Influencing the Part Load Recirculation of a Centrifugal Pump and Avoiding an Instability of the Performance Curve Thereby

2015 ◽  
Author(s):  
Tino Mengdehl ◽  
Evgenii Palamarchuk ◽  
Angela Garlach ◽  
Christian Brix Jacobsen ◽  
Paul Uwe Thamsen
Keyword(s):  
Centrifugal Pump ◽  
Recirculation Zone ◽  
Characteristic Curve ◽  
Suction Side ◽  
Pressure Side ◽  
Performance Curve ◽  
Centrifugal Pumps ◽  
Time Resolved ◽  
Part Load ◽  
Impeller Outlet

Centrifugal pumps of low specific speed display an inherent tendency to generate an unstable pump performance curve [1]. These curves are characterized by a head dropping at low flow rates that limits the operational range. Hence, for example centrifugal pumps with such performance curves are not suitable for a usage in firefighting applications or parallel operation. However, there are a few actions that influence positively the stability of the performance curve [1, 2]. One is adding slots at the rear shroud, e.g. on the pressure side or the suction side of the blade. Slots at the pressure side of the blade stabilize the characteristic curve by increasing the head, while suction-side slots stabilize the characteristic curve by dropping it down [2]. The part load flow pattern of a centrifugal pump includes two recirculation zones. The first is located at the inlet of the impeller and caused by the blade suction geometry. The second recirculation zone forms at the outlet of the impeller. It is known that the recirculation zone at the pressure side of a radial impeller has various positions, sizes and structures depending on initial conditions [3]. This paper deals with the assumption that influencing the pressure side recirculation zone leads to a stable pump performance curve. Therefore the structure of the recirculation zone at the impeller outlet is being investigated and analyzed whereas geometrical changes on a centrifugal pump impeller are performed. The tests contain an experimental setup and compare the results to numerical simulations. Subject of the experimental investigations is a centrifugal pump with a specific speed of 33 min−1, a flow rate of 650 m3/h and head of 47 m for the Nominal Point. Measurements are performed for analyzing the time resolved pressure fluctuations and visualizing the flow structures in the volute casing by using pressure transducers and particle image velocimetry (PIV). These data show the changing pressure and velocity field and enable an analyzing of the part load recirculation. Furthermore, the measured operational points and the time resolved pressure data are compared to numerical simulations that are carried out by Computational Fluid Dynamics (hereafter: CFD). The flow pattern gained by CFD allows analyzing the phenomena of the pressure side recirculation in detail, also in areas where the access with measuring instruments is limited. Within the present study different geometrical parameters are subsequently changed on the original impeller design. This concerns, for example, the earlier named slots in the rear shroud both on suction and pressure side of the blade. Results show an influence of these subsequent design methods on the performance curve as well as on the efficiency of the centrifugal pump. Additionally, the time resolved pressure data are used for a validation of the CFD simulations and both results show a significant influence of the flow structure at the impeller outlet on the performance curve. Therefore, it can be shown that the recirculation zone of the impeller is affected by these actions.

scholarly journals Pressure Fluctuation Reduction of a Centrifugal Pump by Blade Trailing Edge Modification

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1408 ◽  
Author(s):  
Bin Huang ◽  
Guitao Zeng ◽  
Bo Qian ◽  
Peng Wu ◽  
Peili Shi ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
Pressure Fluctuation ◽  
Pressure Side ◽  
Centrifugal Pumps ◽  
Trailing Edge ◽  
Impeller Blade ◽  
Blade Passing Frequency ◽  
Impeller Outlet ◽  
Edge Profile ◽  
Edge Trimming

The pressure fluctuation inside centrifugal pumps is one of the main causes of hydro-induced vibration, especially at the blade-passing frequency and its harmonics. This paper investigates the feature of blade-passing frequency excitation in a low-specific-speed centrifugal pump in the perspective of local Euler head distribution based on CFD analysis. Meanwhile, the relation between local Euler head distribution and pressure fluctuation amplitude is observed and used to explain the mechanism of intensive pressure fluctuation. The impeller blade with ordinary trailing edge profile, which is the prototype impeller in this study, usually induces wake shedding near the impeller outlet, making the energy distribution less uniform. Because of this, the method of reducing pressure fluctuation by means of improving Euler head distribution uniformity by modifying the impeller blade trailing edge profile is proposed. The impeller blade trailing edges are trimmed in different scales, which are marked as model A, B, and C. As a result of trailing edge trimming, the impeller outlet angles at the pressure side of the prototype of model A, B, and C are 21, 18, 15, and 12 degrees, respectively. The differences in Euler head distribution and pressure fluctuation between the model impellers at nominal flow rate are investigated and analyzed. Experimental verification is also conducted to validate the CFD results. The results show that the blade trailing edge profiling on the pressure side can help reduce pressure fluctuation. The uniformity of Euler head circumferential distribution, which is directly related to the intensity of pressure fluctuation, is improved because the impeller blade outlet angle on the pressure side decreases and thus the velocity components are adjusted when the blade trailing edge profile is modified. The results of the investigation demonstrate that blade trailing edge profiling can be used in the vibration reduction of low specific impellers and in the engineering design of centrifugal pumps.

