Planar laser induced fluorescence imaging of solid propellant flames Available to Purchase

We have applied the PLIF technique to solid propellant ignition and deflagration flames to obtain temporally and spatially resolved images of species and temperature profiles. A CO₂ laser was used to supply the igniting pyrolysis flux. A Nd-YAG pumped tunable dye laser beam was expanded into a sheet to excite fluorescence from transient species in the flame and the emitted fluorescence was imaged with a gated intensified diode array camera. Selection of the delay time between CO₂ and diagnostic laser pulses allowed the time dependence of ignition events to be measured. We have studied NO₂, NO, CN, CH, C₂, NH, H₂CO, OH, and OH rotational temperature in this manner. For HMX combustion, NO₂ and NO are found to be primary decomposition products that form a expanding plume until a spherical ignition kernel occurs in the gas phase, which consumes the NO₂ and NO and produces CN, NH, and OH. This kernel rapidly forms into a thin flame sheet which establishes a steep temperature rise to equilibrium values. CH was absent in HMX combustion flames and H₂CO was seen only as a decomposition product of the PEG binder of composite propellants. The imaging PLIF technique has been found to be extremely useful even in very hostile combustion environments such as highly aluminized composite solid propellant flames.