scholarly journals Numerical and Experimental Analysis of Flow and Pulsation in Hump Section of Siphon Outlet Conduit of Axial Flow Pump Device

2021 ◽  
Vol 11 (11) ◽  
pp. 4941
Author(s):  
Fan Yang ◽  
Yiqi Zhang ◽  
Yao Yuan ◽  
Chao Liu ◽  
Zhongbin Li ◽  
...  
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Vortex Structure ◽  
Pressure Fluctuation ◽  
Axial Flow ◽  
Mean Value ◽  
Hydraulic Loss ◽  
Pressure Amplitude ◽  
Measuring Point ◽  
Outlet Conduit

In order to study the variation law of the flow field and pressure fluctuation in the hump section of the siphon outlet conduit, the flow field characteristics and frequency spectrum characteristics of the flow field were analyzed by combining a physical model test and numerical simulation under the conditions of the interaction between the axial flow pump and siphon outlet conduit, and the influence of the residual circulation at the outlet of the guide vane on the siphon outlet flow was investigated. Based on the influence of the flow field and hydraulic loss in the conduit, the equivalent surface method based on the Q criterion was used to analyze the vortex structure in the siphon outlet conduit and to analyze the internal vortex state. The results showed that with the increase of the flow rate, the intensity of the vortices in the cross-section of the hump section of the siphon outlet conduit decreased gradually, the average velocity circulation decreased gradually and the axial velocity distribution uniformity increased and tended to be stable; water flow stratification existed under three characteristic conditions with no circulation, and the hydraulic loss was greater with the circulation flow while it had a circulation under the small flow condition. Under the low flow rate conditions, the hydraulic loss was 6.6 times higher under the condition of circulation than without. Under a high flow condition, it was 1.3 times. Under the condition of a small flow rate, the vortex structure was distributed centrally at the inlet of the flow conduit, and under the other two characteristic conditions, the vortex structure mostly appeared as a strip; the pressure fluctuation in the hump section had obvious periodicity, and with the increase of the flow rate, the maximum pressure fluctuation amplitude in the hump section decreased gradually; with the decrease of the rotational speed, the pressure amplitude at the same measuring point in the hump section decreased gradually and at the optimum condition. Under the following conditions, the mean value of the pressure amplitude at the top of the hump section was reduced by 69.63%, and the mean value of the pressure amplitude at the bottom of the hump section was reduced by 63.5%. Under all the calculation conditions, the main frequency of pulsation at each measuring point of the hump section was twice the frequency of the rotation.

scholarly journals Investigation into the Influence of Division Pier on the Internal Flow and Pulsation in the Outlet Conduit of an Axial-Flow Pump

2021 ◽  
Vol 11 (15) ◽  
pp. 6774
Author(s):  
Fan Yang ◽  
Dongjin Jiang ◽  
Tieli Wang ◽  
Pengcheng Chang ◽  
Chao Liu ◽  
...  
Keyword(s):  
Velocity Distribution ◽  
Pressure Pulsation ◽  
Axial Flow ◽  
Hydraulic Loss ◽  
Main Frequency ◽  
Starting Position ◽  
The Difference ◽  
Axial Flow Pump ◽  
Outlet Conduit ◽  
Flow Pump

