Base Bleed Applications

B. L. Fetherolf
Department of Mechanical Engineering, The Pennsylvania State University University Park, Pennsylvania 16802, USA
Dah-Ming Chen
Department of Mechanical Engineering, The Pennsylvania State University University Park, Pennsylvania 16802, USA
T. S. Snyder
Department of Mechanical Engineering, The Pennsylvania State University University Park, Pennsylvania 16802, USA
T. A. Litzinger
Department of Mechanical Engineering, The Pennsylvania State University University Park, Pennsylvania 16802, USA

ABSTRACT

The pyrolysis and ignition characteristics of an igniter material composed of magnesium, Polytetrafluorethylene, and Viton A have been studied using a high-power CO2 laser as the radiative heating source. Methods of analysis and the instrumentation employed were high-speed direct and schlieren photography to visualize the flame structure and gas-phase dynamics, near-infrared photodiodes to obtain ignition delay data, and probe sampling and a gas chromatograph/mass spectrometer to analyze the gaseous products evolved. Important test variables were incident heat flux, chamber pressure, and oxygen concentration. In addition, the effect of boron addition on the ignition behavior of the igniter charge was studied.
Ignition occurred on the sample surface under all test conditions. Experimental results indicated that the ignition delay time decreased monotonically as the incident heat flux was increased. Also, ignition times decreased as the ambient pressure or the ambient oxygen percentage was reduced; it is believed that this decrease is caused by competitive oxygen and fluorine reactions. The direct and schlieren images showed that the burning behavior was also distinctly different as the chamber pressure or oxygen partial pressure was reduced. At low pressures (~ 0.1 atm), no evident luminous plume evolution and gas-phase dynamics were observed during combustion, and the igniter material decomposed in large fragments. In an inert atmosphere, pure PTFE pyrolyzed into many fluorocarbon compounds and Viton A pyrolyzed into a variety of fluorocarbons and hydrofluorocarbons. However, for combustion of the composite MTV material in air and in an inert helium atmosphere, only hydrocarbon compounds, and CO and CO2 for combustion in air, were observed. The addition of boron or Viton A to a basic Mg/PTFE composition significantly lowered the ignition delay time and the addition of boron also greatly enhanced combustion.