Description of Unsteady Flow Characteristics in a Side Channel Pump with a Convex Blade

2020 ◽  
Author(s):  
Fan Zhang ◽  
Ke Chen ◽  
Desmond Appiah ◽  
Shouqi Yuan ◽  
Kofi Asamoah Adu-Poku ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Theoretical Basis ◽  
High Efficiency ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Distribution Area ◽  
Side Channel ◽  
Concentration Region ◽  
Impeller Blade ◽  
Strong Vortex

Abstract To investigate the unsteady flow characteristics in side channel pumps, the vortex structures and their evolutions in the impeller and side channel flow passages have been comprehensively studied. Systematically, three impeller schemes were designed with different ratios of convex blade height h to impeller blade length l (h/l=0.2, 0.5, and 0.8) for detailed analysis. The findings indicated that the convex blade broadens the high-efficiency range and improves the efficiency at the best efficiency point for scheme h/l=0.2. Impeller scheme h/l=0.2 records the highest vortex concentration region, scheme h/l=0.5 displays as scattered spots, while scheme h/l=0.8 exhibits significant flow pattern changes in the impeller. The vortex distribution area and vortex intensity in the lengthways between the impeller and side channel of h/l=0.2 are almost analogous, but the other two impeller schemes have obvious separation and very chaotic. Although the shrinkages of axial vortexes in the impeller did not reflect on hydraulic performance, impeller schemes h/l=0.5 and 0.8 provided an outstanding performance in reducing the pressure fluctuations. The objective of this study is to provide a theoretical basis for optimal design and analysis of strong vortex flows in side channel pumps.

Cavitation-Induced Unsteady Flow Characteristics in the First Stage of a Centrifugal Charging Pump

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Fan Zhang ◽  
Shouqi Yuan ◽  
Qiang Fu ◽  
Ji Pei ◽  
Martin Böhle ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Nuclear Power ◽  
Power Plants ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Absolute Error ◽  
Impeller Blade ◽  
Frequency Domains ◽  
Vapor Distribution ◽  
Main Factor

Cavitation is the main factor that causes reliability problems in centrifugal charging pumps (CCPs) in nuclear power plants. In this study, the cavitation-induced unsteady flow characteristics of a CPR1000 CCP were investigated by numerical and experimental methods. The vapor distribution in the impeller, velocity fluctuation, and pressure fluctuation results in the time and frequency domains were considered for several typical monitoring points in the impeller and volute. The pressure fluctuations in the impeller occurred at an impeller rotating frequency of fR and its integer harmonics, whereas those in the volute mainly occurred at an impeller blade-passing frequency of fB and its integer harmonics. The absolute error between the simulated and measured NPSHr was 3.6%, and that between the calculated and measured head was 2.9%, validating the simulation of the cavitation performances of a CCP.

Studies on Characteristic Frequency and Length Scale of Shock Induced Motion in Transonic Diffuser Using a High Order LES Approach

2015 ◽  
Author(s):  
Debasish Biswas ◽  
Tomohiko Jimbo
Keyword(s):  
Boundary Layer ◽  
Mach Number ◽  
Unsteady Flow ◽  
Separation Bubble ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Propulsion Systems ◽  
Shock Oscillation ◽  
Shock Location ◽  
Suction Slot

