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Old February 1st, 2013, 08:18 AM   #5421
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CRH pics







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Old February 1st, 2013, 10:30 AM   #5422
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Quote:
Originally Posted by hmmwv View Post
Multiple short tunnels are fine, but multiple long tunnels is more likely to cause problem. I have to agree though, that slowing to 80km/h is extremely unlikely to be caused by tunnels, actually I doubt it will slow to that speed at all, probably from 300km/h to 200km/h, but 80? No.


Of course trains routinely go 300km/h through tunnels around the world, but do they do that when the tunnel is a few kilometers long and the next tunnel is only a couple of hundred meters away? With tunnels of the same diameter, the longer it is the higher pressure will build up inside, similar to a gun barrel
I'd still disagree. Tunnel air is considered high pressure, high drag air; even if there was a significant tunnel boom at the end of the tunnel, it would radiate outwards and not into the second tunnel. If we were to do that, the tunnels would have to be less than 50m apart, not hundreds.

Second, tunnel boom intensity is not determined by the length of the tunnel, but the geometry of the tunnel entrance. Tunnel boom is generated when a train enters the tunnel, the air that was previously pushed aside by the train is suddenly pressurized, and this creates a shockwave that travels down the tunnel at the speed of sound. It is this shockwave that creates "true" tunnel boom.

That being said, the length of the tunnel is irrelevant. You are right in comparing a tunnel boom to a "gun", a longer barrel doesn't make a louder report. I've stood near tunnel entrances (within 7m), and heard no "true" tunnel boom because European-style tunnel entrances are specifically designed to mitigate such issues. Therefore, the only reason why the trains would slow down in tunnels due to concerns about tunnel boom would be because the tunnel entrance geometry hasn't been optimized.
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Old February 1st, 2013, 06:14 PM   #5423
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Originally Posted by hmmwv View Post
Of course trains routinely go 300km/h through tunnels around the world, but do they do that when the tunnel is a few kilometers long and the next tunnel is only a couple of hundred meters away? With tunnels of the same diameter, the longer it is the higher pressure will build up inside, similar to a gun barrel
If that was a problem and you were the engineer designing it would you handicap your own creation in that way? It would be cheaper to build deeper and in one long tunnel, or cover the open section to be a tunnel, to avoid the revenue loss associated with unnecessary speed restrictions.

And the answer is yes - plenty of ICE lines do this.

I've noticed a slight misunderstanding - multiple tunnels (in succession) vs dual-tube tunnels. So I now get you mean the former.

And +1 to Silver Swordsman - the length of tunnel does not cause a build up. In fact it serves to lower the frequency of the impulse as it exits. (Both the ports in your speakers and organ pipes use this fact as the impulse characteristic is determined by the same physics that determines the resonant frequency of the tube, the larger the length/cross-section the longer the wavelength). The air molecules in the tunnel don't like going from zero to high acceleration, necessary to sustain a high-frequency. The impulse will change over distance/time as a result, the energy is not lost, but is converted to lower grade energy, with a higher entropy i.e. lower frequency and longer wavelength. (Same as earth radiates infra red because it would need to be like an air molecule that likes accelerating quickly in order to re-radiate the sun's energy as UV)

Or another way to look at it is to map all the possible vectors within the tunnel from the source of the impulse. There is one direct journey to the other entrance, but a large number requiring one bounce of the wall, more with two, even more with three, etc. The longer the tunnel the bigger this disparity between the direct and indirect, spreading the energy over time at the exit, resulting in the lower frequency of the impulse.
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Last edited by makita09; February 1st, 2013 at 06:43 PM.
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Old February 2nd, 2013, 01:00 AM   #5424
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This picture is mighty interesting....any idea why a conventional train is hooked up to a high speed train?
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Old February 2nd, 2013, 01:05 AM   #5425
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delivering it to the depot for final works?
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Old February 2nd, 2013, 11:27 AM   #5426
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This picture is mighty interesting....any idea why a conventional train is hooked up to a high speed train?
Most likely because it has a fault, or it is not yet a fully functioning and network-authorised unit.
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Old February 3rd, 2013, 01:20 AM   #5427
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Quote:
Originally Posted by FM 2258 View Post
This picture is mighty interesting....any idea why a conventional train is hooked up to a high speed train?
Conventional passenger carriages were too boring and lack the "cool" factor so they now use trailer CRH carriages on select conventional routes. You should see the ones pulled by diesel trains.
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Old February 3rd, 2013, 09:18 AM   #5428
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Quote:
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This picture is mighty interesting....any idea why a conventional train is hooked up to a high speed train?
This also happens during a HSR's cold rolling test (冷滑试验) where the EMU is pulled to traverse the line without powering itself up.
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Old February 4th, 2013, 07:17 PM   #5429
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Cold rolling test? Interesting. What's the point of a cold rolling test?
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Old February 4th, 2013, 08:44 PM   #5430
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Cold rolling test? Interesting. What's the point of a cold rolling test?
I am no expert here, but I think it is to field test specification and tolerance level. No different than the initial sea trial or shake-down cruise for newly launched ships.

