Study On Kinetic Characteristics Of Interaction Between Molten Metal Copper Liquid Column And Water

In the contemporary society with the gradual deepening of industrialization,the demand for metals is expanding,and the demand for electricity drives the rapid development of nuclear energy.However,in the context of the progress of the times,there are many security risks.In recent years,there have been many steam explosion accidents of the interaction between molten metal and water in metallurgical industry.These safety accidents have gradually become serious disasters that can not be ignored in the metallurgical industry.In the field of nuclear energy applications,there may also be explosion scenarios in which molten metals come into contact with coolants,such as world-class disasters such as Chernobyl,three Mile Island and Fukushima.Although the types of molten metals and coolants are different from those in metallurgical accidents,the explosion reaction mechanism contained in the FCI phenomenon(that is,the interaction between melts and coolants)is the same.And because the interaction between molten metal and coolant is a complex multiphase flow reaction process,the short duration of the reaction brings great difficulty to the observation and research,and its mechanism is not fully understood at present.Therefore,the experiment of the interaction between molten metal and cooling water is of great value in the safety analysis of metal smelting and nuclear energy.In order to study the interaction mechanism between molten metal and coolant,this paper chooses molten metal copper as the research focus,and independently studies and designs a set of electric-driven molten metal intermediate frequency furnace and molten metal drop test-bed.with the help of high-speed camera technology,the visual experimental study on the direct contact between molten metal column and cooling water at different scales was carried out.The fragmentation pressure was recorded and analyzed by the transient pressure measurement system,and the interaction mechanism was studied and discussed based on the experimental products.The experiment is divided into two parts: 1.Carry out the experiment of the interaction between molten copper liquid column and cooling water at the scale of less than 500g;2.Experiments on the interaction between molten copper liquid column and cooling water at the scale above 1kg were carried out.An experimental study on the interaction between molten copper liquid column and cooling water at the scale of less than 500 g was carried out.In the experiment,the maximum volume percentage of steam cavity produced by the contact between liquid column and cooling water is analyzed and studied,and it is found that the temperature and mass of molten metal have great influence on the volume percentage of the cavity.Moreover,according to the unified classification of fragmentation phenomena,four typical fragmentation experimental phenomena(initial fragmentation in water and triggering fragmentation proliferation(WY);in water did not trigger fragmentation proliferation(WN);underwater primary fragmentation and trigger fragmentation proliferation(BY);underwater primary fragmentation did not trigger fragmentation proliferation(BN)).Secondly,based on the analysis of the action process and the products,it is found that the temperature change of the molten copper column affects the fragmentation probability.In the temperature range of liquid column in this paper(1200 ℃-1600 ℃),the fragmentation probability of molten metal varies nonlinearly with temperature,that is,the fragmentation probability increases with the increase of temperature,and then decreases when the temperature of copper column is about 1300 ℃.The fragmentation probability reaches the peak,and the higher the molten metal temperature is,the smaller the fragmentation probability is.The mass change of molten copper liquid column affects the fragmentation position.In the scale test range below 500 g in this paper,the higher the quality of the molten metal is,the closer the fragmentation occurs to the bottom of the reaction vessel.In the falling height range(50cm-130cm)of the liquid column in this experiment,the fragmentation probability of the molten metal liquid column increases obviously with the increase of the height,and the fragmentation multiplication is triggered after the initial fragmentation of the molten metal copper liquid column interaction with the cooling water,that is,the shock wave overpressure produced by WY and BY,is much larger than that after the initial fragmentation,that is,WN and BN.It is found that triggering fragmentation and multiplication is the key factor for the occurrence of steam explosion.The main reason for the fragmentation of the streamlined structure is instability(Marangoni effect,Leidenfrost effect,Rayleigh Taylor instability,Kelvin-Helmholtz instability,etc.).The main reason for the fragmentation of the inclusion structure is the explosive expansion of the internal cooling water,the main reason for the fragmentation of the molten copper column is also different.The main reason for the fragmentation of the streamlined structure is instability(Marangoni effect,Leidenfrost effect,Rayleigh Taylor instability,Kelvin-Helmholtz instability,etc.).An experimental study on the interaction between molten copper liquid column and cooling water at the scale above 1kg was carried out.In the experiment,the thickness of the vapor film produced by the contact between the liquid column and the cooling water and the shock wave overpressure caused by fragmentation were analyzed and studied.It was found that the shock wave overpressure caused by fragmentation increased obviously with the increase of the experimental height.Secondly,the numerical study on the overpressure after the fragmentation of molten copper liquid column above 1kg shows that the energy conversion rate of fragmentation between molten copper liquid column and water is very small,indicating that the energy shown in the form of shock wave in the interaction between molten copper liquid column and cooling water is very small,and a large part of the energy is dissipated in air and cooling water through heat transfer.