Unsteady transonic flows in diffuser have become increasingly important, because of its application in new propulsion systems. In the development of supersonic inlet, air breathing propulsion systems of aircraft and missiles, detail investigations of these types of flow behavior are very much essential. In these propulsion systems, naturally present self-sustaining oscillations, believed to be equivalent to dynamically distorted flow fields in operational inlets, were found under all operating conditions. The investigations are also relevant to pressure oscillations known to occur in ramjet inlets in response to combustor instabilities. The unsteady aspects of these flows are important because the appearance of undesirable fluctuations generally impose limitation on the inlet performance. Test results of ramjet propulsion systems have shown undesirable high amplitude pressure fluctuations caused by the combustion instability. The pressure fluctuations originated from the combustor extend forward into the inlet and interact with the diffuser flow-field. Depending on different parameters such as the diffuser geometry, the inlet/exit pressure ratio, the flow Mach number, different complicated phenomena may occur. The most important characteristics are the occurrence of shock induced separation, the length of separation region downstream of the shock location, and the oscillation of shock location as well as the oscillation of the whole downstream flow. Sajben experimentally investigated in detail the time mean and unsteady flow characteristics of supercritical transonic diffuser as a function of flow Mach number upstream the shock location and diffuser length. The flows exhibited features similar to those in supersonic inlets of air-breathing propulsion systems of aircraft. A High-order LES turbulence model developed by the author is assessed with experimental data of Sajben on the self-excited shock oscillation phenomena. The whole diffuser model configuration including the suction slot located at certain axial location around the bottom and side walls to remove boundary layer, are included in the present computation model. The time-mean and unsteady flow characteristics in this transonic diffuser as a function of flow Mach number and diffuser length are investigated in detail. The results of study showed that in the case of shock-induced separation flow, the length and thickness of the reverse flow region of the separation-bubble change, as the shock passed through its cycle. The instabilities in the separated layer, the shock /boundary layer interaction, the dynamics of entrainment in the separation bubble, and the interaction of the travelling pressure wave with the pressure fluctuation region caused by the step-like structure of the suction slot play very important role in the shock-oscillation frequency.

scholarly journals Flow Characteristics in Volute of a Double-Suction Centrifugal Pump with Different Impeller Arrangements

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 669 ◽  
Author(s):  
Yu Song ◽  
Honggang Fan ◽  
Wei Zhang ◽  
Zhifeng Xie
Keyword(s):  
Centrifugal Pump ◽  
High Efficiency ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Weighted Average ◽  
Complex Flow ◽  
Suction Pump ◽  
Impeller Outlet ◽  
Large Flow ◽  
Dominant Frequencies

As an important type of centrifugal pump, the double-suction pump has been widely used due to its high efficiency region and large flow rate. In the present study, the complex flow in volute of a double-suction centrifugal pump is investigated by numerical simulation using a re-normalization group (RNG) k-ε model with experimental validation. Axial flows are observed in volute near the impeller outlet and compared with four staggered angles. The net area-weighted average axial velocities decrease as the staggered angle increases. The axial flows are mainly caused by the different circumferential pressure distribution at the twin impeller outlet. The dominant frequencies of the axial velocities for different staggered angles are fBP and its harmonic. The pressure fluctuations in most regions of the volute are obtained by superimposing the pressure generated by the two impellers.

Study on Flow Characteristics Downstream of Annular Inlet Guide Vanes

2013 ◽  
Author(s):  
Masanori Kudo ◽  
Koichi Nishibe ◽  
Masayuki Takahashi ◽  
Kotaro Sato ◽  
Yoshinobu Tsujimoto
Keyword(s):  
Unsteady Flow ◽  
Flow Instability ◽  
Velocity Ratio ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Flow Instabilities ◽  
Guide Vanes ◽  
Inlet Guide Vanes ◽  
Flow Oscillations ◽  
Measured Pressure

The main objectives of the present study are to identify the dominant parameters responsible for the generation of unsteady flow, determine the conditions under which flow oscillations are produced and the relation between the flow characteristics and the number of vanes with identical solidity. The flow instabilities downstream of inlet guide vanes (IGV) are clarified experimentally and by numerical simulation. The conditions for the onset of flow instability, including the number of cells and the oscillation characteristics of the unsteady flow, are discussed based on measured pressure fluctuations and the propagating angular velocity ratio of the instability for various radius ratios (r3/r2). The effectiveness of adjusting the number of vanes to control the flow instabilities is also discussed.

scholarly journals Numerical Study of Pressure Fluctuation and Unsteady Flow in a Centrifugal Pump

Processes ◽  
2019 ◽  
Vol 7 (6) ◽  
pp. 354 ◽  
Author(s):  
Ling Bai ◽  
Ling Zhou ◽  
Chen Han ◽  
Yong Zhu ◽  
Weidong Shi
Keyword(s):  
Unsteady Flow ◽  
Centrifugal Pump ◽  
Pressure Fluctuation ◽  
Static Pressure ◽  
Numerical Study ◽  
Pressure Fluctuations ◽  
Flow Patterns ◽  
Lower Number ◽  
Centrifugal Pumps ◽  
Impeller Blade

