Noise Investigation of the Picking Mechanism in an Air-Jet Loom.
Noise-Con 81, Proceedings of the 1981 National Conference on Noise Control Engineering, Raleigh, North Carolina, 8-10 June, 1981 1981:191-194
The noise of the picking mechanism in an Investa model-P-125 air jet loom was investigated. The loom was a member of the family of jet pipe looms that move the thread using the kinetic energy of fluid flow. Mechanisms of noise generation in air nozzles were described. At subsonic speeds noise was produced by turbulent mixing, giving rise to fluid momentum flux changes leading to acoustic quadrupoles. The sound power was then dependent on the eighth power of the exit velocity and the square of the jet diameter. Additional noise mechanisms at supersonic jet speeds were discrete tones due to a feedback type of oscillation (screech), a more broadband but strongly peaked noise mechanism (shock associated noise), and a monopole type of noise caused by rapid interruptions of the flow in pulsating jets. For this loom, narrow band investigation showed harmonics below 500 hertz that were governed by the picking rate. The broadband air jet noise was centered in the 4 to 6 kilohertz (kHz) band. The sound power output was dependent on the blowing pressure, doubling with every 10 pounds per square inch (psi) increase in delivery pressure. Except for the low frequency region, the spectra were relatively smooth. The overall power level for the nominal blowing pressure of 50psi was 101.2 decibels linear and 100.2 decibels A-weighted. In anechoic measurements the noise from the jet alone was directional, at 25 degrees to the jet axis. The authors conclude that the smoothness of the spectra together with the directional nature of the noise in anechoic conditions suggests that the shock related noise is not dominant compared with the turbulent mixing noise, and that the noise level is very dependent on blowing pressure and cycle timing.
NIOSH-Grant; Noise-analysis; Textiles-industry; Industrial-noise; Acoustical-measurements; Noise-frequencies; Acoustics; Noise-sources;
Royster-LH; Hart-FD; Stewart-ND;
Noise-Con 81, Proceedings of the 1981 National Conference on Noise Control Engineering, Raleigh, North Carolina, 8-10 June, 1981
Textile Machine Design & Devel North Carolina State Univ P O Box 5006 Raleigh, N C 27650