Direct Mixing and Combustion Efficiency Measurements in Ducted, Particle-Laden Jets

Abstract

Using water-cooled probes and hot-gas valves, gas-particle samples were withdrawn from the secondary duct of an air-augmented laboratory burner. Using a boron-loaded propdlant, air/fuel ratio and secondary duct pressure were varied from 12/1 to 32/1 and from 82 to 127 psia, respectively. From sample analysis of chlorine, argon (air tracer), boron, and boron oxide, radial and axial profiles of air, gaseous fuel, participate fuel and percent of boron combustion were determined. Particles and gases mixed at significantly different rates. Measured gasphase mixing rates were comparable to model predictions, which assumed particles to be in equilibrium with gases. Boron combustion efficiency varied markedly with duct position, air/fuel ratio and secondary chamber pressure. Low boron combustion efficiency resulted principally from delayed ignition of the gaseous fuels after dilution by air reduced resulting gas-phase temperatures below the boron ignition temperature. This was especially true at low secondary duct pressures.