Pressure fluctuation and flow pattern of a mixed-flow pump under design and off-design conditions

2017 ◽  
Vol 232 (13) ◽  
pp. 2430-2440 ◽  
Author(s):  
Yun Xu ◽  
Lei Tan ◽  
Yabin Liu ◽  
Yue Hao ◽  
Baoshan Zhu ◽  
...  
Keyword(s):  
Flow Pattern ◽  
Flow Rate ◽  
Pressure Fluctuations ◽  
Rotation Frequency ◽  
Design Flow ◽  
Mixed Flow ◽  
Partial Load ◽  
Flow Pump ◽  
Dominant Frequencies ◽  
Design Flow Rate

The pressure fluctuations and flow pattern in a mixed-flow pump are numerically investigated under design and off-design conditions. The accuracy and reliability are validated by good agreement of numerical results and experimental data of pump energy performance. At design flow rate, the dominant frequencies of pressure fluctuations are impeller rotation frequency or integer multiples of it, which are mainly induced by the rotor–stator interaction. At overload condition, the dominant frequencies of pressure fluctuations are similar as those of design flow rate, but the maximum amplitudes increase to about 2.5 times of those of design flow rate. At partial load condition, the pressure fluctuations and flow pattern are complicated. The low dominant frequencies below the impeller rotation frequency are related to the process of vortex emergency, movement and disappearance.

Experimental Investigation of Time-Frequency Characteristics of Pressure Fluctuations in a Double-Suction Centrifugal Pump

2011 ◽  
Vol 133 (10) ◽  
Author(s):  
Zhifeng Yao ◽  
Fujun Wang ◽  
Lixia Qu ◽  
Ruofu Xiao ◽  
Chenglian He ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Operating Conditions ◽  
Design Flow ◽  
Flow Rates ◽  
Time Frequency ◽  
Blade Passing Frequency ◽  
Design Flow Rate

Pressure fluctuation is the primary reason for unstable operations of double-suction centrifugal pumps. By using flush mounted pressure transducers in the semispiral suction chamber and the volute casing of a double-suction pump, the pressure fluctuation signals were obtained and recorded at various operating conditions. Spectral analyses were performed on the pressure fluctuation signals in both frequency domain and time-frequency domain based on fast Fourier transform (FFT) and an adaptive optimal-kernel time-frequency representation (AOK TFR). The results show that pressure fluctuations at the impeller rotating frequency and some lower frequencies dominated in the semispiral suction chamber. Pressure fluctuations at the blade passing frequency, the impeller rotating frequency, and their harmonic frequencies were identified in the volute casing. The amplitude of pressure fluctuation at the blade passing frequency significantly increased when the flow rate deviated from the design flow rate. At 107% of the design flow rate, the amplitude increased more than 254% than that at the design flow rate. The time-frequency characteristics of these pressure fluctuations were affected greatly by both operating conditions and measurement locations. At partial flow rates the pulsation had a great irregularity and the amplitudes at the investigated frequencies were much larger than ones at the design flow rate. An asymmetrical pressure fluctuation structure in the volute casing was observed at all flow rates. The pulsation behavior at the blade passing frequency was the most prominent near the volute tongue zone, and the pressure waves propagated in both the radial and circumferential directions.

Large-Eddy Simulation of a Mixed-Flow Pump at Off-Design Conditions

2015 ◽  
Vol 137 (10) ◽  
Author(s):  
Antonio Posa ◽  
Antonio Lippolis ◽  
Elias Balaras
Keyword(s):  
Large Eddy Simulation ◽  
Flow Rate ◽  
Design Flow ◽  
Immersed Boundary ◽  
Mixed Flow ◽  
Eddy Simulation ◽  
Image Velocimetry ◽  
Large Eddy ◽  
The One ◽  
Flow Pump

The flow through turbopumps is characterized by highly unsteady phenomena at part load conditions, involving large separation and generation of vortical structures. This behavior is strongly dependent on the interaction between rotating and steady parts, which is significantly modified, compared to the one at the design flow rate. Therefore, at off-design conditions, eddy-resolving computations are more suitable to analyze the complex physics occurring inside turbomachinery channels. In this work the large eddy simulation (LES), coupled with an immersed-boundary (IB) method, is utilized to study a mixed-flow pump at a reduced flow rate, equivalent to 40% of the nominal one. The present approach has been already validated in a previous study, where a satisfactory agreement with two-dimensional (2D) particle image velocimetry (PIV) experiments has been shown at design conditions. In this paper a comparison with the LES results at the optimal flow rate is also proposed, in order to understand the important modifications of the flow occurring at part loads.

