scholarly journals Experiment on Pressure Pulsation of Axial Flow Pump System with Different Runaway Head

Processes ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1597
Author(s):  
Jing Dai ◽  
Xueqin Liu ◽  
Congbing Huang ◽  
Xuemei Xu ◽  
Ge Bu ◽  
...  
Keyword(s):  
Pressure Pulsation ◽  
Rotation Axis ◽  
Pressure Coefficient ◽  
Pressure Sensors ◽  
Axial Flow ◽  
Rotation Frequency ◽  
Wake Vortex ◽  
Inlet Section ◽  
Pump System ◽  
Dimensionless Pressure

The runaway condition is a damage condition for pumps and turbines which can induce the wake vortex, reverse flow, and severe pressure pulsation. This study aimed to research the characteristics of pressure pulsation of axial flow pumps under different runaway conditions, and the runaway model test was performed with different blade angles and heads. Moreover, four pressure sensors were uniformly arranged at the impeller inlet section to eliminate the random error. The time domain and frequency domain analysis were the main methods to obtain the change regulations. Results showed that the pressure pulsation under the runaway condition are mainly influenced by the rotation frequency, blade passing frequency, and wake vortex frequency. The dimensionless pressure pulsation coefficient of rotation frequency and wake vortex frequency increased obviously with the runaway head increasing, but changed little with different blade angles. In addition, the dimensionless pressure coefficient of wake vortex frequency of the sensors around the impeller inlet section differed a lot, which means that the wake vortex core is not in center of the rotation axis. The average dimensionless pressure pulsation coefficient of wake vortex frequency is higher than that of rotation frequency with the same runaway head, owing to the severer wake vortex.

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.

Foetal bypass: concepts and controversies

Perfusion ◽  
1998 ◽  
Vol 13 (2) ◽  
pp. 111-117 ◽  
Author(s):  
Joseph J Sistino
Keyword(s):  
Heart Defects ◽  
Open Heart Surgery ◽  
Axial Flow ◽  
Right Atrial ◽  
Cyclooxygenase Inhibitors ◽  
Pump System ◽  
Maternal Risk ◽  
Valvular Stenosis ◽  
Axial Flow Pump ◽  
Flow Pump

One of the most controversial and challenging surgical undertakings of the next century promises to be foetal cardiac surgery. Animal studies have been underway for several years to gain an understanding of the physiological mechanisms required to achieve this undertaking. Not since the days of crosscirculation has there been a maternal risk associated with open-heart surgery. The diagnosis of congenital heart defects with foetal ultrasound can now be made as early as 12 weeks gestation. Simple cardiac abnormalities, such as valvular stenosis or atresia, alter intracardiac flow patterns and affect normal cardiac chamber development. Without early intervention, these complex lesions often require major surgical reconstruction, beginning in the neonatal period. Foetal cardiac bypass techniques have evolved from the use of roller pumps and bubble oxygenators primed with maternal blood to the use of an axial flow pump incorporated in a right atrial to pulmonary artery or aortic shunt. Because the blood entering the right atrium is oxygenated by the placenta, an oxygenator in the bypass circuit is probably not needed. The low prime axial flow pump system avoids the dilution of the foetus with the maternal adult haemoglobin and improves the outcome. A major focus of research has concentrated on maintenance of placental blood flow with the use of vasodilators and cyclooxygenase inhibitors. Investigation with primates will be necessary to confirm the placental physiology before human operations can be performed. As the foetal bypass challenges are overcome, there is the potential for a reduction in the number of complex cardiac lesions requiring early surgical intervention in the twenty-first century.

scholarly journals Effect of Suction and Discharge Conditions on the Unsteady Flow Phenomena of Axial-Flow Reactor Coolant Pump

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1592
Author(s):  
Xin Chen ◽  
Shiyang Li ◽  
Dazhuan Wu ◽  
Shuai Yang ◽  
Peng Wu
Keyword(s):  
Unsteady Flow ◽  
Pressure Pulsation ◽  
Flow Reactor ◽  
Axial Flow ◽  
Hydraulic Performance ◽  
Uniform Flow ◽  
Coolant Pump ◽  
Reactor Coolant ◽  
Flow Phenomena ◽  
Rotating Impeller

In order to study the effects of the suction and discharge conditions on the hydraulic performance and unsteady flow phenomena of an axial-flow reactor coolant pump (RCP), three RCP models with different suction and discharge configurations are analyzed by computational fluid dynamics (CFD) method. The CFD results are validated by experimental data. The hydraulic performance of the three RCP models shows little difference. However, the unsteady flow phenomena of RCP are significantly affected by the variation of suction and discharge conditions. Compared with that of Model E-S (baseline, elbow-single nozzle), the pressure pulsation in rotating frame of Model S-S (straight pipe-single nozzle) and Model E-D (elbow-double nozzles) is weakened in different degrees and forms, due to the more uniform flow fields upstream and downstream of the impeller, respectively. It indicates that the generalized rotor-stator interaction (RSI) actually exists between the rotating impeller and all stationary components causing the circumferentially non-uniform flow. Furthermore, improving the circumferential uniformity of the flow upstream and downstream of impeller (suction and discharge flow) also contributes to reducing the radial dynamic fluid force acting on the impeller. Compared with those of Model E-S, the dynamic FX and FY of Model S-S are severely weakened, and those of Model E-D also gain a minor amplitude decrease at fBPF. In contrast, the general pressure pulsation in fixed frame is mainly related to the rotating impeller and barely affected by the suction and discharge conditions.