The outlet conduit is an important construction connecting the outlet of the pump guide vane and the outlet pool; in order to study the hydraulic performance of the straight outlet conduit of the axial-flow pump device, this paper adopts the method of numerical simulation and analyzes the influence of the division pier on the pressure and velocity distribution inside and near the wall of the straight outlet conduit based on three design schemes. Four pressure pulsation measuring points were arranged in the straight outlet conduit, and the low-frequency pulsation characteristic information inside the straight outlet conduit with and without the division pier was extracted by wavelet packet reconstruction. The results show that the addition of a division pier has an effect on the hydraulic loss, near-wall pressure and velocity distribution in the straight outlet conduit. A small high-pressure zone is formed near the wall at the starting position of the division pier, and a large high-speed zone is formed on the left side at the starting position of the division pier. The length of the division pier has no significant effect on the flow distribution of the straight outlet conduit and the pressure and velocity distribution near the wall. Under different working conditions, each monitoring point has the maximum energy in the sub-band (0~31.25 Hz). With the increase of the flow rate, the total pressure energy of the straight outlet conduit decreases gradually. Under each condition, the difference of the energy proportion of the horizontal monitoring points of the straight outlet conduit is small, and the difference of the energy proportion of the two monitoring points at the top and bottom of the outlet channel is relatively large. The energy of the two monitoring points in the straight outlet conduit with a division pier is smaller than that of the two monitoring points in the straight outlet conduit without a division pier. There are differences in the main frequency and the power spectrum corresponding to the main frequency of the monitoring points in the straight outlet conduit, and the reasonable setting of the division pier is conducive to reducing the pressure pulsation of the flow in the straight outlet conduit and is beneficial to the safe and stable operation of the pump device.

scholarly journals Investigation of the Flow Field in the Vicinity of an Axial Flow Fan During Low Flow Rates

2014 ◽  
Author(s):  
Francois G. Louw ◽  
Theodor W. von Backström ◽  
Sybrand J. van der Spuy
Keyword(s):  
Flow Field ◽  
Numerical Simulations ◽  
Flow Rate ◽  
Axial Flow ◽  
Operating Conditions ◽  
Design Flow ◽  
Low Flow ◽  
Axial Flow Fan ◽  
Free Vortex ◽  
Flow Rates

Large axial flow fans are used in forced draft air cooled heat exchangers (ACHEs). Previous studies have shown that adverse operating conditions cause certain sectors of the fan, or the fan as a whole to operate at very low flow rates, thereby reducing the cooling effectiveness of the ACHE. The present study is directed towards the experimental and numerical analyses of the flow in the vicinity of an axial flow fan during low flow rates. This is done to obtain the global flow structure up and downstream of the fan. A near-free-vortex fan, designed for specific application in ACHEs, is used for the investigation. Experimental fan testing was conducted in a British Standard 848, type A fan test facility, to obtain the fan characteristic. Both steady-state and time-dependent numerical simulations were performed, depending on the operating condition of the fan, using the Realizable k-ε turbulence model. Good agreement is found between the numerically and experimentally obtained fan characteristic data. Using data from the numerical simulations, the time and circumferentially averaged flow field is presented. At the design flow rate the downstream fan jet mainly moves in the axial and tangential direction, as expected for a free-vortex design criteria, with a small amount of radial flow that can be observed. As the flow rate through the fan is decreased, it is evident that the down-stream fan jet gradually shifts more diagonally outwards, and the region where reverse flow occur between the fan jet and the fan rotational axis increases. At very low flow rates the flow close to the tip reverses through the fan, producing a small recirculation zone as well as swirl at certain locations upstream of the fan.

Pressure Fluctuation on Casing Wall of Isolated Axial Compressor Rotors at Low Flow Rate

1993 ◽  
Vol 115 (1) ◽  
pp. 19-26 ◽  
Author(s):  
M. Inoue ◽  
M. Kuroumaru ◽  
Y. Ando
Keyword(s):  
Flow Rate ◽  
Pressure Fluctuation ◽  
Correlation Functions ◽  
Pressure Fluctuations ◽  
Axial Compressor ◽  
Axial Flow ◽  
Tip Clearance ◽  
Low Flow ◽  
Flow Compressor ◽  
Low Flow Rate

The pressure fluctuations on the casing wall of two axial flow compressor rotors with various tip clearances have been analyzed by the use of two kinds of correlation functions. The behavior of the pressure fluctuation varies depending on tip clearance and blade solidity. In the case of small tip clearance, the nature of disturbances becomes random as the flow rate is reduced to a stall condition. For moderate tip clearance, coherent-structured disturbances appear intermittently at low flow rate. They appear more frequently as the solidity is increased and the flow rate becomes lower. For large tip clearance, the coherent structured disturbances exist even at considerably higher flow rates. Corresponding to these features, there are peculiar patterns in the correlation designated as “phase-locked correlation functions.”

