Experiment Study On The Oxidation And Combustion Characteristics Of Sodium Droplets

In the operation of the sodium-cooled fast reactor,the accident caused by the leakage and combustion of liquid sodium is common and frequent in sodium-related facilities.The research of sodium droplets is the foundation of the research of all kinds of sodium fire.In this paper,the oxidation and combustion characteristics of sodium droplets were studied by carrying out the experiments of the oxidation and combustion under different conditions of initial temperature(140-370 ?)of the sodium droplet and oxygen concentration(4%-21%).The oxidation and combustion behaviors were visualized by a set of combustion apparatus of sodium droplet and a high speed camera.The experimental results show that the columnar oxides grow longer as the initial temperature of sodium droplet and oxygen concentration become lower.When the oxygen factor is equal to or higher than 16%,the columnar oxides will not be found.Under the same oxygen concentration condition,the sodium droplet with the higher initial temperature is easier to ignite and burn.When the initial temperature of sodium droplet is below 200 ?,it is very difficult to ignite,if there is a turbulence damaging the oxide layer on the surface,the sodium droplet will also burn gradually.The sodium droplet could burn completely and the combustion temperature maximally could nearly reach 600-800 ? with high initial temperature and high oxygen concentration condition.When the oxygen concentration and the initial temperature are low,sodium droplets could not burn completely and the highest combustion temperatures are all below 600 ?.During the procedure of oxidation and combustion,the temperature at a distance of10 mm from the center of the sodium droplet has a distinct rise.The temperature at a distance of 20 mm has a smaller influence,the temperature rise will not exceed 50?.When the sodium droplets oxide and combust,the time that the space temperature begins to rise delays the time that sodium droplet begins to rise.The delaying time that the space temperature beginning to rise delays the sodium droplet beginning to rise is as long as 17 seconds with the condition of the low initial temperature(250?)and the low oxygen concentration(12%).However,the delaying time is only 2 seconds with the condition of high initial temperature(350?)and the high oxygen concentration(21%).Therefore,the differences of initial temperature and oxygenconcentration condition have an obvious affect on the change of the space temperature.The temperature of the environment has affect on the highest combustion temperature,but the affect isn't obvious and the highest combustion temperatures are approximate.AT the same time,the temperature of the environment has an obvious affect on the time of suiface oxidation.The results show that uder the same initial temperature and the same oxygen concentration the time of oxidation section is longer with low environment temperature,the rate of temperature rise is relatively slow.When the environment temperature is high,the time of oxidation section is relatively short and the rate of temperature rise is quick.The results are helpful to the research on the sodium fire in a columnar flow and spray fire.