Study On The Characteristic Of The New Hydro-pneumatic Buffer For Railway Vehicle

Buffer is one of the major devices for rail vehicles energy absorption, bywhich to mitigate and cut the longitudinal impact in the course of train runningand shunting. The performance of buffer can directly affect the speed of the trainrunning, the efficiency of train shunting, passenger comfort and safety. Hydro-pneumatic buffer has the advantages of large capacity, high absorption rate andeasy to adjust. Meanwhile, inert gas is used as the reset element, this not only toeliminate spring fatigue, but also to get lossless, reduce maintenances andimprove the service life. At present, the hydro-pneumatic buffer technology isnot mature in China, the only used CRH5EMU hydro-pneumatic buffer whichwas imported from France s Alston Company.Through comparing the existing hydro-pneumatic buffer for rail vehicles,and according to the design requirement of buffer for rail vehicle, this paperdesigns a novel structure and has three sections of damping structure, andintroduces the structure characteristics and working principle. For the piston rod,damping valve, damping hole, damping ring seam and gas cavity of buffer, thedetailed mathematical models has been established, and solved by four ordersRunge Kutta method. The matlab simulation program is used to analyze staticand dynamic characteristics, the influence of structure parameter of hydro-pneumatic buffer.It can be seen from the static simulation analysis: when the compressionrate is constant, with the increasing of initial pressure, the initial resistance andmaximum resistance of the buffer raised significantly, and the absorbed energy isalso raised. The shape of the characteristic curve basically unchanged. Theselection of suitable initial pressure is helpful to improve the buffer to absorbenergy. When the initial pressure is constant, with the increasing of compressionrate, the initial resistance is also increased, but the increasing of maximumresistance is not high, the rate is maintained between500KN and600KN, and the buffer capacity is doubled. The characteristics of the buffer can ensure railvehicles good comfort and safety in the steady process.The dynamic simulation analysis shows that the buffer stroke, energyabsorption and buffer efficiency increase with the growth of the quality of impact.Under the carrying capacity of the buffer, the maximum resistance basicallykeeps unchanged, and the declining rate of resistance decreases after reaching amaximum. The shape of hysteretic characteristic curve of draft gear remainsunchanged, and maximum resistance, buffer stroke, energy absorption and bufferefficiency increase with the increasing of the impact speed. Along with thegrowth of the initial pressure, the maximum resistance and buffer stroke increase.The absorbed energy is slightly diminished, but buffer time increasessignificantly. With the growth of the viscosity coefficient, maximum resistanceand absorbed energy increase, while the buffer stroke reduces. With theincreasing of damping holes diameter, buffer stroke increases, while maximumresistance and absorbed energy reduce. With the increasing of the length ofdamping holes, maximum resistance increases slightly, and buffer stroke reducesslowly. The effect of the diameter of damping hole on the buffer performance ismuch larger than its length.The application of the new hydro-pneumatic buffer in metro vehiclesshows that this buffer has a large of energy absorption, a high efficiency, and itsenergy absorption rate is over90%. A single buffer can meet the impact speed of11km/h, and under this condition, the buffer has better buffer characteristics. Wecan get buffers at different impact speed according to adjusting the parameters ofhydro-pneumatic buffer. The buffer has a good performance under the specificmaximum impact velocity, and the design index of maximum resistance, bufferstroke, energy absorption rate and so on can meet the design requirement ofmetro vehicle. The buffer characteristic curve can be adjusted as need. Furtherimprovement of the buffer performance can not only meet higher impact velocity,but also provide strong supports for the speedup and the safety of railway vehicle.