Abstract: The cable fire test was carried out in the scaled utilitytunnel model. Linear fire sources were placed on the wall at 15 ,45, 75 ,105 cm from the bottom of utility tunnel to study the fire behavior of the linear fire sources at different heights. It is found that the heat release rate of the linear fire source decreases with the increase of the height, which is different from the point fire source. The effective flame height was modified and the prediction formula of the effective flame height was obtained by fitting. The prediction formulas of the temperature distribution are obtained by analyzing the transverse temperature in plume region and jet region respectively. It provides technical support for the design of utility tunnel fire detection system and automatic fire extinguishing system.

Key words: utility tunnel, linear fire source, heat release rate;flame height, transverse temperature