Effect of incidence angle on cavity blockage and flow stability in the net positive suction head drop of mixed-flow pumps

2020 ◽  
pp. 095440622097305
Author(s):  
Yong-In Kim ◽  
Sung Kim ◽  
Kyoung-Yong Lee ◽  
Young-Seok Choi
Keyword(s):  
Flow Pattern ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Incidence Angle ◽  
Experimental Tests ◽  
Design Flow ◽  
Inlet Pressure ◽  
Stable Flow ◽  
Fft Analysis ◽  
Design Flow Rate

The cavitation is an inevitable factor in pumps used in the whole industry, which is a major cause of energy loss and mechanical breakdown. In this study, the cavitation phenomena at the design flow rate were numerically analyzed for two pumps with different incidence angles. The design flow rate for both models was located near the best efficiency point (BEP). The incidence angle was determined with the impeller inlet diameter and the blade angle. A pump with a smaller incidence angle consistently showed a stable flow pattern as the inlet pressure decreased, whereas a pump with a larger incidence angle contained non-uniform flow streamlines despite a very small amount of the generated cavities. The flow pattern at the impeller inlet was handled by the shape and thickness of the generated cavities which could act as an additional blockage in the pumps. The inception and growth of the cavity with a decrease of inlet pressure were also inferred, which was specifically quantified as the blockage ratio. A pump with a larger incidence angle performed poor cavitation characteristics and obtained the pressure fluctuation and cavity oscillation. The magnitude of pressure fluctuation was indicated using the fast Fourier transform (FFT) analysis. The experimental tests were performed on both pumps to validate the numerical results.

scholarly journals Comprehensive Numerical Investigations of Unsteady Internal Flows and Cavitation Characteristics in Double-Suction Centrifugal Pump

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Xuelin Tang ◽  
Mingde Zou ◽  
Fujun Wang ◽  
Xiaoqin Li ◽  
Xiaoyan Shi
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuations ◽  
Dominant Frequency ◽  
Secondary Flows ◽  
Design Flow ◽  
Sharp Drop ◽  
Blade Loading ◽  
Blade Passing Frequency ◽  
Design Flow Rate

The RNG k-ε turbulence model combined with cavitation model was used to simulate unsteady cavitating flows inside a double-suction centrifugal pump under different flow rate conditions based on hexahedral structured grid. The numerical external characteristic performances agree well with the experimental performances. The predicted results show that the turbulence kinetic energy and the turbulence dissipation rate inside the impeller at design flow rate are lower than those at other off-design flow rates, which are caused by various vortexes. Based on frequency-domain analyses in the volute casing, the blade passing frequency is the dominant one of the pressure fluctuations except the vicinity of volute tongue for all operating cases, and the dominant frequency near the volute tongue ranges from 0 to 0.5 times the blade passing frequency for other off-design points, while the blade passing one near the volute tongue is the dominant one of the pressure fluctuations at design point. The increase of flow rate reduces the pressure fluctuations amplitude. For cavitation cases, the blade loading of the middle streamline increases a bit during the initial stage, but, for serious cavitation, the blade loading near the blade inlet reduces to 0 and even negative values, and the serious cavitation bubbles block the blade channels, which results in a sharp drop in pump head. Under noncavitation condition, the predicted power related to the pressure in the impeller channels increases from the inlet to the exit, while, under different cavitation conditions at the design flow rate, these power-transformation distributions in the impeller channels show that these power conversions are affected by the available NPSHa and the corresponding work in leading regions of the blades increases increases gradually a bit, and then it increases sharply in the middle regions, but it decreases in the blade trailing regions and is greatly influenced by secondary flows.

