Experimental Investigation of Unsteady Characteristics in a Single-Channel Pump

Abstract

Abstract Single-channel pumps are a specific type of centrifugal pump that is widely used in the sewage treatment of raw wastewater and effluent pumping applications. In single-channel pumps, the rotor–stator interactions may generate unbalanced pressures that change during one impeller revolution. A specific experiment rig was constructed to investigate the unsteady characteristics synchronously, including energy performance, head pulsation, pressure pulsation, and radial force. It was found that the difference between the maximum and minimum head was greater than 5 m under all flow rates during a rotation period. With the increase of the flow rate, the head reached its minimum value slowly and achieved its maximum value more quickly. The static pressure distribution at the impeller outlet was the most uniform at 1.0Qd. The high-pressure region located initially downstream of the tongue gradually moved toward the upstream end of the tongue with an increase in the flow rate. When the blade outlet goes through the tongue, the pressure pulsation appears at its peak at the eighth cross section of the volute. The peak position moves toward the upstream with the rotation of the impeller. In the single-channel pumps, the absolute pressure pulsation achieved its peak at the blade passing frequency, and the pressure pulsation amplitude for fBPF varied gradually with an increase in the flow rate. The radial force reached a minimum value near the optimal efficiency point and its direction was mostly downstream of the tongue. To meet the hydraulic balance of the impeller, it was suggested that a balance piece be adapted to counteract the radial force.