The Flow Structure During Onset and Developed States of Rotating Stall Within a Vaned Diffuser of a Centrifugal Pump

2001 ◽  
Vol 123 (3) ◽  
pp. 490-499 ◽  
Author(s):  
Manish Sinha ◽  
Ali Pinarbasi ◽  
Joseph Katz
Keyword(s):  
Centrifugal Pump ◽  
High Speed ◽  
Reverse Flow ◽  
Propagation Rate ◽  
Rotating Stall ◽  
Leakage Flow ◽  
Impeller Blade ◽  
Vaned Diffuser ◽  
Exit Side ◽  
Low Pass

Particle Image Velocimetry (PIV) and pressure fluctuation measurements are used for investigating the onset and development of rotating stall within a centrifugal pump having a vaned diffuser. The experiments are performed in a facility that enables measurements between the diffuser vanes, within part of the impeller, in the gap between them and in the volute. The diffuser is also instrumented with pressure transducers that track the circumferential motion of rotating stall in the stator. The timing of low-pass-filtered pressure signals are also used for triggering the acquisition of PIV images. The data include detailed velocity distributions, instantaneous and phase-averaged, at different blade orientations and stall phases, as well as auto- and cross-spectra of pressure fluctuations measured simultaneously in neighboring vane passages. The cross-spectra show that the stall propagation rate is 0.93 Hz, 6.2 percent of the impeller speed, and that the stall travels from the passages located on the exit side of the volute toward the beginning side, crossing the tongue region in the same direction as the impeller, where it diminishes. Under stall conditions the flow in the diffuser passage alternates between outward jetting, when the low-pass-filtered pressure is high, to a reverse flow, when the filtered pressure is low. Being below design conditions, there is a consistent high-speed leakage flow in the gap between the impeller and the diffuser from the exit side to the beginning of the volute. Separation of this leakage flow from the diffuser vane causes the onset of the stall. The magnitude of the leakage and the velocity distribution in the gap depend on the orientation of the impeller blade. Conversely, the flow in a stalled diffuser passage and the occurrence of stall do not vary significantly with blade orientation. With decreasing flow-rate the magnitudes of leakage and reverse flow within a stalled diffuser passage increase, and the stall-cell size extends from one to two diffuser passages.

Numerical simulation of the stalled flow within a vaned centrifugal pump

2004 ◽  
Vol 218 (4) ◽  
pp. 425-435 ◽  
Author(s):  
K M Guleren ◽  
A Pinarbasi
Keyword(s):  
Numerical Simulation ◽  
Centrifugal Pump ◽  
High Speed ◽  
Stokes Equations ◽  
Reverse Flow ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Navier Stokes Equations ◽  
Low Pass

The main goal of the present work is to analyse the numerical simulation of a centrifugal pump by solving Navier-Stokes equations, coupled with the ‘standard k-∊’ turbulence model. The pump consists of an impeller having five curved blades with nine diffuser vanes. The shaft rotates at 890r/min. Flow characteristics are assumed to be stalled in the appropriate region of flowrate levels of 1.31-2.861/s. Numerical analysis techniques are performed on a commercial FLUENT package program assuming steady, incompressible flow conditions with decreasing flowrate. Under stall conditions the flow in the diffuser passage alternates between outward jetting when the low-pass-filtered pressure is high to a reverse flow when the filtered pressure is low. Being below design conditions, there is a consistent high-speed leakage flow in the gap between the impeller and the diffuser from the exit side of the diffuser to the beginning of the volute. Separation of this leakage flow from the diffuser vane causes the onset of stall. As the flowrate decreases both the magnitude of the leakage within the vaneless part of the pump and reverse flow within a stalled diffuser passage increase. As this occurs, the stall-cell size extends from one to two diffuser passages. Comparisons are made with experimental data and show good agreement.

