是真的吗丨西南交大磁悬浮驶进BBC
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The maglev train uses magnetic levitation to move around rather than wheels. There arealready speedy methods of transportation, reaching around 430 km/h. But SouthwestJiaotong University, the team wants the trains to go even faster, and to do that, let’s startingsmall.
Here is a model of the super maglev train we’re going to see in action, this is in micro. Now Ms Gou has liquid nitrogen, if you could put the liquid nitrogen into the train, please, I am too scared to do that. Now, that cools metal inside it down, and creates a superconductor there we are, and that should levitate the train, and if I just give a little bit ofboost, it not only levitated, but it pushes it around the track. And that’s the same principle as the large model, but it’s a burst of electricity that gives it that initial kick start. The new high temperature super maglevs get their names, because they increase the temperature of the liquid nitrogen, that encases the magnets, but it’s still a very cold minus 196 Celsius, that increases the speed of the train and by placing the whole thing in tube it could really get the speed up.
The fact that your operating vacuum here is different, what is the principle behind that? Usually a maglev train gets up to 400km/h, its resistance is from the air, so if we use this evacuated tube we can get speed much higher. This is just a test track here, how longdo you think before a train like this will actually be running on the track in China? This kind of technology can be realized after the maglev train gets up to 500km/h, so by the time it reaches between 600-800km/h, it can be commercialized and tested. So I foresee that it will take 30-50 years.
Now the next step is to build the straight track and to test it on faster speeds. You have to create a vacuum in the tubes here to make this work, surely in practicethat would be fantastically expensive, it’s not a practical technology, this to create a vacuumacross large stretches of China? It won’t be as costly as people imagine, in order to maintaina low pressure, usually you need to pump every 2 km, so as long as we keep that it willwork, One thought is that we can make use of current underground system, like the Switzerland underground and the US underground. It will take decades more experiment to see if the existing underground tunnels can be converted to accommodate vacuum maglev trains, so the team here uses this track specifically built at the university to test that theories.
At the moment, the vacuum tests are only carried out on trains without passengers, so there is still air in the tube when I am inside, but in the future the train will be designed like airplane cabins to deal with the air pressure. What is the difference in the speed you can achieve between when there isn’t a vacuum or when there is a vacuum? With the air the car can goto 16 km/h because of the resistance, when the air is evacuated, the speed can go up to 40km/h. And theoretically at 3000 km/h, it even has the potential for space travel, but all in good time. I am going 9 km/h, quite fast enough.
译文
磁悬浮列车的运行不是靠车轮，而是利用了磁力悬浮原理。目前磁悬浮列车的速度可以达430公里每小时。尽管如此，来自西南交通大学的科研团队仍想进一步提升车速，想知道他们怎么做的吗？
我们先看微模型。大家马上看到的是运行中的超导磁悬浮列车，注意这是微模型。现在苟女士拿的是液态氮，然后她要把液氮放到列车中去，噢，小心点，我可不敢碰那玩意。液氮冷却了周围的金属，产生出一种可以让列车悬浮的超导体，然后如果再加点量，不仅可以使列车悬浮，还可以推动列车沿轨道运行。原型试验的原理也和微模型一样，区别是原型试验列车的最初启动需要强电流。这种新型高温超导磁悬浮列车之所以得名“高温”，是因为它们用液氮升温所产生的磁性来提高速度，当然液氮温度还是需要低至零下196摄氏度。如果能让列车在管道中运行，就真的可以大幅提高速度。
这种真空管道与众不同，为什么呢？通常磁悬浮列车时速达到400公里每小时后，它受到来自空气阻力的影响，因此如果利用真空管道，就可以大大提高行车速度。这里就是一个试验轨道。你认为这种新型超导磁悬浮列车要多久才可以真正在中国投入使用呢？这种技术在磁悬浮列车时速达到500公里每小时后就可以实现，因此，一旦磁悬浮列车的时速可以达到每小时600至800公里，这种技术就可以实现商业化并开始试运行。因此我估计投入使用需要30到50年的时间。
下一步就是建设笔直的轨道，并在之上试验更高速度的列车。然后还必须要实现管道的真空化才能达到运行条件，当然在实践中这样做造价非常昂贵。这种技术不太现实吧？难道是说要横跨广阔的中国建设真空管道？其实并非大家想象的那么造价高，因为只要每隔两公里就抽压，保持低压力就好了。还有一个方案就是利用现有的地下铁路体系，例如瑞士和美国的地铁。要想实现把现有的地铁隧道转换为能容纳真空磁悬浮列车的环境，还需要几十年的实验过程，所以西南交通大学的科研团队专门建设了一条轨道，通过试验来验证该理论。
目前，投入真空试验的都是无人列车，所以，我一进入这个真空管道就会带来空气，就不算真空了。但是未来的列车会设计成像飞机的机舱一样，来应对空气压力。那么到底采用真空管道会使速度产生怎样的不同呢？ 如果在非真空状态下，由于空气阻力，汽车开到每小时16公里，那么在同等条件真空情况下，速度可以达到每小时40公里。因此，理论上讲，列车的时速可以高达3000公里每小时，甚至还有太空行车的可能性，当然这些还需要很长的时间。不过我还是习惯每小时9公里的速度，已经很快很好了。
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