scholarly journals RANS CFD Analysis of Hump Formation Mechanism in Double-Suction Centrifugal Pump under Part Load Condition

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6815
Author(s):  
Yong Liu ◽  
Dezhong Wang ◽  
Hongjuan Ran ◽  
Rui Xu ◽  
Yu Song ◽  
...  
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Formation Mechanism ◽  
Stokes Equations ◽  
Load Condition ◽  
Simulation Method ◽  
Energy Balance Equation ◽  
Dynamics Simulation ◽  
Hydraulic Loss ◽  
Part Load

The RANS (Reynolds-averaged Navier–Stokes equations) with CFD (Computational Fluid Dynamics) simulation method is used to analyze the head hump formation mechanism in the double-suction centrifugal pump under a part load condition. The purpose is to establish a clear connection between the head hump and the microcosmic flow field structure, and reveal the influence mechanism between them. It is found that the diffuser stall causes a change in the impeller capacity for work, and this is the most critical reason for hump formation. The change in the hydraulic loss of volute is also a reason for hump, and it is analyzed using the energy balance equation. The hump formation mechanism has not been fully revealed so far. This paper found the most critical flow structure inducing hump and revealed its inducing mechanism, and greatly promoted the understanding of hump formation. The impeller capacity for work is analyzed using torque and rotational speed directly, avoiding large error caused by the Euler head formula, greatly enhancing the accuracy of establishing the connection between the impeller capacity for work and the coherent structure in the flow field under a part load condition. When a pump is running in the hump area, a strong vibration and noise are prone to occur, endangering the pump safety and reliability, and even the pump start and the transition of different working conditions may be interrupted. Revealing the hump formation mechanism provides a key theoretical basis for suppressing hump. Hump problems are widespread in many kinds of pumps, causing a series of troubles and hazards. The analysis method in this paper also provides a reference for other pumps.

Numerical Study of Rotor–Stator Interaction of a Centrifugal Pump at Part Load With Special Emphasis on Unsteady Blade Load

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Nicolas Casimir ◽  
Xiangyuan Zhu ◽  
Markus Hundshagen ◽  
Gerhard Ludwig ◽  
Romuald Skoda
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Centrifugal Pump ◽  
Numerical Study ◽  
Measurement Data ◽  
Load Flow ◽  
Secondary Outcome ◽  
Pump Design ◽  
Part Load ◽  
Unsteady Characteristics

Abstract Three-dimensional (3D) unsteady Reynolds-averaged Navier–Stokes (URANS) flow simulations are conducted to investigate the highly unsteady flow field at part load operation of a centrifugal pump. By the availability of unsteady flow field measurement data in the impeller wake region, a thorough validation of the simulation method is performed. Grid independence of the results is ensured. Unsteady characteristics in terms of head and shaft power as well as transient blade loads are evaluated to assess the unsteady pump performance. Significant mis-loading of the blading is revealed when one blade passes the volute tongue and associated with the strong unsteady and 3D flow field in the impeller-volute tongue region. Negative radial velocity in the tongue region is the origin of a vortex at the blade pressure side and a subsequent pressure drop that leads to even temporally negative blade loading. The results provide a detailed insight in the complex part load flow field that might be utilized for an improved pump design. As a valuable secondary outcome, a comparison of results obtained by two widely used computational fluid dynamics (CFD) codes for pump flow simulation is provided, i.e., the commercial code ansyscfx and the branch foam-extend of the open source software openfoam. It is found that the results of both methods in terms of unsteady characteristics as well as local ensemble-averaged velocity field are consistent.

Calculation of Stall Margin Enhancement With Micro-Tip Injection in an Axial Compressor

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Xiaohua Liu ◽  
Jinfang Teng ◽  
Jun Yang ◽  
Xiaofeng Sun ◽  
Dakun Sun ◽  
...  
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Radial Profile ◽  
Computational Cost ◽  
Tip Clearance ◽  
Dynamics Simulation ◽  
Qualitative Assessment ◽  
Force Model ◽  
Tip Leakage Flow ◽  
Stall Margin

