Effect of Solidification on Molten Material Jet Behavior in Coolant

2014 ◽  
Author(s):  
Yuzuru Iwasawa ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Shimpei Saito ◽  
Hideki Nariai ◽  
...  
Keyword(s):  
Melting Point ◽  
Energy Release ◽  
High Speed ◽  
Heat Removal ◽  
Injection Velocity ◽  
Molten Material ◽  
Breakup Length ◽  
Jet Breakup ◽  
Jet Behavior ◽  
Interfacial Temperature

For the safety design of a Fast Breeder Reactor (FBR), if a Core Disruptive Accident (CDA) occurred hypothetically, it is required to suppress the rapid energy release due to a prompt criticality. Even if the rapid energy release does not occur, there is a possibility that a large amount of fuel melts. Therefore it is important to achieve Post Accident Heat Removal (PAHR). In order to achieve PAHR, it is strongly required that the molten material which is released from a core region gets cool and solidifies in the sodium coolant in a reactor vessel by breaking up. It is considered that the molten fuel is injected into the coolant like a jet. Furthermore, in the actual FBR, the interfacial temperature between the molten fuel jet and the coolant is considered to be lower than the melting point of the molten material. Thus for PAHR in CDA, it is important to understand the interaction between the jet and the coolant in such a condition and to estimate the molten jet behavior quantitatively. In order to estimate quantitatively the effects of the solidification on the molten jet behavior, we carried out the experiment in which a simulant material was injected into a simulant coolant. In the experiment, we used low melting point alloy (Bi -Sn) and water as the simulant molten material and the simulant coolant respectively. In the experiments, we chose the temperature range including the condition that the interfacial temperature was lower than the melting point of the molten material. The jet breakup and the fragmentation behavior of the molten material jet were observed with a high speed video camera. Then the jet breakup length is estimated form the results. We changed the initial interfacial temperature condition by adjusting temperature of the molten material and the coolant. We also changed the jet velocity by adjusting the height of the nozzle tip from the water surface. From the experiment, we found that the jet breakup behavior depends greatly on the interfacial temperature and the injection velocity and that the solidification of a molten material jet and the growth of unstable jet surface, which results from the relative velocity of the jet to the coolant, are in a competitive relation for the jet breakup. We also found that when the molten material jet breaks up into fragments, the breakup length is independent of the initial interfacial temperature and the initial injection velocity.

Influence of the Fragmentation Behavior on Molten Material Jet Breakup in Coolant

2013 ◽  
Author(s):  
Yuzuru Iwasawa ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Taihei Kuroda ◽  
Eiji Matsuo ◽  
...  
Keyword(s):  
High Speed ◽  
Density Ratio ◽  
Heat Removal ◽  
Free Fall ◽  
Core Material ◽  
Dominant Factor ◽  
Sodium Coolant ◽  
Molten Material ◽  
Fragmentation Behavior ◽  
Jet Breakup

For the safety design of a Fast Breeder Reactor (FBR), Post Accident Heat Removal (PAHR) is required when a hypothetical Core Disruptive Accident (CDA) occurs. In PAHR, it is strongly required that the molten core material can be solidified and cooled down by the sodium coolant in a reactor vessel. In order to estimate whether the molten material jet is completely solidified by sodium coolant, it is necessary to understand the interaction between the molten core material and the coolant. The objective of the present study is to clarify the dominant factor of the jet breakup length and the size of the fragments experimentally. In this study, we injected molten material (Sn–Bi alloy) into coolant (water) at free fall speed. We can simulate an actual FBR system by using Sn-Bi alloy and water because the density ratio of them is similar to that of an actual FBR system. The jet breakup and the fragmentation behavior of the molten material jet were observed with a high speed video camera. In the previous study which we conducted, solidified crust is generated by the solidification on the molten material jet surface and affects the jet breakup and the fragmentation behavior. Then from the experimental results, in order to predict the size of fragments, it is constructed that the instability model based on hydrodynamic and material mechanics. Then in this paper, the surface close-up of the molten material jet was observed in order to investigate the effect of the solidification on the molten material jet surface.

