Experimental study on the maximum temperature and flame extension length driven by strong plume in a longitudinal ventilated tunnel

Abstract

In order to study the maximum temperature and flame extension length when flame impinges on the tunnel ceiling, experiments were carried out with different longitudinal velocities, heat release rates and ceiling-source heights considered. The results showed that: (1) The maximum temperature without ventilation was not sensitive to heat release rate and ceiling-source height, and the longitudinal velocity was a key factor for the reduction of the maximum temperature. A new hypothesis based on the decease of real effectual heat release rate in a ventilated tunnel was given and a new model to predict the maximum temperature at the flame impingement region was proposed. (2) The correlation of the flame extension length was built with the modified flame height and heat release rate. And, the cylindrical and ellipse flame shape hypotheses were used to verify the experimental data in this study. It was found that the theoretical value of the flame extension length agreed well with the corresponding experimental results. In addition, the cylindrical flame hypothesis was more consistent with experimental data, compared to ellipse flame hypothesis.