Entropy production analysis for the clocking effect between inducer and impeller in a high-speed centrifugal pump

2019 ◽  
Vol 233 (15) ◽  
pp. 5302-5315 ◽  
Author(s):  
Baofeng Yang ◽  
Bin Li ◽  
Hui Chen ◽  
Zhanyi Liu
Keyword(s):  
Entropy Production ◽  
Centrifugal Pump ◽  
High Speed ◽  
Rocket Engine ◽  
Leading Edge ◽  
Entropy Production Rate ◽  
Pump Efficiency ◽  
Impeller Blade ◽  
Turbulent Dissipation ◽  
Production Analysis

The clocking effect between the inducer and the impeller has a certain impact on the performance of the high-speed centrifugal pump, which however, is often ignored by designers. In the present study, three-dimensional numerical simulation based on Reynolds-averaged Navier–Stokes method is adopted to evaluate the influence of this clocking effect on the performance of a full-scale liquid rocket engine oxygen turbopump. A novel entropy production method with the correction of wall effects was introduced to evaluate the energy loss generated in the pump and to clarify the formation mechanism of this clocking effect from the perspective of the second law of thermodynamics. Results show that the best performance is captured when the relative circumferential angle between the inducer blade trailing edge and the impeller blade leading edge was set as 0° and the maximum difference in pump efficiency is approximately 1.5% at different clocking positions. The entropy production analysis of each component of the pump reveals that the clocking effect on the pump performance mainly originates from the turbulent dissipation in the impeller and the diffuser. The study of the local entropy production rate and the streamline distributions shows that the formation of this clocking effect is owing to the different extent of the separation vortices in the impeller passage near the shroud and the impeller blade wake in the diffuser inlet as well as the backflow vortices in the diffuser blade passage near the volute tongue.

Investigation of Internal Flow and Characteristic Instability of a Mixed Flow Pump

2009 ◽  
Author(s):  
Masahiro Miyabe ◽  
Akinori Furukawa ◽  
Hideaki Maeda ◽  
Isamu Umeki
Keyword(s):  
Flow Rate ◽  
Internal Flow ◽  
Rotating Stall ◽  
Leakage Flow ◽  
Suction Surface ◽  
Mixed Flow ◽  
Vaned Diffuser ◽  
Flow Angle ◽  
Pressure Surface ◽  
Flow Pump

The relationship between pump characteristic instabilities and internal flow was investigated in a mixed flow pump with specific speed of 700 (min−1 m3/min, m) or 1.72 (non-dimensional) by using a commercial CFD code and a dynamic PIV (DPIV) measurement. This pump has two positive slopes of a head-flow characteristic at the flow rates of about 60%Qopt and 82%Qopt. In the authors’ previous study, it was clarified that the characteristic instability at 82%Qopt is caused by the diffuser rotating stall (DRS) and the backflow near the hub of the vaned diffuser plays an important role on the onset of the diffuser rotating stall. In the present paper, the investigation is focused on the instability at about 60% Qopt. Based on both of experimental and numerical results, it was clarified that the characteristic instability at 60%Qopt is caused by the backflow at the inlet of the impeller tip and the leakage flow from the impeller pressure surface to the suction surface plays an important role on the onset of the backflow. The behaviors of backflow at the impeller inlet were visualized by the DPIV measurements and CFD simulation. Moreover, internal flow was investigated in detail and the occurrence of characteristic instability is assumed as follows: At the partial flow rate, the flow angle at the inlet of the impeller tip decreases and the flow hits the impeller pressure surface. Then, the blade loading at the inlet of impeller tip is increased and the recirculation at the leading edge and the leakage flow rate from pressure surface to suction surface increases. The leakage flow causes to generate vortices at the inlet of the suction surface of the impeller. As the flow rate is further decreased, the vortices develop to backflow with swirl. The leakage flow has peripheral component of absolute velocity and the swirling energy is continuously supplied by the backflow. Therefore, even the passage flow at the inlet of the impeller has been getting pre-swirling. The theoretical head, the Euler head is decreased due to the pre-swirling. Moreover, based on the CFD results, the pre-swirling and unsteady vortices near the suction surface of the impeller causes pump characteristic instability. When the flow rate is decreased further more, total head rises because the flow pattern in the impeller changes to centrifugal type due to the backflow from the vaned diffuser at the hub region.

