Jet fans efficiency in tunnel emergency situations

Abstract

Tunnel construction has become an important and growing activity. Tunnelling is an important part of transport infrastructure and is a part of the sustainable development of the country. The tunnel ventilation during construction and operation is part of the whole design procedure. Although ventilation might be performed with different approaches, longitudinal ventilation with jet fans is most often employed. The efficiency of such devices depends on several factors – design parameters, location in the tunnel, interaction with main current. The last one is crucial in emergency situations, especially during fires when both temperature and density of main current change. One important point in normal and emergency ventilation design is the downwind influence of jet fans. This paper presents a longitudinal scheme with jet fans. Based on energy and mass conservation, the interaction between the jet fan and the main current is considered, leading to expressions for areas of impact. Several models for fire temperature distribution downstream are presented, outcomes are compared and suggestions for use are made. Additionally, jet fan efficiency coefficients are adjusted due to modelling results.