Experimental Study on Jet Breakup Behavior With Surface Solidification

2010 ◽  
Author(s):  
Takashi Wada ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Yuta Uchiyama ◽  
Hideki Nariai ◽  
...  
Keyword(s):  
Size Distribution ◽  
Reactor Vessel ◽  
Image Processing Technique ◽  
Core Material ◽  
Dominant Factor ◽  
Sodium Coolant ◽  
Molten Material ◽  
Breakup Length ◽  
Jet Breakup ◽  
Median Diameter

For the safety design of the Fast Breeder Reactor (FBR), the Post Accident Heat Removal (PAHR) is required when a hypothetical Core Disruptive Accident (CDA) occurs. In the PAHR, it is strongly required that the molten core material can be cooled down and solidified by the sodium coolant in the reactor vessel. There is high possibility for molten material to be ejected as a liquid jet into sodium coolant in the reactor vessel. In order to estimate whether the molten material jet is completely solidified by sodium coolant or not, it is necessary to understand the interaction between molten core material and coolant such as jet breakup and fragmentation behavior in coolant. The jet breakup behavior is the phenomenon that the front of molten material breaks up in coolant. To clarify the mechanism of jet breakup and fragmentation during the CDA for the FBR, it is necessary to understand the correlation between jet breakup lengths and size distribution of fragments when molten material jet interacting with coolant. The objective of the present study is to clarify the dominant factor of the jet breakup length and the size distribution of fragments experimentally. Molten jet of U-alloy 138 is injected into water as simulated core material and coolant by free-fall. The density ratio of core material and coolant is almost same as that of the real FBR system. The jet breakup behavior as interaction of molten material with coolant is observed with high speed video camera. Front velocity of the molten material jet is estimated by using the image processing technique. It suddenly decreases when the jet fall into the coolant. The jet breakup length estimated from observed images is compared with the breakup theories to understand the effect of experimental parameters for the jet breakup length. The solidified fragments are gathered and classified in size, and the mass in each size is measured. Median diameter is obtained from the mass distribution of the fragments. In comparison with interfacial instabilities, the median diameter of fragments shows the independent of relative velocity. The jet breakup lengths and median diameters compared with existing theories is discussed.

Visual Observation of Fragmentation Behavior on Molten Material Jet Surface in Coolant

2008 ◽  
Author(s):  
Yuta Uchiyama ◽  
Yutaka Abe ◽  
Akiko Fujiwara ◽  
Hideki Nariai ◽  
Eiji Matsuo ◽  
...  
Keyword(s):  
Water Surface ◽  
High Speed ◽  
Internal Flow ◽  
Core Material ◽  
Generation Process ◽  
High Speed Camera ◽  
Sodium Coolant ◽  
Molten Material ◽  
Fragmentation Behavior ◽  
Jet Breakup

For the safety design of the Fast Breeder Reactor (FBR), it is strongly required that the post accident heat removal (PAHR) is achieved after a postulated core disruptive accident (CDA). In the PAHR, it is important that the molten core material is solidified in sodium coolant which has high boiling point. Thus it is necessary to estimate the jet breakup length which is the distance that the molten core material is solidified in sodium coolant. In the previous studies (Abe et al., 2006), it is observed that the jet is broken up with fragmenting in water coolant by using simulated core material. It is pointed out that the jet breakup behavior is significantly influenced by the fragmentation behavior on the molten material jet surface in the coolant. However, the relation between the jet breakup behavior and fragmentation on the jet surface during a CDA for a FBR is not elucidated in detail yet. The objective of the present study is to elucidate the influence of the internal flow in the jet and fragmentation behavior on the jet breakup behavior. The Fluorinert™ (FC-3283) which is heavier than water and is transparent fluid is used as the simulant material of the core material. It is injected into the water as the coolant. The jet breakup behavior of the Fluorinert™ is observed by high speed camera to obtain the fragmentation behavior on the molten material jet surface in coolant in detail. To be cleared the effect of the internal flow of jet and the surrounding flow structure on the fragmentation behavior, the velocity distribution of internal flow of the jet is measured by PIV (Particle Image Velocimetry) technique with high speed camera. From the obtained images, unstable interfacial wave is confirmed at upstream of the jet surface, and the wave grows along the jet-water surface in the flow direction. The fragments are torn apart at the end of developed wave. By using PIV analysis, the velocity at the center of the jet is fast and it suddenly decreases near the jet surface. This means that the shear force acts on the jet and water surface. From the results of experiment, the correlation between the interfacial behavior of the jet and the generation process of fragments are discussed. In addition, the influence of surface instability of the jet induced by the relative velocity between Fluorinert™ and coolant water on the breakup behavior is also discussed.

