Experimental investigation of combinational fans influencing on the effective ventilation in an undersea metro interval tunnel

Abstract

Based on the metro undersea interval from Wawuzhuang Station to Guizhou Road Station of Qingdao Metro Line 1, a physical model system is built for the sake to further study the Ventilation and Smoke Exhaust System (VSES) of this interval tunnel. In the VSES experimental system, it gains data of variable frequencies inputting to fans, consumed-power values of fans, velocities in carriageways and SEDs (Smoke Exhaust Ducts), static pressure in carriageways under the conditions of the TP (Two Pressing-in) and TP+OE (Two Pressing-in + One Extracted-out) combinations of fans. The experimental data are shown that the static pressure field in horizontal carriageways has a symmetrical distribution, whose symmetry axis is as the plane of a smoke ceiling, whether TP or TP+OE. Under the TP+OE, the velocities in SEDs and carriageways are influenced dominantly by an extracted-out fan; two pressing-in fans of the TP combination influence mainly those velocities. A velocity is capable to dilute and coerce a smog flue. The pushing force of the smog flue is supplied by a pressing-in fan with consumed-power values, and another pressing-in fan with the lower values prevents this flue from another carriageway; furthermore, the pulling force of this flue is supplied by an extracted-out fan with the largest consumed-power values. The ratio of the total values of fans to the discharged volume flow rates in both SEDs is proposed as a new criterion, which can quantify VSES performance and is equivalent to airflow pressure; it is shown that the VSES performance of the TP+OE combination promotes gradually and becomes superior to one of the TP. Finally, it is advisory that the TP+OE should be a preferential combination of fans in designs and engineering situ management of extra length and large section tunnel ventilation.