Although steady micro-injection is experimentally validated as an attractive method in improving the stall margin of axial compressors, up to now a fast prediction of stall boundary remains some way off. This investigation is to propose such a prediction model. A flow stability model is developed to further consider the effect of high-speed micro-injection. After the base flow field is calculated by steady computational fluid dynamics simulation, a body force model is applied to reproduce the effect of blade on the flow turning and loss. A group of homogeneous equations are obtained based on linearized Navier–Stokes equations and harmonic decomposition of small flow disturbance. The stall onset point can be judged by the imaginary part of the resultant eigenvalue. After the existing experimental results are summarized, an unsteady numerical simulation reveals that the computed characteristics and radial profile of pressure rise coefficient are almost unchanged. The unsteady response of compressor to the micro-injection is preliminarily verified based on the observation of the disturbed spillage of tip leakage flow. It is verified that this approach can provide a qualitative assessment of stall point with acceptable computational cost. Both high injection velocity and short axial gap between injector and rotor leading edge are beneficial for the stall margin extension. These theoretical findings agree well with experimental measurements. It is inferred that the spillage of tip clearance flow, which is inward pushed by higher speed injection with shortened distance away from rotor, could lead to further stable flow field.

The effect of wear ring clearance on flow field in the impeller sidewall gap and efficiency of a low specific speed centrifugal pump

2017 ◽  
Vol 232 (17) ◽  
pp. 3062-3073 ◽  
Author(s):  
M DaqiqShirazi ◽  
R Torabi ◽  
A Riasi ◽  
SA Nourbakhsh
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Volumetric Efficiency ◽  
Centrifugal Pumps ◽  
Disk Friction ◽  
Low Specific Speed ◽  
Overall Efficiency ◽  
Specific Speed

In this paper, the flow in the impeller sidewall gap of a low specific speed centrifugal pump is analyzed to study the effect of wear ring clearance and the resultant through-flow on flow field in this cavity and investigate the overall efficiency of the pump. Centrifugal pumps are commonly subject to a reduction in the flow rate and volumetric efficiency due to abrasive liquids or working conditions, since the wear rings are progressively worn, the internal leakage flow is increased. In the new operating point, the overall efficiency of the pump cannot be predicted simply by using the pump characteristic curves. The flow field is simulated with the use of computational fluid dynamics and the three-dimensional full Navier–Stokes equations are solved using CFX software. In order to verify the numerical simulations, static pressure field in volute casing and pump performance curves are compared with the experimental measurements. The results show that, for the pump with minimum wear ring clearance, the disk friction efficiency is the strongest factor that impairs the overall efficiency. Therefore, when the ring clearance is enlarged more than three times, although volumetric efficiency decreases effectively but the reduction in overall efficiency is remarkably smaller due to improvement in the disk friction losses.

scholarly journals Analysis of Unsteady Flow Characteristics of Centrifugal Pump under Part Load Based on DDES Turbulence Model

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Tang Xin ◽  
Liu Zhili ◽  
Zhao Meng ◽  
Yang Haotian ◽  
Jiang Wei ◽  
...  
Keyword(s):  
Velocity Distribution ◽  
Radial Velocity ◽  
Centrifugal Pump ◽  
Turbulence Model ◽  
Vortex Structure ◽  
Guide Vane ◽  
Load Condition ◽  
Wake Flow ◽  
Part Load ◽  
Load Conditions

To better reveal the mechanism of the rotor-stator interference between the impeller and the guide vane and the evolution process of the stall vortex under the part-load conditions, numerical simulation is carried out based on the DDES turbulence model, which can better capture vortex structure. And the pressure pulsation and the radial velocity distribution of the centrifugal pump are studied. The vortex structure and pressure fluctuation of pump internal flow field under part-load condition of Q = 0.4 Qdes are mainly analyzed. The analysis results show that the stall vortex is formed at the inlet of the impeller and evolves to the outlet of the impeller, the front cover to the rear cover according to the fluid flow direction, and then disappears. Besides, under the part-load condition, the vorticity of the impeller outlet is always obviously less than that of the impeller inlet as the flow rate increases. Due to the asymmetric action of the volute, the radial velocity distribution law of flow channel C1 is different from other flow channels at different blade heights. By analyzing the radial velocity, the phenomenon that the jet-wake flow impacts the guide vane with the rotation of the impeller is the main reason for the rotor-stator interference. And large radial velocity gradients appear at the front and rear cover plates, which will cause high energy loss and reduce pump efficiency. Besides, the conclusion can be drawn that the region with the strongest rotor-stator interference is the inlet region of the guide vane suction surface. It also occurs near the volute tongue but is lower due to the effect of the guide vane. This research may serve as a reference for the safe operation of centrifugal pumps under part-load conditions.

