Experimental Investigation of Time-Frequency Characteristics of Pressure Fluctuations in a Double-Suction Centrifugal Pump

Abstract

Pressure fluctuation is the primary reason for unstable operations of double-suction centrifugal pumps. By using flush mounted pressure transducers in the semispiral suction chamber and the volute casing of a double-suction pump, the pressure fluctuation signals were obtained and recorded at various operating conditions. Spectral analyses were performed on the pressure fluctuation signals in both frequency domain and time-frequency domain based on fast Fourier transform (FFT) and an adaptive optimal-kernel time-frequency representation (AOK TFR). The results show that pressure fluctuations at the impeller rotating frequency and some lower frequencies dominated in the semispiral suction chamber. Pressure fluctuations at the blade passing frequency, the impeller rotating frequency, and their harmonic frequencies were identified in the volute casing. The amplitude of pressure fluctuation at the blade passing frequency significantly increased when the flow rate deviated from the design flow rate. At 107% of the design flow rate, the amplitude increased more than 254% than that at the design flow rate. The time-frequency characteristics of these pressure fluctuations were affected greatly by both operating conditions and measurement locations. At partial flow rates the pulsation had a great irregularity and the amplitudes at the investigated frequencies were much larger than ones at the design flow rate. An asymmetrical pressure fluctuation structure in the volute casing was observed at all flow rates. The pulsation behavior at the blade passing frequency was the most prominent near the volute tongue zone, and the pressure waves propagated in both the radial and circumferential directions.

Experimental and numerical investigations on pressure pulsation in a pump mode operation of a pump as turbine

“…Moreover, the pressure pulsations induced by the rotor‐stator interactions in axially split centrifugal pumps were investigated by Yao et al at design and off‐design operation conditions. They demonstrated that the blade passing frequency is very high around the volute region.…”

“…Khalifa et al, 10 Pavesi et al, 11 and Spece 12 all investigated the pressure pulsation fields in centrifugal pumps and concluded that the magnitude of the pulsation is induced by the rotor-stator interactions at all operating conditions. Moreover, the pressure pulsations induced by the rotorstator interactions in axially split centrifugal pumps were investigated by Yao et al 13 at design and off-design operation conditions. They demonstrated that the blade passing frequency is very high around the volute region.…”

Numerical Investigation of Pressure Fluctuation Characteristics in a Centrifugal Pump with Variable Axial Clearance

“…Pressure fluctuation is one of the most common phenomena of unsteady flows. Considerable investigations [1][2][3][4][5][6][7][8][9][10][11][12] have been performed on pressure fluctuation characteristics in volute casings and impellers of centrifugal pumps, concluding that blade-tongue interaction plays a dominant role in causing fluctuating main flows, and the influencing factors including flow rate and impeller-tongue gap size have been analyzed. But flows in sidewall gaps, which refer to the space between impeller shrouds and casing covers, are usually ignored.…”

Evaluation of Flow-Induced Dynamic Stress and Vibration of Volute Casing for a Large-Scale Double-Suction Centrifugal Pump

“…Toussaint [4] experimentally studied the unsteady flow in a centrifugal pump at off-design point operation and found that the unsteady pressures due to the rotorstator interactions took place at the following characteristic frequencies: rotation frequency, blade passing frequency, and their harmonics. Lately, Yao et al [5] carried out several tests on double-suction centrifugal pumps. He found that the impeller rotating frequency and some lower frequencies dominated in suction chamber.…”