Numerical and Experimental Investigation of Cavitating Characteristics in Centrifugal Pump with Gap Impeller

Passive flow control techniques, and particularly vortex generators have been used successfully in a broad range of aero-and hydrodynamics applications to alter the characteristics of boundary layer separation. This study aims to review how such techniques can mitigate the extent and impact of cavitation in incompressible flows. This review focuses first on vortex generators to characterize key physical principles. It then considers the complete range of passive flow control technologies, including surface conditioning and roughness, geometry modification, grooves, discharge, injection, obstacles, vortex generators, and bubble generators. The passive flow control techniques reviewed typically delay and suppress boundary layer separation by decreasing the pressure gradient at the separation point. The literature also identifies streamwise vortices that result in the transfer of momentum from the free stream to near-wall low energy flow regions. The area of interest concerns hydraulic machinery, whose performance and life span are particularly susceptible to cavitation. The impact on performance includes a reduction in efficiency and fluctuations in discharge pressure and flow, while cavitation can greatly increase wear of bearings, wearing rings, seals, and impeller surfaces due to excessive vibration and surface erosion. In that context, few studies have also shown the positive effects that passive controls can have on the hydraulic performance of centrifugal pumps, such as total head and efficiency. It is conceivable that a new generation of design in hydraulic systems may be possible if simple design features can be conceived to maximize power transfer and minimize losses and cavitation. There are still, however, significant research gaps in understanding a range of impact factors such as manufacturing processes, lifetime, and durability, and essentially how a static design can be optimized to deliver improved performance over a realistic range of operating conditions.

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“…Zhu et al and Bing and Hongxun 154,155 studied gap drainage in the centrifugal pump impeller as illustrated in Figs. 15(a) and 15(b).…”

Section: Drainage and Injectionmentioning

confidence: 99%

Cavitation control using passive flow control techniques

et al. 2021

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“…There are many technologies for the measurement of flow in centrifugal pumps, such as high-speed photography (HSP) (He et al , 2021; Stel et al , 2019; Zhao et al , 2021; Zhu et al , 2014), particle image velocimetry (PIV) (Shao et al , 2015; Westra et al , 2010; Wu et al , 2011) and laser Doppler velocimetry (LDV) (Cader et al , 1992; Nicholas et al , 2003; Shigemitsu et al , 2009; Feng et al , 2011). Among them, high-speed photography is the most intuitive and simplest technology.…”

Section: Introductionmentioning

confidence: 99%

Study on the prediction method and the flow characteristics of gas-liquid two-phase flow patterns in the suction chamber

Shao

Bao

Wang

et al. 2021

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Purpose The purpose of this paper is to propose a prediction method of gas-liquid two-phase flow patterns and reveal the flow characteristics in the suction chamber of a centrifugal pump. Design/methodology/approach A transparent model pump was experimentally studied, and the gas-liquid two-phase flow in the pump was numerically simulated based on the Eulerian–Eulerian heterogeneous flow model. The numerical simulation method was verified from three aspects: the flow pattern in the suction chamber, the gas spiral length and the external characteristics of the pump. The two-phase flow in the suction chamber was studied in detail by using the numerical simulation method. Findings There are up to eight flow patterns in the suction chamber. However, at a certain rotational speed, only six flow patterns are observed at the most. At some rotational speeds, only four flow patterns appear. The gas spiral length has little relationship with the gas flow rate. It decreases with the increase of the liquid flow rate and increases with the increase of the rotational speed. The spiral flow greatly increases the turbulence intensity in the suction chamber. Originality/value A method for predicting the flow pattern was proposed. Eight flow patterns in the suction chamber were identified. The mechanism of gas-liquid two-phase flow in the suction chamber was revealed. The research results have reference values for the stable operation of two-phase flow pumps and the optimization of suction chambers.

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“…However, it is very difficult to predict the flow pattern and design a high efficiency pump via a theoretical study. Common measurement technologies for the internal flow in the centrifugal pump, such as particle image velocimetry (PIV) (Westra et al ., 2010; Wu et al ., 2011; Si et al ., 2015; Li et al ., 2016), laser Doppler velocimetry (LDV) (Nicholas et al ., 2003; Shigemitsu et al ., 2009; Feng et al ., 2011) and high-speed photography (HSP) (Zhu et al ., 2014; Zhang et al ., 2016), can be used as reference to the study of the molten salt pump. The velocity distribution can be obtained by PIV and LDV, but the cost and difficulty of the test are much higher than those of HSP.…”

Section: Introductionmentioning

confidence: 99%

Numerical study of the dimensionless characteristics and modeling experiment of a molten salt pump that transports viscous fluids

Shao

Zhao

2017

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Purpose The purpose of this paper is to study the dimensionless characteristics of a molten salt pump and propose an approach to carry out the modeling experiment by using water instead of molten salts. Design/methodology/approach External characteristics of the pump were estimated by using the steady flow model and compared with the experimental results. By taking water as the working fluid, the pathlines in the volute of the model pump were validated by the results obtained of high-speed photography. According to the derived dimensionless characteristics of the molten salt pump, the modeling experimental schemes were proposed. Adopting the validated numerical simulation model, the performance of the molten salt pump was studied in detail. Findings The modeling experimental schemes designed according to the dimensionless characteristics are theoretically feasible. However, to carry out the experiment successfully, factors such as rotational speed, geometric size, flow rate and head should be taken into account. The flow in the pumps is similar under the similar operating condition and the external characteristics of the similar pump can be converted to each other. Compared with transporting water, the decline of the head and efficiency is within 5 per cent when the viscosity is lower than 0.01453 Pa · s. The pump is not suitable for running under the critical Reynolds number of 1.0 × 107. Originality/value The current work revealed the relationships among the dimensionless performances of a molten salt pump and proposed a critical Reynolds number ReQcr for the pump running.

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Numerical and Experimental Investigation of Cavitating Characteristics in Centrifugal Pump with Gap Impeller

Cited by 9 publications

References 7 publications

Cavitation control using passive flow control techniques

Cavitation control using passive flow control techniques

Study on the prediction method and the flow characteristics of gas-liquid two-phase flow patterns in the suction chamber

Numerical study of the dimensionless characteristics and modeling experiment of a molten salt pump that transports viscous fluids

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