Experimental study on maximum temperature beneath tunnel ceiling under the condition of double fire sources

In order to study the maximum temperature beneath tunnel ceiling of double fire sources, experiments were carried out in a model tunnel (1:10) with different heat release rates, longitudinal ventilation velocities and fire source pitches considered. Results showed that under the condition without wind effect, two flames merging phenomenon gradually disappeared as the increase of fire source pitch. Larger fire source pitch resulted in less impact on maximum temperature beneath tunnel ceiling. Under the condition with longitudinal ventilation, the maximum temperature beneath tunnel ceiling decreased significantly, however, the effect of fire source pitch on the maximum temperature beneath tunnel ceiling is only reflected in the tests with relatively higher fire heat release rates. Based on previous single fire source model, a prediction model for maximum temperature beneath tunnel ceiling of double fire sources was developed. It is showed that the proposed model has a good correlation with the experimental results.