Research On The Method Of Determining The Key Aerodynamic Coefficient Of High Speed Train Passing Through Tunnel

With the rapid development of China's high-speed railway industry,mountainous high-speed railways have high speed grades and dense tunnels.The number of long tunnels,especially extra-long tunnels,is more significant,and the aerodynamic effect is more significant,which puts higher requirements on the safety,comfort and energy saving of high-speed trains.Because the one-dimensional flow model does not need to use a large amount of high-performance computing resources,and has the characteristics of high efficiency and accuracy,it is more advantageous in the comparative study of multi-parameter multi-operating conditions and the study of long tunnels,especially the extra-long tunnel air flow.However,in the one-dimensional flow model,it is necessary to calculate the aerodynamic coefficients such as the input train surface friction coefficient,the front end pressure loss coefficient,and the tunnel surface friction coefficient.In addition,the country is still developing a 400-kilometer high-speed train and a 600-kilometre maglev transportation system,which are all required to improve the numerical simulation theory of one-dimensional flow model for high-speed rail transit air flow.Therefore,the method for determining the key aerodynamic coefficients of high-speed trains in tunnels has important academic significance and engineering application value.The main research work of this paper is as follows:(1)This paper systematically summarizes the research results at home and abroad from the 1950 s to the present,especially on the one-dimensional tunnel aerodynamics flow model,and summarizes the commonness and difference of the governing equations,boundary conditions and application scope of each model.(2)The governing equations,turbulence models,overlapping grid design and calculation methods,calculation regions,boundary conditions and grid design for solving tunnel pressure wave and air resistance by 3d numerical simulation are summarized systematically.Then by comparing the difference in solving method between 3d numerical simulation and 1d flow model,the limitation of 3d numerical simulation is discussed.(3)By summarizing the one-dimensional tunnel aerodynamic flow models at home and abroad,the determination methods of the friction coefficient of tunnel wall,the friction coefficient of train wall and the pressure loss coefficient of the locomotive and the tail under the incompressible model are emphatically analyzed.On this basis,the key aerodynamic coefficient determination method under compressible model is established,as follows:1)Train surface friction coefficient(?)2)Head pressure loss coefficient(?)3)Tail pressure loss coefficient(?)4)Tunnel surface friction coefficient(?)(4)The use of the compressible model is established in this paper the key,and a method for determining aerodynamic coefficient of CRH2,CRH380 AL and CR400 AF vehicles,for example,solving the the tunnel through the tunnel wall friction coefficient,train wall friction coefficient and the front to the rear of the pressure loss coefficient,and numerical simulation in one dimensional characteristic line program and the European standard BSEN 14067-8-2006 analytical method of the application of these coefficients,the tunnel pressure wave is calculated,and the calculated results with the test results were compared.(5)These coefficients were applied in the one-dimensional characteristic line numerical simulation program and the European standard BSEN 14067-8-2006 respectively to calculate the air resistance when CR400 AF passes through the tunnel,and the calculated results were compared and verified with the results of the three-dimensional numerical simulation.At present,the key aerodynamic coefficients used in the tunnel aerodynamics calculation based on the one-dimensional flow model are those obtained from the incompressible model.Compressible model have been established for the first time,and a method for determining the coefficient of able to involve not only the existing one-dimensional flow model in the case of high-speed train running speed aerodynamics calculation for reference,also can be deployed for the current state of 400 km/h emu and 600 km/h the one dimensional flow model of high-speed maglev train aerodynamics calculation to offer help.