A pump is one of the most important machines in the processes and flow systems. The operation of multistage centrifugal pumps could generate pressure fluctuations and instabilities that may be detrimental to the performance and integrity of the pump. In this paper, a numerical study of the influence of pressure fluctuations and unsteady flow patterns was undertaken in the pump flow channel of three configurations with different diffuser vane numbers. It was found that the amplitude of pressure fluctuation in the diffuser was increased gradually with the increase in number of diffuser vanes. The lower number of diffuser vanes was beneficial to obtain a weaker pressure fluctuation intensity. With the static pressure gradually increasing, the effects of impeller blade passing frequency attenuated gradually, and the effect of diffuser vanes was increased gradually.

Unsteady flow characteristics of energy conversion in impeller of centrifugal pump as turbine

2021 ◽  
pp. 095440622110207
Author(s):  
Senchun Miao ◽  
Hongbiao Zhang ◽  
Jiawei Zhang ◽  
Xiaohui Wang ◽  
Fengxia Shi
Keyword(s):  
Unsteady Flow ◽  
Energy Conversion ◽  
Centrifugal Pump ◽  
Time Domain ◽  
Power Loss ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Input Power ◽  
Impeller Blade ◽  
The Time Domain

To study unsteady flow characteristics of energy conversion in impeller of centrifugal pump as turbine (PAT), the overall and sub-section methods are used to calculate the unsteady flow of the PAT under six working conditions. Through numerical calculations, the net input power of the impeller, the time domain change law of the fluid's work on the impeller, the time domain change law of power loss in the impeller, and the time domain change law of energy conversion in different regions of the impeller are analyzed. Results show that: the dynamic and static interference between the impeller blades and the tongue caused the fluctuation of energy conversion; with the increase of area between the head of the impeller blade and the opposite tongue, the power loss in the impeller decreases. And when the blade head completely deviates from the position of the tongue about 10°, the power loss in the impeller is minimized. The power output of the PAT at different flow rates is related to its internal flow conditions and the geometric structure of each region of the impeller. The above research results can provide guidance on how to operate the PAT impeller stably and efficiently.

Numerical Study of the Unsteady Flow Inside a Centrifugal Fan and its Downstream Pipe Using Detached Eddy Simulation

2020 ◽  
Author(s):  
Jian-Cheng Cai ◽  
Jia-Qi Zhang ◽  
Can Yang
Keyword(s):  
Unsteady Flow ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Computational Domain ◽  
Centrifugal Fan ◽  
Detached Eddy Simulation ◽  
Impeller Blade ◽  
Eddy Simulation ◽  
Maximum Value ◽  
Outlet Pipe

Abstract The 3-D unsteady turbulent flow inside a centrifugal fan and its downstream pipe is investigated at the best efficiency point (BEP) flow rate using the computational fluid dynamics (CFD) package ANSYS FLUENT. The impeller with an outlet diameter of 400 mm has 12 forward curved blades. The computational domain comprises four parts: the inlet part, the impeller, the volute, and the downstream pipe. The flow domain was meshed in ANSYS ICEM-CFD with structured hexahedron cells, and nearly 9 million cells were used. The Detached Eddy Simulation (DES) turbulence modelling approach was employed with this fine enough mesh scheme. The impeller was set as the rotating domain at a speed of 2900 rpm. A sliding mesh technique was applied to the interfaces in order to allow unsteady interactions between the rotating impeller and the stationary parts; the unsteady interactions generate pressure fluctuations inside the centrifugal fan. One impeller revolution is divided into 2048 time steps, in order to capture the transient flow phenomena with high resolution. Monitoring points were set along the volute casing profile, and along the downstream pipe centerline. When the numerical simulation became stable after several impeller revolutions, the statistics of the unsteady flow was initiated with a total of 16384 time steps (8 impeller revolutions) data. The time history data of the pressure and velocity magnitude at the monitoring points were saved and with Fourier transform applied to obtain the frequency spectra. The time-averaged flow fields show clearly the static pressure rises gradually through the impeller, and further recovers from the velocity in the volute, and decreases gradually along the downstream pipe due to the friction. The mean pressure at the pressure side of the impeller blade is larger than it at the suction side, forming the circumferential nonuniform flow pattern. Owing to the forward-curved blades, large velocity region exists around the impellor exit, and the maximum velocity near the trailing edge can reach 1.5u2, where u2 is the circumferential velocity at the impeller outlet. The root mean square (rms) value distribution of pressure fluctuations show that most parts inside the centrifugal fan undergo large pressure fluctuation with the magnitude about 10% of the reference dynamic pressure pref = 0.5ρu22; the maximum value locating at the tongue tip can reach 30% of pref. The pressure fluctuation magnitude decreases quickly along the outlet pipe: after 5D (D is the outlet pipe diameter) the magnitude is 0.5% of pref. The pressure and velocity fluctuation spectra at the monitoring points in the volute show striking discrete components at the blade-passing frequency (BPF) and its 2nd, 3rd harmonics. The BPF component has the maximum value of 15% of pref in the tongue region, and it decreases dramatically along the downstream pipe with the amplitude less than 0.2% of pref after 5D distance.

