Main Nozzle Design and Air Flow Principles
topic
Air-jet main nozzles use a convergent-divergent nozzle geometry that accelerates the yarn-carrying air stream through the venturi throat to the supersonic velocities required for reliable yarn insertion, with the yarn fed through the nozzle centre and entrained in the air stream that carries it into the shed, with main nozzle air pressure of 3 to 6 bar and nozzle orifice diameter of 1.5 to 3.5 millimetres optimised for each yarn count and type to achieve the insertion force required without excessive yarn tension that would cause breaks.
Role
Generates the initial high-velocity air stream that entrains the weft yarn and propels it into the shed, with main nozzle design being the foundational element of the air insertion system whose performance in terms of air-to-yarn force transfer efficiency and yarn tension during acceleration determines the maximum yarn count range and minimum reliable insertion speed that the air-jet system achieves.