Velocity measurement of particles ejected from a small-size solid rocket motor

This paper describes a nonintrusive technique suitable for engineering measurement of particle velocity ejected from a solid rocket motor. The background radiation, the high velocities and temperature of gases, and the small time scales characterizing the flow downstream of the nozzle make the diagnostics difficult to achieve. In fact, the thrust curve and time history of the head-end pressure often are the only data available. In this work, the flow is studied by analyzing the overall radiative emissions of the plume in the UV-visible band (0.4-1.1 μm wavelength band). The main result is that the particles ejected along with the exhaust gases are well suited as seeding for a correlationbased velocimetry technique. Furthermore, a wavelet expansion of the radiative emission signal provides the extraction of an averaged time scale and the time location of the radiant signature associated to the particles. A conditioned cross-correlation is computed to measure the velocity of the ejected particles that is representative of the flow velocity. From the radiative emission sampled at two locations along the rocket plume, a transition from quasiperiodic to turbulent flow is also observed.