Suction Sump Research Articles

Trajectory analysis of air-entrainment vortex in a suction sump

Abstract We attempt to develop the algorithm that identify the trajectory of the air strings from the image data. As a result, we reveal the behaviour of the vortex. Furthermore, we extract the air string with the longest life, and reveal its trajectory with poor regularity. In some cases, the air string tends to turn back and to attract to the pipe. But in some cases, the air string tends to move linearly and to have the trajectory that moves away from the pipe. In addition, the air string sometimes takes the trajectory that wraps around the wake along the pipe.

An experimental study on air entrainment in a suction sump over critical-submergence condition

In pump’s sumps, the air entrainment sometimes occurs. In various industrial and environmental problems, the air entrainment often induces vibration, noise, low pumping efficiency or pump’s collapse at the worst. The present aim is to understand the air entrainment appearing inside a simple and basic suction sump in the vertical-wet-pit-pump configuration. In particular, we focus upon the influences of governing parameters upon the occurrence-time ratio γ of the air entrainment, using a conductance-type electric sensor which can detect the existence of air bubbles through a suction pipe with no disturbances by the sensor probe and with a fine spatial resolution in order to achieve accurate measurements. As a result, we reveal the influences of the Froude number, the Reynolds number, the Weber number (or the Bond number) and three geometric parameters upon the air entrainment in over-critical-submergence condition.

Three-dimensional flow observation on the air entrainment into a vertical-wet-pit pump

The authors consider the air entrainment into a suction pipe which is vertically inserted down into a suction sump across a mean free-water surface. This configuration is often referred to as the “vertical wet-pit pump,” and has many practical advantages in construction, maintenance and operation. Most of the flows appearing in various industrial and environmental problems like the present suction- sump flow become often complicated owing to both of their unsteadiness with poor periodicity and their fully-three-dimensionality. In order to understand the complicated flow inside a suction sump in the vertical-wet-pit-pump configuration, the authors experimentally observe the flow using the three-dimensional particle tracking velocimetry (3D-PTV) technique, which includes more unknown factors in accuracy and reliability than other established measuring techniques. So, the authors examine the simultaneous measurement by the 3D-PTV with another velocimetry the ultrasonic velocity profiler. As a result, under the suitable condition with high accuracy, the authors have revealed the complicated flow.

The eddy-eliminating method of guide cone in the closed sump

In order to explore the effect on eddy-eliminating method of guide cone in the closed sump, the simple factor analysis and CFD numerical simulation are applied to calculate the flow field of closed sump and select ω-shaped back wall. ω-shaped back wall is consistent with the stream line in the suction sump, on this basis, CFD numerical simulation is conducted with the eddy-eliminating of the triangle guide cone and traditional guide cone. The results show that, for eddy-eliminating measures, with the height of triangular guide cone from 0 to 0.407HZ/DL, the excessive triangle guide cone hinder water into the flared pipe. With the width of triangular guide cone from 0.5 to 1.0BZ/DL, increasing width of triangular guide cone may increase the pumping hydraulic performance and pumping efficiency. However with the width of triangular guide cone from 0.5 to 1.0 BZ/DL, too broad traditional guide cone hinder water into the flared pipe. In the design discharge, whether triangle guide cone or traditional guide cone have a little effect on the efficiency of the pumping station. But in terms of the eddy-eliminating on the bottom of suction sump, it is necessary to set up guide cone.

The effect of suction pipe leaning angle on the internal flow of pump sump

A better flow condition for the intake of pump is provided by the sump pump that connects the forebay to the intake of the pump station. If the suction sump is improperly shaped or sized, air-entraining vortices or submerged vortices may develop. These phenomena may greatly affect pump operation if vortices become sufficiently large. Moreover, any remaining vortices in the pump flow passage may result in an increase in the noise and vibration of the pump. Therefore, the vortices in the pump flow passage must be reduced to achieve good pump sump station performance. In this study, the effect of suction pipe leaning angle on the pump sump’s internal flow is investigated. Additionally, a pipe type with an elbow shape is investigated. The results show that the air entraining vortices occur under the condition of a water level ratio H/D = 1.31 for each suction pipe type.

