| Based on the longitudinal ventilation assumption of highway tunnel, the paper utilizes the most famous international CFD software-FLUENT and CFX that has powerful functions in calculating incompressible internal lower-speed constant turbulent to simulate and analyze the important parts of the highway tunnel ventilation system. And distributed losses, bending-duct losses, reducing and expanding duct losses, tee-pipe losses, short duct, connecting tube, jet ventilation and the cross pollution of the shaft and tunnel opening are analyzed and researched. The main conclusions gained are as following.(1) The bending-angle of highway tunnel ventilation is not greater than 90 degrees properly.(2) The velocity rate is not less than 0.3 in designing expanding duct and not less than 0.35 in designing reducing duct.(3) The proper expanding-angle or reducing-angle of ventilation duct is not greater than 30 degrees. When the expanding-angle or reducing-angle is not greater than 15 degrees, the proper maximum expanding-length of ventilation duct is not greater than 10 meters and the proper maximum reducing-length of ventilation duct is not greater than 16 meters. When the expanding-angle or reducing-angle is equal to 30 degrees, the proper maximum expanding-length or reducing-length of ventilation duct is not greater than 3 meters.(4) When the tee-pipe of straight and oblique diffluence is designed, the dip angle is advised to set the proper angle of not greater than 45 degree. Flow ratio of affluent and total flux should be 0.4 to 0.7 properly; When the dip angle is equal to 75 degree, flow ratio of affluent and total flux should be 0.3 to 0.5 properly.(5) Considering the ventilation optimum design, the short-duct length between delivery and exhaust airway can be 60 to 80 meters.(6) The cross-section of connecting tube in fan room designed to square cross section is better.(7) If pressure regulation of highway tunnel is considered, single jet fan is advised to be assembled. And when installed position is lower, ventilation efficiency gets better.(8) In order to prevent the cross pollution of the shaft and tunnel opening, the axial space length should not be less the 40 meters; as for double-arc or short-range tunnel, longitudinal space length between the two tunnel openings should be over 50 meters. The proper axial space length between the air outlet and inlet of the shaft should not be less than 50 meters. If the distance between air outlet and inlet of the shaft is very close, it is suggested that the air outlet should be 5 meters higher than the air inlet at least.Finally, the ventilation system of Yan Men Guan lengthy highway runnel is analyzed as the numerical simulation model, including its local and integral ducts. And lots of useful conclusions are achieved and the corresponding optimizational suggestions are supplied in the paper. |
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