I spent some time reading the EPA’s requirements for their T3 mandate for non-road vehicles and was surprised at thier target of 15 ppm for HC. Maybe I’m missing something here but that number seems low to me (let alone NoX and the others). A new locomotive passing certification is one thing but how is it maintained/regulated after the fact? Do/will the loco engine maintainers/rebuilders have exhaust analysers to maintain this standard?
There’s been a lot of hand-wringing and gnashing of teeth on this one, of the ‘oh woe is me’ variety. But the fact of the matter is it really isn’t that hard to do. The key to it is that the new engines – both railroads and other off-road vehicles, such as construction equipment – have engines which have much more sophisticated (but, oddly, easier to maintain) controls than older engines. It used to be, for a diesel, for instance, that the amount of fuel sent to the engine was determined mechanically by the power demand (the throttle directly for a truck, for instance; the governor in most other applications). This was – even when the thing was new – not very precise (ever watch an Alco spool up?!). However, in new engines (including automobiles!) the amount of fuel delivered is determined by a small computer, which takes into account how much power is required, but also a whole raft of other things and determines – quite accurately – how much fuel is needed: often (in larger engines) for each cylinder for each stroke. So long as the computer is working, and its various sensors, and the engine is not so badly out of whack (or damaged) that it is operating anywhere in its normal range, meeting the Tier III target is no problem – in fact, most engines will exceed it, often by an order of magnitude (the limitations have to do with the interaction between HC, CO, NOx, and particulates: it is very difficult to optimise all of them all at once). If, for instance, an injector is a little worn, the computer just tells it to shorten its stroke or open time. And so on.
The engine itself carries its own exhaust analyser, in the form of some of the sensors which drive the computer – so it is constantly adjusting itself to produce optimum conditions (and, not incidentally, optimum fuel usage).
Maintenance is actually easier. You still have the usual bits of checking for ring and cylinder and bearing wear, and making sure all your fluids are changed or properly filtered, but all of th
I know I may be acused of Raising the Dead, but I bring this up to illustrate how far back these comments and concerns go in these FORUMS. This in light of a new revelation that California may be possibly acused of "Cooking the Books’ on Locomotive Emissions to prod an agenda on promoting local issues of potentially national implications.
This is another Trains Forum discussion link referencing California’s Agency CARB:
http://cs.trains.com/TRCCS/forums/t/179861.aspx?PageIndex=1
This is a lin that references an apparent revelation that California has been passing somewhat draconian rules on Diesel Engines ( Automotive and Railroad). Linked from a SF Chronicle on-line article :
“Overestimate fueled state’s landmark diesel law”
By:Wyatt Buchanan, Chronicle Sacramento Bureau
San Francisco Chronicle October 8, 2010 04:00 AM Copyright San Francisco Chronicle. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Linked here:
The article refers to the law as dealing with off-road diesels, such as construction vehicles. No reference to rail there at least.
Interesting and informative explanation, Jamie - and at about my level of understanding of things mechanical. [swg] Thanks ! [tup]
- Paul North.