Particle size distribution measurements in a subscale motor for the Ariane 5 solid rocket booster

Motor and plume particle size measurements in solid propellant micromotors

“…At the nozzle exit the particle mean size remained in the lower limit size range (submicron to micron) of the diagnostic device (Malvern 2600 HSD with a 100-mm range lens). The mass fraction of particles smaller than 2 jit at the nozzle exit was found to be 8-35% for pressures greater than 3.2 MPa, in some contrast to other reported results 6 where the mass fractions were less than 10%. It should be noted that the particle breakup requires not only the attainment of a critical Weber number but also time at this condition.…”

“…Those results ( Table 2) had a higher mass percentage of <2-ju particles (approximately 9 vs Q.2%) and a smaller maximum particle size (12 vs 84 jn). Traineau et al 6 reported (for a different propellant and operating conditions) approximately 10% of the mass in particle with diameters <2 /A, most particles smaller than 75 /x, and a maximum diameter of 120 ju. Although these results for the nozzle entrance vary somewhat for the different propellants and test conditions, they give a consistent picture.…”

“…Throat diameter was varied (nominally 0.5 cm) to control the chamber pressure. Following the work of Traineau et al, 6 another motor was constructed with the addition of a helium quench manifold 10 cm from the motor head-end. The idea in this case was to quench the particulates within the motor (hopefully without shattering the particles) so that they would not change in size distribution into the plume.…”

“…Strand et al 9 did report a bimodal distribution in the plume, but from speculative argumentation only. Traineau et al 6 have reported a bimodal distribution with modes at 3 and 20 IJL. Laredo and Netzer 10 have reported quadramodal distributions with modes at <2, 5, 10, and 20 p. The code qualified as the state-of-the-art for the calculation of the infrared radiation emitted by exhaust plumes has been validated only for a factor-of-two accuracy over the 2-25-jiun spectral range.…”

“…3 - 5 The second mode is also thought to be log-normal with particles between 5-150 ju, although particle diameters up to 500 ^ have been reported. A recent investigation 6 using quenched and unquenched combustion products and exhaust plume light scattering measurements has indicated that the nozzle entrance size distribution is trimodal with modes at 1.7, 9, and 45 ^.…”