Jet, Wake and Intrinsic Motion in Impellers of Centrifugal Compressors

1996 ◽  
Author(s):  
Y. N. Chen ◽  
U. Seidel ◽  
U. Haupt ◽  
M. Rautenberg
Keyword(s):  
Reverse Flow ◽  
Vortex Pair ◽  
Leading Edge ◽  
Rotating Stall ◽  
Secondary Flows ◽  
Low Flow ◽  
Experimental Result ◽  
Vaned Diffuser ◽  
Measured Velocity ◽  
Intrinsic Motion

It was shown in a previous paper of the authors (1991) that jet and wake in the flow of the impeller of the centrifugal compressor are developed from the Dean’s type vortex pair formed in the curvature of the blade channel. The jet rotating against the sense of the impeller is weakened, and the wake rotating in the sense of the impeller is enhanced during travelling with the flow toward the outlet. This property is attributed to the conservation of the potential vorticity of the vortex. The experimental result obtained by Krain (1984) has confirmed this theory. The secondary flows found by Farge and Johnson (1990) enable the determination of the vorticity of the wake at the outlet of the impeller. It amounts to 6.9 Ω and 5.8 Ω for the radial-blading and the 60°-backswept blading impeller, respectively. The intensity of the vortex jet is weakened to undetectable value for both the impellers. The patterns of these secondary flow fields are also quite different between these two kinds of impellers. Whilst that of the former is controlled by the intrinsic motion, that of the latter is governed by the relative velocity along the blades. Furthermore, the experimental result obtained by the injection of colored dye at the impeller outlet and the measured velocity field around the impeller reveal an intense reverse flow in the radial blading impeller, travelling from the outlet toward the inlet, along the shroud. It can be shown that this reverse flow is caused by the intrinsic motion occuring in this impeller and impinging on the leading edge of the diffuser vane. As the rotating stall is introduced by the reverse flow, the low-solidity vaned diffuser, and still better the vaneless diffuser can therefore shift the stall line to a very low flow rate.

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.

Spike and Modal Stall Inception in an Advanced Turbocharger Centrifugal Compressor

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Z. S. Spakovszky ◽  
C. H. Roduner
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Pressure Ratio ◽  
Pressure Sensors ◽  
Rotating Stall ◽  
Vaned Diffuser ◽  
Stall Inception ◽  
Compression System ◽  
The Impact ◽  
Highly Loaded

In turbocharger applications, bleed air near the impeller exit is often used for secondary flow systems to seal bearing compartments and to balance the thrust load on the bearings. There is experimental evidence that the performance and operability of highly-loaded centrifugal compressor designs can be sensitive to the amount of bleed air. To investigate the underlying mechanisms and to assess the impact of bleed air on the compressor dynamic behavior, a research program was carried out on a preproduction, 5.0 pressure ratio, high-speed centrifugal compressor stage of advanced design. The investigations showed that bleed air can significantly reduce the stable flow range. Compressor rig experiments, using an array of unsteady pressure sensors and a bleed valve to simulate a typical turbocharger environment, suggest that the path into compression system instability is altered by the bleed flow. Without the bleed flow, the prestall behavior is dominated by short-wavelength disturbances, or so called “spikes,” in the vaneless space between the impeller and the vaned diffuser. Introducing bleed flow at the impeller exit reduces endwall blockage in the vaneless space and destabilizes the highly-loaded vaned diffuser. The impact is a 50% reduction in stable operating range. The altered diffuser characteristic reduces the compression system damping responsible for long-wavelength modal prestall behavior. A four-lobed backward traveling rotating stall wave is experimentally measured in agreement with calculations obtained from a previously developed dynamic compressor model. In addition, a self-contained endwall blockage control strategy was employed, successfully recovering 75% of the loss in surge-margin due to the bleed flow and yielding a one point increase in adiabatic compressor efficiency.

