Study On Filling Movement In Jet Flow Within The Main Nozzle Of Air-jet Loom

Main nozzle is the key part of the weft-insertion system in an Air-Jet Loom.Thehigh-speed airflow characteristics and filling movement in the air are the important factorsthat affect efficiency of air-jet loom and fabric quality. How to improve the stability andrapidity of filling movement has always been the key and difficult point for many scholars.Based on the study of weft-insertion of air-loom system, the thesis respectively adopts themethods of numerical and experimental test to study the filling movement at the exit ofhigh-speed high pressure gas on the main nozzle jet flow field.The numerical simulation applies the single phase coupling model during the research.The thesis studies how some respectively changed relative factors affect the filling movementon the main nozzle jet flow field, which include inlet air flow speed, filling diameter, fillingdensity, velocity and location. The conclusion follows as:1.The mainstream direction in the process of flow in jet flow field developmentchanges constantly and is accompanied by the generation and development ofvortex,disappearance, jet cross section gradually expending,the axial velocity graduallydecreases.2. Nozzle inlet air velocity plays an important role in filling speed within a certainrange. The faster the air in the nozzle moves, the greater the filling moving velocity is. Ideallyfilling fluctuation is not obvious within a certain velocity.With filling running in the jet flowfield and moving away from the entrance of the nozzle, filling fluctuation will graduallybecome obvious. The thinner the filling is, the smaller the filling speed. And bend andfluctuate will be more obvious. The smaller the filling liner density is, the greater the speedwill be.3.Initial velocity of filling had important effect on the filling movement in the jet flowfield. The smaller the initial axial velocity is, the more obvious the bending deformation ofthe filling will be. But the direction is stable. The greater the initial transverse speed is, theeasier direction of filling movement departs from the axis of the flow field, which will makethe weft insertion more unfavorable. If the distance from the initial position of filling to thecenter of jet flow field is within the scope of the length of guide tube radius,the initialposition of filling will have a little influence on the filling movement. Although the initialpositions of filling are different, the filling movement does not make obvious changes.The experiment of the thesis includes testing the filling movement by using high speed camera system, which is the main part of the test and analysis device and records the dynamicprocess of filling movement under different main nozzle air supply pressure, filling fitness,filling length. Then we analyze photographs of the filling movement process by usingprofessional image analysis software. The conclusion follows as:1.when filling moves in jet flow field, the filling fluctuation closes to the main nozzlehas almost no fluctuations. The fluctuation in this position is not obvious, but in a relativelystable state. Only the head end of the filling has been in a state of fluctuation.2.The bigger the main nozzle gas supply pressure is, the greater the extent of fillinghead fluctuations will be; the higher the frequency of the filling head wave will be; and thegreater the speed of the filling head will be. During the process, it is easy to cause the fillingtwist. Under the same condition of gas supply pressure the same material, the thinner thefilling is, the greater the extent of filling head fluctuations is and the smaller the frequency ofthe filling head wave is. The longer the filling is, the greater the extent of filling headfluctuations and the smaller the frequency of the filling head wave.The thesis studies the relationship between weft insertions and filling speed, bending,trajectory deviation and head swing. And it offers some reference information forunderstanding the filling movement in the jet flow field,thus improving the efficiency ofair-jet loom for further optimization.