Numerical investigation on characteristics of transient process in centrifugal pumps during power failure

Feng, Jianjun; Ge, Zhenguo; Zhang, Yunlong; Zhu, Guojun; Wu, Guangkuan; Jiang, Liting; Luo, Xingqi

doi:10.1016/j.renene.2021.01.104

Cited by 38 publications

(18 citation statements)

References 31 publications

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“…Chalghoum et al studied the transient characteristics of a centrifugal pump during the starting period, and found that the pressure evolution is influenced by the valve opening percentage and starting time [18]. To establish stopping conditions, Feng et al studied the transient process of centrifugal pumping during stopping experiences, mainly in four modes, namely, pump mode, breaking mode, turbine mode, and runaway mode [19].…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamic Behavior of a Pump as Turbine under Transient Flow Conditions

Huang

et al. 2022

Processes

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Centrifugal pumps as turbines (PATs) are widely used in chemical engineering for recycling the abundant energy from high-pressure fluid. The operation of PATs is significantly affected by their upstream conditions, which are not steady (i.e., with a constant flow rate) in reality, thus, research on the flow mechanism of PATs under transient conditions should be considered of higher importance. In this study, a numerical model of a PAT was developed by employing the sliding mesh method to describe turbine rotation, and a user-defined function (UDF) for characterizing transient flow conditions. Corresponding experiments were also conducted to provide validation results for the simulation, and the simulation results agreed well with the experimental outcomes. The instantaneous characteristic curves under the current working conditions were obtained for different transient flow rates. The results show that the turbine’s efficiency is significantly affected by transient flow conditions. In particular, a rapid increase (large time derivative) of flow rate results in a large energy dissipation at the turbine outlet, and therefore, the turbine efficiency decreases. In addition, as the flow rate increases, the hydrodynamic force on the impeller, and the pressure fluctuation amplitude in the volute first decrease and then increase, reaching the minimum near the design flow rate. The current study provides a reliable and precise approach for the estimation of hydrodynamic performance of fluid machinery under transient flow conditions.

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Section: Introductionmentioning

confidence: 99%

Hydrodynamic Behavior of a Pump as Turbine under Transient Flow Conditions

Huang

et al. 2022

Processes

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“…The runaway condition of pumps is an extreme turbine condition in which the flow and rotation direction are the same with those of turbine condition. When a pump or turbine suddenly loses power by incident, the water in the pipe system will flow back and the impeller will rotate in the opposite direction [1,2]. Under the influence of the water level difference between the upstream and the downstream, the rotation speed of the impeller continues to speed up until the maximum value, called runaway speed.…”

Section: Introductionmentioning

confidence: 99%

Experiment on Pressure Pulsation of Axial Flow Pump System with Different Runaway Head

Liu

Huang²,

et al. 2021

Processes

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The runaway condition is a damage condition for pumps and turbines which can induce the wake vortex, reverse flow, and severe pressure pulsation. This study aimed to research the characteristics of pressure pulsation of axial flow pumps under different runaway conditions, and the runaway model test was performed with different blade angles and heads. Moreover, four pressure sensors were uniformly arranged at the impeller inlet section to eliminate the random error. The time domain and frequency domain analysis were the main methods to obtain the change regulations. Results showed that the pressure pulsation under the runaway condition are mainly influenced by the rotation frequency, blade passing frequency, and wake vortex frequency. The dimensionless pressure pulsation coefficient of rotation frequency and wake vortex frequency increased obviously with the runaway head increasing, but changed little with different blade angles. In addition, the dimensionless pressure coefficient of wake vortex frequency of the sensors around the impeller inlet section differed a lot, which means that the wake vortex core is not in center of the rotation axis. The average dimensionless pressure pulsation coefficient of wake vortex frequency is higher than that of rotation frequency with the same runaway head, owing to the severer wake vortex.

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“…Thereafter, the rotational speed of impeller continues to increase until a stable maximum rotational speed, called runaway speed, is reached. Under runaway condition, the flow pattern inside the conduit will inevitably face violent instability phenomenon, which will easily induce severe pressure pulsations and sharp change of blade stress 5 . Therefore, the research on the transient process of pump system is of great significance for safe and stable operations of pump stations.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, some scholars also studied the influence of different start-up modes and discharge valve openings on the external characteristics of pumps during the transient process 10 , 11 . With the rapid development of modern numerical software, computational fluid dynamics (CFD) has become a useful tool to simulate the evolution law of the internal flow field in pump units 5 , 12 , 13 . At the same time, three-dimensional (3D) numerical method has been widely applied on the simulation of various transient processes, such as start-up, shut down, runaway process, power off and so on 3 , 4 , 14 .…”

Section: Introductionmentioning

confidence: 99%

Study on a horizontal axial flow pump during runaway process with bidirectional operating conditions

Kan

Zhang

et al. 2021

Sci Rep

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The ultra-low head pump stations often have bidirectional demand of water delivery, so there is a risk of runaway accident occurring in both conditions. To analyze the difference of the runaway process under forward runaway condition (FRC) and backward runaway condition (BRC), the whole flow system of a horizontal axial flow pump is considered. The Shear-Stress Transport (SST) k–ω model is adopted and the volume of fluid (VOF) model is applied to simulate the water surface in the reservoirs. Meanwhile, the torque balance equation is introduced to obtain the real time rotational speed, then the bidirectional runaway process of the pump with the same head is simulated. In addition, the vortex transport equation and swirl number are proposed to reveal the flow characteristics during the runaway process. The results show that the runaway process can be divided into five stages: the drop, braking, rising, convergence and runaway stages, according to the changing law of torque curve. In the rising stage, the pressure difference on the blade surface continues to increase, which contributes to the abnormal torque increase. In this stage, the flow hits the pressure surface (PS) at a faster speed enlarging the pressure on PS, and the flow separation takes place on the suction surface (SS) weakening the pressure on SS. During the convergence and runaway stage, the pulsation amplitude of torque and axial force under FRC is obviously larger than those under BRC. This is because the rotation frequency of the vortex rope is the same as main pressure fluctuation frequency in impeller under FRC, which enhances the pulsation amplitude. Whereas the vortices are broken due to the inhibitive effect from guide vanes under BRC.

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Numerical investigation on characteristics of transient process in centrifugal pumps during power failure

Cited by 38 publications

References 31 publications

Hydrodynamic Behavior of a Pump as Turbine under Transient Flow Conditions

Hydrodynamic Behavior of a Pump as Turbine under Transient Flow Conditions

Experiment on Pressure Pulsation of Axial Flow Pump System with Different Runaway Head

Study on a horizontal axial flow pump during runaway process with bidirectional operating conditions

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