Specificity of Flow Structure in a Dual Elbow and Its Visualization by PIV Measurement

2008 ◽  
Author(s):  
Kazuhiro Yoshida ◽  
Yuki Kazuhisa ◽  
Hidetoshi Hashizume ◽  
Saburo Toda
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Flow Structure ◽  
Nuclear Power ◽  
Power Plants ◽  
Curvature Radius ◽  
Complex Flow ◽  
Unstable Flow ◽  
Straight Pipe ◽  
Piv Measurement

A large number of pipe failures caused by wall thinning have been reported in nuclear power plants, some of which occur in a dual elbow or the vicinity of it. These pipe failures could be influenced by complex flow induced in the elbow. This study, therefore, aims at predicting the whole flow structure in the dual elbow as the first step by taking a secondary flow after the elbow by PIV measurement. A test section consists of two elbows that are 2-dimentionally connected with/without a straight pipe. They are made of acrylic resin. The diameter of the elbow is 56mm and the curvature radius ratio is 1.5. Reynolds number in this experiment is 4×104. It is confirmed that the flow structure in the dual elbow has specificity depending on the inlet flow condition to the elbow and that the secondary flow itself has swirling motion in a streamwise direction. The dual elbow seems to generate more complex and unstable flow field even when the flow field at the inlet of the elbow slightly changes from a fully developed flow. However, there is a strong possibility that putting a straight pipe between the two elbows makes it ease the occurrence of the complex flow field.

PIV Measurement of Secondary Flow in a Rotating Two-Pass Cooling System With an Improved Sequencer Technique

2011 ◽  
Vol 134 (3) ◽  
Author(s):  
Martin Elfert ◽  
Michael Schroll ◽  
Wolfgang Förster
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Cooling System ◽  
Flow Direction ◽  
Rotational Flow ◽  
Complex Flow ◽  
Reference Length ◽  
Rotation Numbers ◽  
Piv Measurement ◽  
Image Position

The flow field characteristics of a two-pass cooling system with an engine-similar layout have been investigated experimentally using the nonintrusive particle image velocimetry (PIV). It consists of a trapezoidal inlet duct, a nearly rectangular outlet duct, and a sharp 180 deg turn. The system has been investigated with smooth and ribbed walls. Ribs are applied on two opposite walls in a symmetric orientation inclined with an angle of 45 deg to the main flow direction. The applied rib layout is well proven and optimized with respect to heat transfer improvement versus pressure drop penalty. The system rotates about an axis orthogonal to its centerline. The configuration was analyzed with the planar two-component PIV technique, which is capable of obtaining complete maps of the instantaneous as well as the averaged flow field even at high levels of turbulence, which are typically found in sharp turns, in ribbed ducts, and, especially, in rotating ducts. In the past, a slip between motor and channel rotation causes additional non-negligible uncertainties during PIV measurements due to an unstable image position. These were caused by the working principle of the standard programmable sequencer unit used in combination with unsteady variations in the rotation speed. Therefore, a new sequencer was developed using FPGA-based hardware and software components from National Instruments (NI), which revealed a significant increase in the stability of the image position. Furthermore, general enhancements of the operability of the PIV system were achieved. The presented investigations of the secondary flow were conducted in stationary and, with the new sequencer technique applied, in rotating mode. Especially in the bend region, vortices with high local turbulence were found. The ribs also change the fluid motion as desired by generating additional vortices impinging the leading edge of the first pass. The flow is turbulent and isothermal; no buoyancy forces are active. The flow was investigated at a Reynolds number of Re=50,000, based on the reference length d (see Fig. 3). The rotation numbers are Ro=0.0 (nonrotating) and 0.1. Engine relevant rotation numbers are in order of 0.1 and higher. A reconstruction of some test rig components, especially the model mounting, has become necessary to reach higher values of the rotational speed compared with previous investigations such as the work of Elfert et al. (2008, “Detailed Flow Investigation Using PIV in a Rotating Square-Sectioned Two-Pass Cooling System With Ribbed Walls,” ASME Turbo Expo, Berlin, Germany, Jun. 9–13, Paper No. GT-2008-51183). This investigation is aimed to analyze the complex flow phenomena caused by the interaction of several vortices, generated by rotation, flow turning, or inclined wall ribs. The flow maps obtained with PIV are of good quality and high spatial resolution and therefore provide a test case for the development and validation of numerical flow simulation tools with special regard to the prediction of flow turbulence under the rotational flow regime, which is typical of turbomachinery. Future work will include the investigation of buoyancy effects to the rotational flow. This implicates wall heating, which results from the heater glass in order to provide transparent models.

