A Study of Cavitation Flow in a Centrifugal Pump at Part Load Conditions Based on Numerical Analysis

2012 ◽  
Author(s):  
Jianping Yuan ◽  
Yanxia Fu ◽  
Shouqi Yuan
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Suction Side ◽  
Cavitation Number ◽  
Flow Coefficient ◽  
Inlet Pipe ◽  
Part Load ◽  
Cavitation Inception ◽  
Wide Range ◽  
Load Conditions

In order to predict cavitation performance of the centrifugal pump, including cavitating structures and vapour volume at the blade suction side, as well as its relationship with the backflow in the impeller eye, a 3D numerical simulation of detailed steady and unsteady cavitating flow was applied to reproduce its inner flow fields at part load conditions (0.5Qd and 0.4Qd). The comparisons of cavitation characteristics of the current centrifugal pump at an on-design point (1.0Qd) and a high flow rate (1.2Qd) were achieved as well. In addition, Frequency analysis of pressure fluctuations at the blade passages and the inlet pipe were also obtained during cavitation for a flow coefficient of 50%. The results further show that successive blade cavitation patterns and the creeping cavitation number dropping appear for a wide range of flow rates when the inlet total pressure decreases from cavitation inception to the breakdown of the centrifugal pump, as is quite different from that when cavitation occurs at 1.0Qd or 1.2Qd. Unbalanced attached cavities on the blade suction side were also observed at 0.5Qd. Meanwhile, the unsteady behaviour of cavities attached to the blade suction side and cavitation number dropping depend on the flow rate and cavitation number. Another significant characteristic of the phenomenon is that all the domain frequencies in blade passages and inlet pipe at part load conditions are 0.048Hz∼48.285Hz, which is typically lower than the shaft rotational frequency of the model centrifugal pump.

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.

scholarly journals Numerical Analysis of Cavitation Instabilities In Inducer Blade Cascade

2005 ◽  
Author(s):  
Benoiˆt Pouffary ◽  
Regiane Fortes Patella ◽  
Jean-Luc Reboud
Keyword(s):  
Flow Rate ◽  
Rocket Engine ◽  
Suction Side ◽  
Cavitation Number ◽  
Vapor Mixture ◽  
Cavitation Model ◽  
Flow Parameters ◽  
Blade Cascade ◽  
Cavitation Behavior ◽  
Unsteady Behavior

The cavitation behavior of a four-blade rocket engine turbopump inducer was simulated by the CFD code Fine/TurboTM. The code was modified to take into account a cavitation model based on a homogeneous approach of cavitation, coupled with a barotropic state law for the liquid/vapor mixture [1–4]. In the present study, the numerical model of unsteady cavitation was applied to a four-blade cascade drawn from the inducer geometry. Unsteady behavior of cavitation sheets attached to the inducer blade suction side depends on the flow rate and cavitation number σ. Numerical simulations of the transient evolution of cavitation on the blade cascade were performed for nominal flow rate and different cavitation numbers, taking into account simultaneously the four blade-to-blade channels. Depending on the flow parameters, steady or unsteady behaviors spontaneously take place. In unsteady cases, sub synchronous or super synchronous regimes were observed. Some mechanisms responsible for the development of these instabilities are proposed and discussed.

Flow at the Tip of a Forward Curved Centrifugal Fan

1984 ◽  
Author(s):  
A. Goulas ◽  
B. Mealing
Keyword(s):  
Flow Rate ◽  
Rotational Speed ◽  
Reverse Flow ◽  
Suction Side ◽  
Flow Coefficient ◽  
Low Flow ◽  
Centrifugal Fan ◽  
Single Vortex ◽  
Curvature Effects ◽  
Corner Vortex

The velocity profiles, radial and circumferential components, were measured at the tip of a forward curved centrifugal fan. Three sets of measurements are presented. Two at peak efficiency for different rotational speeds and a third at the lower rotational speed and for a reduced flow rate. A reverse flow region was formed near the hub, and almost in the middle, between pressure and suction sides of the blade. Near the shroud a high velocity region was observed and a low one near the suction side, picture similar to the jet-wake structure found in the literature. At the lower rotational speed and low flow rate the flow was affected mainly by the system rotation. A “wake” was formed along the suction side of the blade. Increasing the flow rate blade curvature effects became more dominant. Increasing the rotational speed and for the same flow coefficient the system of two vortices observed in the previous case disappears and a single vortex takes its place. In this case the wake is positioned on the hub. Corner vortices also affect the main flow by changing the turbulence intensities. A corner vortex observed on the pressure side reduced the turbulence intensities in the region and a wake was formed locally. However, another corner vortex on the suction side caused an increase to the local turbulence intensities and consequently a high local velocity.