Numerical simulation of flow patterns in the forebay and suction sump of Tianshan pumping station

Tianshan Pumping Station takes water from the Yellow River. A three-dimensional (3D) mathematical model of turbulence flow patterns in the forebay and suction sump was developed and a 3D turbulent flow simulation technique applied to numerical calculation of the flow pattern characteristics in both the original and rebuilt forebays of the pumping station. The numerical simulation results were analyzed and contrasted. The results showed that, with technical improvement, surface backflow was avoided, and bottom velocity in the forebay was increased while bottom velocity in the suction sump was unchanged. Because of this, there was no sediment deposition in the bottom of the forebay, and flow velocities in the forebay and suction sump were more evenly distributed.

Occurrence Condition of Air Entrainment into a Vertical Wet-Pit Pump

In the present study, we consider the air entrainment into a suction pipe which is vertically inserted down into a suction sump across a mean free-water surface. This configuration is often referred to as the “vertical wet-pit pump”, and has many practical advantages in construction, maintenance and operation. In particular, we focus our concern upon the critical submergence depth Sc, which is one of the prime and conventional indicators for the air-entrainment occurrence. By a systematic approach, we experimentally investigate the influences of kinetic and geometric parameters upon Sc. As the kinetic parameters, we consider the Reynolds number Re and the Weber number We, in addition to the Froude number Fr, on such a basis as Fr is not much larger than unity in many actual cases. As the geometric parameters, we consider back clearance X, sump breadth B and bottom clearance Z. Here, all parameters are non-dimensionalised by the outside diameter D and the intake velocity Vi of the suction pipe. As a result, we reveal the effects of such six parameters upon Sc. The We effect, namely, the surface-tension effect can be ignored at We > 12. And, the Re effect, namely, the viscous effect becomes negligibly small at Re > 3×104. Under such conditions for We and Re, we could consider only the Fr effect, namely, the gravitational effect. Concerning the X/D and B/D effects, Sc/D attains the maximum at a certain X/D or B/D. On the other hand, the Z/D effect is monotonic, and becomes small at Z/D > 2.5. Some aspects of these geometric effects can be evaluated by a local-Froude-number effect on the basis of the global relation between Sc/D and Fr. And, the other aspects is necessarily considered to be related with the flow structure in the suction sump.

Experimental study on occurrence-time ratio measurements of air entrainment in a suction sump

In order to get accurate measurements of air entrainment in a suction sump, we design some new simple bubble sensors, which can detect the existence of air bubbles inside a suction pipe with no disturbances by the sensors and with a fine spatial resolution. We force on an intermittency factor γ, that is, an occurrence-time ratio of the air entrainment, and compare the result by the present sensor with those by conventional two methods; namely, visual and auditory ones. As a result, we show the criteria which specify lower-accuracy conditions in the conventional methods. By the visual method, the accuracy of the γ becomes low, when γ is less than 0.05. By the auditory method, the accuracy of γ becomes low, when the submergence depth S of the suction pipe is close to the critical one Sc.

Flow Measurements in a Suction Sump by UVP

In the present study, to reveal the air entrainment mechanism into a suction pipe in a suction sump, the authors conduct flow-velocity measurements by UDM (Ultrasonic Doppler Method). Here, we consider the simplest geometry as a suction sump, that is, a straight channel with rectangle-cross section and a simple suction pipe near the end of the channel. Ultrasonic transducers are fixed outside the side, bottom and back walls with right/near-right angles and, we get three-dimensional time-mean velocity distributions and equi-vorticity contours. At first, measurement accuracy is checked by comparing velocity profiles by UDM with hydrogen bubble method. As a result, the authors show typical flow fields in the sump, and show the relation between flow pattern and air entrainment. Especially, we compare two cases where the air entrainment is often observed.

Occurrence-Time-Ratio Measurements on Air Entrainment in a Suction Sump

In order to get accurate measurements of air entrainment in a suction sump, we design a new and simple conductance-type electric bubble sensor, which can detect the existence of air bubbles inside a suction pipe with no disturbances by the sensor and with a fine spatial resolution. We focus on occurrence-time ratio γ of the air entrainment, and compare the result by the present sensor with those by conventional two methods, namely, visual and auditory ones. As a result, we show the criteria which specify lower-accuracy conditions in the conventional methods. By the visual method, the accuracy of γ becomes low, when γ is less than 0.05. By the auditory method, the accuracy of γ becomes low, when submergence depth S of the suction pipe is close to the critical one Sc.