PIV-Measurement of Secondary Flow in a Rotating Two-Pass Cooling System With an Improved Sequencer Technique

2010 ◽  
Author(s):  
M. Elfert ◽  
M. Schroll ◽  
W. Fo¨rster
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Cooling System ◽  
Flow Direction ◽  
Flow Simulation ◽  
Rotational Flow ◽  
Complex Flow ◽  
Reference Length ◽  
Piv Measurement ◽  
Image Position

The flow field characteristics of a two-pass cooling system with an engine-similar lay-out have been investigated experimentally using the non-intrusive Particle Image Velocimetry (PIV). It consists of a trapezoidal inlet duct, a nearly rectangular outlet duct, and a sharp 180 degree turn. The system has been investigated with smooth and ribbed walls. Ribs are applied on two opposite walls in a symmetric orientation inclined with an angle of 45 degrees to the main flow direction. The applied rib lay-out is well-proved and optimized with respect to heat transfer improvement versus pressure drop penalty. The system rotates about an axis orthogonal to its centreline. The configuration was analyzed with the planar two-component PIV technique (2C PIV), which is capable of obtaining complete maps of the instantaneous as well as the averaged flow field even at high levels of turbulence, which are typically found in sharp turns, in ribbed ducts and, especially, in rotating ducts. In the past, slip between motor and channel rotation causes additional not negligible uncertainties during PIV measurements due to unstable image position. These were caused by the working principle of the standard programmable sequencer unit used in combination with unsteady variations of the rotation speed. Therefore, a new sequencer was developed using FPGA-based hardware and software components from National Instruments which revealed a significant increase of the stability of the image position. Furthermore, general enhancements of the operability of the PIV system were achieved. The presented investigations of the secondary flow were conducted in stationary and, with the new sequencer technique applied, in rotating mode. Especially in the bend region vortices with high local turbulence were found. The ribs also change the fluid motion as desired by generating additional vortices impinging the leading edge of the first pass. The flow is turbulent and isothermal, no buoyancy forces are active. The flow was investigated at Reynolds number of Re = 50,000, based on the reference length d (see Fig. 3). The rotation number is Ro = 0 (non-rotating) and 0.1. Engine relevant rotation numbers are in order of 0.1 and higher. A reconstruction of some test rig components, especially the model mounting, has become necessary to reach higher values of the rotational speed compared to previous investigations like in Elfert [2008]. This investigation is aimed to analyze the complex flow phenomena caused by the interaction of several vortices, generated by rotation, flow turning or inclined wall ribs. The flow maps obtained with PIV are of good quality and high spatial resolution and therefore provide a test case for the development and validation of numerical flow simulation tools with special regard to prediction of flow turbulence under rotational flow regime as typical for turbomachinery. Future work will include the investigation of buoyancy effects to the rotational flow. This implicates wall heating which result from the heater glass in order to provide transparent models.

Experimental and Numerical Investigation of Stator Exit Flow Field of an Automotive Torque Converter

1996 ◽  
Vol 118 (4) ◽  
pp. 835-843 ◽  
Author(s):  
B. V. Marathe ◽  
B. Lakshminarayana ◽  
Y. Dong
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Numerical Investigation ◽  
Three Dimensional ◽  
Axial Flow ◽  
Torque Converter ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Complex Flow ◽  
Rate Of Decay

The objective of this investigation is to understand the nature of the complex flow field inside each element of the torque converter through a systematic experimental and numerical investigation of the flow field. A miniature five-hole probe was used to acquire the data at the exit of the stator at several operating conditions. The flow field is found to be highly three dimensional with substantial flow deviations, and secondary flow at the exit of the stator. The secondary flow structure, caused by the upstream radial variation of the through flow, induces flow overturning near the core. Flow separation near the shell causes flow underturning in this region. The rate of decay of stator wake is found to be slower than that observed in the wakes of axial flow turbine nozzles. The flow predictions by a Navier–Stokes code are in good agreement with the pressure and the flow field measured at the exit of the stator at the design and the off-design conditions.

Stress Analysis of the Canned Nuclear Coolant Pump Based on FSI

2014 ◽  
Author(s):  
Zhang Ji-Ge ◽  
Zhu Yue
Keyword(s):  
Power Plant ◽  
Flow Field ◽  
Nuclear Power ◽  
Power Plants ◽  
Maximum Stress ◽  
Guide Vane ◽  
Von Mises Stress ◽  
Impeller Blade ◽  
Coolant Pump ◽  
Large Power

