Numerical Simulation And Characteristics Of Piston Wind In Railway Tunnels

Since the implementation of the“eight vertical and eight horizontal" railway development strategy,China's railway industry has entered a new historical period,and the number and mileage of railway tunnels have increased.To maintain environmental sanitation in the tunnel and ensure the safety of train operation,the tunnel should not be ventilated.Under the policy of“saving energy and reducing emissions",reducing tunnel ventilation energy consumption and effectively utilizing piston wind as a necessary supplement for tunnel ventilation have become a hot spot in tunnel ventilation research.In this paper,the theoretical analysis and numerical simulation method are used.According to the existing railway tunnel piston wind theory,the formation mechanism,flow field characteristics and piston wind speed theoretical calculation method of the piston wind generated during the operation of the train are described.The FLUENT software is used.The finite volume method and the domain dynamic layering method are used to simulate the piston wind generated when the train is running in the tunnel.To verify the reliability of the numerical calculation and theoretical calculation,the measured data of the British Patchway tunnel and the test train are prototype,establish relevant mathematical model,do numerical simulation and theoretical calculation,the calculation result is in good agreement with the measured data,indicating that the numerical and theoretical calculation reliability is better;analyze the main influencing factors of the piston wind speed,carry out the main factor combination,do the series the numerical simulation calculation studies the characteristics and variation of the train piston wind,and the following conclusions are obtained:?1?The piston wind speed is positively correlated with train speed,train length and blocking ratio,and negatively correlated with tunnel length.The dimensionless piston wind speed is positively correlated with train length and blocking ratio,and negatively correlated with tunnel length.Its changing trend has nothing to do with train speed.?2?When the main value is fixed,the train wind speed increases by 40km/h,the piston wind speed increase rate is 23.01%;when the blocking ratio increases from 0.207 to 0.232 and the train length increases from 203m to 428m,the piston wind speed increase rate is 10.43%and 11.67%respectively.The increase of the wind speed of the piston is 7.81%for each 2km increase of the tunnel length.The versatility of each calculation condition is considered,so the conclusion has certain practical value.?3?When other main causes are given,when the blocking ratio is increased from 0.207 to 0.232 and the train length is increased from 203m to 428m,the increase rate of the dimensionless piston wind speed v₁/v₀ is 10.11%and 11.24%respectively;for each 2km increase of the tunnel length,The dimensionless piston wind speed v₁/v₀ reduction rate is 7.4 1%.In this paper,the measured data,theoretical analysis values and simulation results are used to verify that the relative differences between the three are within a reasonable range.This aspect indicates that the simulation calculation method and model are used to establish feasibility.There is the accuracy of the piston wind theory calculation formula,which not only provides a reference for the study of the use of piston wind to ventilate single-track railway tunnels,but also serves as a reference for studying the use of piston winds in other tunnels.