Experimental Investigation of Fluid Flow Behavior in a Centrifugal Compressor under Surge Conditions Utilizing Hot Wire Anemometer

In the present research work, flow behavior in a centrifugal compressor has been experimentally investigated at various operating conditions from far to near surge and different compressor rotational speeds. Having introduced the experimental set-ups, results of velocity fluctuations at compressor inlet, as a surge precursor, have been presented. Hot-wire anemometry of high frequency response was used to measure these fluctuations at three compressor rotational speeds of 9000, 10000 and 13000 rpm and three operating conditions of maximum flow coefficient, near design point and surge conditions. Experimental results showed that reduction from maximum flow coefficient towards the surge point can increase fluctuations of instantaneous velocity signals at aforementioned rotational speeds by the factor of 2.6, 1.9 and 1.57, respectively. In addition, increase of compressor rotational speed increases fluctuation of instantaneous velocity signals at surge condition by an average factor of 1.17. Finally, analysis of frequency spectrums of velocity fluctuations, showed a dominant frequency of surge at about 30 percent of the blade passing frequency.