Propellant strand

In an attempt to understand the combustion mechanism of catalyzed double-base propellants, several investigators have conducted experiments to measure the burning rates of strands of liquid nitrate esters. The various measurement techniques were very similar to that employed in a conventional solid propellant strand burner. The liquid esters were placed in a tubular container, and the liquid surface regression speeds were measured by optical methods or by the fuse-wire method used in solid-propeUant strand burners. The only important difference between the solid and the liquid strand burning-rate measurements is that the liquid strand burning speed is very much dependent on the diameter of the container. 

Eisenreich, N., A Photographic Study of the Combustion Zones of Burning Double-Base Propellant Strands, Propellants and Explosives, Vol. 3, 1978, pp. 141-146. 

As might be expected from its effect on flame temperature, increased oxidizer content also increases the burning rate. [All burning rates reported in this paper were measured by the strand-burning technique in a nitrogen atmosphere. Propellant strands, in a vertical position, approximately 4 mm. square (or 4 mm. in diameter), and inhibited by dip-coating... 

At pressures below ca. 0.05 atm. it was not possible to photograph the propellant strand through the bell jar window because white fumes evolved during the burning and coated the window (recall the discussion about combustion inefficiency at very low pressure). The problem was alleviated by washing a thin film of oil (silicone diffusion pump fluid) down the inside of the window. 

When a propellant strand is ignited under nitrogen gas purge conditions, the pressure in the strand burner increases because of the addition of the propellant burned gas. However, the pressure valve attached to the nitrogen gas supplier is regulated automatically to reduce the nitrogen gas flow rate in order to maintain the pressure constant. Thus, the pressure in the burner is maintained at the desired pressure. 

Wormhoudt J., Kebabian P L., and Kolb C. E., Embedded infrared fiber optic absorption studies of nitramine propellant strand burning. Combust. Flam, 111, 73-86, 1997. 

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