Flow Characteristics in the Double Coaxial Pipe Jets

Abstract

To obtain basic data for an optimum of the main nozzle for an air-jet loom, we have made measurements of static pressures on the walls of the main nozzle and analyzed flow velocity changes in the nozzle tube by changing air tank pressures and acceleration tube lengths. The flow may reach a critical condition of Mach 1 at two positions, the needle tip and the acceleration tube exit. Increased tank pressure brings about the critical throat condition at these two positions, so the flow in the nozzle can be completely defined. The tank pressure <i>P_T</i> to bring the needle tip to the critical condition depends on the acceleration tube length, and <i>P_T</i> is higher for longer acceleration tubes. The <i>P_T</i> value required to bring the acceleration tube exit to the critical condition is nearly constant regardless of acceleration tube length. For the nozzle used in this experiment, tank pressure was about 2&#8765;6 kg_f/cm².