Hydraulic Performance and Jet Breakup Characteristics of the Impact Sprinkler with Circular and Non-circular Nozzles

2019 ◽  
Vol 35 (6) ◽  
pp. 911-924 ◽  
Author(s):  
Yue Jiang ◽  
Hong Li ◽  
Chao Chen ◽  
Lin Hua ◽  
Daming Zhang
Keyword(s):  
High Speed ◽  
Cone Angle ◽  
Hydraulic Performance ◽  
High Speed Photography ◽  
Breakup Process ◽  
Breakup Length ◽  
Jet Breakup ◽  
Circular Jets ◽  
Square Jets ◽  
The Impact

HighlightsThe hydraulic performance of the impact sprinkler with circular and non-circular nozzles were measured.A High-Speed Photography (HSP) technique was employed to extract the jet breakup process of the impact sprinkler.Two index equations of jet characteristic lengths and equivalent diameters of non-circular nozzles were fitted. Abstract. An experiment was carried out to investigate the hydraulic performance of an impact sprinkler by using circular and non-circular nozzles. A High-Speed Photography (HSP) technique was employed to extract the breakup process and flow behavior of low-intermediate pressure water jets issued from the different types of orifices. These orifices were selected by the principle of equal flowrate with the same pressure. Moreover, two characteristic lengths: the jet breakup length and the initial amplitude of surface wave were measured. It was found that the sprinkler with circular nozzles produced the largest radius of throw followed by square nozzles and regular triangular nozzles when the cone angle of nozzle and pressure were unchanged, while the sprinkler with regular triangular nozzle had the best variation trend of water distribution and combination uniformity coefficient. Regular triangular jets exhibited a higher degree in breakup and the shortest breakup length compared with the square jets and the circular jets. The initial amplitudes of surface waves of regular triangular jets were larger than the square jets and the circular jets with the same cone angle. Two index equations of jet characteristic lengths and equivalent diameters of both circular and non-circular orifices were fitted with a relative error of less than 10%, which means the fitting formulas were accurate. Keywords: Breakup length, Fitting formula, Hydraulic performance, Initial amplitude, Non-circular jets.

Numerical Simulation of Liquid Jet Behavior in Shallow Pool by Interface Tracking Method

2020 ◽  
Author(s):  
Takayuki Suzuki ◽  
Hiroyuki Yoshida ◽  
Naoki Horiguchi ◽  
Sota Yamamura ◽  
Yutaka Abe
Keyword(s):  
Numerical Simulation ◽  
Hydrodynamic Interaction ◽  
Reactor Vessel ◽  
Severe Accident ◽  
Water Pool ◽  
Molten Material ◽  
Jet Breakup ◽  
Jet Behavior ◽  
Lattice Resolution ◽  
Core Materials

Abstract In the severe accident (SA) of nuclear reactors, fuel and components melt, and melted materials fall to a lower part of a reactor vessel. In the lower part of a reactor vessel, in some sections of the SAs, it is considered that there is a water pool. Then, the melted core materials fall into a water pool in the lower plenum as a jet. The molten material jet is broken up, and heat transfer between molten material and coolant may occur. This process is called a fuel-coolant interaction (FCI). FCI is one of the important phenomena to consider the coolability and distribution of core materials. In this study, the numerical simulation of jet breakup phenomena with a shallow pool was performed by using the developed method (TPFIT). We try to understand the hydrodynamic interaction under various, such as penetration, reach to the bottom, spread, accumulation of the molten material jet. Also, we evaluated a detailed jet spread behavior and examined the influence of lattice resolution and the contact angle. Furthermore, the diameters of atomized droplets were evaluated by using numerical simulation data.

Experimental Investigation of Liquid Jet Breakup in a Cross Flow of a Swirling Air Stream

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Tushar Sikroria ◽  
Abhijit Kushari ◽  
Saadat Syed ◽  
Jeffery A. Lovett
Keyword(s):  
Experimental Investigation ◽  
Momentum Flux ◽  
High Speed ◽  
Cross Flow ◽  
Flux Ratio ◽  
Liquid Jet ◽  
Breakup Process ◽  
Breakup Length ◽  
Jet Breakup ◽  
Penetration Behavior

This paper presents the results of an experimental investigation of liquid jet breakup in a cross flow of air under the influence of swirl (swirl numbers 0 and 0.2) at a fixed air flow Mach number 0.12 (typical gas turbine conditions). The experiments have been conducted for various liquid to air momentum flux ratios (q) in the range of 1 to 25. High speed (@ 500 fps) images of the jet breakup process are captured and those images are processed using matlab to obtain the variation of breakup length and penetration height with momentum flux ratio. Using the high speed images, an attempt has been made to understand the physics of the jet breakup process by identification of breakup modes—bag breakup, column breakup, shear breakup, and surface breakup. The results show unique breakup and penetration behavior which departs from the continuous correlations typically used. Furthermore, the images show a substantial spatial fluctuation of the emerging jet resulting in a wavy nature related to effects of instability waves. The results with 15 deg swirl show reduced breakup length and penetration related to the nonuniform distribution of velocity that offers enhanced fuel atomization in swirling fuel nozzles.

