Spray Characteristics of Particle-laden Type Injector Using Powder Fuel

Abstract

Spray characteristics of particle-laden injector were experimentally investigated for the particle (aluminum, magnesium) as a fuel. Spray characteristics of gas centered gas-liquid shear coaxial injector were investigated varying injection condition under seawater injected as a liquid phase. Similarity characteristics of particle and carrier gas were investigated in particle-laden jet, and mixing characteristics between particle and coaxial gas also investigated using shear and swirl coaxial injector. Mass flow rate and direct photograph were used to investigte the spray characteristics such as breakup process of liquid sheet in gas centered gas-liquid shear coaxial injector. Self-pulsation occurs in that injector and it is accompanied by an intensive noise. Self-pulsation generate the pressure and flow rate oscillation in gas and liquid phase. Because of this oscillation can argument combustion instabilities, self-pulsation should be suppressed. Effect of recess and Reynolds number of liquid and gas phase on self-pulsation characteristics were studied by measured frequency of liquid sheet under self-pulsating condition. It was found that the different self-pulsation occurred by the recess number of injector. Self-pulsation occurred by the liquid bubble collapse process under low recess case, however liquid sheet and central gas interaction in nozzle inside dominate the oscillation of liquid sheet. Small particle of 1μm represent a fluid characteristics and large particle with 42.5 mean diameter used as a fuel were simultaneously injected for investigate effect of particle on a carrier gas and particle characteristics in particle-laden jet. Particle mass loading ratio effects on a velocity and turbulence intensity of carrier gas, and carrier gas and particle can agreed with similarity. Effect of particle mass loading ratio on carrier gas in jet developing region differs from fully developed region. Accordingly, centerline velocity decay of carrier gas were formulated in jet developing region and fully developed region, respectively, and were compared with the previous results. Centerline velocity decay of particle were formulated with particle Reynolds number, because particle drag force determined by the particle Reynolds number. Previously study, change in turbulence intensity can determined by the ratio of particle diameter and turbulence length scale. The present experimental data suggests that, consideration of the characteristic length scales (particle diameter and turbulence length scale) is insufficient to predict gas-phase turbulence modulation in particle-laden flow, because as slip velocity between gas and particle increases turbulence intensity also increased. Therefore, slip velocity also considered to predict gas-phase turbulence modulation. In addition, Mie scattering and acetone PLIF technique were used for particle and coaxial gas, respectively, to investigate mixing characteristics between particle and coaxial gas. Mixing efficiency of shear coaxial was higher than swirl coaxial under injector without recess, and mixing efficiency was sensitive to the change of velocity ratio between coaxial and central jet. As for the swirl coaxial injector with recess, mixing efficiency was higher than shear coaxial and less sensitive the change of velocity ratio, so swirl coaxial injector can be used for solid particle propulsion system with large operating range.