Flow Characteristics in Weft-Acceleration Pipe of Air-Jet Loom

This paper describes the experimental study concerning air-flow characteristics in the weft-acceleration pipe of an air jet loom when forced flow is given to the weft-guide pipe of the nozzle trially made. Central flow through the weft-guide pipe is composed of both flow naturally sucked by the pressurized annular flow, and positively gushed-inflow (forced flow). To study the flow condition useful for acceleration and flight of a weft, the flow in the weft-acceleration pipe was measured with a hot-wire anemometer when M was changed stepwise, where M is the ratio of flow rate of the central flow to that of the annular flow through the nozzle. During the experiments, R, the ratio of the annular-exit area to the central-exit area and Re, Reynolds number of air flow in the weft-acceleration pipe, were kept constant (R=0.343, Re=1.7×104).The following results were obtained: When M is increased: (1) velocity defect along the axis of the weft-acceleration pipe is reduced. (2) turbulence in that pipe is weakened.As a result, it is sure that a flow useful for acceleration and flight of the weft is generated. This fact can also explain the reason why the modern tandem main nozzle can achieve steady flight of weft.