Experimental Investigation on Diffuser Rotating Stall in a Three-Stage Centrifugal Pump

2017 ◽  
Author(s):  
Taiki Takamine ◽  
Satoshi Watanabe ◽  
Daichi Furukawa ◽  
Hiroyoshi Watanabe ◽  
Kazuyoshi Miyagawa
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Suction Side ◽  
Rotating Stall ◽  
Leakage Flow ◽  
The Troubles ◽  
Second Stage ◽  
The Third ◽  
Shaft System ◽  
Third Stage

Rotating stall phenomenon frequently causes the troubles such as vibrations acting on the shaft system and reduces the reliability of turbomachines. In the present study, the diffuser rotating stall in a three-stage centrifugal pump was experimentally studied. Special emphasises were placed on the geometrical conditions; an axial offset of rotor against the stationary part, which might be unavoidable due to accumulation of geometrical tolerances and assembling errors., and the radial clearances of annular leakage paths which increases the thru-flow rate at the impellers and the first and second stage diffusers. As a result, with the rotor axial offset to the suction side, the rotating stall appeared only at the third stage diffuser, while with that to the discharge side, the rotating stall was more significant. By enlarging the leakage flow passages at the inter-stage bush and the balancing flow channel, the onset range of rotating stall became narrower in the first and second stage diffusers, which was well explained by the increase of the thru-flow rate. On the other hand, with the enlarged leakage passage at the liner ring, the onset range became slightly wider.

scholarly journals Numerical Analysis of Cavitation Instabilities in Inducer Blade Cascade

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Benoît Pouffary ◽  
Regiane Fortes Patella ◽  
Jean-Luc Reboud ◽  
Pierre-Alain Lambert
Keyword(s):  
Flow Rate ◽  
Rocket Engine ◽  
Suction Side ◽  
Cavitation Number ◽  
Vapor Mixture ◽  
Cavitation Model ◽  
Flow Parameters ◽  
Blade Cascade ◽  
Computational Fluid Dynamics Cfd ◽  
Cavitation Behavior

The cavitation behavior of a four-blade rocket engine turbopump inducer was simulated by the computational fluid dynamics (CFD) code FINE∕TURBO™. The code was modified to take into account a cavitation model based on a homogeneous approach of cavitation, coupled with a barotropic state law for the liquid∕vapor mixture. In the present study, the numerical model of unsteady cavitation was applied to a four-blade cascade drawn from the inducer geometry. Unsteady behavior of cavitation sheets attached to the inducer blade suction side depends on the flow rate and cavitation number σ. Numerical simulations of the transient evolution of cavitation on the blade cascade were performed for the nominal flow rate and different cavitation numbers, taking into account simultaneously the four blade-to-blade channels. Depending on the flow parameters, steady or unsteady behaviors spontaneously take place. In unsteady cases, subsynchronous or supersynchronous regimes were observed. Some mechanisms responsible for the development of these instabilities are proposed and discussed.

Measurements of Axial and Radial Thrust Forces Working on a Three-Stages Centrifugal Pump Rotor

2015 ◽  
Author(s):  
Tetsuya Yamashita ◽  
Satoshi Watanabe ◽  
Yoshinori Hara ◽  
Hiroyoshi Watanabe ◽  
Kazuyoshi Miyagawa
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Axial Direction ◽  
Low Flow ◽  
Axial Thrust ◽  
Rate Range ◽  
Wide Range ◽  
Flow Rate Range ◽  
Three Stages ◽  
Thrust Forces

In this study, radial and axial thrust forces working on the whole rotor in a three-stages centrifugal pump are measured in a wide range of flow rate. The forces are measured at two floating journal bearings and one floating ball bearing, which are supported by the individual load cells. The effects of the offset of rotor position in the axial direction on the thrust forces are investigated. It is found that the effect of the axial offset is significant for the axial thrust force in the low flow rate range, whereas it has little influence on the head and efficiency performances in the whole flow rate range.