You can only find out the truth when the "rubber hits the road" so to speak.

Last edited by stoneybee; February 4th, 2013 at 08:49 PM.
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Old February 4th, 2013, 10:14 PM   #5431
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I am no expert here, but I think it is to field test specification and tolerance level. No different than the initial sea trial or shake-down cruise for newly launched ships.

You can only find out the truth when the "rubber hits the road" so to speak.
Wouldn't they have testing tracks for that?
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Old February 5th, 2013, 04:35 AM   #5432
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CRH passing Cangshan, Sichuan Province



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Old February 5th, 2013, 09:56 AM   #5433
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Wouldn't they have testing tracks for that?
Test tracks only help so much.
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Old February 5th, 2013, 06:13 PM   #5434
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can someone provide me latest update regarding 600 km/hr CIT500 trains. When they will announce it for public opening.
Additional details can be found here : http://www.carnewschina.com/2011/12/...-record-train/

Last edited by admns; February 5th, 2013 at 06:19 PM.
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Old February 5th, 2013, 09:12 PM   #5435
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can someone provide me latest update regarding 600 km/hr CIT500 trains. When they will announce it for public opening.
Additional details can be found here : http://www.carnewschina.com/2011/12/...-record-train/
It seems to have slipped off the radar for the time being, this is the place where any news on that kind of develpoment is quickly posted.
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Old February 6th, 2013, 12:34 AM   #5436
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Quote:
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can someone provide me latest update regarding 600 km/hr CIT500 trains. When they will announce it for public opening.
Additional details can be found here : http://www.carnewschina.com/2011/12/...-record-train/
I really want to know more about this project as well. I hope they've been able work with physics to have a train that runs economically at 500km/h. At this point I can only hope and dream. I'm not an engineer so I have no answers.
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Old February 6th, 2013, 01:53 PM   #5437
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By 荆棘鸟 from a Chinese photography forum :



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Old February 7th, 2013, 09:45 AM   #5438
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hi , can someone also provide me latest update regarding 1000 km/hr chinese maglev trains.
Additional details can be found here : http://blog.chinatravel.net/planes-t...ess-coach.html

Last edited by admns; February 7th, 2013 at 10:06 AM.
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Old February 7th, 2013, 09:52 AM   #5439
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http://blog.chinatravel.net/planes-t...ess-coach.html
double post

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Old February 9th, 2013, 08:41 PM   #5440
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据广铁集团客运部门介绍,武广、广深港高铁调图后,共安排开行动车组列车117对,其中直通动车组列车68对,管内动车组列车列车49对。各区段对数为:武汉~岳阳东间68对,岳阳东~长沙南间70对,长沙南~广州南间89对,广州南~深圳北间48对。

直通动车组列车68对

1、北京西~深圳北1对,车次:G71/2。这是我国目前运行里程最远的高铁列车,行驶距离超过3000公里。

2、西安北~深圳北2对,车次:G824/1 G822/3、G828/5 G826/7。

3、郑州东~深圳北2对,车次:G73~G76。

4、武汉~深圳北10对,车次:G77/8、G1001~G1018。

5、北京西~广州南2对,车次:G79~G82。

6、西安北~广州南5对,车次:G98/5 G96/7、G831~G846。

7、太原~广州南1对,车次:G624/1 G622/3。

8、石家庄~广州南1对,车次:G531/2。

9、郑州(东)~广州南5对,车次:G93/4、G541~G548。

10、信阳东~广州南2对,车次:G551~G554。

11、武汉~广州南32对(含“D”字头2对),车次:G1101~G1160、D2101~D2104。

12、北京西~长沙南4对,车次:G83/4、G501~G506。

13、西安北~长沙南1对,车次:G854/1 G852/3。

管内动车组列车49对

1、长沙南~深圳北10对,车次:G6001~G6020。

2、广州南~深圳北23对,车次:G6201~G6246。

3 、岳阳东~广州南2对,车次:G6131~G6134。

4、长沙南~广州南14对(含“D”字头2对),车次:G6101~G6124、D7801~D7804。
Oh ok i understand now
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