Experimental Investigation On The Modulation Law Between The Phases In Gas-solid Round Jets

With the financial help from the National Nature Science Foundation, systemic experimental investigation was carried out to study the modulation law from the particle-phase to the gas-phase in gas-particle turbulent round jets. The physical mechanism of the modulation law from the particle-phase to the gas-phase was discussed from several points of view by means of flow visualization, PDA and PIV measurement. The gas-particle round jet coherent structure experimental system and the visualization system were successfully designed and manufactured. The key technology of particle supplying equably, continuously and quantificationally was solved. Synchronously supplying the 50μm to 400μm particles and the gas tracer particles and synchronously measuring the velocities of the two-phases were achieved. An MQD method PIV program was compiled in this paper. PIV standard images provided by the Visualization Society of Japan were analyzed. The PIV program was approved to be reliable and used to analyze the modulation law from the particle-phase to the gas-phase. The gas-phase flow coherent structures, the axial and radial mean velocities, turbulent intensities and Reynolds stresses near the jet nozzle region were provided under the particle-phase influence in the gas-particle turbulent jet. The gradual gas-phase intensity change process in the X/D=0~20 region under the change of particle diameter was provided for the first time. The modulation physical mechanism from the particle-phase to the gas-phase was put forward. The presence of particle-phase will restrain and destroy the gas-phase coherent structure and make the gas-phase develop to isotropy. The big particles will penetrate and destroy the gas-phase large eddy. At the same time they produce small eddies in the wakes; the small particles cannot penetrate the gas-phase large eddy and they will follow the large eddy. So small particles cannot contribute to the form of small eddies. The work done to the small particles will restrain the big gas eddy and attenuate the turbulence of the gas-phase. The results from the quantificational PDA, PIV test and the qualitative flow visualization proved the guess from the physical mechanism from different point of view. The jet control method with mixing jet tabs were firstly introduced to the two-phase jet in this paper. Form the visualization of the jet with tabs it was found that the tabs could accelerate the jet mixing in single-phase jet intensively, but the effect in the two-phase jet was not as intensively as in the single-phase jet.