Unsteady flow fluctuations in a centrifugal pump measured by laser Doppler anemometry and pressure pulsation

Abstract

Turbulent flow generated by the intense rotor–stator interaction is detrimental to the safe running of the centrifugal pump. In order to gain more insight into unsteady velocity pulsation characteristics, this research applies the laser Doppler anemometry technique to capture velocity signals at various flow rates. Besides, pressure transducers are arranged on the model pump to sample transient pressure pulsation signals. The study paid particular attention to pulsation signals in the diffusion section of the volute. Results show that at low flow rates, a prominent hump phenomenon generated within the pump head curve, which indicates the development of rotating stall in the model pump. As noted from the spectra, the discrete blade passing frequency and impeller rotating frequency dominate the velocity and pressure spectra. Root mean square values of velocity signals increase rapidly at off-design flow rates, especially within the rotating stall region, and a similar trend is observed for pressure amplitude at the blade passing frequency. From the measuring point (P3) at the inlet of the discharge channel upstream of the volute tongue to the point (P10) at the volute outlet, pressure amplitude rises significantly. Meanwhile, the minimum point of pressure amplitude vs flow rate occurs around 0.4ΦN, and again, the findings show differences for comparisons between measuring points in the core flow region of the volute. This resulting phenomenon can be attributed to flow patterns in the diffusion section.