Investigation of The Effects Of Various Parameters On A Subsonic Axial Flow Fan Performance And Tonal Noise

Open Access
Author:
Matai, Racheet
Graduate Program:
Aerospace Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
June 16, 2015
Committee Members:
  • Savas Yavuzkurt, Thesis Advisor
Keywords:
  • Axial Fan
  • Fan Parametric study
  • Fan performance
  • fan noise
  • Fan CFD
Abstract:
This work was aimed at improving the efficiency and decrease the noise generated by a cooling fan used by GE transportation to cool a row of resistor networks which dissipate excess energy generated by regenerative power in an inverter application. The first part of study focused on determining the effect of various parameters on the performance of the fan quantitatively by using FLUENT, a general purpose CFD code. The effects of parameters such as hub to tip ratio, chord length/thickness and solidity/number of blades was studied. Once the effect of these parameters was found a new fan was designed which increased the efficiency at the operating point from 73% to 77%. This new fan had a longer blade (increased by 0.75 inches), less number of blades (24 reduced to 18) and a larger chord length (the airfoil scaled by 1.5 time). The hub shape was also modified to reduce separation at the hub. Although a more efficient design, this new fan was found to make more noise with the peak dB levels increasing from 89dB to 110dB due to a higher rate of change of axial force on blades which is proportional to the sound pressure level. Thus a different approach was adopted, an inlet guide vane (IGV) with different lean angles were experimented with. It was seen that a 6 degree lean angle eliminated the peak at the first harmonic of the blade pass frequency (2400Hz) and a 15 degree lean angle eliminated the first and the second harmonic of the blade pass frequency (2400Hz and 3600Hz). The first peak at the blade passing frequency remained approximately the same (~89dB) with the IGV lean.