| Ventilation shaft sectioned longitudinal ventilation is commonly used in extra-long undersea tunnels,although some tunnels are constrained by sea area protection and navigation requirements,making it hard to install ventilation shafts in the sea.As a result,a new type of marine ventilation is proposed,which will complement air supply and exhaust via service tunnels and top exhaust ducts.Considering the smoke exhaust in case of fire,a certain number of smoke exhaust valves need to be set in the flue,and the leakage of smoke exhaust valves will directly affect the operation of the ventilation effect and the smoke exhaust effect in case of fire;At the same time,the number of ventilation equipment configured in the extra-long undersea tunnels is huge,and opening ventilation equipment only according to the most unfavorable design conditions will lead to excess ventilation capacity and energy waste.In this paper,the Qingdao Second Subsea Tunnel is used as the supporting proj ect,and the research on the air leakage and ventilation control system of the new ventilation scheme of the extra-long undersea tunnel is carried out.Ventilation network analysis was used to investigate the effect of smoke valve leakage on tunnel operation ventilation and fire smoke evacuation when different smoke evacuation methods were used;the control system of multi-mode ventilation conversion is studied.Through the research,the main research results obtained in this paper are as follows:(1)Based on the basic theory of ventilation network,a ventilation network solution model considering the pressure increment of air supply and exhaust outlet and the leakage resistance of smoke exhaust valve in highway tunnel is established,and the air volume correction formula considering the pressure increment of air supply and exhaust vent and air leakage of smoke exhaust valve in the ventilation network of highway tunnel is derived using the Scott-Hinsley method,and the ventilation network solution procedure is improved.The program can solve the ventilation network of the highway tunnel with multiple ventilation shafts and exhaust valves,and then macroscopically study the air flow law of the tunnel with complex ventilation system,and provide guidance for the ventilation design of the tunnel.(2)In view of the Qingdao Second Subsea Tunnel in the sea to send exhaust ventilation method,a modified ventilation network solution procedure was used to analyze the effect of air leakage from smoke dampers in the semi-transverse smoke exhaust mode and the flue segmented longitudinal smoke exhaust mode during operation;and the influence of air leakage of exhaust valve on fire in the middle of tunnel is simulated and analyzed.After comparative analysis,it is recommended that the Qingdao Second Subsea Tunnel adopt the flue segmented longitudinal smoke exhaust mode.(3)For the Qingdao Second Subsea Tunnel,which adopts the sectioned longitudinal smoke exhaust method of the exhaust duct,combined with the current situation of large air leakage from the exhaust valve in China,the airtightness of the air valve is reduced,and the pressure increment of air supply and exhaust vent and the air leakage of the exhaust valve and the influence of natural wind are considered.The ventilation network is calculated,and the most unfavorable case is taken to obtain the design long-term operation ventilation fan configuration,as well as the air supply volume of the axial fan and the number of opening of the jet fan under different driving speeds.(4)Based on the new ventilation scheme of Qingdao Second Subsea Tunnel,a method that can realize ventilation mode conversion according to the dynamic change of traffic volume is proposed,and a multi-mode conversion ventilation control system is designed.According to the simulation test results,it is recommended that the control system switch between single ventilation shaft ventilation mode and dual ventilation shaft ventilation mode during operation. |
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