Flow Measurements in a Transparent Centrifugal Pump by Using 3-D PIV Technique

2011 ◽  
Author(s):  
Hua Yang ◽  
Ji-ren Zhou ◽  
Fang-ping Tang ◽  
Chao Liu ◽  
Hao-ran Xu
Keyword(s):  
Centrifugal Pump ◽  
Measurement Technique ◽  
Suction Side ◽  
Flow Fields ◽  
Design Flow ◽  
Water Tank ◽  
Pressure Side ◽  
Centrifugal Pumps ◽  
Piv Measurement ◽  
Component Velocity

With the development of laser measurement technique, LDV (Laser Doppler Velocimeter) and PIV (Particle Image Velocimetry) have been widely used to measure the flow fields. Comparison with LDV, PIV is a multiple point measurement technique and the flow fields can be measured convenient. Nowadays, 2-D (two Dimensional) PIV have been used to investigate the flow fields in the centrifugal pump, while 3-D (three Dimensional) PIV is seldom to be used. The reason is that the calibration for 3-D PIV in a small space of centrifugal pumps in very difficult. In this paper, a special water tank was used for 3-D PIV calibration in rotation impeller. The 3-D transient relative velocity in one impeller passage at three axial sections were obtained, when the pump run under the design flow rate. The radial component velocity Wr showed a concave distribution except R = 45 mm. With the increase of radius, the circumference location of minimum Wr moved from the pressure side to the suction side and the tangential component velocity Wθ on the suction side decreases, while on the pressure side increases gradually. The PIV measurement error was investigated based on the mass conservation equation. The maximum error of the PIV measurement was 3.14%, it showed that the test results have higher accuracy and the measured data was reliable.

Part Load Flow and Hydrodynamic Instabilities of a Centrifugal Pump: Part 1 — Experimental Investigations

2015 ◽  
Author(s):  
Laurent Gros ◽  
Anthony Couzinet ◽  
Daniel Pierrat
Keyword(s):  
Centrifugal Pump ◽  
Load Flow ◽  
Experimental Investigations ◽  
Performance Curve ◽  
Centrifugal Pumps ◽  
Transient Phenomena ◽  
Part Load ◽  
Numerical Studies ◽  
Saddle Type ◽  
Operating Points

Rotor-stator interactions have been widely studied for thirty years especially concerning part load operating points. Transient phenomena are mainly the focus of these experimental or numerical studies. Depending on type of centrifugal pumps, an unstable characteristic (saddle-type characteristic) can appear at part load; the consequence is an unstable local head drop of the performance curve and this singularity exhibits a positive slope in the decreasing performance curve. An experimental work is proposed to identify this instability and the investigations led on a high specific speed centrifugal pump have allowed to study the interaction with the upstream circuit and the cavitation, the translation on other speed of rotation and the effect on the vibrations level.

An Experimental Investigation of Flow Fields Within Miniature Scale Centrifugal Pumps

2006 ◽  
Author(s):  
D. Kearney ◽  
J. Punch ◽  
R. Grimes
Keyword(s):  
Centrifugal Pump ◽  
Characteristic Curve ◽  
Flow Fields ◽  
Velocity Profiles ◽  
Heat Fluxes ◽  
Model Verification ◽  
Air Cooling ◽  
Centrifugal Pumps ◽  
Test Bed ◽  
Forced Air

Thermal management has become a key point in the development of contemporary electronics systems. It is evident that heat fluxes are currently approaching the limits of conventional forced air cooling, and that liquid technologies are now under consideration. The objective of this paper is to investigate the flow fields within a miniature scale centrifugal pump in order to determine velocity profiles describing the flow. The experimental setup consisted of a hydrodynamic test bed constructed to measure the pressure-flow characteristic of a centrifugal pump with a rated volumetric flow of 9 l/min. The impeller diameter of the pump under consideration was 34.3mm, and the characterisation experiments were carried out at a constant impeller speed. Particle-Image Velocimetry (PIV) was used to measure velocity profiles within the volute section of the pump. Synchronised velocity profiles are illustrated for three operating points on the pump characteristic curve. A hydrodynamic analysis of the velocity vectors at the impeller tip is also included, and pump model verification is then discussed based on the comparison between the theoretical predictions and the PIV data.

