Development of Numerical Simulation for Jet Breakup Behavior in Complicated Structure of BWR Lower Plenum: 1 — Preliminary Analysis of Jet Breakup Behavior in Complicated Structure by TPFIT

2013 ◽  
Author(s):  
Takayuki Suzuki ◽  
Hiroyuki Yoshida ◽  
Fumihisa Nagase ◽  
Yutaka Abe ◽  
Akiko Kaneko
Keyword(s):  
High Speed ◽  
Measured Data ◽  
Severe Accident ◽  
Interface Tracking ◽  
Phase Flow ◽  
Complicated Structure ◽  
Support Plate ◽  
Jet Breakup ◽  
Multi Phase ◽  
Developing Method

In order to improve the safety of Boiling Water Reactor (BWR), it is required to know the behavior of the plant when an accident occurred as can be seen at Fukushima Daiichi nuclear power plant accident. Especially, it is important to estimate the behavior of molten core jet in the lower part of the containment vessel at severe accident. In the BWR lower plenum, the flow characteristics of molten core jet are affected by many complicated structures, such as control rod guide tubes, instrument guide tubes and core support plate. However, it is difficult to evaluate these effects on molten core jet experimentally. Therefore, we considered that multi-phase computational fluid dynamics approach is the best way to estimate the effects on molten core jet by complicated structure. The objective of this study is to develop the evaluation method for the flow characteristic of molten core jet including the effects of the complicated structures in the lower plenum. So we are developing a simulation method to estimate the behavior of molten core jet falling down through the core support plate to the lower plenum of the BWR. The method has been developed based on interface tracking method code TPFIT (Two Phase Flow simulation code with Interface Tracking). To verify and validate the applicability of the developed method in detail, it is necessary to obtain the experimental data that can be compared with detailed numerical results by the TPFIT. Thus, in this study, we are carrying out experimental works by use of multi-phase flow visualization technique. In the experiments, time series of interface shapes are observed by high speed camera and velocity profiles in/out of the jet will be measured by the PIV method. In this paper, the outline of the developing method based on the TPFIT was explained. And, the developing method was applied to preliminary experiment with/without modeled complicated structures. As the results, predicted interface shapes were almost agreed with measured data. However, predicted falling down velocity of the jet was lower than measured data. We considered causes of this underestimation and improved the method and simulation conditions to resolve this problem.

Development of Numerical Simulation for Jet Breakup Behavior in Complicated Structure of BWR Lower Plenum: (4) Multi-Channel Experimental Analysis by Detailed Two-Phase Analysis Code TPFIT

2014 ◽  
Author(s):  
Takayuki Suzuki ◽  
Hiroyuki Yoshida ◽  
Fumihisa Nagase ◽  
Yutaka Abe ◽  
Akiko Kaneko
Keyword(s):  
High Speed ◽  
Evaluation Method ◽  
Simulation Method ◽  
Severe Accident ◽  
Interface Tracking ◽  
Phase Flow ◽  
Complicated Structure ◽  
Two Phase ◽  
Support Plate ◽  
Multi Phase

In order to improve the safety of Boiling Water Reactor (BWR), it is required to know the behavior of the plant when an accident occurred as can be seen at Fukushima Daiichi nuclear power plant accident. Especially, it is important to estimate the behavior of molten core jet in the lower part of the reactor pressure vessel at a severe accident. In the BWR lower plenum, the flow characteristics of molten core jet are affected by many complicated structures, such as control rod guide tubes, instrument guide tubes and core support plate. However, it is difficult to evaluate these effects on molten core jet experimentally. Therefore, we considered that multi-phase computational fluid dynamics approach is the best way to estimate the effects on molten core jet by complicated structure. The objective of this study is to develop the evaluation method for the flow characteristic of molten core jet including the effects of the complicated structures in the lower plenum. So we are developing a simulation method to estimate the behavior of molten core jet falling down through the core support plate to the lower plenum of the BWR. The simulation method is based on interface tracking method code TPFIT (Two Phase Flow simulation code with Interface Tracking). To verify and validate the applicability of the developed method in detail, it is necessary to obtain the experimental data that can be compared with detailed numerical results by the TPFIT. Thus, the authors are carrying out experimental works by use of multi-phase flow visualization technique. In the experiments, time series of interface shapes are observed by high speed camera and velocity profiles in/out of the jet are measured by the PIV method. In this paper, we carried out analysis of the multi-channel experiment using the analytical method based on the TPFIT. Specifically, predicted results including interface shape and velocity profile in and out simulated molten material were compared with measured results. In the results, predicted results agreed with measured results qualitatively.