A Numerical Investigation of Loss Coefficient Variation in Various Incidence Angles in Tandem Blades Cascade

2014 ◽  
Author(s):  
Arash Soltani Dehkharqani ◽  
Masoud Boroomand ◽  
Hamzeh Eshraghi
Keyword(s):  
Pressure Ratio ◽  
Axial Flow ◽  
Suction Side ◽  
Loss Coefficient ◽  
Flow Coefficient ◽  
Flow Angle ◽  
Multi Stage ◽  
Wide Range ◽  
And Performance ◽  
Flow Compressor

There is a severe tendency to reduce weight and increase power of gas turbine. Such a requirement is fulfilled by higher pressure ratio of compressor stages. Employing tandem blades in multi-stage axial flow compressors is a promising methodology to control separation on suction sides of blades and simultaneously implement higher turning angle to achieve higher pressure ratio. The present study takes into account the high flow deflection capabilities of the tandem blades consisting of NACA-65 airfoil with fixed percent pitch and axial overlap at various flow incidence angles. In this regard, a two-dimensional cascade model of tandem blades is constructed in a numerical environment. The inlet flow angle is varied in a wide range and overall loss coefficient and deviation angles are computed. Moreover, the flow phenomena between the blades and performance of both forward and afterward blades are investigated. At the end, the aerodynamic flow coefficient of tandem blades are also computed with equivalent single blades to evaluate the performance of such blades in both design and off-design domain of operations. The results show that tandem blades are quite capable of providing higher deflection with lower loss in a wide range of operation and the base profile can be successfully used in design of axial flow compressor. In comparison to equivalent single blades, tandem blades have less dissipation because the momentum exerted on suction side of tandem blades confines the size of separation zone near trailing edges of blades.

Secondary Flows in Centrifugal Pump Impellers: PIV Measurements and CFD Computations

2009 ◽  
Author(s):  
R. W. Westra ◽  
L. Broersma ◽  
K. van Andel ◽  
N. P. Kruyt
Keyword(s):  
Reynolds Number ◽  
Centrifugal Pump ◽  
Flow Rate ◽  
Stokes Equations ◽  
Suction Side ◽  
Velocity Profiles ◽  
Secondary Flows ◽  
Design Flow ◽  
Low Velocity ◽  
Flow Rates

Two-dimensional Particle Image Velocimetry measurements and three-dimensional Computational Fluid Dynamics (CFD) analyses have been performed of the flow field inside the impeller of a low specific-speed centrifugal pump operating with a vaneless diffuser. Flow rates ranging from 80% to 120% of the design flow rate are considered in detail. It is observed from the velocity measurements that secondary flows occur. These flows result in the formation of regions of low velocity near the intersection of blade suction side and shroud. The extent of this jet-wake structure decreases with increasing flow rate. Velocity profiles have also been computed from Reynolds-averaged Navier-Stokes equations with the Spalart-Allmaras turbulence model, using a commercial CFD-code. For the considered flow rates the qualitative agreement between measured and computed velocity profiles is very good. Overall, the average relative difference between these velocity profiles is around 7%. Additional CFD computations have been performed to assess the influence of Reynolds number and shape of the inlet velocity profile on the computed velocity profiles. It is found that the influence of Reynolds number is mild. The shape of the inlet profile only has a weak effect at the shroud.

scholarly journals Analysis of Bulb Turbine Hydrofoil Cavitation

2021 ◽  
Vol 11 (6) ◽  
pp. 2639
Author(s):  
Andrej Podnar ◽  
Marko Hočevar ◽  
Lovrenc Novak ◽  
Matevž Dular
Keyword(s):  
Regression Model ◽  
Flow Characteristics ◽  
Suction Side ◽  
Cavitation Number ◽  
Design Parameters ◽  
Cavitation Inception ◽  
Measuring Station ◽  
Runner Blade ◽  
Cavitation Tunnel ◽  
Bulb Turbine

The influence of a bulb runner blade hydrofoil shape on flow characteristics around the blade was studied. Experimental work was performed on a bulb turbine measuring station and a single hydrofoil in a cavitating tunnel. In the cavitation tunnel, flow visualization was performed on the hydrofoil’s suction side. Cavitation structures were observed for several cavitation numbers. Cavitation was less intense on the modified hydrofoil than on the original hydrofoil, delaying the cavitation onset by several tenths in cavitation number. The results of the visualization in the cavitation tunnel show that modifying the existing hydrofoil design parameters played a key role in reducing the cavitation inception and development, as well as the size of the cavitation structures. A regression model was produced for cavitation cloud length. The results of the regression model show that cavitation length is dependent on Reynolds’s number and the cavitation number. The coefficients of determination for both the existing and modified hydrofoils were reasonably high, with R2 values above 0.95. The results of the cavitation length regression model also confirm that the modified hydrofoil exhibits improved the cavitation properties.

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