Study On Pressure Fluctuations Charateristics In High-speed Train Carriages

China's huge population,resulting in the number of high-speed trains continue to increase the number of open lines will cause the car will increase the working conditions,and China's vast geographical hills occupy a larger proportion of geomagnetism makes the tunnel mileage is growing,the train cycling through the tunnel and the number of vehicles will gradually Climbing,along with the speed and line conditions to improve the people on the train on the train staff pressure comfort issues more and more attention.In view of the present research situation and the existing problems of pressure fluctuation characteristics of high-speed trains,this paper proposes a three-dimensional coupling calculation method for the inside and outside flow field of high-speed trains which takes into account the efficiency and accuracy,and establishes the relevant coupling calculation program.Internal pressure fluctuations,and the cause of the pressure fluctuations in the carriage,hysteresis,fluctuations,comfort,control methods to carry out a series of studies.The internal and external flow field of the high-speed train is divided into two subsystems.The calculation of the external flow field system is completed by the 3D fluid calculation method.The internal flow field system is completed by the 1D fluid calculation method,and the modified 1D&3D coupling calculation method,to achieve the train inside and outside the flow field system simultaneous joint solution.And 1D&3D coupled computing program for the internal and external flow fields of high-speed trains was built by using computer language,which was used to calculate the coupled numerical simulation of internal and external flow fields.According to the shape of the vehicle and the design parameters and geometric model of the ventilation system,the necessary simplification is made on the basis of the calculation results.The model of the 1D train flow system is established.To build the external flow field model and the coupled model of internal and external flow field.The initial value of the coupled boundary of the transient calculation is the train running in the open air.The pressure of the intake and exhaust ports and the interior of the train are both negative and inversely proportional to the square of the speed.Of the mass flow is always to maintain a balance with the speed of a linear relationship,with the increase in speed showed a downward trend.The mechanism of the inlet and outlet pressure,which is the boundary of the flow field system in the high-speed train,is studied in three typical transient conditions:trains passing each other in the open air;train through a tunnel;trains passing each other through a tunnel.The positive and negative pressure zones generated by the running of the reference train at the trains passing each other in the open air and the research train come into contact with the intake and exhaust vents to cause the pressure fluctuations.The pressure fluctuations of intake and exhaust ports in the condition of train through a tunnel is formed by the alternation and superposition of several compressional and expansion waves.The change of the pressure at the intake and exhaust vents of the train caused the change of the flow rate,resulting in the imbalance.The variation of the total mass in the carriage caused the pressure fluctuations,and the flow imbalance is the carriage pressure fluctuations formation of incentives,interior pressure and intake and exhaust air flow is proportional to the linear relationship.The existence of the ventilation pipe makes the pressure fluctuations in the carriage have lagging behind the pressure of the intake and exhaust ports.The delay time is decided by the peak time and velocity of the intake and exhaust ports.The higher the flow velocity is,the shorter the peak response time is.The influence of train speed and line condition on the pressure fluctuations in the three kinds of typical conditions of high speed train,such as trains passing each other in the open air,train through a tunnel and trains passing each other through a tunnel,are analyzed.Usually the speed will change the pressure inside the carriage and the rate of change with time trends,pressure and the rate of change and the speed of power was a power function relationship,the speed increases the two amplitudes.The increase of the distance between the open lines and the reduction of the tunnel obstruction ratio will relieve the pressure fluctuations in the carriage.The pressure inside the carriage and the amplitude of the change rate are both exponential functions.When the line spacing is large enough or the tunnel is blocked than the small enough,the train is similar to the train running in the open air;the carriage pressure is basically constant.The length of the tunnel changes the pressure and the rate of change with time,and exponentially with the maximum amplitude of the pressure,the length of the shortest tunnel model is 5 times longer.Through the analysis of the pressure amplitude and the rate of change comfort standard line and the variation of the parameters obtained under the pressure curve fitting curve,a series of intersection point of pressure amplitude and rate of change is the comfort critical point for Comparing the two standards to get the pressure change rate amplitude comfort standard than the pressure magnitude comfort standard strictly,this article only has 10 calculation conditions simultaneously satisfies two comfort standards.The special structure of the air-conditioning unit caused the pressure distribution law of "high positive pressure-high negative pressure-low negative pressure-high negative pressure-high positive pressure",and optimized the two inlets of "low negative pressure" High positive pressure "region,get the three kinds of typical working conditions of the car under pressure have been some improvement.The calculation method of reverse thinking was established to obtain the valve opening and the fan speed to maintain the comfort of the carriage pressure.The optimized pressure and amplitude of the pressure change rate under the specific working conditions were reduced significantly compared with those before optimization.The two kinds of control methods can effectively solve the comfort problem of pressure fluctuations inside the carriage,and can be put into practical application.