Particle-Gas Mixing in Confined Nonparallel Coaxial Jets

Abstract

XTENSIVE experimental studies of the mixing of gaseous, turbulent, coaxial flows have been conducted using configurations in which the primary and secondary streams are parallel.1 However, very little work has been reported on the mixing of turbulent particle-laden streams,2 especially with nonparallel injection of the secondary coaxial jet.3 This synoptic summarizes the results of 52 tests where mixing rates of a primary helium/aluminum particle/air jet with a secondary, nonparallel air jet were measured. Injection angle, primary density, and secondary velocity were varied and mixing rates of the gas and particles were measured. Results are applicable to the design of airbreathing propulsion systems. Contents The test facility is illustrated in Fig. 1. The one-in.-diam, primary jet was composed of a heated, two-phase mixture of helium, air, and aluminum powder. The coaxial, secondary jet was unheated air. The facility was designed to collect radial profile data at various axial locations. Gas and particle samples were obtained with isokinetic collection probes, and gas velocities were determined from the measured stagnation and static pressures. To determine axial profiles, a series of tests was conducted with the instrument collar at various fixed distances aft of the primary nozzle exit. Injection angles of 0, 30, 60, and 90° were tested. The crosssectional areas for both primary and secondary flow were held constant as the injection angle was varied. Helium composition was determined by gas chromatographic analysis. Particle mass flux was determined from time for collection of a particle sample and sample weight. Pressure and temperature measurements, together with the throat area of choked control nozzles established the gas flow rates of the primary and secondary jets. Fifty-two tests at near-atmosphe ric pressure were completed during this study. All of the tests were conducted with 20 weight percent of 6-micron aluminum powder in the primary jet stream. Four major test variables were investigated: 1) secondary velocity; 2) primary density; 3) secondary injection angle; and 4) test quantity being measured (helium composition, velocity, or particle mass flux). Data from two sets of test conditions are