Influence of Hydrodynamic Interaction on Jet Breakup and Fragmentation Behavior

2014 ◽  
Author(s):  
Shimpei Saito ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Yuzuru Iwasawa ◽  
Eiji Matsuo ◽  
...  
Keyword(s):  
High Speed ◽  
Hydrodynamic Interaction ◽  
Heat Removal ◽  
Leading Edge ◽  
Air Entrainment ◽  
Video Camera ◽  
Liquid System ◽  
Core Material ◽  
Edge Region ◽  
Jet Breakup

Mitigative measures against a Core Disruptive Accident (CDA) are important from the viewpoints of safety of a Fast Breeder Reactor (FBR). If a CDA occurs, Post Accident Heat Removal (PAHR) must be surely achieved. In the PAHR, molten materials are likely to be injected into the coolant like a jet and they must satisfy two requests simultaneously: fast ejection and stable cooling after quenched. In order to estimate the quench behavior of the molten jet, it is important to understand how the jet breaks up. The objective of this study is to clarify that the influence of hydrodynamic interaction between a jet and the surrounding fluid on jet breakup. Previous works have clarified that one cause of the jet breakup is provoked by fragmentation at the side of a jet. However, there are few detailed results describing the correlation between jet breakup and hydrodynamic interaction at the leading-edge region of a jet. Additionally, air entrainment with a jet is always observed in our past experiments using simulants, but its influence has not been discussed yet. In this study, jet injection experiments in liquid-liquid system were conducted for investigating the interaction a jet and an ambient fluid, and the effect of air entrainment on jet breakup behavior. Both simulant core materials and coolants were transparent liquids for visualization. The stored simulant core material was injected into a tank filled with the simulant coolant. In order to realize the condition without air entrainment, the air remaining within the nozzle was removed using a syringe. The jet breakup behavior was observed with a high speed video camera. A normal backlight system and a Laser Induced Fluorescence (LIF) system were employed for visualization. The inner velocity distribution of a jet was measured by Particle Image Velocimetry (PIV). As a result, in the experiments without air entrainment the jet breakup lengths were described by Epstein’s equation. In addition, a pair of vortices was observed at the leading-edge region. The vortices were generated at the leading edge and the leading edge rolled up by the vortices returned toward a jet core. Thus, it was very likely that the vortices at the leading edge region promoted jet breakup.

Experimental Study on Jet Breakup Morphologies and Jet Characteristic Parameters of Non-circular Nozzles under Low-intermediate Pressures

2019 ◽  
Vol 35 (4) ◽  
pp. 617-632
Author(s):  
Yue Jiang ◽  
Hong Li ◽  
Lin Hua ◽  
Daming Zhang ◽  
Zakaria Issaka
Keyword(s):  
Surface Wave ◽  
High Speed ◽  
Flow Behavior ◽  
Initial Section ◽  
Droplet Formation ◽  
High Speed Photography ◽  
Breakup Length ◽  
Jet Breakup ◽  
Circular Jets ◽  
Pressure Water

Abstract. A High-Speed Photography (HSP) technique was used to investigate the breakup process and flow behavior of low-intermediate pressure water jets issued from square and triangular shaped nozzles. The non-circular orifices were designed based on the principle of equal flowrate with the same pressure in relation to the circular orifice. The breakup morphologies and boundary structures of the jets were studied under different nozzles and working pressures. Two forms of droplet formation and the process of droplet formation, in addition to the jet breakup lengths, initial amplitudes of surface waves and jet diffusion angles of different nozzles were evaluated. It was found that the jet presented a good continuity and fluidity in the initial section, and the fluid bands gradually appeared due to the air resistance and the jet break up as the disturbance intensifies. The degree of jet breakup was enhanced with the increase of pressure and cone nozzle angle. The random appearance of the fluid band structures and the dactylitic textures near the nozzles for non-circular jets appeared earlier than those produced by the circular jets. The small satellite droplets with different shapes and sizes were seen inside and outside the jet interface. Triangular jets exhibited the shortest breakup length, the initial amplitude of surface wave, and the diffusion angle of the jet at the same pressure were largest compared with square and circular jets. Two index equations of jet characteristic lengths and equivalent diameters of both circular and non-circular nozzles were fitted with a relative error of less than 10%, which means the fitting formulas are accurate. Keywords: Breakup length, High-speed photography, MATLAB simulation, Non-circular nozzle, Surface wave amplitude.

