Research On The Characteristics Of Yarn-air Flow Field Stimulated By Series Nozzles

Air-jet loom is a kind of shuttleless loom using high-speed air jet to carry weft yarn across the shed. The air flow given away by incentive nozzle and the dynamic characteristic of its coupling with weft yarn have something important to do with the insertion process. But in present designs and applications of air jet looms, it is rarely attended from the perspective of flowing to the distribution of main nozzle and relay nozzles, the appropriate pressure of air flow and the flow flux, the effect of weft yarn parameter on the weft insertion process. Research in this paper is based on the system of weft insertion of RFJA10 air-jet loom. Experiments, simulations and theoretical derivations are used to investigate the internal and external flow fields of incentive nozzle and the resultant flow field. Also the dynamic characteristic of weft in the resultant flow field is investigated. We have reached to below research points:1) A mathematical model of the incentive nozzle is developed; the effect of some parameters on internal and external flow fields, such as the shape of rectifier tank, the length of thread tube and input pressure etc., were investigated.2) Reynolds time average equations were applied as governing flow equations to develop a model of the resultant flow field, the numerical simulation was carried out on finite-spaced flow field with several incentive nozzles; the setting of the main nozzle, relay nozzles and the reeds and the effect of input pressure on the characteristics of resultant flow field were analyzed; the main factors to gas consume were put foward and the best distribution of nozzles were proposed.3) An experimental method on research of high-speed flow field was developed; the velocities of main nozzle, relay nozzle and resultant field were tested and then compared with the simulation results. 4) The model of weft insertion was simplified; a test platform for flying weft yarn was designed; high-speed video camera and related instruments was applied to investigate the behavior of yarn flying in the resultant field; the relationship between the variables of resultant field and the flying yarn was also analyzed.5) The optimal parameter and process of weft insertion system to decrease the air consume and increase weft insertion rate were discovered. This paper deals with the weft insertion process of an air jet loom from the perspective of fluid dynamics. Yarn-air coupling mechanism and behavior of yarn are revealed; the mechanism of incentive nozzle, the arrangement of main nozzle and relay nozzle are researched; a method is provided to optimize the insertion mechanism from fluid dynamics view. These can provide instructions to further designs and applications of higher performance air-jet looms.