科研之友
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摘要
The temperature field of high speed railway tunnel located in cold region was studied through the research on the thermal insulation design of the tunnel for high-speed railway from Moscow to Kazan in Russia. The aim of this study is to propose a new testing system of modeling to investigate the air temperature field in the tunnel influenced by the varying variables such as the temperature outside the tunnel, the temperature of rock, the speed and the running intervals of trains. The system is typically comprised of five components, i.e., the driving device of high speed train model, the small-scale tunnel model, the temperature controlling device, and the measurement system together with the train model. Utilizing the programmable logic controller(PLC), the servo motor driving device of the high speed train model realizes the expected speed of the train model though accelerating, maintaining and reducing the velocity. The polymethyl methacrylate casing is connected by the flange, bolt and sealing strip and the entire test process is thus visible. The model is extendable in length. The temperature controlling system is composed of devices for outside tunnel and rock temperature and the measurement system consists of a high sensitivity temperature measurement instrument, a wind speed sensor and a data acquisition unit. Typically, the train model according to CHR 380A high-speed train, is made of polymethyl methacrylate as well, with the geometric similarity ratio of the prototype to model 50∶1. The testing results indicates that the deceasing of air temperature of 5℃outside tunnel may increase 104 m of the minus temperature length from the portal and the minus temperature length for the portal reduces by 145 m if the rock temperature increases by 5℃. For the tunnel with the train running interval less than 15 minutes, the design of anti-freezing thermal protection has to take into account the significance of train running interval on the thermal insulation length.
