| The construction of the Sichuan-Tibet Railway is a major measure to implement the Party’s strategy of governing Tibet in the new era.It is of great significance to safeguarding national unity,promoting ethnic unity,consolidating stability in the border areas,and promoting economic and social development in the western region,especially in Sichuan and Tibet.On November 8,2020,the construction of Yalin section,the most difficult part of the Sichuan-Tibet Railway,was started,marking that the Sichuan-Tibet Railway has entered the final stage of development.Compared with other railway lines,Sichuan-Tibet railway tunnel has the characteristics of high altitude,large slope,long tunnel and so on.The tunnel has obvious aerodynamic effect,which puts forward higher requirements for trains.In this thesis,combining with the characteristics of the tunnel in Yaling section of Sichuan-Tibet Railway,the CR300 AF Chinese standard EMU is selected as the calculation prototype.Based on the one-dimensional compressible unsteady unentropy flow model,the time evolution process of tunnel pressure wave and train air resistance is analyzed.The correlation between pressure fluctuation and air resistance,propagation,reflection and superposition of compression wave and expansion wave in tunnel is revealed.The effects of altitude,slope,tunnel slope,tunnel length and train speed on the external pressure and air resistance of a single train through a tunnel are systematically studied.The research work of this thesis is supported by the Key Project of Science and Technology Research and Development Program of China Railway Eryuan Engineering Group Co.,Ltd.The main research work of this thesis is as follows:(1)In this thesis,a one-dimensional compressible unsteady unentropy flow model and the generalized Riemann variable characteristic line method are used to preliminarily study the characteristics of pressure and aerodynamic resistance of a single train passing through the extra-long tunnel of Sichuan-Tibet Railway.In this thesis,the one-dimensional compressible unsteady unequal entropy flow model is verified by comparing with the data of foreign scholars.The verification results show that the error of the one-dimensional flow model in predicting the pressure wave of high-speed train tunnel and the train air resistance is less than10%,which meets the requirements of engineering design.And through the analysis of the time evolution process of tunnel pressure wave and train air resistance,this thesis reveals the correlation between the pressure wave and air resistance in the tunnel and the propagation,reflection and superposition of compression wave and expansion wave.(2)Based on the one-dimensional compressible unsteady unequal entropy flow model and the generalized Riemann variable characteristic line method,the influences of tunnel altitude,slope,slope,tunnel length and train speed on the external pressure wave and the maximum pressure value of the train when a single train passes through an extra-long and extra-long and large-slope tunnel are systematically studied.The results show that the altitude of the tunnel has little influence on the wave form of the train external force,but has a great influence on the pressure value outside the train.The higher the altitude of the tunnel,the smaller the fluctuation of the train external pressure when a single train passes through the extra-long tunnel.When a single train passes through an ultra-long tunnel uphill,the overall pressure history curve of the train car shows a downward trend,which has a great influence on the maximum negative pressure value of the train car,and the downward trend is more obvious with the increase of the tunnel slope and tunnel length.When a single train goes downhill through an extra-long tunnel,the overall pressure history curve outside the train shows an upward trend,which has a great influence on the maximum positive pressure value outside the train,and the upward trend becomes more obvious with the increase of tunnel slope and tunnel length.When a single train passes through an extra-long tunnel with a slope of 30‰ at 180 km /h,200km/h and 220km/h respectively,there is little difference in the maximum external pressure at different speeds.(3)The influence characteristics of altitude,uphill,slope,tunnel length and train speed on train air resistance are systematically studied.The results show that the higher the altitude,the smaller the fluctuation of the train air resistance,the smaller the maximum and average value of the train air resistance.Compared with the single train downhill through the tunnel and through the straight tunnel,when the single train uphill through the tunnel,the average and maximum of the train air resistance is larger,and the situation is worse.When a single train passes through an extremely long tunnel with a slope of 30‰,the maximum and average values of the train air resistance increase with the increase of the tunnel slope,tunnel length and train speed,and the increasing trend increases almost linearly. |
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