Abstract:

Objective The key technology to improve the quality and reduce the cost of air-jet loom was to increase the flying speed of weft yarn, improve the quality of air-flow synthesis and reduce the air consumption. In order to improve the comprehensive performance of the auxiliary nozzle for weft insertion of air-jet weaving machines, the optimal model structure of the auxiliary nozzle orifice was simulated and optimized, so as to achieve the optimal weft insertion performance.
Method The Flow Simulation plug-in module in Solidworks software was used in the research, which is a CFD numerical simulation plug-in based on the finite volume method. Flow Simulation is a fully integrated software in Solidworks. The proven computational fluid dynamics (CFD) technology was used to calculate the fluid (gas or liquid) flow inside and outside the Solidworks model. At the same time, the heat transitive model (from models, between models and inside models) caused by convective radiation and conduction will also have an impact. The structural optimization method of Solidworks software was employed to simulate the fluid performance of the auxiliary nozzle orifice. Three dimensional models of the flow field of the auxiliary nozzle orifice with single round hole, double round hole and rectangular hole was constructed to evaluate, the velocity distribution at the section 40 mm away from the nozzle, maximum flow rate of auxiliary nozzle and the mass flow at the inlet of the auxiliary nozzle under the working environment pressure of 0.4 MPa.
Results For a single circular hole auxiliary nozzle, when the cone angle was set to 4°in the positive direction, better results were obtained, and the weft insertion stability was good. A high airflow speed and minimum mass flow rate could increase the weft insertion speed while ensuring the stability of the weft insertion without increasing gas consumption. Compared to the unoptimized model with a cone angle of 0°, when the cone angle was set to 4 ° in the positive direction, the stability of the weft insertion slightly increased, and the maximum flow velocity of the airflow field increased by 3.03%, with the same gas consumption as at 0°.For the double circular hole auxiliary nozzle, group D achieved relatively good results, with good weft insertion stability and slight airflow velocity and mass flow rate increase, which could increase the weft insertion speed while ensuring the stability of the weft insertion, but slightly increased the gas consumption. Compared to the group C before optimization, the stability of group D slightly increased, with a maximum flow rate increase of 0.908%, increased gas consumption by 6.25%. For the rectangular auxiliary nozzle, group B achieved relatively good results. At this time, the stability of weft insertion was good, the airflow speed was slightly increased, and the mass flow rate remained unchanged. On the basis of ensuring the stability of weft insertion, the weft insertion speed could be increased without increasing gas consumption. Compared to group A before optimization, the stability of group B was slightly increased and its maximum flow rate was 2.8%.
Conclusion Flow Simulation plug-in module in Solidworks software is used to analyze the velocity distribution of the section of the auxiliary nozzle with single circular hole, double circular hole and rectangular circular hole at the distance of 40 mm from the nozzle, maximum flow rate of auxiliary nozzle and the mass flow at the inlet of the auxiliary nozzle under the working environment pressure of 0.4 MPa, and then optimize the structure of the auxiliary nozzle to obtain the optimal results. ①For the single round hole auxiliary nozzle, when the cone angle is 4° in the positive direction, the better results are obtained. At this time, the weft insertion stability is good, and the high air velocity and the minimum mass flow rate are obtained. On the basis of ensuring the weft insertion stability, the weft insertion speed can be increased without increasing the gas consumption. ②For the auxiliary nozzle with double round holes, the center distance between the two holes is 2.2 mm, and the cross section air velocity at 40 mm from the nozzle is higher than 90 m/s. The symmetry and the stability of weft insertion is good, which can meet the different requirements of actual weft insertion.③ For the auxiliary nozzles with rectangular shapes, when the length of the jet shapes is 2.034 mm and the width of the jet shapes is 0.885 mm, the air flow velocity at the section 40 mm from the jet shapes is higher than 90 m/s, with good symmetry and stability of weft insertion. The air flow speed is slightly improved, and the mass flow remains unchanged, which can increase the weft insertion speed without increasing the gas consumption on the basis of ensuring the stability of weft insertion.

Key words: air-jet loom, auxiliary nozzle, orifice, numericalsimulation, optimization analysis