The reactor coolant pump (RCP) is one of the most important components in nuclear power plants. It operated in high temperature, high-pressure, high speed and radiative environment, so a long-term security and reliable operations is required. Many internal flow analysis of RCPs was carried out, mainly foucs on steady and unsteady flow field at different operating points in RCP. The research about flow passage components, such as the blade of the RCP, is relatively few. When the RCPs operates in the nuclear power plant, the flow field lashed against the impeller of the RCP, results in a network of small cracks is found on the surface of impeller. For example, periodic vibration caused by a break in a guide vane leaded to cracking of two pieces blades of impeller in a large power plant in southwest of China, and this accident caused much economic loss. The computational method of stress due to the hydraulic reason is an important problem of the RCP. In this work, at first the CFD simulation including the case, guide vane, impeller, inlet and outlet at different operation points is studied, and the result of the pressure distribution on impeller blade is loaded on the impeller using fluid-structure interation (FSI) method. The result showed that the maximum von Mises stress appears on the trailing edge close to the impeller hub which has a large change in gradient of stress and which is prone to fatigue failure. The maximum stress on the impeller is mainly in proportion to the operating power. The maximum stress on the impeller have periodical characteristic, which is due to the number of blade of diffuser. All of these equip us with better understand of the fatigue and fracture of RCP, and it make sense to protect the fatigue damage and promote the stability of RCP.

Visualization experiment of complex flow field in a sphere-packed pipe by detailed PIV measurement

2014 ◽  
Vol 89 (7-8) ◽  
pp. 1251-1256 ◽  
Author(s):  
Shinji Ebara ◽  
Mohammad Reza Nematollahi ◽  
Hidetoshi Hashizume
Keyword(s):  
Flow Field ◽  
Complex Flow ◽  
Piv Measurement ◽  
Visualization Experiment

Numerical Analysis of Unsteady Flow Field in the RWT for the Prediction of the Potential for Air Ingression Into the ECC Supply Lines During the SBLOCA at the KSNPs

2007 ◽  
Author(s):  
Jong Chull Jo ◽  
Seon Oh Yu
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Water Level ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Vortex Flow ◽  
Air Entrainment ◽  
Water Tank ◽  
Outlet Valve

This paper addresses the three-dimensional analysis of unsteady flow in the RWT (Refueling Water Tank) for the prediction of the potential for air ingression into the ECC (Emergency Core Cooling) pump during the SBLOCA (Small Break Loss Of Coolant Accident) at KSNPs (Korean Standard Nuclear Power plants). Upon the receipt of RAS (Recirculation Actuation Signal) by the occurrence of SBLOCA, the RWT outlet valve is designed to be isolated manually. At the nuclear power plants without the provision of automatic isolation operation of the valve on the downstream of the RWT line, the refueling water begins to discharge from the RWT, which may result in forming and developing the vortex flow in the RWT, under the condition of the minimum pressure of containment and minimum water level of containment recirculation sump during the phase of RAS. Due to the vortex flow, when the water level is below the critical height, a dip starts to develop, causing air ingression before the refueling water drains fully. Hence it can be surmised that there is a possibility of ECC pump failure due to air ingression into the ECC supply line even before the RWT is fully drained. Therefore, in this work, when the RAS is actuated followed by the SBLOCA occurrence, a quantitative evaluation for the maximum limiting allowable time for the manual closing of RWT outlet valve is carried out to eliminate the possibility of air ingression into the ECC pump from the RWT. To do this, the unsteady flow field in the RWT including the drain pit with the connected discharge piping in the process of SBLOCA is analyzed using a CFD (Computational Fluid Dynamics) code. In addition, the transient flow behavior accompanying air entrainment resulting from the dip formation due to vortex flow at the upper part of RWT is examined and the applicable limiting time of the isolation valve closing for preventing air ingression is assessed.

scholarly journals Preferred Site Selection Using GIS and AHP: Case Study in Bangka Island NPP Site

2021 ◽  
Vol 23 (1) ◽  
pp. 51
Author(s):  
Ari Nugroho ◽  
Eko Kusratmoko ◽  
Tito L. Indra
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Site Selection ◽  
Nuclear Power ◽  
Power Plants ◽  
Cooling System ◽  
Final Decision ◽  
Unstable Flow ◽  
Energy Agency

PREFERRED SITE SELECTION USING GIS AND AHP: CASE STUDY IN BANGKA ISLAND NPP SITE. Industrial growth affects the increasing demand for electricity in various places, this also occurs on the island of Bangka. So far, electricity supply has only been obtained from fossil fuel power plants with inadequate capacity, unstable flow and depending on fuel supplies from outside the island. For this reason, it is necessary to build a Nuclear Power Plant (PLTN) which is believed to be reliable and able to overcome these problems. In order to prepare a safe and economical nuclear power plant site, influential parameters such as population density, cooling system, land clearing, cut and fill, and granite for the foundation have been analyzed. The novelty of this analysis lies in 2 methods which gradually used before come up with a final decision, namely spatial analysis and pairwise comparison using Geographic Information Systems (GIS) and Analytical Hierarchy Process (AHP), respectively. The scope of study area is based on the site vicinity (1:5.000) scale, located in the districts of West and South Bangka. The siting process refers to the rules set by the International Atomic Energy Agency (IAEA). Based on the final results of the analysis using the expert choice program, the numerical weights for West Bangka and South Bangka were 0.709 and 0.291, respectively, with a consistency value of 0.03.

