| Highway tunnel ventilation in the operational state is a dynamic, changing system. The changes of environmental temperature, vehicle speed and traffic volume will result in the changes of wind pressure and volume in tunnel. Air flow into tunnel from entrance and flow along the tunnel. Due to various factors, air temperature will be constantly changing, then the thermal potential difference will change, which will affect the tunnel ventilation system. It is necessary to study the temperature distribution in tunnel and calculation method of thermal potential difference. In order to save energy, it is a good way to effectively utilize thermal potential difference and traffic wind pressure to ventilate. Firstly, based on present research situation, temperature distribution in tunnel and calculation method of thermal potential difference were researched through theoretical calculation and numerical simulation. Secondly, energy saving ventilation methods of highway tunnel based on temperature effect were studied.The main research work is as follows:1. The influence factors of temperature changes in tunnel and the unsteady heat transfer mechanism between surrounding rock and wind were analyzed. A mathematic model of longitudinal wind temperature for highway tunnel was established. The formulas for calculating longitudinal wind temperature were derived. Compared the results of longitudinal wind temperature calculated by model with the results of test on site, reliability of the model was verified.2. The laws of air temperature changes in shafts were studied due to air compression, wall rock heat transfer and moisture evaporation. The mathematic models of wind temperature for blowing-in shaft and blowing-out shaft were established.3. Mechanism of thermal potential difference caused by wind temperature differences inside and outside tunnel was analyzed. Based on the principles of ventilation and connected vessels, the view that thermal potential difference was caused by the different weights of air columns was put forward. The formulas for calculating thermal potential difference were derived. The software Fluent of the finite volume method was combined to analyze the distributions of wind pressure and volume in tunnel with longitudinal slope under the gravities of air columns, and the reliability of the model used to calculate the thermal potential difference was verified.4. Based on relevant grid models, the influence of environmental temperature changes on the shaft centralized exhausting(blowing) ventilation and subsection longitude ventilation with air ejecting and blowing system. The distribution characteristics of wind velocity, temperature and density in tunnel, blowing-in shafts and blowing-out shafts were studied under different environmental temperatures and ventilation way. The different weights of air columns method was combined to analyze the change law of thermal potential difference under different ventilation way.5.The method combined air density and wind network was proposed to study distribution characteristics of wind pressure and wind volume in tunnel under the condition of wind pressure changing, analyzing air volume balance law, air pressure balance law and resistance law of tunnel ventilation network, establishing tunnel wind resistance model and dynamic model, including the ventilation resistance calculation model, fan wind pressure calculation model, the transportation of wind pressure calculation model, the natural wind pressure calculation model, the fire wind pressure calculation model and shaft ventilation calculation model, the ventilation resistance calculation model, fan wind pressure calculation model, the transportation of wind pressure calculation model, the natural wind pressure calculation model, the fire wind pressure calculation model and shaft ventilation calculation model.6. Relying on Qinling mountain highway tunnel engineering, analyzing air volume air pressure characteristic of tunnel exhaust hole and air supply hole, using network method under the condition of different environmental temperature and speed different traffic conditions. Compare calculation results and the tunnel air volume, puts forward the optimal ventilation modes under different operating conditions, which provide guidance for tunnel ventilation operation decision. |
