| High-speed maglev can fill the gap between aviation and high-speed rail passenger transportation.At present,China has begun to carry out relevant research on the aerodynamics of high-speed maglev transportation tunnels,and the study of high-speed maglev tunnel clearance area play an important role in the development of maglev transportation.The value of the tunnel clearance area directly determines the construction cost of the tunnel,and is also one of the main factors affecting the severity of tunnel aerodynamic effect.It also directly affects the safe operation of the high-speed maglev train.When measures such as reducing the cross-sectional area of the vehicle and improving the sealing performance,the minimum effective clearance area of the tunnel can be reduced accordingly.The aerodynamics of high-speed maglev trains and high-speed wheel-rail trains are basically similar,and the research methods used are similar.Therefore,this paper uses the one-dimensional compressible unequal entropy flow model generalized Riemann variable characteristic line method to study effect of pressure wave on high-speed maglev train passing through tunnel.According to the existing aerodynamics research experience of high-speed railways,it is reasonable to determine the minimum clearance area of high-speed maglev tunnels through parameters such as in-vehicle comfort level and vehicle dynamic airtightness index.In this paper,whether the pressure inside the train meets the pressure comfort standard is the only evaluation basis.The problem of the most unfavorable tunnel length based on the transient pressure in the vehicle is studied,and the influence of train airtightness on the most unfavorable tunnel length is determined.The recommended value of the tunnel clearance area that meets different pressure comfort standards when a high-speed maglev train passes through the most unfavorable tunnel length is given.The main conclusions are as follows:(1)The external pressure fluctuation of high-speed maglev train is the result of the combined effect of train running trajectory,compression wave and expansion wave,and it is closely related to its running time in the tunnel.The pressure waves outside the bicycle and the meeting car are also formed by the reflection of the compression wave and expansion wave induced by the train entering the tunnel.The biggest difference is that when a single train passes through the tunnel,only one train enters or exits the tunnel,and expansion waves and compression waves are generated.The compression wave and expansion wave caused by the incoming train at the intersection will be superimposed with the pressure wave induced by the earlier entering train,affecting the pressure distribution outside the train.(2)High-speed maglev trains have similar external pressure fluctuation curves;from the head car to the tail car,the maximum positive pressure value of the external pressure gradually decreases,the maximum negative pressure value increases first and then decreases,and the maximum negative pressure of the intermediate car(the fifth car)The maximum value;the train head pressure increases slowly and linearly as the train enters the tunnel.When the full length of the train enters the tunnel,the external pressure of the head car reaches the maximum positive pressure value;during the process of the train passing through the tunnel,the whole pressure of the measuring point is basically in a negative pressure state;(3)In the process of the train entering the tunnel,the pressure of the head train increases slowly and linearly.When the full length of the train enters the tunnel,the external pressure of the head car reaches the maximum positive pressure value;during the process of the train passing through the tunnel,the whole pressure of the measuring point is basically at a negative pressure;as the length of the tunnel increases,the head and tail of the train The maximum positive pressure value is almost unchanged,and the maximum negative pressure value decreases;the maximum positive and negative pressure values outside the train increase with the increase of vehicle speed.The higher the speed,the earlier the maximum positive and negative pressure values appear,and In a 500m tunnel,the maximum positive and negative pressure values are the largest.(4)The distribution characteristics of the pressure in the car at different time intervals are as follows:the pressure curve in the car is similar in 3 time intervals of every 1s,every 3s,and every 10s,and the head and tail vehicles show a trend of increasing first and then decreasing.When the vehicle test points encounter the compression wave generated when the head car enters the tunnel and propagates to the exit of the tunnel,the maximum pressure in the car appears;the pressure curve in the car is similar at two time intervals every 30s and every 60s.When entering the tunnel,the maximum pressure in the vehicle appears,and the maximum pressure is equal.For maglev trains of the same speed class,the time constant has no effect on the length of the most unfavorable tunnel based on different time intervals in the train.(5)After the preliminary calculation and analysis,it is found that the transient pressure in the vehicle specified in the standard is the loosest every 1s,and the strictest in the whole process of passing through the tunnel.That is,the longer the time interval,the stricter the transient pressure in the vehicle and the minimum tunnel clearance area.The bigger;for short tunnels,the in-vehicle pressure limit in UIC standards per 60s is looser than in per 10s;and for medium and long tunnels,etc.,the in-vehicle pressure limit in UIC standards per 60s is the strictest,that is,meet the standards The recommended minimum tunnel clearance area of the transient pressure within per 60s can also meet the transient pressure within per 10s,per 3s,and per 1s;(6)In the case of a single train passing and the intersection of two trains,as the time constant increases,it satisfies?1.0k Pa/10s,?1.5kPa/30s,?2.0kPa/60s,?1.5kPa/full process,?2.0kPa/full process The recommended value of the minimum tunnel clearance area of the pressure comfort standard at different time intervals decreases linearly.(7)In the case of a single train passing and the intersection of two trains,as the speed of the maglev train increases,the recommended value of the minimum tunnel clearance area in different time intervals also increases,and the influence law presents a law of quadratic function.(8)Based on the four selected pressure comfort standards,this paper puts forward the recommended value of the clearance area of the maglev tunnel with a speed of 600 kilometers per hour.Among them,UIC(first edition in 2002)has a limit of 1.5kPa/60s less than UIC(second edition in 2005).The clearance area of single-line tunnels differs by 83m~2,and that of double-line tunnels differs by 63m~2,so the longer the time interval,The greater the tunnel headroom required;when the time constant is large,the increase in the pressure in the car is much smaller than the increase in the headroom of the tunnel;when the pressure in the car increases by 500Pa,the 68m~2 tunnel headroom needs to be increased to meet the car Internal pressure comfort standard.In this paper,by studying the pressure fluctuation characteristics of high-speed maglev trains inside and outside,the proposed value of the headroom of the high-speed maglev single and double line tunnels under different airtightness and different speed grades of trains can be further improved to supplement the"Maglev Railway Design Standard(Trial)".The relevant part of the clearance area of the middle tunnel provides basic data support for the construction of the high-speed maglev tunnel. |
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