The Analysis Of The Weft Insertion Gas Flow Of The Sub-Nozzle In Air-Jet Looms

In the modern weaving machines, there are mainly adopting the gas flow weft inserting system, which includes the main nozzle, the sub-nozzles and the reed. The weft is accelerated by the gas flow in the main nozzle, and flies into the reed. Some sub-nozzles are put behind and opened up to jet out the gas flow in turn. The gas flow is jetted into the reed, and can prevent the weft from dropping coursed by the gravity and the attenuation of gas flow, and keep the weft flying. The weft inserting process therefore would be finished by the help of those sub-nozzles. But the disposing and setting of the sub-nozzles are depended on the experiences at the present time. There is devoid of some systemic and effective theory to guide how to form an effective and steady gas flow field, which course lost of energy expenditure and increase the instability of the weft flying. Thus if the factors which will affect the character of the gas flow field can be well and truly predominated, it will be very significant for the advance of the weft insertion efficiency and the fall of the energy expenditure. As a result, it is necessary to use the Computation Fluid Dynamics (CFD) to simulate the gas flow field of the sub-nozzle numerically, and analyze the character of the gas flow field, which can provide a guide for the design and amelioration of weft insertion system in the air-jet loom.The gas flow distribution of a single sub-nozzle was numerically simulated at first. The effects of some factors, such as air tank pressures and the size and shape of the sectional area at the exit of sub-nozzle etc, to the gas flow field were analyzed, and their weft inserting efficiencies were compared with each other. It is said that the velocity, turbulence intensity, consumption and potential core length of the gas flow are increasing with the air tank pressures rising. The gas consumption is in direct proportion to the sectional area at the exit of sub-nozzle, whose effects to the gas flow field are different at different range. The influence by the shape of the sectional area at the exit of sub-nozzle was lightly. Synchronously, the dilatation wave was found at the exit of sub-nozzle. In succession, the gas flow distribution in the reed formed by multi sub-nozzles was numerically simulated as previously. The effects of air tank pressures, injection angles of the sub-nozzle and spaces between two sub-nozzles etc to the gas flow field were analyzed, and the efficiencies of couples sub-nozzles controlled by one electromagnetic valve were compared. The result shows that the space between two sub-nozzles has the greatest influence to the complex gas flow field. The gas consumption is fewest when one electromagnetic valve only controlles 2 sub-nozzles. The average velocity of the complex gas flow is maximal, and its average turbulence intensity is minimal when one electromagnetic valve controlles 3 sub-nozzles in general conditions. The average velocity of the complex gas flow is highest when one electromagnetic valve controlles 4 sub-nozzles in the context of space between two sub-nozzles is 50mm.The study of this thesis indicates that the analysis shall provide a guide for the design and amelioration of weft insertion system in the air-jet loom, and it is feasible to simulate the gas flow field of the sub-nozzle in air-jet loom numerically.