Estimation of Fragmentation on Jet Breakup in Coolant

2012 ◽  
Author(s):  
Taihei Kuroda ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Iwasawa Yuzuru ◽  
Hideki Nariai ◽  
...  
Keyword(s):  
Flow Field ◽  
Tap Water ◽  
Energy Ratio ◽  
Liquid Jet ◽  
Sodium Coolant ◽  
Molten Material ◽  
Colorless Liquid ◽  
Fragmentation Behavior ◽  
Breakup Length ◽  
Jet Breakup

Fast Breeder Reactor (FBR) is designed with safety in mind. However, there is billion to one possibility that a hypothetical Core Disruptive Accident (CDA) occurs. When CDA occurs, the Post Accident Heat Removal (PAHR) must be achieved. In the PAHR, the molten material is required to be fragmented and solidified in sodium coolant. In order to estimate whether the molten material jet is completely solidified in sodium coolant or not, it is significant to estimate jet breakup length. Although, the jet breakup length is influenced with fragmentation behavior, the correlation between them is not clear yet. Therefore, it is strongly required to clarify the mechanism of the fragmentation behavior on the jet surface. The objective of the present study is to estimate fragmentation on jet breakup in coolant experimentally. Tap water and Fluorinert™ (FC-3283) are used as simulated coolant and molten material, respectively. Flourinert is transparent and colorless liquid and its density is higher than water, therefore we can observe internal flow structure of Fluorinert. Fluorinert injected into water, and the jet breakup behavior and the fragmentation behavior of the jet are observed by using high speed video camera. In order to estimate fragmentation on liquid jet, we identified the position of the interface with back lighting technique and also, we conducted velocity measurement with Particle Image Velocimetry (PIV) technique simultaneously. It is observed that interfacial waves of the jet are generated. Waves are pulled with surrounding liquid and grown up. Finally, a fragment is separated as a droplet from front edge of the wave. Also, the vorticity is evaluated from the velocity data in order to investigate influence of the flow field in detail. From the result of calculating vorticity, the high value was estimated when jet was fragmented. It is suggested that fragmentation behavior correlates with the surrounding flow field. And the energy ratio contributing to fragmentation is calculated from velocity field. The energy ratio is important to investigate the amount of the fragmentation on liquid jet. Fragmentation on jet breakup in coolant is estimated.

Experimental Investigation of Liquid Jet Breakup in Cross Flow of Swirling Air Stream

2013 ◽  
Author(s):  
Tushar Sikroria ◽  
Abhijit Kushari ◽  
Saadat Syed ◽  
Jeffery A. Lovett
Keyword(s):  
Experimental Investigation ◽  
Momentum Flux ◽  
High Speed ◽  
Cross Flow ◽  
Flux Ratio ◽  
Liquid Jet ◽  
Breakup Process ◽  
Breakup Length ◽  
Jet Breakup ◽  
Penetration Behavior

This paper presents the results of an experimental investigation of liquid jet breakup in a cross-flow of air under the influence of swirl (swirl numbers 0 and 0.2) at a fixed air flow Mach No. 0.12 (typical gas turbine conditions). The experiments have been conducted for various liquid to air momentum flux ratios (q) in the range of 1 to 25. High speed (@ 500 fps) images of the jet breakup process are captured and those images are processed using MATLAB to obtain the variation of breakup length and penetration height with momentum flux ratio. Using the high speed images, an attempt has been made to understand the physics of the jet breakup process by identification of breakup modes — bag breakup, column breakup, shear breakup and surface breakup. The results show unique breakup and penetration behavior which departs from the continuous correlations typically used. Furthermore, the images show a substantial spatial fluctuation of the emerging jet resulting in a wavy nature related to effects of instability waves. The results with 15° swirl show reduced breakup length and penetration related to the non-uniform distribution of velocity that offers enhanced fuel atomization in swirling fuel nozzles.

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