Combustion following turbulent mixing in muzzle flows.

The intermediate flash region, that develops downstream from the Mach disk during the discharge of a 7.62 mm rifle into ambient air, is examined by laser-Doppler velocimetry. The objective ist to investigate whether or not slip lines are formed which would prevent the extrainment of oxygen and, therefore, the initiation of combustion reactions in the intermediate flash region. In addition, local temperature histories are measured in this flow region during the discharge of the rifle into atmospheres of: air, nitrogen, and oxygen. Here, the objective is to examine whether or not oxygen is entrained and induces combustion processes in the intermediate flash region. If so, local temperatures should increase or decrease as the oxygen content in the surrounding increases or decreases. It has been found from velocity data that slip lines are formed in the first few millimeters downstream from the Mach disk and then are absent. Also, the oberserved temperatures are ranked in the order T(N sub 2) is less than T(air) is less than T(O sub 2). It follows , that oxygen is entrained, and combustion reactions take place in the vincinity of the axis of the intermediate flash region. These combustion reactions control the ingnition sequence leading to the secondary flash, and they are affected by inhibiting alkali salts.