Analysis Of Aerodynamic Parameters On The Special Shape Hood Of High Speed Raiway Tunnel Portal

The high-speed railway is booming since the21st century. Experts and scholars from all around the world have conducted sufficient in-depth researches on the train aerodynamic problems both theoretically and practically. However, there are still many new theoretical and technical difficulties of high-speed railway tunnel aerodynamics to be solved due to the improvement of the train model, the increasing speed of trains and the difference on the actual situation of tunnel. China is a mountainous country, the large and long tunnels is widespread. The continuous improvement of the train operation speed will make high-speed railway tunnel aerodynamics become our country’s key basic subjects on the high-speed rail transportation. At present, our mian line passenger tain design speed of350km/h railway project operations of Beijing-Shanghai, Beijing-Tianjin inter-city, Wuhan-Guangzhou, Guangzhou-Shenzhen-Hong Kong Express Rail Link and the Zhengzhou-Xi’an high-speed railway has already delivered.This paper is based on the program of the technology research of the Beijing-Shanghai hight-speed railway tunnel, and employs the numerical simulation, to study the aerodynamic effect of the train running through the double line tunnel which has an expanding section of the buffer structure at a speed of350km/h. The hood is divided into no opening hood and single opening hood. The expanding section of hood has two types:arch and rectangular cross-section. By reducing the compression wave pressure gradient in the tunnel, the analysis and calculation of the numerical simulation of a large number of conditions concludes the optimal cross-section expansion rate, the length of the buffer segment, the opening positon, opening rate, the aspect ratio of opening, the ratio of width to high of rectangular cross-section, and the parameters of the buffer structure’s opening of cross-section area of155m2and200m2. The main conclusions are as follows:1. When the tunnel has an arch expanding cross-section hood with no opening, the section expansion rate of2.0can cut the peak of pressure gradient to a minimum. But when we concern each additional cross-section area, the section expansion rate of1.6has the highest rate of reduction of the peak of pressure gradient per square meter, which is more affordable and superior to other section expansion rate.2. The impact of changing the length of the hood on the peak pressure gradient is very limited. It is recommended to set its length to20m. 3. When we use the155m2expanding arch cross-section hood with a single opening at its top, the optimal position of the opening is3m from the portal of the hood to the sideline of the opening. The best opening rate is24%to30%. The aspect raio of the opening is not the same when the opening rate is different. It is recommended to use the project of6.4m X3.75m and5m X6m rectangular single opening practically.4. The best aspect ratio of width to high of rectangular expanding cross-section of the hood is1.7. The influence of its section expansion rate and opening form to the pressure gradient is similar to the arch expanding cross-section hood. It is recommended to use the project of6m×3.2m and5m×4.7m rectangular single opening practically.5. The optimal opening parameters are not the same when the section expansion rate is different.