Model-based airflow controller design for fire ventilation in road tunnels

This paper describes a new approach to design the proportional-integral-derivative (PID) controller of the longitudinal airflow velocity in road tunnels for fire situations. Our work shows clearly that the use of a proper model provides valid data for model-based tuning of tunnel controllers, which is demonstrated by real tunnel tests. The design uses the simplified mathematical model of airflow dynamics based on Bernoulli and continuity equations, which describe the airflow dynamics in one dimension. Optimizing controller parameters on site is very time consuming and this problem increases in the case of complex tunnels with several entrance and exit ramps, which typically have occurrences of traffic congestion. Our approach is based on the design of the controller through simulations, which use the mathematical model of airflow velocity in the tunnel. This approach spares a lot of work and time with the controller tuning within tunnel tests. Moreover, it can discover potential problems, which can occur during real instances of fire in the tunnel. The additional advantage of this approach is a possibility to simulate a scenario of errors and failures of some devices, which are important for reliable control of longitudinal airflow velocity. Although this approach is focused primarily on complex road tunnels, due to their complexity and significant time savings with the controller tuning, it can be also used for simpler tunnels with no ramps (usually highway tunnels) where the design of the airflow controller is not as complex compared to the case of road tunnels. This paper also includes a case study of the airflow controller design for the Blanka tunnel complex in Prague, Czech Republic, which is the largest city tunnel in Central Europe.