Investigation on Flow Characteristics of Pump-Turbine Runners With Large Blade Lean

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Baoshan Zhu ◽  
Lei Tan ◽  
Xuhe Wang ◽  
Zhe Ma
Keyword(s):  
High Pressure ◽  
High Efficiency ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Control Flow ◽  
Pump Turbine ◽  
Good Efficiency ◽  
Operating Modes ◽  
Partial Load

Frequent changes in the operating modes pose significant challenges in the development of a pump-turbine with high efficiency and stability. In this paper, two pump-turbine runners, one with a large positive blade lean and the other with a large negative lean, are investigated numerically and experimentally. These two runners are designed by using the optimum stacking condition at the high pressure edge (HPE). The experimental and the numerical results show that both runners have good efficiency performances, and pressure fluctuations for the runner with a negative blade lean are much lower than those for the runner with a positive blade lean. The internal flow field analyses clarify the effects of the blade lean on the pressure distribution around the runner blades. In the turbine mode at partial load, the negative blade lean can control flow separation in the high pressure side of the runner and then reduce the pressure fluctuations in the vaneless space.

Theoretical Study of Pressure Fluctuations Downstream of a Diffuser Pump Impeller—Part 2: Effects of Volute, Flow Rate and Radial Gap

1997 ◽  
Vol 119 (3) ◽  
pp. 653-658 ◽  
Author(s):  
W. Qin ◽  
H. Tsukamoto
Keyword(s):  
Experimental Data ◽  
Unsteady Flow ◽  
Flow Rate ◽  
Theoretical Study ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Trailing Edge ◽  
Pump Impeller ◽  
Impeller Blade ◽  
Radial Gap

The fundamental analysis in the first report was extended to calculate the unsteady flow induced by the interaction between impeller blades and diffuser vanes/volute casing in a diffuser pump. The unsteady flow in the diffuser vane passage, as well as the volute casing, is assumed to be induced by the five kinds of singularities—the bound vortices distributed on the impeller blades, diffuser vanes and volute casing wall, the sources at volute outlet, and the free vortices shed from the trailing edge of diffuser vanes. Calculated unsteady pressures agree with the corresponding experimental data. And the calculated results showed the effects of the flow rate, volute casing and the radial gaps between impeller blade trailing edge and diffuser vane leading edge on the magnitude of unsteady pressure downstream of impeller.

Shape Design and Flow Simulation of Mixing Impeller for Industrial Waste Oil Purification

2013 ◽  
Vol 361-363 ◽  
pp. 1050-1053
Author(s):  
Xu Dong Wang ◽  
Xian Ming Zhang
Keyword(s):  
Industrial Waste ◽  
High Efficiency ◽  
Flow Characteristics ◽  
Flow Simulation ◽  
Oil Field ◽  
Shape Design ◽  
Waste Oil ◽  
Impeller Blade ◽  
Oil Purification ◽  
And Performance

High efficiency of mixing impeller is an important target of the reactor for industrial waste oil purification. The structural and geometric characteristics of mixing impeller is ploted and presented. The shape design and performance analysis of airfoil section in impeller blade is introduced. Then using solidworks software, the design mixing impeller model under the industrial waste oil field is obtained. Finally, the flow characteristics are simulated to learn the performance of design mixing impeller.

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