SIMULTANEOUS LDV MEASUREMENTS OF GAS AND PARTICLE VELOCITIES IN TWO-PHASE FLOW

摘要: An experimental investigation was conducted to simultaneously measure the instantaneous velocities of large particles and air in two-phase flow using Laser Doppler Velocimeter. Measurements at different Photo-Multiplier voltage settings are used separating signals from small seeding that trace suspended solid particles. The method applied obtain measurements a vertical tunnel for 500 micron slip velocities. associated mean velocity, turbulent intensity with without show reduce velocity increase turbulence near center. INTRODUCTION Two-phase considerable engineering importance wide range applications such as rocket motors, ramjet combustion, jet cutting blast nozzles. Improving performance devices requires knowledge gaseous phases. Velocity fields complicated by particle-probe interactions blockage transmitted scattered light dispersed phase. Different techniques have been developed Velocimeter (LDV). Lee Dust [1] an electronic processing scheme based on amplitude discrimination filtering separate They measured glass ranging 100 μm 800 diameter pipe flow. Their profiles spheres results showed increased slip-velocity larger particles, reversed region wall case Tsuji et al [2,3] separated particle setting threshold values against pedestal components photo multiplier signals. plastic 0.2 mm 4 pipe. Large were found through out section while reduced it. Hussainov al, [4] two power lasers displaced probe volumes sizes gas 700 bead downward channel investigated modulation grid-generated reported caused attenuation streamwise direction, decreased energy spectra high frequencies. Larger occur supersonic twophase flows than described subsonic studies. Hamed al. [5] predicted 200 m/s convergent divergent nozzles, depending loading initial conditions. purpose present study is investigate separation large-particle tracer LDV data obtained measuring varying PhotoMultiplier involving highspeed EXPERIMENTAL SETUP A schematic test facility shown Figure 1. It consists following components: feeder, main supply pipe, injector, acceleration tunnel, section, exhaust filter cyclone. 1 Copyright © 2001 ASME Schematic equipment functions follows; amount placed into where they fed secondary source blown up mix supply. then accelerated 12 ft long rectangular duct section. equipped optical window 6.3 thick order enable access (LDV) measurements. cyclone filtered exhausted top atmosphere. TSI 6-jet atomizer filled propylene glycol aerosol supplied seed 1μm. introduced inch upstream via 6-inch high-pressure horizontal reservoir, consisting 7 tanks whose total volume 102 m. ambient pressurizes psig filtered, dried before it stored reservoir. LASER DOPPLER VELOCIMETER SYSTEM Two-component system study. blue (488 nm wavelength) green (514.5 lines 5-Watt Spectra Physics argon-ion laser create measurement volume. collected backward mode 250 focal length lens system’s Real Time Signal Analyzer allowed reading standard deviation, acquisition rate each channel. coincidence, validation criteria bias inherent this type experiment. event recognized only if signal both channels arrived within specified time interval. its table could move axial, traverse directions accuracy 0.025 mm. Air Supply PROCEDURE Four sets carried follows: A. Gaseous-phase airflow seeded atomized B. Polydispersed solid-phase C. Simultaneous phase D. Same condition C, Photo-Multiplier, PM, extract polydispersed data. RESULTS AND DISCUSSION Tests characterize histograms flows, establish requirements extraction poly-dispersed held constant 0.1 kg/sec all cases ranged between 60 m/sec. Sample center presented Figures 2 5 90 6 Tracer Solid tests Combined PM 594. 248. Axial RMS listed Table Summary tunnel. Exit Particle Injector Acceleration Tunnel