Study On The Critical Velocity Under Multiple Factors Of Highway Tunnel Fires

The road traffic network in our country is being improved, and the number of hi ghway tunnels is increasing year by year. The tunnel fire has gradually become the bi ggest threat to the safety of highway tunnel operation, and the tunnel ventilation whic h ensured the same as the size of the critical velocity is an effective means of contro l the scale of fires and reduce fire hazards, which has attracted reserch from home an d abroad. The critical velocity is affected by many factors, most of the scholars have carried out a detailed study on a certain factor, but not a systematic study on the criti cal velocity. On this basis, this paper will use theoretical analysis and FDS numerical simulation to study the change laws of the critical velocity under different influence f actors and some comprehensive factors.Firstly, according to the specification, this paper establishs a 300 m long dual carri ageway approximately arched-shaped cross-section tunnel model, which set up correspo nding fire parameters, environment parameters and model parameters. With the use of FDS, the critical velocity will be researched under different influence factors, such as the fire heat release rate, fire size and fire source location, slope of the tunnel, obstac les and so on. The change law of the critical velocity and temperature fields under di fferent conditions are analysed and compared with the conclusions of the previous.Secondly, the dimensionless formula is given to simplify the critical velocity, and a calculation formula is presented with simulation datas, which compared with the pr evious formula and experimental data to verify the correctness and the applicability.Finally, the critical velocity is simulated under multiple factors and the fire size i s the same as the bus size. At the same time, according to the different proportion of each factor to the critical velocity, the the calculation formula is modified.