Smoke temperature distribution in non-smoke evacuation under different mechanical smoke exhaust rates of semi-transverse tunnel fire were studied by FDS numerical simulation in this paper. The effect of fire heat release rate (10MW 20MW and 30MW) and exhaust rate (from 0 to 160m 3 /s) on the maximum smoke temperature in non-smoke evacuation region was discussed. Results show that the maximum smoke temperature in non-smoke evacuation region decreased with smoke exhaust rate. Plug-holing was observed below the smoke vent when smoke exhaust rate increased to a certain value. Smoke spreading distance can be divided into three stages according to changes of smoke exhaust rate. The maximum smoke temperature model concluded that the peak temperature rise at tunnel vault is proportional to 0.75 power of dimensionless fire power. The maximum temperature in non-smoke evacuation region decays exponentially with the increase of smoke exhaust rate. However smoke vent interval influences the dimensionless maximum temperature in nonsmoke evacuation region slightly. Smoke vent interval influences the dimensionless maximum temperature in non-smoke evacuation region slightly.

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The aim of this work is to present an experiment to study the characteristics of a laminar diffusion flame under acceleration. A Bunsen burner (nozzle diameter 8 mm), using liquefied petroleum gas as its fuel, was ignited under acceleration. The temperature field and the diffusion flame angle of inclination were visualised with the assistance of the visual display technology incorporated in MATLAB™. Results show that the 2-D temperature field under different accelerations matched the variation in average temperatures, they both experience three variations at different time and velocity stages. The greater acceleration has a faster change in average temperature with time, due to the accumulation of combustion heat, the smaller acceleration has a higher average temperature at the same speed. No matter what acceleration was used, in time, the flame angle of inclination increased, but the growth rate decreased until an angle of 90°. This could be explained by analysis of the force distribution within the flame. It is also found that, initially, the growth rate of angle with velocity under the greater acceleration was always smaller than that at lower accelerations, and it was also different in flames with uniform velocity fire conditions.

In this paper, the influence of slope on the spreading characteristics of fire smoke in the semitransverse ventilated tunnels was studied by using the FDS simulation. Through simulation experiments, the reasonable smoke exhaust strategies for preventing fire smoke from spreading in the sloping tunnel were obtained. Simulation results showed that: under 30MW fire power, the two-way balanced smoke exhaust strategy had good effect for the semi-transverse ventilated horizontal tunnel. However, in the sloping tunnel, due to the high stack effect, more smoke flowed to the upgrade direction. When the slope angle was greater than 1.5%, the smoke in the downgrade direction was controlled within the smoke vent opening range due to the effect of fire wind pressure. At this time, in order to effectively exhaust the smoke and reduce the energy consumption of the smoke exhaust fan, the unilateral smoke exhaust strategy in the upgrade direction was adopted. When the tunnel slope was less than 2%, appropriately increasing the smoke exhaust amount could strengthen the smoke exhaust effect and prevent the smoke from spreading to the exit of the tunnel. When the slope was greater than 3%, due to the high stack effect, the smoke in the tunnel spread rapidly to the exit. Then adding the vertical ventilation in the upgrade direction and preventing the smoke from returning could better limit the smoke spreading scope.