Role of blade rotational angle on energy performance and pressure fluctuation of a mixed-flow pump

2017 ◽  
Vol 231 (3) ◽  
pp. 227-238 ◽  
Author(s):  
Tan Lei ◽  
Yu Zhiyi ◽  
Xu Yun ◽  
Liu Yabin ◽  
Cao Shuliang
Keyword(s):  
Pressure Fluctuation ◽  
Guide Vane ◽  
Pressure Fluctuations ◽  
Maximum Amplitude ◽  
Energy Performance ◽  
Mixed Flow ◽  
Rotational Angle ◽  
Flow Pump ◽  
Dominant Frequencies

The role of blade rotational angle in the energy performance and pressure fluctuation of a mixed-flow pump is investigated through an experimental measurement and numerical simulation. The mixed-flow pump head increases at a blade rotational angle of 4° and decreases at a blade rotational angle of −4° compared with a blade rotational angle of 0°. Meanwhile, the highest efficiency decreases by 0.3% at a blade rotational angle of 4° and increases by 0.8% at a blade rotational angle of −4°. The pressure fluctuation characteristics in the mixed-flow pump at different blade rotational angles are also revealed. The dominant frequencies of pressure fluctuations in the impeller are the axis rotation frequency or six times this frequency corresponding to six guide vanes. The dominant frequencies of pressure fluctuations at the middle plane of impeller and guide vane are the blade-passing frequencies or twice this frequency. The maximum amplitude of pressure fluctuation in the impeller at a blade rotational angle of −4° is greater than that of blade rotational angle 0° and 4° because of strong vortex intensity. The maximum amplitude of pressure fluctuation at the middle span of the impeller and vane occurs at a blade rotational angle of 4° because of the largest pressure gradient.

Influence of T-shape tip clearance on performance of a mixed-flow pump

2017 ◽  
Vol 232 (4) ◽  
pp. 386-396 ◽  
Author(s):  
Tan Lei ◽  
Xie Zhifeng ◽  
Liu Yabin ◽  
Hao Yue ◽  
Xu Yun
Keyword(s):  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Rotation Frequency ◽  
Tip Clearance ◽  
Mixed Flow ◽  
Impeller Blade ◽  
Movement Trajectories ◽  
Blade Thickness ◽  
Flow Pump

Influence of original and T-shape blade end on performance of a mixed-flow pump is investigated by using experimental measurement and numerical simulation. The new proposed T-shape blade end is formed at 95%–100% blade height with a linear increase of blade thickness. In comparison with original blade end, the efficiency of pump with T-shape blade end increases by 1.86%, and the leakage flow decreases by 15.95%. Space streamlines across the blade tip clearance can be divided into three beams with different movement trajectories, and the swirl motions of streamlines directly correspond to the swirling strength. The highest amplitude of pressure fluctuation appears at the blade leading edge along the tip clearance. In comparison with original blade end, the highest amplitude of pressure fluctuation for T-shape blade end decreases by 27.45%. The dominant frequencies of the pressure fluctuations in tip clearance region for original blade end and T-shape blade end are both five times of the axis rotation frequency, corresponding to the impeller blade number of five.

scholarly journals Effect of Stall Cells on Pressure Fluctuations Characteristics in a Centrifugal Pump

Symmetry ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1116 ◽  
Author(s):  
Peijian Zhou ◽  
Jiacheng Dai ◽  
Chaoshou Yan ◽  
Shuihua Zheng ◽  
Changliang Ye ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuations ◽  
Low Frequency ◽  
Rotating Stall ◽  
Design Flow ◽  
Eddy Simulation ◽  
Leading Role ◽  
Stall Cells ◽  
Design Flow Rate

Rotating stall is an unsteady flow phenomenon, which always leads to instability and efficiency degradation. In order to reveal pressure fluctuations in the impeller of centrifugal pump induced by stall cells, the flow structures in a volute-type centrifugal pump were calculated using Large Eddy Simulation (LES) method. The predicted results of the numerical model were compared with experimental flow-head curve. The simulation results were in good agreement with the experimental results. The stall phenomenon occurred when the flow rate dropped to 70% of design flow rate. Three stall cells located at the entrance of passages could be observed, which remained stationary relative to the rotating impeller. With the decrease of flow rate, the area occupied by stall cells gradually increased. The peak value of pressure fluctuation at 25% of design flow rate is obviously larger than that at 50% of design flow rate. For the unstalled or stalled passage, the impeller-volute interaction played a leading role in the pressure fluctuations of the impeller. For the stalled passage, the amplitude of the low frequency induced by stall cell is relatively insignificant.

