Study On The Airflow Properties At The Fork For Super Long Highway Tunnels’ Ventilation System

With the rapid development of highway tunnels construction, the length of highwaytunnels is increasing. In the context of energetically promoting low-carbon society, it isparticularly important to research some new road tunnel ventilation technology. Not only thedraft control system must satisfy the tunnel daily driving operation health, the safe request,moreover must reduce the energy consumption and the resources waste satisfied, reduces thetunnel operation cost. The purpose of this paper is to study of three problems in the tunnelventilation system, they are：(1) Analyzing rising pressure calculation formula at exhaust outlet in exhaust ventilationmodel tunnel by numerical simulation method.(2) The influence analysis on exhaust efficiency by exhaust angle and the local structureoptimization.(3) The influence analysis on opening the cross aisle’s protective doors between doublecaves tunnel to airflow characteristics in tunnel.By using one of the most popular CFD FEM software—FLUENT, analysis these threequestions and the main conclusions are:(1) When calculation the rising pressure at exhaust outlet in blow and exhaust ventilationmodel’s tunnel, the rising pressure calculation formula at exhaust outlet from Specificationsfor Design of Ventilation and Lighting of Highway Tunnel need refine the curve between theKe and Qe/Qr. Using the expansion of the Bernoulli equation can achieve a good applicationeffect, but need further correct parameters.(2)45°exhaust Angle is more efficient than90°exhaust Angle，but the main reason isnot caused by the exhaust Angle, exhaust outlet’s opening size has a great influence on theexhaust efficiency, Therefore in this paper, optimization of exhaust outlet’s opening sizemodel has been proposed.(3) For double caves tunnel, opening the cross aisle’s protective door has a greatinfluence on the air flow state and the air flow of two tunnels is easily happened which couldresult in waste of resources during permanent ventilation, so it should be prevented openingthe protective doors for no reason.