scholarly journals Numerical and experimental investigation of the pressure fluctuation in a mixed-flow pump under low flow conditions

2019 ◽  
Vol 234 (1) ◽  
pp. 46-57 ◽  
Author(s):  
Xi Shen ◽  
Desheng Zhang ◽  
Bin Xu ◽  
Ruijie Zhao ◽  
Yongxin Jin ◽  
...  
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Flow Separation ◽  
Pressure Fluctuation ◽  
Static Pressure ◽  
Leading Edge ◽  
Low Flow ◽  
Flow Conditions ◽  
Mixed Flow ◽  
Flow Pump

In this paper, the large eddy simulation is utilized to simulate the flow field in a mixed-flow pump based on the standard Smagorinsky subgrid scale model, which is combined with the experiments to investigate pressure fluctuations under low flow conditions. The experimental results indicated that the amplitude of fluctuation at the impeller inlet is the highest, and increases with the reduction of the flow rate. The main frequencies of pressure fluctuation at the impeller inlet, impeller outlet, and vane inlet are blades passing frequency, while the main frequency at the vane outlet changes with the flow rate. The results of the simulation showed that the axial plane velocity at impeller inlet undergoes little change under 0.8 Qopt. In case of 0.4 Qopt, however, the flow field at impeller inlet becomes complicated with the axial plane velocity changing significantly. The flow separation is generated at the leading edge of the suction surface at t* = 0.0416 under 0.4 Qopt, which is caused by the increase of the incidence angle and the influence of the tip leakage flow. When the impeller rotates from t* = 0.0416 to t* = 0.1249, the flow separation intensified and the swirling strength of the separation vortex is gradually increased, leading to the reduction of the static pressure, the rise of adverse pressure gradient, and the generation of backflow. The static pressure at the leading edge of the impeller recovers gradually until the backflow is reached. In addition, the flow separation is the main reason for the intensification of the pressure fluctuation.

Analysis of Off-Design Flow Field and Prediction of Performance in Hydraulic Turbine

2014 ◽  
Vol 496-500 ◽  
pp. 877-880
Author(s):  
Feng Xia Shi ◽  
Jun Hu Yang ◽  
Xiao Hui Wang
Keyword(s):  
Flow Field ◽  
Pressure Distribution ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Pressure Pulsation ◽  
Guide Vane ◽  
Hydraulic Turbine ◽  
Design Flow ◽  
External Characteristic ◽  
Distribution Of Flow

Two models of hydraulic turbine based on pump in reversal were simulated. Pressure distribution of flow field in Variable conditions was analysed and external characteristic was forecasted for hydraulic turbine. It was shown: the head increased with flow increased, with increasing of flow rate, efficiency first increased and then decreased. Compared with the turbine with a guide vane, the head of two models was almost equal, but the disparity of efficiency was large, and the efficiency of hydraulic turbine with a guide vane above on the efficiency of hydraulic turbine without guide vane. Pressure pulsation was existent in runner inlet. From runner inlet to runner outlet, the pressure distributed evenly from high to low. Added with a guide vane, the pressure distribution was more evenly than before and the Amplitude of pressure fluctuation decreased.

scholarly journals Effects of an Inlet Vortex on the Performance of an Axial-Flow Pump

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2854
Author(s):  
Wenpeng Zhang ◽  
Fangping Tang ◽  
Lijian Shi ◽  
Qiujin Hu ◽  
Ying Zhou
Keyword(s):  
Pressure Fluctuation ◽  
Axial Velocity ◽  
Guide Vane ◽  
Shape Change ◽  
Axial Flow ◽  
Weighted Average ◽  
Stable Operation ◽  
Hydraulic Loss ◽  
Axial Flow Pump ◽  
Flow Pump

