I understand that diesel locomotives operating in a tunnel can use up available oxygen faster than it can be replenished through the portals. And since the engine fuel delivery remains the same, the reduction of oxygen results in too much fuel in the fuel/air mixture, thus making excessive black smoke. I assume that fan ventilation helps overcome this problem.
Take a look at this video, and tell me what is happening.
Some have commented that it is just the 4th unit that is making all the smoke because you can see the distinction as they pull past the camera. But I have a feeling that they were all smoking due to a lack of oxygen in the tunnel, and they generally cleared up when they got out into the fresh air. Even the 4th unit, which appears to be smoking the most as it passes the camera, seems to be in the process of reducing its smoke.
I would like to know if this much smoke is normal for such a train, pulling that hard in such a tunnel.
Basically what you are looking at is plain and simply oxygen starvation in the engine. The older engines do not have the computers on them to prevent the smoke display you saw from the leading engines. If you watched that clip to the end you would have seen a total of 4 SD70ACe’s and not one of them was smoking as bad. A diesel engine does not have throttle plate at all all that regulates it is fuel injected into the cylinder to burn. As long as it will start to burn it will burn if there is to much it will just go black as night.
Even with forced air ventilation in the tunnel, you have to keep in mind the first locomotive is exhausting hot gas, which the second engine is drawing through it’s intake, while it too is exhausting, so by the time you get to the third and fourth locomotive, they are drawing in an extremely hot mix of exhaust gas and dirty air, so the ability to combust is limited.
Had any of those been GEs, you would have seen a dead locomotive in the fourth position!
Not quite. Tunnel motors cool down faster between tunnels, so they don’t overheat as bad in the 2nd or 3rd tunnel. D&RGW had higher pressure radiator caps, to allow a higher temperature before boil-over and overheating. The combustion air intake is in the same place on tunnel motors and regular ones.
True enough, but by drawing the air into the radiators from “ground level”, the cooling water does not reach such a high temperature as it otherwise would and also forces a more oxygen-rich air up to where the combustion air intake is. Both items contribute to a cooler running locomotive which in turn permits a quicker cool-down and better combustion which also contributes to a cooler running engine because the “unburnt” fuel exiting the combustion chamber is hotter than fully consumed exhaust and also displaces “clean air” within the tunnel which itself also contributes to less efficient combustion and cooling.
Simply changing the radiator cap on a unit will not permit it to operate at a higher temperature. It will prevent boilover until that higher radiator pressure/tempature is reached, but unless you also change out the temperature sensor/hot engine shut down switch, the engine will still shut down at the “factory” setting.
I never could quite understand why the BN didn’t buy some Tunnel Motors for use through the Rockies and Cascades because of those “long” tunnels (two of them are really long), but the only reason that I can come up with is price - a tunnel motor did cost a bit more because of its non-standard features.
And for the same reasons, why the UP doesn’t keep its former SP and DRGW Tunnel Motors close to Moffett Tunnel assignments out of Grand Junction and Denve
IIRC there was a Trains article on Mullan and its leader and helper units. It was about two three years ago. Was very instructive. IIRC the crew are required to use oxygen packs. Apparently the units MRL used, according to the article IIRC, were ideal for the work and were maintained to a high standard. Still and all that’s an awful lot of smoke, for the pusher crews especially, to have to deal with as again, IIRC, head end controlled distributed power useage wasn’t possible in that particular tunnel.
I have seen locomotives pulling with failed turbochargers. It looks like a traveling tire fire. Because there is so little air compared to the fuel, the combustion cycle continues right out the stacks. Inside the black smoke, you can see orange flames rising six feet above the locomotive. I have heard this same kind of flaming can occur due to lack of oxygen inside of tunnels. I think they call it torching.
I could be wrong, but my understanding was that tunnel motors were intended to prevent torching inside of tunnels by relocating the air intakes to pickup the fresher air from lower in the tunnel. But I can understand the explanation given here that the tunnel motors pick up fresher air through re-located cooling air intakes and that this air feeds the combustion air intake as well. I can see that, when operating in tunnels, overheating would be another, separate problem in addition to combustion oxygen starvation.
Apparently this excessive smoke condition coming out of Mullan Tunnel is somewhat typical. I see that the tunnel is 3847 feet long, and apparently, it has no power ventilation. Here is a photo of another MRL train emerging from the tunnel:
Keep in mind that turbocharged EMDs use an inertial air filter that is located at the top of the long hood, directly ahead of the turbocharger. This location is the same on all turbocharged EMDs, from the GP20 to the SD70ACe and everything in between.
The relocated air intake on the tunnel motors is purely for the radiators, none of that air goes into the engine for combustion purposes.
These Honda “Mr Opportunity” commercials on TV … well … they need to go away! Just sayin’.