Yucheng Ji

Bio: Yucheng Ji is an academic researcher. The author has contributed to research in topics: Impeller & Centrifugal pump. The author has an hindex of 1, co-authored 1 publications receiving 18 citations.

Statistical characteristics of suction pressure signals for a centrifugal pump under cavitating conditions

Abstract: Centrifugal pumps are often used in operating conditions where they can be susceptible to premature failure. The cavitation phenomenon is a common fault in centrifugal pumps and is associated with undesired effects. Among the numerous cavitation detection methods, the measurement of suction pressure fluctuation is one of the most used methods to detect or diagnose the degree of cavitation in a centrifugal pump. In this paper, a closed loop was established to investigate the pump cavitation phenomenon, the statistical parameters for PDF (Probability Density Function), Variance and RMS (Root Mean Square) were used to analyze the relationship between the cavitation performance and the suction pressure signals during the development of cavitation. It is found that the statistical parameters used in this research are able to capture critical cavitation condition and cavitation breakdown condition, whereas difficult for the detection of incipient cavitation in the pump. At part-load conditions, the pressure fluctuations at the impeller inlet show more complexity than the best efficiency point (BEP). Amplitude of PDF values of suction pressure increased steeply when the flow rate dropped to 40 m3/h (the design flow rate was 60 m3/h). One possible reason is that the flow structure in the impeller channel promotes an increase of the cavitation intensity when the flow rate is reduced to a certain degree. This shows that it is necessary to find the relationship between the cavitation instabilities and flow instabilities when centrifugal pumps operate under part-load flow rates.

Cavitation-Vortex-Pressure Fluctuation Interaction in a Centrifugal Pump Using Bubble Rotation Modified Cavitation Model Under Partial Load

Abstract: Cavitation is a complicated phenomenon in the centrifugal pump. In this work, the improved unsteady calculation model based on bubble-rotation-based Zwart–Gerber–Belamri (BRZGB) cavitation model is used to investigate the cavitation-vortex-pressure fluctuation interaction in a centrifugal pump under partial load with experimental validation. Spatial–temporal evolution of cavitation can be classified into three stages: developing stage, shedding stage, and collapsing stage. The cavitation evolution period is found as 1/4T (T is impeller rotation period), corresponding to the frequency 4fi (fi is impeller rotation frequency). On the analysis of the relative vorticity transport equation, it is revealed that the cavity is stretched by the relative vortex stretching term (RVS) and developed by the relative vortex dilation term (RVD), and they have great influence on the cavity shedding. The peak value of pressure fluctuation intensity occurs near the vapor–liquid interface at cavity rear, and shifts downstream with the cavitation development. The hysteresis between the vapor volume fraction, vorticity, and pressure fluctuation is observed, and the variation of vapor volume fraction is the source of cavitation-vortex-pressure interaction.

An experimental study on the cavitation vibration characteristics of a centrifugal pump at normal flow rate

Abstract: Cavitation is a challenging flow abnormality that leads to undesirable effects on the energy performance of the centrifugal pump and the reliable operation of the pump system. The onset and mechanism of a phenomenon that results in unsteady cavitation must be realised to ensure a reliable operation of pumps under the cavitation state. This study focuses on cavitation instability at normal flow rate, at which point the unsteady cavitation occurs as the available net positive suction head (NPSHa) falls below 5.61 m for the researched pump. An ameliorative algorithm–united algorithm for cavitation vibration analysis is proposed on the basis of short time Fourier transform (STFT) and Wigner–Ville distribution (WVD). The STFT–WVD method is then tested using vibration data measured from the centrifugal pump. The relationship between vibration and suction performance indicates that the inception and development of cavitation can be effectively detected by the distribution and intensity of the united algorithm at the testing points. Intermediate frequency components at approximately 6 kHz fluctuate initially with the development of cavitation. A time–frequency characteristic is found to be conducive to monitoring the cavitation performance of centrifugal pumps.

Unsteady flow characteristics and cavitation prediction in the double-suction centrifugal pump using a novel approach:

Abstract: The recent advances in centrifugal pump design do not only require a better suction performance but also there have been attempts to reduce design time at a lower cost. The traditional trial-and-er...

Detection of Inception Cavitation in Centrifugal Pump by Fluid-Borne Noise Diagnostic

Abstract: This paper presents an experimental methodology that is capable of sensitively detecting the cavitation inception in a centrifugal pump. Firstly, with a centrifugal pump of as research object, the cavitation performance, the bubble pattern distribution at impeller inlet, and the vibration and noise were synchronously measured at different flow conditions each with several cavitation coefficients. The change laws of total level of vibration and noise signals throughout the cavitation process were emphatically investigated. After comparing the sensitivity and reliability of different detection methods, the method based on overall sound pressure level of liquid-borne noise is found to present high sensitivity to cavitation. Secondly, by comparing the affected 1/3 octave spectrum by changing flow and cavitation coefficients, the highly sensitive frequency band to cavitation was obtained. Then, a new inception cavitation detection method was proposed based on Pauta principle. Finally, the method was verified through an ultra-low-specific speed pump ( ). The results show that the total pressure level of liquid-borne noise increases firstly and then decreases with the development of cavitation. The broadband SPL of liquid-borne noise between 2000 and 3000 Hz can be used to detect the inception cavitation, and the cavitation detection threshold is determined as 1.0%.