scholarly journals Pressure torque of torsional Alfvén modes acting on an ellipsoidal mantle

2020 ◽  
Vol 222 (1) ◽  
pp. 338-351 ◽  
Author(s):  
F Gerick ◽  
D Jault ◽  
J Noir ◽  
J Vidal
Keyword(s):  
Fluid Dynamics ◽  
Rotation Axis ◽  
Fluid Velocity ◽  
Rotation Frequency ◽  
Length Of Day ◽  
Core Mantle Boundary ◽  
The Core ◽  
Fluid Core ◽  
Spherical Core ◽  
Net Pressure

SUMMARY We investigate the pressure torque between the fluid core and the solid mantle arising from magnetohydrodynamic modes in a rapidly rotating planetary core. A 2-D reduced model of the core fluid dynamics is developed to account for the non-spherical core–mantle boundary. The simplification of such a quasi-geostrophic model rests on the assumption of invariance of the equatorial components of the fluid velocity along the rotation axis. We use this model to investigate and quantify the axial torques of linear modes, focusing on the torsional Alfvén modes (TM) in an ellipsoid. We verify that the periods of these modes do not depend on the rotation frequency. Furthermore, they possess angular momentum resulting in a net pressure torque acting on the mantle. This torque scales linearly with the equatorial ellipticity. We estimate that for the TM calculated here topographic coupling to the mantle is too weak to account for the variations in the Earth’s length-of-day.

An Experimental Study of Rotor-Filter Pump Performance

1982 ◽  
Vol 104 (3) ◽  
pp. 259-268
Author(s):  
K. M. Marshek ◽  
M. R. Naji ◽  
G. C. Andries
Keyword(s):  
Pressure Pulsation ◽  
Flow Characteristics ◽  
Hydraulic Pressure ◽  
Motor Speed ◽  
Rotor Vibration ◽  
Pump Frequency ◽  
Pump System ◽  
Pump Performance ◽  
Filter Pump ◽  
Pulsing Flow

The performance of a rotor-filter pump has been studied experimentally. To develop an understanding of pump performance, and in particular to discern the mechanism of hydraulic pulsing, flow visualization in the rotor, vibration analyses of the pump, frequency analysis of the pump hydraulic pressure pulsation, and analyses of flow characteristics for different pick-up tubes in combination with different impellers and cover plates were conducted. The frequencies of the pump’s hydraulic pulsation is shown to be a function of the number of pick-up arms and the motor speed. The pump vibration and its pulsation amplitude were reduced by increasing the number of pick-up arms or by adding a radial impeller. These actions increased the lowest frequency of pulsation and decreased the chance of excitation of the pump system parts.

scholarly journals Normal forces exerted upon a long cylinder oscillating in an axial flow

2014 ◽  
Vol 752 ◽  
pp. 649-669 ◽  
Author(s):  
L. Divaret ◽  
O. Cadot ◽  
P. Moussou ◽  
O. Doaré
Keyword(s):  
Flow Velocity ◽  
Normal Force ◽  
Pressure Coefficient ◽  
Axial Flow ◽  
Fluid Forces ◽  
Normal Forces ◽  
Pressure Distributions ◽  
Damping Rate ◽  
Static Approach ◽  
Yaw Angle

AbstractThis work aims to improve understanding of the damping induced by an axial flow on a rigid cylinder undergoing small lateral oscillations within the framework of the quasistatic assumption. The study focuses on the normal force exerted on the cylinder for a Reynolds number of $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\mathit{Re}=24\, 000$ (based on the cylinder diameter and axial flow velocity). Both dynamic and static approaches are investigated. With the static approach, fluid forces, pressure distributions and velocity fields are measured for different yaw angles and cylinder lengths in a wind tunnel. It is found that for yaw angles smaller than $5{^\circ }$, the normal force varies linearly with the angle and is fully dominated by its lift component. The lift originates from the high pressure coefficient at the front of the cylinder, which is found to depend linearly on the angle, and from a base pressure coefficient that remains close to zero independent of the yaw angle. At the base, a flow deficit and two counter-rotating vortices are observed. A numerical simulation using a $k\mbox{--}\omega $ shear stress transport turbulence model confirms the static experimental results. A dynamic experiment conducted in a water tunnel brings out damping-rate values during free oscillations of the cylinder. As expected from the linear dependence of the normal force on the yaw angle observed with the static approach, the damping rate increases linearly with the axial flow velocity. Satisfactory agreement is found between the two approaches.

