Experimental investigation of maximum temperature and longitudinal temperature distribution induced by linear fire in portals-sealed tunnel

A set of experimental tests were conducted to investigate the maximum gas temperature rise and longitudinal temperature distribution beneath the centerline ceiling in a portals-sealed arched tunnel, taking fuel tank central angle location along the sidewall (expressed by effective ceiling height) and linear fire size into account. A linear fuel tank burner, placed on the arched sidewall of the tunnel, was utilized to simulate the fire source. A new empirical formula was proposed to predict the maximum excess temperature beneath the ceiling in a portals-sealed tunnel fire, based on dimensional analysis. The experimental results show that the non-dimensional maximum excess temperature has an exponential decaying relationship with non-dimensional fuel tank length. A predecessor's equation is modified to present the longitudinal temperature distribution beneath the centerline of arced-ceiling in a portals-sealed tunnel fire, which is consists of the sum of two exponential equations. The comparison of longitudinal temperature distribution between fire in portals-sealed tunnel and natural ventilation tunnel was conducted. The study is expected to provide some references for actual tunnel fire-fighting.