Development of Numerical Simulation for Jet Breakup Behavior in Complicated Structure of BWR Lower Plenum: 2 — Flow Observation With Visualized Experimental Apparatus

2013 ◽  
Author(s):  
Ryusuke Saito ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Takayuki Suzuki ◽  
Hiroyuki Yoshida ◽  
...  
Keyword(s):  
Single Channel ◽  
Flow Channel ◽  
Type Model ◽  
Interface Tracking ◽  
Phase Flow ◽  
Complicated Structure ◽  
Support Plate ◽  
Jet Breakup ◽  
Experimental Apparatus ◽  
Multi Phase

In order to improve the safety of Boiling Water Reactor (BWR), it is required to know the behavior of the plant when an accident occurred as can be seen at Fukushima Daiichi nuclear power plant accident. Especially, it is important to estimate the behavior of molten core jet in the lower part of the containment vessel at severe accident. In the BWR lower plenum, the flow characteristics of molten core jet are affected by many complicated structures, such as control rod guide tubes (CRGT), instrument guide tubes and core support plate. However, it is difficult to evaluate these effects on molten core jet experimentally. Therefore, we considered that multi-phase computational fluid dynamics approach is the best way to estimate the effects on molten core jet by complicated structure. The objective of this study is to develop the evaluation method for the flow characteristic of molten core jet including the effects of the complicated structures in the lower plenum. So we are developing a simulation method to estimate the behavior of molten core jet falling down through the core support plate to the lower plenum of the BWR. The method has been developed based on interface tracking method code TPFIT (Two Phase Flow simulation code with Interface Tracking). To verify and validate the applicability of the developed method in detail, it is necessary to obtain the experimental data that can be compared with detailed numerical results by the TPFIT. Thus, in this study, we are carrying out experimental works by use of multi-phase flow visualization technique. For the experiment works, we constructed two experimental apparatuses, one is single-channel experimental apparatus and the other is multi-channel experimental apparatus. The single-channel experimental apparatus simply simulate single flow channel between four CRGTs. The multi-channel experimental apparatus is a 1/10 planar type model of a lower plenum of BWR. In the experiments, we will obtain the jet breakup behavior and surrounding velocity profiles of the jet by using LIF and PIV. In this paper, the outline of two-experimental apparatuses are shown. And the results of the single-channel experimental apparatus with/without modelled complicated structures are also shown. In the results, it was confirmed that the complicated flow channel affects the jet injection and breakup behavior. And it was also confirmed that the complicated structures restrain diffusion of fragments of the jet.

SIMMER-III Code Assessment for Material Expansion Dynamics During Core Disruptive Accidents in Sodium-Cooled Fast Reactors

2014 ◽  
Author(s):  
Hidemasa Yamano ◽  
Yoshiharu Tobita
Keyword(s):  
High Speed ◽  
Phase 1 ◽  
Computer Code ◽  
Severe Accident ◽  
Phase 2 ◽  
Assessment Program ◽  
Multi Phase Flow ◽  
Integral Assessment ◽  
Multi Phase ◽  
Physical Phenomena

The sodium-cooled fast reactor (SFR) severe accident analysis computer code SIMMER-III has been developed and assessed comprehensively and systematically in a code assessment (verification and validation) program which consists of a two-step effort: Phase 1 for fundamental or separate-effect assessment of individual code models; and Phase 2 for integral assessment of key physical phenomena relevant to SFR safety. This paper describes the achievement of the code assessment on material expansion dynamics in the framework of the Phase 2 assessment program. Detailed descriptions are given for two representative experimental analyses (VECTORS and OMEGA), which are intended to validate high speed multi-phase flow dynamics in pin bundle structure and large vapor bubble expansion dynamics into a coolant pool, respectively. Through the assessment program, the SIMMER-III code has proved to be basically valid both numerically and physically, with current applicability to integral reactor safety calculations.

