LES Simulation of Backflow Vortex Structure at the Inlet of an Inducer

Fukao, Shinji; Yamanishi, Nobuhiro; Qiao, Xiangyu; Kato, Chisachi; Tsujimoto, Yoshinobu

doi:10.1299/kikaib.70.3058

Cited by 4 publications

(2 citation statements)

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“…Although the solution from the RANS equations has inherent limitation in simulating the development of backflow vortex structure, 11 , 25 it can predict the performance and the impact of the backflow. 26 – 29 Thus, the turbulence model of k - ω shear stress transport (SST) was utilized to simulate the inner flow field of pump in this study, due to its advantage of low cost and high accuracy for rotating machinery.…”

Section: Methodsmentioning

confidence: 99%

Backflow effects on mass flow gain factor in a centrifugal pump

Kang

Zhou

Liu³

et al. 2021

Science Progress

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Previous researches has shown that inlet backflow may occur in a centrifugal pump when running at low-flow-rate conditions and have nonnegligible effects on cavitation behaviors (e.g. mass flow gain factor) and cavitation stability (e.g. cavitation surge). To analyze the influences of backflow in impeller inlet, comparative studies of cavitating flows are carried out for two typical centrifugal pumps. A series of computational fluid dynamics (CFD) simulations were carried out for the cavitating flows in two pumps, based on the RANS (Reynolds-Averaged Naiver-Stokes) solver with the turbulence model of k- ω shear stress transport and homogeneous multiphase model. The cavity volume in Pump A (with less reversed flow in impeller inlet) decreases with the decreasing of flow rate, while the cavity volume in Pump B (with obvious inlet backflow) reach the minimum values at δ = 0.1285 and then increase as the flow rate decreases. For Pump A, the mass flow gain factors are negative and the absolute values increase with the decrease of cavitation number for all calculation conditions. For Pump B, the mass flow gain factors are negative for most conditions but positive for some conditions with low flow rate coefficients and low cavitation numbers, reaching the minimum value at condition of σ = 0.151 for most cases. The development of backflow in impeller inlet is found to be the essential reason for the great differences. For Pump B, the strong shearing between backflow and main flow lead to the cavitation in inlet tube. The cavity volume in the impeller decreases while that in the inlet tube increases with the decreasing of flow rate, which make the total cavity volume reaches the minimum value at δ = 0.1285 and then the mass flow gain factor become positive. Through the transient calculations for cavitating flows in two pumps, low-frequency fluctuations of pressure and flow rate are found in Pump B at some off-designed conditions (e.g. δ = 0.107, σ = 0.195). The relations among inlet pressure, inlet flow rate, cavity volume, and backflow are analyzed in detail to understand the periodic evolution of low-frequency fluctuations. Backflow is found to be the main reason which cause the positive value of mass flow gain factor at low-flow-rate conditions. Through the transient simulations of cavitating flow, backflow is considered as an important aspect closely related to the hydraulic stability of cavitating pumping system.

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Section: Methodsmentioning

confidence: 99%

Backflow effects on mass flow gain factor in a centrifugal pump

Kang

Zhou

Liu³

et al. 2021

Science Progress

View full text Add to dashboard Cite

show abstract

“…Kimura et al [1] investigated the relationship between the geometric parameters of the inlet pipe and the upstream flow structure of the inducer through experiments and numerical simulations. Fukao et al [2] conducted a simulation work of a model inducer using the LES (Large Eddy Simultion) method and found that the backflow gradually extends upstream to the impeller inlet with the decreasing flow rate. Xin et al [3] analyzed the jet-wake flow structure at the impeller outlet and proposed that these structures would induce unstable vortices and produce periodic pressure and velocity fluctuations around the outflow of the impeller.…”

Section: Introductionmentioning

confidence: 99%

Flow Characteristics and Energy Loss of a Multistage Centrifugal Pump with Blade-Type Guide Vanes

Zhai

Guo

et al. 2022

JMSE

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Multistage pumps with blade-type guide vanes are widely used in offshore oil production, the petrochemical and coal-chemical industries, and nuclear power fields for its advantages of large flow rate, high pressure, and excellent operation stability. However, the internal flow of this kind of pump is complex; in particular, the hydraulic, flow, and pressure pulsation characteristics of the different stages are quite different, which has a great impact on the design and performance predictions of this kind of pump. Thus, in this paper, the hydraulic performance, unsteady flow characteristics, evolution of vortex structures and pressure pulsation characteristics in a 10 stage centrifugal pump are investigated numerically. The results show that inverse flow, jet-wake flow, and rotor-stator interaction flow are the key factors causing energy loss and efficiency decline at every stage and in the whole pump. The vortex evolution at the rotor–stator interaction regions is actually the process that the vortex structures fall off and impact on the pressure surface at the leading edge of the guide vane blade at a frequency that equals to the impeller blade passing frequency. Furthermore, under the actions of the guide vane with confluence cavity, the pressure pulsation within the final-stage guide vane contains low-frequency components with large bandwidths, which mainly results from the confluence flow disturbance at the outlet of the cylindrical guide passage.

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Influence of axial clearance on the performance characteristics of a turbopump

Ren

Fan

et al. 2021

J Mech Sci Technol

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LES Simulation of Backflow Vortex Structure at the Inlet of an Inducer

Cited by 4 publications

References 0 publications

Backflow effects on mass flow gain factor in a centrifugal pump

Backflow effects on mass flow gain factor in a centrifugal pump

Flow Characteristics and Energy Loss of a Multistage Centrifugal Pump with Blade-Type Guide Vanes

Influence of axial clearance on the performance characteristics of a turbopump

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