Proportion coefficient of mass flow rate of smoke from a tunnel fire in an opposite jet smoke extraction system
To investigate the flow characteristics of smoke during a fire in a tunnel opposite jet smoke extraction system,and to provide a reference for the design of longitudinal airflow velocity to control smoke spread under opposite jet smoke extraction conditions,the variation of upstream and downstream smoke mass flow rates under different upstream and downstream longitudinal velocities in the tunnel were investigated through FDS numerical simulations.The concept of equivalent velocity was proposed,and the equivalent velocity values under different opposite jet longitudinal velocities were obtained by numerical simulation,and the relationship between the equivalent velocities and the upstream and downstream longitudinal velocities was established.Based on the theoretical analysis and numerical simulation results,the relationship between the upstream and downstream longitudinal velocity and the smoke mass flow rate proportion coefficient was obtained.The results show that the temperature decay coefficients vary in three stages with the increase of the equivalent velocity,which can be divided into a low-velocity stage,medium-velocity stage,and high-velocity stage according to the velocity.The upstream and downstream smoke mass flow rate ratios and proportion coefficient show a two-stage variation with increasing equivalent velocity.When the equivalent velocity is less than the critical velocity,there is a linear relationship between the equivalent velocity and the ratio of upstream and downstream smoke mass flow rate,and the upstream and downstream smoke mass flow rate ratios and proportion coefficients decrease as the equivalent velocity increases.When the equivalent velocity is greater than the critical velocity,the back-layering length is zero and the upstream and downstream smoke mass flow rate ratio and the smoke mass flow rate proportion coefficient are zero.
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万方数据
维普
