No abstract

Centrifugal fans usually operate at high rotating speeds and hence generate high levels of noise whose reduction over a broad range of operating conditions is a key concern for the designer. An important first step in this direction is identification of noise sources and its quantification. For this purpose, Computational Fluid Dynamics (CFD) and computational aeroacoustic analyses is performed on centrifugal fans with backward impeller, radial impeller and forward impellers using CFD code FLUENT. To validate these results noise measurements are performed on centrifugal fans with backward impeller, radial impeller and forward impellers. The results so obtained from numerical analyses are compared with the measurement results. It is found that there is good agreement between numerical and experimental results. From these results it is observed that least noise of 92.6 dB(A) and high flow rate of 0.399 m 3 /sec occurs with backward impeller whereas large noise of 102.5 dB(A) and least discharge of 0.365 m 3 /sec is observed with forward impeller. The present study concludes that backward impeller radiates less noise and high discharge compared to radial and forward impellers.

This paper deals with the experimental results obtained using different shapes of multi-port averaging device at different gauge pressure. The cross-section of the multiport averaging device is essential factor which effects the meter performance. A closed loop air test facility(CLATF) is used for testing and calibration of the flowmeter, which is used to measure the air flow rate or velocity of flow.The circular probe is a commercial design while the diamond shape with slight modification is analyzed for providing better performance and appreciable result with less disturbance in the flow line. The prototype test of the flowmeter is done at a defined length of upstream straight pipe after an elbow bend, for a condition of well defined turbulent flow profile. The calibration is done at 2 and 5 gauge pressure while the flow rate varied from 0.0283 to 0.1121m 3 /s. As a result, the diamond shaped probe with curved edges provided appreciable differential pressure and flow coefficient compared to circular probe keeping the same blockage to both the probe facing the flow.