Comparison and analysis of combustion characteristics and interference effect between single burning sodium jet and the dual-jets

Abstract

Liquid sodium can be treated as a prominent medium in many industrial fields, such as photovoltaic technology, chemical synthesis, nuclear industry, etc. However, it poses significant threats to the normal operation of related systems and facilities, and human life as well, due to its potential combustion risk, particularly when multi-leakages take place. Sodium spray combustion is the most severe one, in which spray dynamic process may intensify the heat transfer and subsequent combustion process. In this work, the applicability of the droplet break-up model is firstly confirmed using numerical simulations of liquid sodium spray by Fluent code, and the impact of spray interference on combustion kinetics is examined. The Euler-Lagrange approach, which accounts for droplet break-up, collision, and agglomeration during the spray combustion process, is used in the simulation. Three-dimensional simulations of liquid sodium spray fire are then conducted, in the light of two classical experiments all around the world. The simulated volume-mean air temperature shows an error margin of less than 4%. The thermodynamic characteristics of sodium spray fire in the situation of dual-jets is further investigated. The findings indicate that the spray interference has a greater impact on the sodium content threshold and the corresponding time at which the threshold can be achieved than temperature. When the nozzle spacing varies, the consequences of the spray interference on the droplets’ combustion change. The break-up impact outweighs the agglomeration effect when the nozzle spacing is larger, while the agglomeration effect is relatively stronger when the nozzle spacing is short. This conclusion can be appropriate under both low and high flow rate of liquid sodium. The present work can provide detailed information and mechanism on spray combustion under both single jet and dual-jets conditions, which is beneficial for the evaluation of the risk of real sodium spray fire in any closed environment.