Development of Numerical Simulation for Jet Breakup Behavior in Complicated Structure of BWR Lower Plenum: (3) Influence by Complicated Structure on Jet Breakup and Fragmentation Behavior

2014 ◽  
Author(s):  
Ryusuke Saito ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Takayuki Suzuki ◽  
Hiroyuki Yoshida ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Nuclear Power ◽  
Constant Term ◽  
Severe Accident ◽  
Shearing Stress ◽  
Complicated Structure ◽  
Simulation Code ◽  
Fragmentation Behavior ◽  
Jet Breakup ◽  
Image Velocimetry

To estimate the state of Reactor Pressure Vessel (RPV) of Fukushima Daiichi nuclear power plant, it is important to clarify the breakup and the fragmentation behavior of molten material jet in BWR lower plenum by a numerical simulation. To clarify the effects of complicated structures on jet breakup and fragmentation behavior experimentally and construct the benchmarks of the simulation code, we conduct the visualized experiments simulating the severe accident in the BWR. In this study, the jet breakup behavior, the fragmentation behavior and internal/external velocity profiles of the jet were observed by the backlight method and the particle image velocimetry (PIV). From experimental results, it is clarified that the complicated structures prolong the jet breakup length or make the fragments fallen together to the lower plenum similar to the bulk state. In addition, it is clarified that strong shearing stress occurs at the crest of interfacial waves at side of the jet when fragments are generated. Finally, the fragment diameters measured in the present study well agree with the theory suggested by Kataoka et al. (1983) by changing the coefficient term at each experimental condition. Thus, it is suggested that the fragmentation mechanism is mainly controlled by shearing stress and the fragment diameter can be estimated by adjusting the constant term.

Behavior of Autoignition in Polydisperse Jet-A Fuel Spray With High Temperature Co-Flow

2019 ◽  
Author(s):  
Aimee Williams ◽  
Nishant Jain ◽  
Jerry Seitzman ◽  
Ben T. Zinn
Keyword(s):  
High Temperature ◽  
Gas Turbine ◽  
High Speed ◽  
Equivalence Ratio ◽  
Chemical Processes ◽  
Fuel Spray ◽  
Phase Flow ◽  
Gas Turbine Combustor ◽  
Multi Phase Flow ◽  
Multi Phase

Abstract Liquid fueled combustors are commonly used in the gas turbine industry in situations such as high temperature fuel mixing ducts, liquid fueled reheat combustors, and other high temperature liquid fueled combustors. Modern combustors operate at high inlet temperatures, increasing the likelihood of autoignition events. Autoignition is primarily characterized using a single-step Arrhenius rate equation. Generally, this method is ideal for modeling the chemical processes involved in simplistic settings such as for analyzing ignition delays with premixed reactive mixtures in shocktubes, however it may not fully encapsulate the underlying physio-chemical processes involved in the presence of a multi-phase flow which can significantly affect the chemical processes such as autoignition. These conditions are often encountered in reality, for example, in a gas turbine combustor using fuel sprays where interactive phenomena such as fuel droplet evaporation, mixing, and chemical reactions may occur simultaneously and non-homogeneously. The results presented in this report begin to elucidate the role of droplets in determining the behavior of autoignition kernels with an attempt to improve our capability to predict autoignition phenomena in liquid fuel injector application in gas turbine industry. To investigate the autoignition phenomena in a multi-phase flow inside a gas turbine combustor, a simplified co-flow type geometry is considered at atmospheric pressure where a single Jet-A fuel spray enters the co-flowing high temperature vitiated products of a pilot burner. Fuel is injected using an aerodynamically shaped pressure-swirl atomizing injector installed co-axially with the flow inside an optically accessible quartz test section. The air temperatures and oxygen content of the flow can range from 950–1300K and 9–11%, respectively. It has previously been found that while average ignition delay times agree or nearly agree with prior theoretical and experimental studies (eg. for prevaporized fuel, electrically heated), high speed imaging experiments illustrate that the spatial location of the formed kernels can be broadly scattered. Also, this variation in autoignition kernel location is higher at lower temperatures. Simultaneous high speed CH and OH chemiluminescence also suggest that the kernels are formed at lower equivalence ratios at lower preheat temperatures and then proceed to increase in equivalence ratio. While at higher preheat temperatures, kernels form at a higher equivalence ratio and stay at the ratio as they propagate downstream. In the current study, a 5000fps, 283nm laser sheet is introduced along the center axis of the test section. Two synchronized, intensified, high-speed cameras simultaneously captured the fluorescence of Jet-A and OH chemical reaction at 308nm and the Mie scattering of droplets at 283nm. Autoignition kernels and that droplets are visualized at flow velocities ranging from 40–50 m/s and temperatures ranging from 1100–1300K. This technique allows the fuel and reaction fluorescence to be differentiated and from this image, information is obtained on the proximity of fuel droplets and autoignition kernels during their formation and subsequent propagation.

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