Fan conceptual design as applied to the marmaray tunnel ventilation system

The idea of a railway tunnel under the Bosphorus Strait linking the European and Asian sides of Istanbul was first raised in 1860. Today the project is nearing completion with a design placing the tunnel on the seabed. In this paper the rationale for the tunnel is presented, and the practical problems associated with such a large civil engineering project in a busy urban area considered. Challenges associated with design of the tunnel ventilation system are reviewed, and the implications for tunnel ventilation fan design clarified. The design of three tunnel ventilation fan concepts is presented. First a two-stage counter rotating fan. Second a single-stage high speed fan. Third a two-stage fan with a single motor and impeller on each end of the motor shaft. The relative merits of each concept are considered in detail. The paper concludes with a description of the tunnel ventilation fan installation and maintenance philosophy. The practicality of installing and maintaining tunnel ventilation fans have a primary impact on the on-going ability of the tunnel ventilation fans to operate reliably and therefore on the tunnel's availability. Lessons learnt and implications for on-going best practice are then summarised. Copyright © 2013 by ASME.