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.

Effects of Centrifugal Pumps Outlet Angle on Flow Induced Vibration and Noise

2012 ◽  
Vol 249-250 ◽  
pp. 460-465 ◽  
Author(s):  
Yong Wang ◽  
Jian Wang ◽  
Dong Xi Liu ◽  
Hou Lin Liu
Keyword(s):  
Centrifugal Pump ◽  
Virtual Instrument ◽  
Noise Signal ◽  
Centrifugal Pumps ◽  
Flow Induced Vibration ◽  
Vibration Intensity ◽  
Minimum Value ◽  
Outlet Angle ◽  
Frequency Peak ◽  
Impeller Outlet

In order to research the effects of impeller outlet angles on flow induced vibration and noise of centrifugal pumps, a single grade end suction centrifugal pump is employed as a research object. The outlet angles were varied from 33° to 29°and 37°, but the volute and the other geometric parameters keep constant. Based on the virtual instrument data acquisition system, pump product testing system and in the centrifugal pump closed experimental rig, the flow induced vibration and noise signals of model pump with different outlet angles in the full flow range are measured and analyzed. Experimental results show that the influence of flow induced vibration on volute is the largest. With the increase of impeller outlet angle, the variation tendency of vibration intensity for 4 measure points decrease. The vibration intensity of model pump gets the minimum value, when the outlet angle is 37°. Under different conditions, the shaft frequency peak of noise signal varied intricately with the increase of impeller outlet angle. When the outlet angle is 33°, the shaft frequency peak of the model pump is relatively small under each operating condition, and gets the minimum value at the design condition.

Numerical Simulation of Hysteresis on Head/Discharge Characteristics of a Centrifugal Pump

2003 ◽  
Author(s):  
Masamichi Iino ◽  
Kazuhiro Tanaka ◽  
Kazuyoshi Miyagawa ◽  
Takeshi Okubo
Keyword(s):  
Numerical Simulation ◽  
Hysteresis Loop ◽  
Centrifugal Pump ◽  
Characteristic Curve ◽  
Swirl Flow ◽  
Centrifugal Pumps ◽  
Pump Impeller ◽  
Discharge Characteristics ◽  
Discharge Characteristic ◽  
Partial Load

The objectives of the present study were to investigate influences of fins, set in a suction part, on the positive slope and hysteresis loop in head/discharge characteristic curves of centrifugal pumps in the experiment as well as in the numerical prediction. The fins were located in upstream side of a pump impeller to suppress swirl flow occurring before the impeller inlet at partial load operation. We had two kinds of centrifugal pump with/without the fins, the number of which is 16. These two centrifugal pumps had a shrouded impeller with 7 blades and a diffuser with 20 guide vanes with the same configuration. In the experiment, the pump with them had a large hysteresis loop at partial load operation in the head/discharge characteristic curve, although the pump without them had no hysteresis loop. In the numerical simulation based on periodic flow, the incompressible turbulent flow field was calculated for partial blade-passages with periodic boundary conditions. As a result, the simulated characteristics had the same tendencies as the experimental results. Furthermore, the causes of the discontinuous head/discharge characteristics depending on the direction of partial load operation were clarified through calculating and comparing the internal flow fields in the cases with/without the fins. The pumps had the large backflow and recirculation areas in two places, one of which was near the shroud at the impeller inlet including the fins area and another near the central part of the diffuser. The difference in the hysteresis loop between with and without the fins was caused by the existence of the fins, which suppressed or promoted the backflow at the impeller.

scholarly journals Comparison of energy parameters of a centrifugal pump with a multi-piped impeller in cooperation either with an annular channel and a spiral channel

2018 ◽  
Vol 8 (1) ◽  
pp. 513-522 ◽  
Author(s):  
Bartłomiej Chomiuk ◽  
Janusz Skrzypacz
Keyword(s):  
Centrifugal Pump ◽  
Annular Channel ◽  
Operating Parameters ◽  
Centrifugal Pumps ◽  
Impeller Outlet ◽  
Flow Geometry ◽  
Quantitative Verification ◽  
Flow Through ◽  
Low Specific Speed ◽  
Specific Speed

