Study On Temperature Field And Critical Velocity Of Highway Tunnel Bus Fire

Fire source and ventilation control are the two vital aspects in highway tunnel fireresearch, on one hand, fire source controls the scale and development process of a fire, on theother hand, ventilation control, which major ensures the minimum longitudinal not less thanthe critical velocity, prevents the smoke backflow. Large research have been carried out on thetwo aspects at home and broad, the heat release rate of a fire is expressed by square growthmodel and the blockage ratio is not considered in the calculation of critical velocity, whichdon’t consist with the reality. In this context, the dissertation discusses the temperature fieldof bus fire in a tunnel and the critical velocity in blockage condition through the comparativestudy of FDS simulation and fire test data.Firstly, the dissertation takes the Yutong bus as a reference to build an original model,sets the material parameters of chairs, tires and internal decorations of the model busaccording to the actual part, studies the combustion process, maximum temperature and heatrelease rate when the bus is ignited from the front, middle and back chair respectively andgives the worst igniting position.Secondly, the blockage ratio of the fire φ1and the blockage ratio upstream of the fire φ2are introduced to modify the computational formula of critical velocity. Three formulas,considering φ1，φ2，φ1and φ2respectively，are acquired and then verified with the existing firetest data.Finally, the temperature field and smoke field of a tunnel model, which takes a burningbus and20MW fire as the fire source separately, is discussed in different longitudinalventilation condition. The results show that simulating the tunnel fire with FDS burningmodel conforms to the actual reality better.