Heat Release Rate Prediction for High-Altitude Highway Tunnel Fires Based on Field Tests of Combustion Characteristics

Heat release rate, HRR, is significance for the design of rescue and evacuation engineering of highway tunnels, which can be estimated by multiplying mass loss rate, \( \dot m\) , and effective combustion heat, ΔHceff. In previous paper, only the pressure effect on \(\dot m\) and ΔHceff was investigated, and \(\dot m \propto {P^n}\) was summarized. There was no agreement on pressure effect on ΔHceff. Thus, field tests of \(\dot m\) and ΔHceff were conducted at 523, 3160, 3500, 3960 and 4160 m. The test environment and free flame matched those of high-altitude tunnel fire to ensure that the measured data were correct, regardless of whether the tests were performed inside or outside the tunnel. Adopting a small vehicle as an example, the HRRs of highway tunnel fires were numerically predicted based on the field test results. The results revealed the following: (1) Both pressure and temperature are important factors of \(\dot m\) . . (2) Based on a global model and flame temperature correlation, a correction method of \(\dot m\) was established. (3) The equation of \(\dot m\)  = 3.226 × 10−3 T∞ + 1.621 × 10−3P1.0959 − 1.186 × 10−3 T∞P1.0959 − 0.03127 was obtained, which can predict \(\dot m\) under different pressures and temperatures. (4) A prediction model of ΔHceff = 0.5548P-16.9580 was established based on field test data. (5) The peak HRR of highway tunnel fires at 523, 3160, 3500, 3960 and 4160 m ranged from 3.56 ~ 5.55, 1.20 ~ 2.33, 0.47 ~ 1.54, 0.33 ~ 1.20 and 0.21 ~ 0.90 MW, respectively. The results in this work could provide a basis for other HRR prediction and smoke diffusion studies of high-altitude highway tunnels.