Application and precautions of nozzles in water jet loom accessories

The inside of the nozzle of the water jet loom accessory is ring-shaped. The weft thread is introduced from the weft guide tube along the axial direction, and the high-pressure water flows in from the nozzle body, and is rectified by the rectifying sleeve to reduce the vortex state of the jet and improve its bundling. When the jet is ejected from the nozzle orifice, relying on the friction force between the water flow and the weft thread, the weft insertion thread will pass through the shed. Nozzle is one of the key components of water jet loom accessories, and its bundling is closely related to the weaving performance of water jet weft insertion.
The diameter of the ring nozzle can be adjusted according to the fineness and variety of the weft yarn. Rotating the weft guide tube and adjusting its relative position with the nozzle body 3 can change the annular area of ​​the nozzle opening. The nozzles of water jet looms are made of stainless steel and ceramics. They have high requirements for the smoothness of the conical inner cavity and outer wall, and also have high requirements for the concentricity of the nozzle body and the weft guide, especially when adjusting the nozzle diameter. At this time, the deviation of the concentricity will seriously affect the bundling and spray direction of the water flow, and make the performance of the water jet loom worse.
The jet velocity at the nozzle outlet of the water jet loom accessories is determined by the pressure of the water. When the water pressure is high, the jet velocity at the outlet is also high. Since the resistance of the water jet is proportional to the square of its jet velocity, the higher the jet velocity at the nozzle outlet, the faster the jet will drop after jetting. When the speed in front of the jet drops below the speed of the weft yarn, it will move next to the weft yarn at the front end, while the subsequent weft yarn still advances at a high speed, resulting in a weft shrinkage defect of "crowding in front and squeezing in back". Therefore, it is very important to choose the water pressure and the initial velocity of the jet reasonably.
Although the viscosity of water is much greater than that of air, after the jet leaves the nozzle, it expands in a conical shape; a precise water jet sprayed by a nozzle with a diameter of 2-3mm, after flying 1. 8m, its diameter Approximately 20mm. Due to the influence of gravity, the axis of the water jet is a parabola, so the axis of the nozzle should be inclined upwards at an appropriate angle.