Tunnel fire smoke control based on the PID method: A numerical study

Numerical analysis of the performance of a PID control based real-time mechanical ventilation system to prevent smoke back-layering in tunnel fires

“…Figure 1 shows the configuration considered in this study. The cross-section of the tunnel is a rectangle with (variable) dimensions H × W. As in Hong et al (2022), the length (L) of the tunnel is fixed as 60 m, which is shorter than many tunnels, but is sufficient for use in this study, because this work aims to quantitatively illustrate the concept of using the PID algorithm for preventing back-layering in tunnels with longitudinal ventilation. The longitudinal ventilation system is installed at the inlet of the tunnel and is assumed to provide a fresh airflow with uniform velocity.…”

“…However, in reality the fire HRR is not known a priori and will be variable in time. Hence, as explained in Hong et al (2022), there is a potential significance and practical advantage in the use of variable velocity fans: if the ventilation velocity can be kept to the minimum, there is less air supply to the fire source (which can be under-ventilated in case of large fires with limited crosssectional area (Beard and Carvel, 2012;Ingason et al, 2014) and there is a better chance for smoke stratification downstream of the fire source. For large fire, smoke stratification is (at least partially) destroyed downstream of the fire, and the main advantage of variable ventilation velocity, kept to the minimum required, compared to a fixed velocity (typically designed for a large design fire), is that less oxygen is fed to a potentially under-ventilated fire.…”

“…For large fire, smoke stratification is (at least partially) destroyed downstream of the fire, and the main advantage of variable ventilation velocity, kept to the minimum required, compared to a fixed velocity (typically designed for a large design fire), is that less oxygen is fed to a potentially under-ventilated fire. This requires real-time automatic control of the fans (Hong et al, 2022).…”

“…In Hong et al (2022), it was explained how, based on temperature data, a PID control system (proportional-integral-derivative-controller) enables to determine the ventilation velocity that allows a certain smoke back-layering distance. In Hong et al (2022), a relatively large fire was considered, and the assumption was made that smoke corresponds to a temperature of 100 o C and the smoke can be controlled at any desired back-layering distance by the PID control system. However, the previous work only considered the smoke control upstream: the situation where the smoke is controlled at the fire source (i.e., no smoke back-layering), was not considered.…”

Effect of the Metro Train on the Smoke Back-Layering Length under Different Tunnel Cross-Sections

“…Wu et al [20] applied the framework of artificial intelligence (AI) and big data to predict fire sources in a numerical model of tunnels. Hong et al [21] proposed a method to automatically control fire-induced smoke by coupling a full-field CFD model and a PID algorithm. The ventilation system is controlled by the PID algorithm to automatically adjust the ventilation speed, so that the smoke back-layering is controlled within a certain range.…”