Research On Air Flow Atomization Mechanism And Exploitation Of Secondary Atomization Nozzle

Airflow dyeing machine is a new printing and dyeing equipment in the printing and dyeing industry.It uses the principle of airflow atomization to atomize the dyeing liquid into small size particles and mix with the airflow in the atomization chamber and then enter the guide cloth room together.During the movement,the dyeing liquid in the airflow impacts the cloth,and the very fine dyeing liquid is in full contact with the fibers in the cloth,so that the cycle is repeated and the cloth is finally dyed.The mechanism of dyeing liquid atomization is similar to that of water atomization which is affected by many factors,including external environmental factors(staining speed,airflow speed,atomization area pressure,etc.),dyeing properties(density,viscosity of different dyeing liquids,etc.).The external environmental factors are controlled by the nozzle’s structural parameters(nozzle dye outlet diameter,air outlet diameter,dye outlet and airflow outlet spacing)and process parameters.In this paper,the way of numerical simulation and experimental research are used to study the effects of jet pressure on atomization and fracture characteristics during atomization of airflow dyeing liquor.The atomization process inside the gas-liquid two-phase secondary atomizing nozzle of the airflow dyeing machine is taken as the calculation object,and the water flow is used to replace the dyeing liquid,which shows the influence of the gas-liquid two-phase secondary atomizing nozzle on the atomizing effect of the liquid jet under different jet pressures.Through the subsequent experiments to verify the reliability of the mathematical model and simulation results,the specific content and conclusions of this study are as follows:The gas-liquid two-phase atomization process and characteristics of gas-liquid two-phase secondary atomizing nozzle are introduced.The principle and mathematical model of primary flow and secondary droplet breakage are analyzed.The evaluation criteria of nozzle atomization performance are briefly described.And do a brief introduction to the gas-liquid two-phase two-stage atomizing nozzle designed and developed in this paper.A new type of gas-liquid two-phase dyeing atomizing nozzle was designed based on the gas-liquid two-phase atomizing principle so that we can explore the method which can improve the atomization performance of the atomizing nozzle of the airflow dyeing machine.Combined with Fluent software,the velocity flow field distribution inside the air hose,the crushing state of the liquid flow jet in the internal flow field of the gas-liquid two-phase dyeing atomizing nozzle,particle size distribution of primary crushing under different air pressures and the secondary crushing state of the large particle diameter of the dye outlet flow field were analyzed.The VOF model,DPM model and k-SST turbulence calculation model were used to calculate the primary fracture of the liquid jet.The VOF model and the realizable k-turbulence model were used to calculate the secondary fragmentation of the large particle size droplets.The numerical calculation results show the air flow field inside the air hose and explain the process of the primary crushing of the liquid jet and the secondary crushing of the large particle droplets in the gas-liquid two-phase secondary atomizing nozzle.Design and build an experimental system platform for gas-liquid two-phase secondary atomizing nozzle liquid jet primary crushing.The high-speed photographic image of the jet stream was captured by a high-speed camera,and the high-speed photographic images obtained from the experiment were summarized and analyzed.The primary fracture characteristics of the jet at different jet pressures were studied.According to the high-speed photographic image,the atomization cone angle and the penetration distance of the liquid jet crushing increase with the increase of the air compressor jet pressure.The degree of crushing also increases with increasing jet pressure.However,since the excessive jet pressure increases the energy loss,the jet pressure is set to 0.6PMa.A certain agreement is found by compared the experimental results with the simulation results.The selected numerical calculation model can be applied to the initial fracture calculation of the liquid jet.