Experimental investigation on the influence of linear fire source along the wall on the temperature distribution in tunnel

Abstract

A sequence of experimental tests were conducted in a circular-section tunnel to investigate the effect of linear fire source along the wall on the temperature distribution beneath the arced ceiling. 3 different ethanol tank sizes (1.5 m, 1.7 m, 1.9 m, respectively) were deposed at the arced wall of 4 central angles (45°, 60°, 75°, 90°, respectively), which all were spaced 10 cm from the tunnel wall. A semi-empirical formula to predict the maximum temperature rise in utility was suggested, with a dimensionless heat release rate correlated to linear fire and the Q˙ that takes into account the effective ceiling height. The above formula applies the following limitation: Lf<Hef. The results show that the maximum excess temperature is positively correlated with the heat release rate and negatively associated with the fuel tank length and Hef. In addition, a comparison between predecessor's predict equation and experimental data was presented. Results show that experimental data is slightly lower than predict data. A modified inhomogeneous linear differential equation of first order was proposed to predict the longitudinal distribution of maximum excess smoke temperature under the centerline ceiling, taking Hef into account.