Computational investigation and passive control of vehicle sunroof buffeting

2019 ◽  
Vol 26 (9-10) ◽  
pp. 747-756
Author(s):  
Yansong He ◽  
Quanzhou Zhang ◽  
Changfa An ◽  
Yong Wang ◽  
Zhongming Xu ◽  
...  
Keyword(s):  
Flow Field ◽  
Passive Control ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Simulation Method ◽  
Dynamics Simulation ◽  
The Road ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Utility Vehicle

A computational fluid dynamics simulation method based on large eddy simulation is presented and applied to compute the sunroof buffeting of a sport utility vehicle. The simulation result, i.e. the buffeting level curve, coincides well with the road test. The simulation method is then employed to investigate the sunroof buffeting of a vehicle during the development process in the range of 30 km/h–90 km/h. The results show that the most severe sunroof buffeting occurs at 70 km/h, which corresponds to the resonant frequency of the cabin. Flow field visualizations reveal that strong pressure fluctuations are generated inside the cabin due to vortex shedding from the leading edge and impinging onto the trailing edge of the sunroof opening, which explains the mechanism of sunroof buffeting. A new deflector with a gap and a notched upper edge is designed to replace the original castle type deflector. The simulation results show that the newly designed deflector can reduce the buffeting level to 97.9 dB; that is, the sunroof buffeting is completely eliminated. Moreover, the phenomenon of sunroof buffeting reduction is explained by comparing and analyzing the flow field between the newly designed deflector and the original deflector.

Numerical study on characteristics of unsteady flow in a centrifugal pump volute at partial load condition

2015 ◽  
Vol 32 (6) ◽  
pp. 1549-1566 ◽  
Author(s):  
Lei Tan ◽  
Baoshan Zhu ◽  
Yuchuan Wang ◽  
Shuliang CAO ◽  
Shaobo Gui
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Numerical Study ◽  
Pressure Fluctuations ◽  
Load Condition ◽  
Dominant Frequency ◽  
Content Type ◽  
Cavitation Effect ◽  
Partial Load ◽  
Large Pressure Gradient

Purpose – The purpose of this paper is to elucidate the detailed flow field and cavitation effect in the centrifugal pump volute at partial load condition. Design/methodology/approach – Unsteady flows in a centrifugal pump volute at non-cavitation and cavitation conditions are investigated by using a computation fluid dynamics framework combining the re-normalization group k-e turbulence model and the mass transport cavitation model. Findings – The flow field in pump volute is very complicated at part load condition with large pressure gradient and intensive vortex movement. Under cavitation conditions, the dominant frequency for most of the monitoring points in volute transit from the blade passing frequency to a lower frequency. Generally, the maximum amplitudes of pressure fluctuations in volute at serious cavitation condition is twice than that at non-cavitation condition because of the violent disturbances caused by cavitation shedding and explosion. Originality/value – The detailed flow field and cavitation effect in the centrifugal pump volute at partial load condition are revealed and analysed.

Numerical Simulation of Cavity Flow within the Flow Field

2013 ◽  
Vol 712-715 ◽  
pp. 1259-1262
Author(s):  
Jian Yu Cai ◽  
He Juan Chen
Keyword(s):  
Numerical Simulation ◽  
Temperature Field ◽  
Flow Field ◽  
Centrifugal Pump ◽  
Calculation Method ◽  
Simulation Method ◽  
Cavity Flow ◽  
Mechanical Seal ◽  
Seal Ring ◽  
Temperature And Pressure

Analysis of numerical simulation was used on flow field and temperature field in mechanical seal cavity. It borrowed a new calculation method, which was more visual and simpler than before. And this method analysed the change in temperature field of mechanical seal ring and the distribution of temperature and pressure in the flow field when mechanical seal was working. The result showed that the numerical simulation method was effect to the flow field in centrifugal pump.

Experimental Comparison of Flow Fields at the Inlet and the Outlet of an Inducer With Shrouded and Unshrouded Configurations

1997 ◽  
Vol 119 (4) ◽  
pp. 954-959 ◽  
Author(s):  
C. Offtinger ◽  
C. Henry ◽  
R. Morel ◽  
F. Spettel
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Radial Distribution ◽  
Axial Flow ◽  
Flow Fields ◽  
Experimental Comparison ◽  
Lower Efficiency ◽  
Flow Rates ◽  
Part Load ◽  
Loss Level

The flow field was measured near the inlet and the outlet of an axial flow inducer with shrouded and unshrouded configurations combined with a centrifugal pump. Investigations were conducted using a five-hole probe for several flow rates. The shroud induces a counterrotating flow at the inlet and a blockage effect at the outlet in the region of the tip and for all flow rates. The radial distribution of losses keeps the same shape in both configurations, however, the loss level is higher with the shroud, giving a lower efficiency for the combined inducer-impeller configuration. Effects of shrouded inducer on part load instability are not clear and deserve more research, which is in progress.

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