O-144 Combustion Behaviour of MTV under Reduced Atmospheric Pressure

In many cases countermeasure flares are applied in high altitudes with air pressure of less than 10 kPa. Also under such conditions the flare compositions aim to intensive emission and high temperatures. The combustion behaviour of a MTH composition consisting in 60% Mg, 30% PTFE and 10% Hycar was investigated at 30 to 90 kPa inside a window bomb using a colour high-speed camera and various emission spectrographs that cover a wavelength range of 200 nm to 5.5 μm. Temperatures were derived from continuum radiation assuming grey-body emission and from diatomic MgO. The results were compared with thermodynamic calculations of chemical equilibrium received from ICT-Code. The investigations show a drastic influence of pressure below 60 kPa on the combustion temperature, which mainly is caused by the exothermic decomposition and increasing cocombustion with air (especially oxidation of magnesium). At higher pressure the influence of temperature diminish but afterburning processes outside the core of primary flame zone could be verified. This may have a positive effect on total emissivity and size of the flare corona.