Referencing this video of a train starting from a dead stop on an uphill grade:
Starting around 1:30, there are several points at which the locomotives put out large amounts of dense black smoke. At one point around 1:58, it looks like it may even be emitting white smoke, but that could just be the lighting. It’s notable that each locomotive emits smoke, all three do it intermittently, and there doesn’t appear to be any noticeable degree of locomotive-to-locomotive synchrony WRT the smoke emissions.
Some people in the comments are suggesting that this is somehow related to the traction/slip management system, but if that’s true, they don’t explain it very clearly.
So…what’s with all the smoke?
nm. (I think I misunderstood the question)
Throttle up! I think that is all that is happening.
An idling diesel prime mover tends to ‘load up’ – have soot accumulate post-turbo – and when accelerating, it takes a few seconds for things to warm up plus the turbochargers to spool up.
They don’t all smoke at the same time because the engineer, believe it or not, does not have direct control over how much fuel is going through the injectors. Instead s/he decides, “I need this much tractive effort,” available in an instrument on the panel, moves the throttle, and the locomotive decides what the rpms in the prime mover and field winding voltage in the generator need to be to produce that T.E. most efficiently.
A locomotive constantly blowing black smoke indicates something wrong, compression loss in a cylinder, perhaps or the injectors set way too rich. The white smoke in the lead unit is especially troubling, likely being totally unburnt fuel being expelled.
GE locomotives, about 85% of the road engine fleet in the US are notorious for shooting not just smoke, but flames out the exhaust when things are not just right.
https://youtu.be/PPYZroaURy4?t=39
So this is (probably) just soot that’s caking up on the walls of the exhaust pipe downstream of the turbo, and getting blown loose as the exhaust flow ramps up?
Plus inefficiently burned fuel until the turbos can supply enough air to burn the suddenly greater amount of fuel.
