| A noise prediction scheme using time domain noise theory was developed for low speed fans with high in flow distortion. Basic design parameters such as thrust, torque, blade shape and blade thickness are used to predict a baseline noise signature using the Ffowcs Williams and Hawkings equation. Flow disturbances from simple, common shapes in the flow path are approximated and used to determine the noise level produced with installed conditions that ingest such disturbances into the fan. The inputs to the program are restricted to commonly available information that can be determined early in the design cycle.;The process has been verified with an experimental set up in an anechoic chamber. The results of the experiment and the prediction from the program agree within 3 dB over a wide range of angles for the first two blade passing frequencies and a reasonable range of broadband noise. |