Time-Resolved Stereo PIV Measurements of Flow Fields Inside a Rotating Cavity

2014 ◽  
Author(s):  
Junya Kouwa ◽  
Takahisa Nagao ◽  
Shinsuke Matsuno ◽  
Yukie Sasaki ◽  
Koutarou Hisaeda
Keyword(s):  
Flow Field ◽  
Flow Structure ◽  
Flow Fields ◽  
Experimental Result ◽  
Rossby Number ◽  
Complex Flow ◽  
Experimental Conditions ◽  
Time Resolved ◽  
Rotating Cavity ◽  
Structure Of Flow

This paper describes the experimental and numerical results of flow fields inside a rotor-stator rotating cavity. The rotational speeds and the axial throughflow are varied as experimental conditions. In the experiment, 3-components velocity vectors on the r–θ and r–z sections are obtained by a stereo dynamic PIV system to understand complex flow fields in detail such as flow structure and unsteadiness. A large eddy simulation (LES) is also carried out to confirm the analytical capability for the rotating cavity and to complement the understanding of the flow field. From the results, axisymmetric steady flow fields are observed under high Rossby number conditions, while several vortices are captured in the cavity in the r – θ section under low Rossby number conditions. The visualization results with seeding tracers for PIV show the flow structure of flow fields. LES can predict the flow field of the experimental result and the behavior of vortices which are varied as to the change of Ro conditions.

Coriolis Effects on the Flow Field Inside a Rotating Triangular Channel for Leading Edge Cooling

2013 ◽  
Vol 136 (3) ◽  
Author(s):  
Matteo Pascotto ◽  
Alessandro Armellini ◽  
Claudio Mucignat ◽  
Luca Casarsa
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Flow Structure ◽  
Cross Section ◽  
Working Conditions ◽  
Rotation Axis ◽  
Leading Edge ◽  
Channel Cross Section ◽  
Smooth Channel ◽  
Static Conditions

The flow field inside a rotating smooth radial channel with a triangular shaped cross section is investigated. Test conditions resemble those pertaining to the passages used for the internal cooling of the gas turbine blade's leading edge. Heat transfer data are also available from the literature on the same geometry and at comparable working conditions and have been profitably used for a combined aerothermal analysis. The model consists of a straight smooth channel with an equilateral triangle cross section. The rotation axis is aligned with one of the triangle bisectors. Two dimensional particle image velocimetry (PIV) and stereo-PIV were used in order to characterize the inlet flow (in static conditions) and the rotation-induced secondary flow in the channel cross section at Re = 20,000, Ro = 0.2 and Re = 10,000, Ro = 0.4. A wider range of working conditions (Re = 10,000–40,000, Ro = 0.2–0.6) was explored by means of Reynolds averaged Navier–Stokes (RANS) simulations carefully validated by the available PIV data. The turbulence was modeled by means of the shear stress transport (SST) model with a hybrid near-wall treatment. The results show that the rotation-induced flow structure is rather complicated and show relevant differences compared to the flow models that have been considered thus far. Indeed, the secondary flow turned out to be characterized by the presence of two or more vortex cells, depending on channel location and Ro number. No separation or reattachment of these structures is found on the channel walls but they have been observed at the channel apexes. The stream-wise velocity distribution shows a velocity peak close to the lower apex and the overall flow structure does not reach a steady configuration along the channel length. This evolution is fastened (in space) if the rotation number is increased while changes of the Re number have no effect. Finally, due to the understanding of the flow mechanisms associated with rotation, it was possible to provide a precise justification of the channel thermal behavior.

An Experience on the Elimination of Check Valve Chattering in a NPP

2016 ◽  
Author(s):  
Tae Ryong Kim
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Nuclear Power ◽  
Incidence Angle ◽  
Cooling Water ◽  
Check Valve ◽  
Field Analysis ◽  
Vibration Measurement ◽  
Curved Pipes ◽  
Flow Field Analysis

Tapping noise and vibration was observed at a swing check valve located on an auxiliary cooling water line during operation in a nuclear power plant. For the identification of the main cause and its elimination of continuous tapping noise in check valve, site inspection, vibration measurement and flow field analysis was done. FLUENT code was used to analyze the flow field in piping and elbow. It can be concluded as follows from inspection, measurement and analysis: A check valve should be installed so that the axis of hinge is perpendicular to the plane of the curved pipes, considering the secondary flow to be formed in the cross-section of the pipe. In this configuration the secondary flow impinged to the front side of valve disk could increase the effective incidence angle, which makes the disk kept in the fully open position.

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