A comparative study on smoke temperature profile and corresponding different-exponential form correlation in single-line and bifurcated tunnel fires. (June 2023) - Chen, Changkun
Highlights: Fire tests were performed in the model-scaled single-line tunnel and T-shaped tunnel. Longitudinal attenuation of smoke temperature shows obvious region-variation feature. Double-exponential correlation can better characterize temperature attenuation in entire region. A modified double-exponential prediction of longitudinal temperature attenuation is proposed. Prediction results are in good agreement with the model-scaled and full-scaled experimental data. Abstract: A series of model-scaled tunnel fire tests were performed to investigate the temperature attenuation characteristics of thermal smoke. The internal temperature profiles of single-line tunnel and T-shaped tunnel were measured and compared. Results indicate that within the current measurement range, for the fire scenario with same fire power, the maximum smoke temperature of T-shaped bifurcated tunnel is slightly lower than that of the single-line tunnel under natural ventilation, which can be attributed to the reduction of smoke accumulation and the increase of air entrainment induced by bifurcation region. The longitudinal temperature decay of fire smoke in entire spread region shows an obvious region-variation feature. The temperature attenuation rate in the region near fire source is larger significantly than that of one-dimensional spreading region. Compared with the representation in the form of single exponential correlation, the double-exponential correlation can better characterize the temperature decay process in entire spreading region of fire smoke. While, if the single-exponential representation is adopted, the correlation formula is piecewise. Based on the analysis and physical observations of the longitudinal decay rate of smoke temperature in different spreading regions, a modified double-exponential correlation for longitudinal temperature attenuation is obtained. By comparing with the model-scaled measurement results in current work and the full-scaled experimental data of previous scholars, the proposed correlation is reasonably verified to be within an acceptable error range. This work is anticipated to serve as a resource for firefighters to evaluate the temperature profile and decay characteristics of fire smoke in tunnel-like space.