Influence Of Aerodynamic On Comfort Of High-Speed Train

As the continual construction of high-speed railway, trains with speed of above200km/h and300km/h were extensively operated, and problems of aerodynamic turned to be more and more prominent. Pressure pulse and lateral aerodynamic force as trains passing by each other, and pressure wave as trains traveling through tunnel, will influence stability of train and riding comfort of passengers.At the same time, passengers’demand of comfort becomes higher and higher. Passengers want trains running stably and comfortable thermal environment. This will need enough fresh air, and appropriate temperature, air speed, pressure, humidity, and carbon dioxide concentration in compartment. In China construction of high-speed railway and development of high-speed train are so fast, but a lot of aerodynamic problems which influence passengers’riding comfort are not very clear. For example, when two trains are running by each other, aerodynamic forces (moments) produced by passing train will act on observing train, then become excitation source and induce vibration of train bodies in many directions. So it is necessary to study on values of aerodynamic forces (moments), their relations with train speed, track distance, and locomotive shape, and their effect on passengers’vibration comfort. On the other hand, high-speed air-conditioned train is airtight, only fresh air inlet is connected with external atmosphere, therefore air-conditioning system controls thermal environment in train completely. So what kind of air-conditioning system can realize thermal comfort hoped at the vast expense of our country is a problem, which needs to be seriously studied. Pressure-waves produced as trains passing by each other and traveling through tunnel can transfer into compartment via fresh air inlet, and make pressure indoor to change, and then induce uncomfortable feeling of passengers’ears. So what kind of air-conditioning system can resist external pressure-waves and make passengers comfortable is another problem need to be seriously studied. High-speed train is being developed for a so short time in China, and there is no standard to evaluate thermal comfort in compartment. The design of air-conditioning system and evaluation standard of thermal environment in high-speed train are necessary to be studied.At the assistance of National Science&Technology Support sub-Project during the11th five-year plan period 《control technology of air flow field in high-speed train》, preliminary study work was made about following problems:1. Pressure-pulses as trains passing by each other were analyzed in conditions of various speeds, various track distances, and various shapes of locomotive. The variation regularity of the pressure-pulse amplitude along with speed and track distance was found, and the distribution of amplitude along with height of train body was obtained. Aerodynamic characteristic as trains passing by each other was analyzed from comparing pressure-pulse of different shapes of locomotive. Finally, the pressure-pulses at fresh air inlet of CRH2train were obtained, preparing to calculate pressure-wave in train.2. The changes of air resistance force, side force, vertical force, capsizing moment, pitching moment, and yawing moment, were analyzed as trains passing by each other at speed of200km/h-400km/h. Variation regularities of every aerodynamic force (moment) peak along with speed and track distance were obtained. Train-shape effect on aerodynamic forces (moments) was analyzed. Then train body vibration induced by aerodynamic force (moment) was analyzed, and passengers’ vibration comfort was evaluated as trains passing by each other.3. The distributions of temperature, air velocity, CO2volume concentration, and relative humidity in compartment were calculated in summer of south and winter of north. And the thermal comfort was evaluated by air flow field indexes and thermal comfort indexes. Then based on the evaluation, some suggestions were given.4. According to the pressure-pulse at fresh air inlet as trains passing by each other in open air and in tunnel, the pressure-change in compartment was calculated when the train uses high property fan in air-conditioning system to resist the external pressure-pulse. The resistance effect was judged based on amplitude and reducing rate of pressure-change indoor. Effect of two kind of fan on pressure-change indoor was compared when external pressure-pulse is constant. The difference between frequency-fixed fan and frequency-convertible fan in resistance way and resistance result of pressure-pulse was analyzed, according to the comparison of pressure amplitude indoor and reducing process of amplitude along pipes.