Prediction of Smoke Back-layering Length and Critical Velocity in a Utility Tunnel

The prediction smoke back-layering length and critical velocity in the event of a fire in a utility tunnel are studied. In this paper, the method of numerical simulation is used to study the combustion characteristics of the cable tray in a utility tunnel. The prediction of smoke back-layering length is related to factors such as heat release rate, longitudinal ventilation velocity, and fire source location. The smoke back-layering length is determined by the temperature record. The temperature measurement is made by thermocouple tree in the utility tunnel. Results show that the dimensionless critical velocity has a certain influence on the dimensionless heat release rate in utility tunnel. The numerical simulation results show that there is an exponential relationship between the dimensionless smoke back-layering length with two fire locations (locations A and C) in the utility tunnel. This paper proposes a method for predicting the smoke back-layering length based on the correlation of numerical simulation data. In two fire locations (locations A and C), the numerical simulation data of the smoke back-layering length has a good correlation with the results of the Li model. The main contribution of this paper is to prevent the smoke propagation in utility tunnels and provide technical guidance. Therefore, this paper has certain guiding significance for the smoke propagation below the ceiling of the electric compartment in utility tunnel.