Vortices' Characteristics to Explain the Flange Height Effects on the Aerodynamic Performances of a Diffuser Augmented Wind Turbine

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Rym Chaker ◽  
Mouldi Kardous ◽  
Mahmoud Chouchen ◽  
Fethi Aloui ◽  
Sassi Ben Nasrallah
Keyword(s):  
Wind Velocity ◽  
Particle Image ◽  
Flow Direction ◽  
Pressure Coefficient ◽  
Inlet Section ◽  
Wind Tunnel Experiments ◽  
Piv Measurements ◽  
Velocity Increase ◽  
Image Velocimetry ◽  
Aerodynamic Performances

Flange height is between the geometric features that contribute efficiently to improve the diffuser aerodynamic performances. Results obtained from wind tunnel experiments, particle image velocimetry (PIV) measurements, and numerical simulations reveal that at the diffuser inlet section, the wind velocity increases as the flange height increases. Nevertheless, there is an optimal ratio (flange height/inlet section diameter, Hopt/Da ≈ 0.15) beyond it, the flange height effect on the velocity increase diminishes. This behavior can be explained by both the positions of the two contra-rotating vortices generated downstream of the diffuser and the pressure coefficient at their centers. Indeed, it was found that, as the flange height increases, the two vortices move away from each other in the flow direction and since the flange height exceeds (Hopt/Da), they became too distant from each other and from the flange. While the pressure coefficients at the vortices' centers increase with (H/Da), attain a maximum when (Hopt/Da) is reached, and then decrease. This suggests that the wind velocity increase depends on the pressure coefficient at the vortices' centers. Therefore, it depends on the vortices' locations which are in turn controlled by the flange height. In practice, this means that the diffuser could be more efficient if equipped with a control system able to hold the vortices too near from the flange.

scholarly journals Experimental investigation on the correlation of pressure pulsation and vibration of axial flow pump

2019 ◽  
Vol 11 (11) ◽  
pp. 168781401988947
Author(s):  
Xiaohui Duan ◽  
Fangping Tang ◽  
Wenyong Duan ◽  
Wei Zhou ◽  
Lijian Shi
Keyword(s):  
Pressure Pulsation ◽  
Axial Flow ◽  
Domain Analysis ◽  
Vertical Vibration ◽  
High Flow ◽  
Design Flow ◽  
Flow Rates ◽  
Horizontal Vibration ◽  
Axial Flow Pump ◽  
Flow Pump

Pressure and vibration displacement value are relatively measured by 14 pressure sensors and 2 vibration sensors distributing inside the tank-type model axial flow pump device under different flow rates. By comparison, it is found that the pressure pulsation on the inlet of the impeller is the main cause of hydraulic induced vibration of the pump device, and it is found to have similar amplitude trend with the vertical vibration as the flow rates increases and large correlation coefficient with the horizontal vibration under high flow rates through time-domain analysis. By frequency-domain analysis, it is found that the main frequency of pressure pulsation is three multiplies of the shaft frequency, but it is one multiplies of vertical vibration, and it changes from one multiplies to three multiplies of horizontal vibration. Combining with the analysis of phase-flow rates characteristics of both pressure pulsation and vibration, it is concluded that, for the horizontal vibration, the frequency ingredient of one multiplies ranging from low to high flow rates and three multiplies removing from unstable and high flow rates zone are possibly induced by pressure pulsation on the inlet of impeller, while for the vertical vibration, the frequency ingredient of one multiplies under design flow rates and high flow rates are possibly induced by pressure pulsation on the inlet of impeller. Both the horizontal and vertical vibrations with frequency of two multiplies have little relationship with the pressure pulsation on the inlet of impeller.

scholarly journals Study on the Performance Improvement of Axial Flow Pump’s Saddle Zone by Using a Double Inlet Nozzle

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1493
Author(s):  
Weidong Cao ◽  
Wei Li
Keyword(s):  
Flow Rate ◽  
Three Dimensional ◽  
Axial Flow ◽  
Rotating Stall ◽  
Stable Operation ◽  
Inlet Section ◽  
Pump Impeller ◽  
Rate Condition ◽  
Axial Flow Pump ◽  
Flow Pump

The operating range of axial flow pumps is often constrained by the onset of rotating stall. An improved method using a double inlet nozzle to stabilize the performance curve is presented in the current study; a single inlet nozzle and three kinds of double inlet nozzle with different rib gap widths at the inlet of axial flow pump impeller were designed. Three dimensional (3D) incompressible flow fields were simulated, and the distributions of turbulence kinetic energy and velocity at different flow rates located at the inlet section, as well as the pressure and streamline in the impeller, were obtained at the same time. The single inlet nozzle scheme and a double inlet nozzle scheme were studied; the experimental and numerical performance results show that although the cross section is partly blocked in the double inlet nozzle, the head and efficiency do not decline at stable operation flow rate. On small flow rate condition, the double inlet nozzle scheme effectively stabilized the head-flow performance, whereby the block induced by the backflow before the impeller was markedly improved by using a double inlet nozzle. It has also been found that the rib gap width impacts the efficiency curve of the axial flow pump.

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