Motor and plume particle size measurements in solid propellant micromotors

Abstract

Particle size distributions were measured in the chamber, nozzle, and plume of a subscale solid propellant rocket motor. A significant reduction in the mean size of the aluminum/aluminum oxide particles occurred within the motor chamber. The mass fraction of small particles (<2 ft) at the nozzle entrance was less than 10%. Also, most particles were smaller than 50 ft, although a few as large as 85 ft were present. In the converging and throat portions of the nozzle it appeared that particle breakup dominated over collision coalescence. Collision coalescence was observed to occur more dominantly in the supersonic nozzle flow. At the nozzle exit the particle mean size was usually less than 2.5 ft. The particle size distributions were bimodal or trimodal, with the larger particles concentrated near the plume centerline. Because of the short nozzle residence times it is not known whether or not these results are also applicable to full-scale motors. The mean size of the small A1 2 O 3 particles in the plume edges was less than 0.5 ft in diam, with an index of refraction of 1.64 ± 0.04 (apparently y-Al 2 O 3 ), independent of propellant composition, motor operating conditions and nozzle geometry.

Study on Size Distribution and Flow Characteristics of Condensed Products in Solid Rocket Motor

“…The influence of AP size on the agglomeration process of aluminum particles was analyzed by means of windowing engine and SEM, XPS, and XRD by DeLuca [14]. Hovland [5], Laredo et al [15], and Haiqing [16] have used noncontact measurement technology to promote the application and development of laser forward scattering technology in the field of size distribution detection in plume. Weilun et al [17] have used laser forward scattering technology to study the influence of propellant components on the particle size of condensed products.…”

Numerical Investigation of Head-On Binary Collision of Alumina Droplets

“…Subsequently, alumina (Al 2 O 3 ) droplets are generated as one of the combustion products of aluminum droplets. These droplets vary in size from submicrometer to a few hundred micrometers [1][2][3]. It is reasonable to expect that such droplets with different sizes will collide with one another when they are accelerated at different rates, which is what tends to occur in rocket nozzles and in complex evolving geometries, such as star grains.…”

“…As an important initial parameter for two-phase numerical calculation, the size distribution of droplets in a combustion chamber is understood well [1][2][3]. However, only a few studies on droplet collision in a solid rocket motor have been reported in the literature.…”

Quantitative, three-dimensional imaging of aluminum drop combustion in solid propellant plumes via digital in-line holography

“…Optical techniques for measuring molten aluminum sizes and/or velocities have included point-wise phase Doppler anemometry [4], line-of-sight laser diffraction [5], videography [6], shadowgraphy [7], Schlieren [8], and holography [9]. Among these techniques, imagingbased methods (videography, shadowgraphy, Schlieren, and holography) are particularly advantageous because images allow for differentiation of reacting aluminum drops from other particulates and provide insight into the flow physics.…”

“…Many experimental investigations of aluminum droplet behavior in propellant plumes have been performed [4][5][6][7][8][9]. Optical techniques for measuring molten aluminum sizes and/or velocities have included point-wise phase Doppler anemometry [4], line-of-sight laser diffraction [5], videography [6], shadowgraphy [7], Schlieren [8], and holography [9].…”