The formation of an inlet vortex seriously restricts axial-flow pump device performance and poses a great threat to the safe and stable operation of the entire system. In this study, the change trends of an inlet vortex and its influence on an axial-flow pump are investigated numerically and experimentally in a vertical axial-flow pump device. Four groups of fixed vortex generators (VGs) are installed in front of the impeller to create stable vortices at the impeller inlet. The vortex influence on the performance of pump device is qualitatively and quantitatively analyzed. The vortex patterns at different positions and moments in the pump device are explored to reveal the vortex shape change trend in the impeller and the pressure fluctuation induced by the vortex. The reliability and accuracy of steady and unsteady numerical results are verified by external characteristics and pressure fluctuation experimental results. Results show that it is feasible to install VGs before the impeller inlet to generate stable vortices. The vortex disturbs the inlet flow fields of the impeller, resulting in significant reductions of the axial velocity weighted average angle and the axial velocity uniformity. The vortex increases the inlet passage hydraulic loss and reduces the impeller efficiency, while it only slightly affects the guide vane and outlet passage performance. The vortex causes a low-frequency pressure pulsation and interacts with the impeller. The closer the vortex is to the impeller inlet, the more significant the impeller influence on the vortex. The blade cuts off the vortex in the impeller; afterwards, the vortex follows the blade rotation, and its strength weakens.

Performance Prediction and Experimental Verification of Axial Flow Pump Based on CFD

2012 ◽  
Vol 152-154 ◽  
pp. 1566-1571
Author(s):  
De Sheng Zhang ◽  
Guang Jian Zhang ◽  
Wei Dong Shi ◽  
Tong Tong Li
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Performance Prediction ◽  
Prediction Error ◽  
Axial Flow ◽  
Maximum Error ◽  
Experimental Results ◽  
Complex Flow ◽  
Axial Flow Pump ◽  
Flow Pump

The full flow field numerical simulation of the axial-flow pump model is carried out to predict the pump performance based on RNG k-ε model and SIMPLE algorithm and the method of calculating head and efficiency. The numerical results show that the head and efficiency prediction curves have a good agreement with the experimental results. In the optimal operating condition, the prediction error of head is 0.04% and the efficiency error is 0.39% which could meet the requirements of engineering applications. The prediction error based on RNG k-ε turbulence model is larger in the off-design condition owing to the complex flow field of axial-flow pump. The predicted head is lower than the experimental results in the small flow rate conditions and its maximum error is 5.12%, while is higher than the experimental data in the large flow rate conditions and its maximum error is 17.39%. The conclusions will provide the basis and reference for the performance prediction of axial-flow pumps based on CFD.

Numerical investigation of clocking effect on a centrifugal pump with inlet guide vanes

2016 ◽  
Vol 33 (2) ◽  
Author(s):  
WANSHI QU ◽  
lei tan ◽  
Shuliang CAO ◽  
YUCHUAN WANG ◽  
YUN XU
Keyword(s):  
Flow Field ◽  
Numerical Investigation ◽  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Design Methodology ◽  
Design Flow ◽  
Guide Vanes ◽  
Inlet Guide Vanes ◽  
Design Flow Rate

Purpose The paper aims to investigate the clocking effect on a centrifugal pump with inlet guide vanes (IGVs). Design/methodology/approach The paper uses a computation fluid dynamics (CFD) framework to solve the unsteady flows in a centrifugal pump with inlet guide vanes. The relative position between the stationary vanes and the stationary volute tongue is defined as the clocking position when IGVs inside the suction pipe rotate along the circumferential direction. Findings The results show that clocking positions have little effect on the pump head and efficiency, however their influences are obvious for the pressure fluctuation and flow field in the centrifugal pump. The maximum difference of pressure amplitude at dominant frequency reach up to 28% on the monitoring point V8 at different clocking positions under design flow rate. For the large flow rate, the clocking effect on flow field and pressure fluctuation in centrifugal pump is similar to that of design flow rate. However, the clocking effect is nearly negligible at partial flow rate, because there are reverse flows around the tongue tip and obvious vortexes forming and developing in the impeller. Those complex phenomena interacting in the centrifugal pump make the clocking effect less evident. Originality/value The numerical investigation reveals the clocking effect on a centrifugal pump with inlet guide vanes, which also valuable for the stable operation and optimal design of centrifugal pumps.