Abstract The article presents results of numerical analyzes, which raise a subject of influence of the cooperation the multi-piped impeller with a rationalized flow geometry of annular casing and volute casing for liquid flow through centrifugal pump and their operating parameters in the extremely low specific speed nq<10. The multi-piped impeller (patented by authors) is a major alternative to classic vane impellers. The stator type is responsible for the conversion of the kinetic energy of the liquid by the impeller outlet into potential energy, which determines the overall efficiency of the pump. Also, the article presents qualitative and quantitative verification of results obtained by computer modeling and an attempt to estimate their accuracy. The article focuses mainly on the comparison of the performance parameters of the pump with a multi-piped impeller in cooperation with two stator types with a rationalized flow geometry. Both outlet elements were tested in various configurations of constructional features. The complexity of the construction of the stator can significantly affect the manufacturing costs of pump unit. Knowledge concerning construction of hydraulic elements of centrifugal pumps working in the range of parameters corresponding specific speed (nq<10) is insufficient. As shown in the paper, the annular type casing model pump cooperating with a multi-piped impeller, designed in accordance with literature, reached far poorer operating parameters than the rational annular construction in a configuration with the same impeller.

Film Cooling Jet Injection Effect in Heat Transfer Coefficient Augmentation for the Pressure Side Cooling of Turbine Vane

2014 ◽  
Author(s):  
Hossein Nadali Najafabadi ◽  
Matts Karlsson ◽  
Mats Kinell ◽  
Esa Utriainen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Suction Side ◽  
Pressure Side ◽  
Time Resolved ◽  
Turbine Vane

Improving film cooling performance of turbine vanes and blades is often achieved through application of multiple arrays of cooling holes on the suction side, the showerhead region and the pressure side. This study investigates the pressure side cooling under the influence of single and multiple rows of cooling in the presence of a showerhead from a heat transfer coefficient augmentation perspective. Experiments are conducted on a prototype turbine vane working at engine representative conditions. Transient IR thermography is used to measure time-resolved surface temperature and the semi-infinite method is utilized to calculate the heat transfer coefficient on a low conductive material. Investigations are performed for cylindrical and fan-shaped holes covering blowing ratio 0.6 and 1.8 at density ratio of about unity. The freestream turbulence is approximately 5% close to the leading edge. The resulting heat transfer coefficient enhancement, the ratio of HTC with to that without film cooling, from different case scenarios have been compared to showerhead cooling only. Findings of the study highlight the importance of showerhead cooling to be used with additional row of cooling on the pressure side in order to reduce heat transfer coefficient enhancement. In addition, it is shown that extra rows of cooling will not significantly influence heat transfer augmentation, regardless of the cooling hole shape.

Effects of Blade Pressure Side Modification On Unsteady Pressure Pulsation and Flow Structures in a Centrifugal Pump

2021 ◽  
Author(s):  
Chengshuo Wu ◽  
Wenqi Zhang ◽  
Peng Wu ◽  
Jiale Yi ◽  
Haojie Ye ◽  
...  
Keyword(s):  
Velocity Distribution ◽  
Centrifugal Pump ◽  
Pressure Pulsation ◽  
Internal Flow ◽  
Flow Structures ◽  
Pressure Side ◽  
Unsteady Pressure ◽  
Operation Conditions ◽  
Impeller Outlet ◽  
Steady State Simulation

Abstract In this paper, the effects of modifying the blade pressure side on unsteady pressure pulsation and flow structures in a low specific speed centrifugal pump are carried out by experimental and CFD. Seven monitor points are arranged in the circumferential direction of the impeller outlet to capture the pressure signals in the volute at the flow rate of 0.2-1.6Qd. Results show that blade PS modification introduced here can significantly alleviate the amplitude of pressure pulsation at blade passing frequency in all concerned operation conditions. The volute domain is replaced by an even outlet region for CFD analysis to study the effects on internal flow field. The SST turbulence model is adopted for steady-state simulation while the DDES based on the SST approach is adopted for transient simulation. Results show that local velocity fluctuation is the dominant reason for pressure pulsation in the volute. After PS modification, the relative velocity distribution at impeller outlet is more uniform and the intensity of shedding vortex at the blade trailing edge decreases significantly. The change of internal flow structure improves the uniformity of circumferential velocity distribution at downstream of impeller outlet, which leads to the decrease of pressure fluctuation amplitude in the volute. Meanwhile, the Local Euler Head distribution and the blade loading of PS are presented and compared. Results show that the reduction of pressure pulsation attributes to the more uniform energy distribution at impeller outlet which is achieved by actively unloading the PS of the modified blades.

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