Spike and Modal Stall Inception in an Advanced Turbocharger Centrifugal Compressor

2007 ◽  
Author(s):  
Z. S. Spakovszky ◽  
C. H. Roduner
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Pressure Ratio ◽  
Pressure Sensors ◽  
Rotating Stall ◽  
Vaned Diffuser ◽  
Stall Inception ◽  
Compression System ◽  
The Impact ◽  
Highly Loaded

In turbocharger applications bleed air near the impeller exit is often used for secondary flow systems to seal bearing compartments and to balance the thrust load on the bearings. There is experimental evidence that the performance and operability of highly loaded centrifugal compressor designs can be sensitive to the amount of bleed air. To investigate the underlying mechanisms and to assess the impact of bleed air on the compressor dynamic behavior, a research program was carried out on a pre-production, 5.0 pressure ratio, high-speed centrifugal compressor stage of advanced design. The investigations showed that bleed air can significantly reduce the stable flow range. Compressor rig experiments, using an array of unsteady pressure sensors and a bleed valve to simulate a typical turbocharger environment, suggest that the path into compression system instability is altered by the bleed flow. Without bleed flow, the pre-stall behavior is dominated by short wavelength disturbances, or so called ‘spikes’, in the vaneless space between the impeller and the vaned diffuser. Introducing bleed flow at impeller exit reduces endwall blockage in the vaneless space and destabilizes the highly-loaded vaned diffuser. The impact is a 50% reduction in stable operating range. The altered diffuser characteristic reduces the compression system damping responsible for long wavelength, modal pre-stall behavior. A four-lobed backward traveling rotating stall wave is experimentally measured, in agreement with calculations obtained from a previously developed dynamic compressor model. In addition, a self-contained, endwall blockage control strategy was employed, successfully recovering 75% of the loss in surge-margin due to bleed flow and yielding a 1 point increase in adiabiatic compressor efficiency.

Investigation on the effect of complex impeller on vibration characteristics for a high-speed centrifugal pump

2019 ◽  
Vol 234 (5) ◽  
pp. 611-624 ◽  
Author(s):  
Ye Yuan ◽  
Shouqi Yuan ◽  
Lingdi Tang
Keyword(s):  
Centrifugal Pump ◽  
High Speed ◽  
Internal Flow ◽  
Vibration Characteristics ◽  
Water Addition ◽  
Impeller Blade ◽  
Time Frequency ◽  
Blade Passing Frequency ◽  
Experimental Apparatus ◽  
Complex Impeller

In this article, to improve the vibration characteristics of a high-speed centrifugal pump, two new types of complex impeller were designed for replacing the original long-blade impeller. The experimental apparatus of pump vibration was designed and used to test the vibration signals of the model pump with the original impeller in frequency field. The vibration amplitude of 0.12 mm/s2 is observed on the shaft rotating frequency, while the amplitudes of 0.04 mm/s2, 0.14 mm/s2, and 0.2 mm/s2 respectively on the conditions of 0.8 QN, QN, and 1.2 QN appear on the impeller blade passing frequency. The computational fluid dynamics method was used to study internal flow characteristics in the pumps with three impellers for mitigating the pump vibration. Steady pressure nephogram shows big pressure difference existed in the complex-impeller pump, which means that the complex impeller can provide the high-lift water. Addition of the splitter blade can make the pressure-fluctuation amplitude of model pump to reduce obviously by the unsteady time–frequency analyses. Furthermore, two complex impellers were machined and used to conduct the contrast experiment on the vibration characteristics between the pumps with the original impeller and complex impeller. The results reveal that the water head of pump with the complex impeller is higher than that of the original pump, which verifies the simulated results. Meanwhile, the complex impeller has a positive effect on the decrease of pump vibration on the frequency domain, especially on the blade passing frequency the vibration amplitudes decrease by 0.08 mm/s2.

Rotating stall characteristics in the vaned diffuser of a centrifugal pump

2021 ◽  
Vol 229 ◽  
pp. 108955
Author(s):  
Jianjun Feng ◽  
Zhenguo Ge ◽  
Honghong Yang ◽  
Guojun Zhu ◽  
Chenhao Li ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
Rotating Stall ◽  
Vaned Diffuser
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