The Cavitation-Induced Pressure Fluctuations in a Mixed-Flow Pump under Impeller Inflow Distortion

Machines ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 326
Author(s):  
Huiyan Zhang ◽  
Fan Meng ◽  
Yunhao Zheng ◽  
Yanjun Li
Keyword(s):  
Frequency Domain ◽  
Pressure Fluctuation ◽  
Dynamic Pressure ◽  
Pressure Fluctuations ◽  
Pressure Sensors ◽  
Mixed Flow ◽  
Guide Vanes ◽  
Time Frequency ◽  
Critical Cavitation ◽  
Flow Pump

To reduce cavitation-induced pressure fluctuations in a mixed-flow pump under impeller inflow distortion, the dynamic pressure signal at different monitoring points of a mixed-flow pump with a dustpan-shaped inlet conduit under normal and critical cavitation conditions was collected using high-precision digital pressure sensors. Firstly, the nonuniformity of the impeller inflow caused by inlet conduit shape was characterized by the time–frequency-domain spectra and statistical characteristics of pressure fluctuation at four monitoring points (P4–P7) circumferentially distributed at the outlet of the inlet conduit. Then, the cavity distribution on the blade surface was captured by a stroboscope. Lastly, the characteristics of cavitation-induced pressure fluctuation were obtained by analyzing the time–frequency-domain spectra and statistical characteristic values of dynamic pressure signals at the impeller inlet (P1), guide vanes inlet (P2), and guide vanes outlet (P3). The results show that the flow distribution of impeller inflow is asymmetric. The pav values at P4 and P6 were the smallest and largest, respectively. Compared with normal conditions, the impeller inlet pressure is lower under critical cavitation conditions, which leads to low pav, pp-p and a main frequency amplitude at P1. In addition, the cavity covered the whole suction side under H = 13.6 m and 15.5 m, which led the pp-p and dominant frequency amplitude of pressure fluctuation at P2 and P3 under critical cavitation to be higher than that under normal conditions.

scholarly journals Modeling Study of Design Flow Rates for Cascade Water Supply Systems in Residential Skyscrapers

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2580
Author(s):  
Yang Zhou ◽  
Eric Lee ◽  
Ling-Tim Wong ◽  
Kwok-Wai Mui
Keyword(s):  
Water Supply ◽  
Mathematical Models ◽  
Flow Rate ◽  
Supply System ◽  
Water Supply System ◽  
Design Flow ◽  
Water Volume ◽  
Water Supply Systems ◽  
Supply Systems ◽  
Design Flow Rate

Skyscrapers are common nowadays around the world, especially in cities with limited development area. In order to pump water up to the higher level of a skyscraper, a cascade water supply system has to be installed. Currently, cascade water supply systems are mainly designed based on practical experiences or requirements of existing standards/guidelines that, in fact, are not specifically for skyscrapers. However, thorough studies on cascade water supply system designs are still limited in the literature. This study proposes mathematical models and uses Monte Carlo simulations to evaluate the design flow rate of a typical cascade water supply system that feeds various appliances in a residential skyscraper in Hong Kong. Graphs that showed the correlations between the inflow rate in the supply pipe and water volume in the tank are obtained. While tank storage volume is confirmed, the design flow rate of the cascade water supply system can be determined from these graphs. The proposed mathematical models can also be applied to evaluate the design flow rate of cascade water supply systems in other types of skyscrapers (e.g., office, commercial building) as well as with the changes in water demand patterns in the models.

scholarly journals Experimental Analysis on Pressure Fluctuation Characteristics of a Centrifugal Pump with Vaned-Diffuser

Water ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 126
Author(s):  
Houlin Liu ◽  
Ruichao Xia ◽  
Kai Wang ◽  
Yucheng Jing ◽  
Xianghui He
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Dominant Frequency ◽  
Design Flow ◽  
Signal Source ◽  
Vaned Diffuser ◽  
Impeller Outlet ◽  
Variation Tendency ◽  
Design Flow Rate

Experimental measurements to analyze the pressure fluctuation performance of a centrifugal pump with a vaned-diffuser, which its specific speed is 190. Results indicate that the main cause of pressure fluctuation is the rotor-stator interference at the impeller outlet. The head of the pump with vaned-diffuser at the design flow rate is 15.03 m, and the efficiency of the pump with a vaned-diffuser at the design flow rate reaches 71.47%. Pressure fluctuation decreases gradually with increasing distance from the impeller outlet. Along with the increase of the flow rate, amplitude of pressure fluctuation decreases. The amplitude of pressure fluctuation at the measuring points near the diffusion section of the pump body is larger than other measuring points. The variation tendency of pressure fluctuation at P1–P10 is the same, while there are wide frequency bands with different frequencies. The dominant frequency of pressure fluctuation is the blade passing frequency. The rotor-stator interference between the impeller and the vaned-diffuser gives rise to the main signal source of pressure fluctuation.

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