Solid rocket motor plume particle size measurements using multiple optical techniques in a probe

Abstract

An experimental investigation to measure particle size distributions in the plume of sub-scale solid rocket motors was conducted. A phase-Doppler particle analyzer (pDPA) in conjunction with three-wavelength extinction measurements were used in a specially designed particle collection probe in an attempt to determine the entire plume particle size distribution. In addition, a laser ensemble particle sizer was used for comparative data. The PDPA and Malvem distributions agreed in the observed modes near 1 and 4.5 mm diameter (d). Scanning Electron Microscope (SEM) pictures of collected particles were in good agreement with the measured Malvem Sauter Mean diameter (d,%) of 2.59 mm. Data analysis indicate that less than 3% of the total mass of the particles was contained in particles with diameter d <0.5 mm. Therefore, the PDPA, which can typically measure particles down to a minimum diameter of 0.5 mm with a dynamic range (d max:d min) of 50:1, can be used by itself to determine the particle size distribution. Multiple wavelength measurements were found to be very sensitive to inaccuracies in the measured transmittances.