scholarly journals Influence of Inlet Angle of Guide Vane on Hydraulic Performance of an Axial Flow Pump Based on CFD

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Lei Xu ◽  
Dongtao Ji ◽  
Wei Shi ◽  
Bo Xu ◽  
Weigang Lu ◽  
...  
Keyword(s):  
Working Conditions ◽  
Flow Rate ◽  
Guide Vane ◽  
Axial Flow ◽  
Hydraulic Performance ◽  
Hydraulic Loss ◽  
Rate Region ◽  
Axial Flow Pump ◽  
Inlet Angle ◽  
Flow Pump

Axial flow pump has been widely used in hydraulic engineering, agriculture engineering, water supply and sewerage works, and shipbuilding industry. In order to improve the hydraulic performance of pump under off-design working conditions, the influence of the inlet segment axial chord and inlet angle adjustment of the guide vane on the pump segment efficiency and flow filed was simulated by using the renormalization group (RNG) k − ε turbulent model based on the Reynolds-averaged Navier–Stokes equations. The results indicate that the inlet segment axial chord and inlet angle adjustment of guide vane have a strong influence on the pump segment efficiency. Considering the support function and hydraulic loss of the guide vane, the inlet segment axial chord is set to 0.25 times the axial chord of guide vane. On the basis of the inlet angle of the guide vane under design conditions, when the inlet segment angle is turned counterclockwise, the pump segment efficiency is improved in the lower flow rate region; moreover, the pump segment efficiency is improved in the larger flow rate region when the inlet segment angle is turned clockwise. As the conditions deviate from the design working conditions, the influence of the guide vane inlet angle on the pump segment efficiency increases. If the inlet segment angle is properly adjusted under off-design working conditions, the flow pattern in the guide vane is improved and the hydraulic loss is decreased, because the inlet segment angle matches with the flow direction of impeller outlet; consequently, the pump segment efficiency is increased.

Interaction Between Surge Behavior and Internal Flow Field in an Axial-Flow Compressor

2018 ◽  
Author(s):  
Yuu Sakata ◽  
Nobumichi Fujisawa ◽  
Yutaka Ohta
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Rapid Change ◽  
Internal Flow ◽  
Rotating Stall ◽  
Back Pressure ◽  
Rate Of Change ◽  
Operating Point ◽  
Tank Pressure

Interaction between surge behavior and internal flow field under coexisting phenomena of surge and rotating stall was experimentally investigated. In the experiment, the tank pressure of the compressor during surge was measured to detect the effect of the back-pressure fluctuation on the change in the internal flow field. Furthermore, the rotating stall in the compressor was investigated to define the influence of an unsteady internal flow field change on the surge behavior. From the tank pressure measurements, the amplitude of the tank pressure fluctuation was found to vary depending on the cycle. A larger maximal value for the tank pressure fluctuation led to a higher flow rate where the stall inception occurred. This difference in the flow rate indicated that the stall was induced by a severe adverse pressure gradient in the compressor. Then, the absolute rate of change in the flow coefficient was increased by both a large decrease in the compressor back pressure and performance degradation from stalling. In a case where the rate of decline in the flow rate was large, the scale of the stall cell developed up to a deep stall according to the movement of the operating point. Thus, a large trajectory for the surge cycle was selected, where the unsteady operating point went through the deep stall region. This development in the scale of the stall cell suggested to be influenced by the instability of the inner flow field caused by the rapid change in the flow rate.

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