114 非定常3D-PTVとUVP計測による吸込水槽内の3次元流れ構造(流れ場と空力騒音,騒音・振動評価・改善技術)

In the present study, we try to reveal the instantaneous and three-dimensional flow structures in the suction sumps, because the strong unsteadiness and three-dimensionality of such flow. Specifically, we conduct consecutive flow-velocity measurements in a suction sump both by a three-dimensional particle tracking velocimetry (referred to as 3D-PTV) and an ultrasonic velocity profiler (UVP), assisting each other. As a result, we have confirmed a good agreement on time-mean three-dimensional velocity distributions between the 3D-PTV and the UVP. In addition, we reveal some typical flow fields in the sump by the 3D-PTV, and discuss the relationship between flow patterns and the air entrainment.

Flow Measurements in a Suction Sump by UVP

In the present study, to reveal the air entrainment mechanism into a suction pipe in a suction sump, the authors conduct flow-velocity measurements by UDM (Ultrasonic Doppler Method). Here, we consider the simplest geometry as a suction sump, that is, a straight channel with rectangle-cross section and a simple suction pipe near the end of the channel. Ultrasonic transducers are fixed outside the side, bottom and back walls with right/near-right angles and, we get three-dimensional time-mean velocity distributions and equi-vorticity contours. At first, measurement accuracy is checked by comparing velocity profiles by UDM with hydrogen bubble method. As a result, the authors show typical flow fields in the sump, and show the relation between flow pattern and air entrainment. Especially, we compare two cases where the air entrainment is often observed.

1524 水槽に挿入された吸込管への空気吸込(J11-5 流体連成振動(2),J11 流体関連の騒音と振動)

Regarding the air entrainment into a suction pipe which is vertically inserted into a suction sump across a free surface, critical submergence S_c are specified concerning six parameters, such as the Froude number Fr, the Reynolds number Re, the Weber number We, back clearance X, sump breadth B and bottom clearance Z. Here, all parameters are non-dimensionalized by suction-pipe outer diameter D and suction-pipe intake velocity V_i. Consequently, the authors confirmed that the surface-tension effect is negligible at We≥20, and that the viscous effect become enough small at Re≥3.2×10^4, while Fr effect is significant. Z/D effect also becomes small at Z/D≥2.5. Most of geometric effects can be explained on the basis of the Fr-S_c/D relation.

B221 ポンプ吸込水槽の高流速化に伴う空気連行現象の検討

In order to reduce costs, speed-up in a suction sump is recently suggested. However, it is predicted that excess speedup causes air entrainment and performance of a pump goes down. In this paper, air entrainment caused by speedup in a suction sump is investigated. Recently, in order to speed up development time and reduce development cost, CFD technique is often used. So, investigation was carried out by using CFD analysis. The occurrence of air entrainment was checked by void fraction.

Transport Characteristics of Selected Pressurized Water Reactor LOCA-Generated Debris

In the unlikely event of a loss-of-coolant accident (LOCA) in a pressurized water reactor, break jet impingement would dislodge thermal insulation from nearby piping, as well as other materials within the containment, such as paint chips, concrete dust, and fire barrier materials. Steam/water flows induced by the break and by the containment sprays would transport debris to the containment floor. Subsequently, debris would likely transport to and accumulate on the suction sump screens of the emergency core cooling system (ECCS) pumps, thereby potentially degrading ECCS performance and possibly even failing the ECCS.A systematic study was conducted on various types of fibrous and metallic foil debris to determine their transport in water. Test results reported include incipient movement, bulk movement, accumulation on a screen, the ability of debris to jump over 5-cm (2-in.) and 15-cm (6-in.) curbs, and the effects of accelerating flow and turbulence. These data are currently being used in conjunction with computational fluid dynamics modeling to determine the potential for each debris type to reach the suction screen.

Intermittence of the air entraining vortex and the submerged vortex in a suction sump.

Intermittence of the air entraining vortex and the submerged vortex in a suction sump.