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diesel smoke (sorry again) Rate Topic: -----

#11 User is offline   ErickC 

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Posted 10 October 2017 - 12:34 AM

View Postrailguy, on 09 October 2017 - 02:53 PM, said:

The turbocharged version of the 4-cycle design behaves differently yet, and it is the design that the OR exhaust parameters can not model very well. Here's why: as a 4-cycle prime mover begins to throttle up from idle, there is no supercharger to add air charge to the fuel-air mixture. Concurrently, there is not enough exhaust being produced to spool up the turbocharger, nor can the 4-cycle engine rapidly increase in RPM. The result is an overfueling condition as the prime mover increases off of idle. The result is a very dark cloud of smoke off idle, which lasts until the RPM of the prime mover provides enough exhaust velocity to spool up the turbocharger. Once the RPM is at a sufficient level to run the turbocharger at an adequate RPM, the visible smoke can stop or nearly stop until the throttle is notched out again and the process repeats. HOWEVER, and this what OR struggles to emulate, as the prime mover RPM increases higher, the turbo has an increasing ability to provide sufficient boost to avoid higher levels of "throttle-up turbo lag" smoke. So, while the quantity of exhaust increases as the RPM increases, the amount of throttle-up smoke actually decreases as RPM increases to higher throttle setting levels. Indeed, a well-tuned turbocharged prime mover may exhibit almost no visible smoke (other than heat waves) at high throttle levels. I have yet to find a way that OR can model this behavior accurately.

Hm - I wonder if we could ape this effect by adding a second engine that consumes no fuel and produces no power? We could set up one set of exhaust parameters for the continuous exhaust, and the other for transitions. The continuous exhaust parameters could have a unity multiplier for the exhaust dynamics effect, but an overall positive curve towards higher RPM, while the transition parameters could have a near-null set of continuous exhaust parameters with a negative slope towards high RPM, and large coefficients for the dynamics to produce the transition smoke. When I have some time - and it may be a while - I could try using DPU to quickly set up an ORTS version of the default C44, then see what I can come up with for the exhaust.

#12 User is offline   R H Steele 

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Posted 10 October 2017 - 08:20 AM

View PostErickC, on 10 October 2017 - 12:24 AM, said:

Avoiding what question? You asked no questions, you complained that I didn't post more than what I did. Sorry, I don't respond well to that.

Haven't time to read whole post now...will do so later. Took the time now, read additional comments, we could squabble some more, to what end? ...faults on both sides.
I was unduly abrupt and rude.
Handshake and apologies. Agreed?
Best Regards, Gerry

Ps...hope the OP found the information they needed.
Interesting further info from espee and yourself...Check out the download that espee mentioned at TS...a different take on include files and how to use them.

#13 User is offline   Genma Saotome 

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Posted 11 October 2017 - 12:43 PM

<ADMIN COMMENT>

late to the squabble I see. That said it appears gentlemanly behavior has returned, appropriate apologies all around, what appears to be assertions to move on... all good.

Thank you for behaving like the mature individuals you are. It doesn't usually happen on the internet but it is an expectation for members of this board.


#14 User is offline   ErickC 

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Posted 11 October 2017 - 12:59 PM

View PostR H Steele, on 10 October 2017 - 08:20 AM, said:

I was unduly abrupt and rude.
Handshake and apologies. Agreed?
Best Regards, Gerry

Yeah, we're cool. As to the .eng file - the entire locomotive - very much WIP - is in a thread in the modelling feedback forum (with an updated test cab I put up as a guinea pig in the 3d cab mouse control thread).

#15 User is offline   Genma Saotome 

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Posted 11 October 2017 - 01:15 PM

A question: Where does one go to find appropriate values for all that new stuff? Back in the MSTS days we could count on Bob Boudoin to come up with plausible numbers. Now everything is different and AFAIK there isn't anybody filling Bob's shoes.

#16 User is offline   ErickC 

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Posted 11 October 2017 - 02:13 PM

View PostGenma Saotome, on 11 October 2017 - 01:15 PM, said:

A question: Where does one go to find appropriate values for all that new stuff? Back in the MSTS days we could count on Bob Boudoin to come up with plausible numbers. Now everything is different and AFAIK there isn't anybody filling Bob's shoes.

I did a lot of interpolation based on data from an archived version of Al Krug's web page. Some information (capacities, temperature ranges, et c.) was gleaned from operator manuals. A lot of it is guesswork based on the sole complete HP/FF/RPM graph he had up - for the SD40-2 - and the big list of HP/FF figures he has in the big chart. I reasoned that the turbo 645 gets a pretty big boost from the turbo out of clutch range (7 and 8, I think?), and that the roots-blown 567s figures would be a tad more linear. I came up with a set of percentages of total power by RPM that seemed reasonable, based on the given per-notch fuel flow figures and the fact that the HP/gal/hour figures on the SD40-2 chart are fairly consistent outside of the "huge efficiency boost from turbo" range. I then tested it in-sim with similar sets of freight cars to the ones I had seen and recorded the real locomotive (in this case, RLCX 1703, a GP10), and made sure it more or less moved things as it should with as much power as it used in my videos.

Engine spool-up and spool-down times were empirically measured from videos George Widener sent me of himself switching in an SDM some years ago, where he ran rapidly to maximum power and then back to idle. The smoke parameters were based on videos and photographs of the smoke plume from the real RLCX 1703 that I took many years ago on a whim (the same whim which prompted me to try to photograph it from every angle to build a model). The smoke colour came from a photograph I took of a dense region of smoke generated during power-up. The opacity was then adjusted until the overall colour in the sim against the sky matched the photograph.

The reference Al got the SD40-2 specs from seems like it might be a good source for more complete information - if it has similar data for other types, that is. The OR system seems like a godsend if you've got the raw data. No more goofing off with inconsistent parameters, just plug in and go. It's a superior method, but you need the data first. I ought to just pick up a copy of that book and create a master list of OR diesel engine parameters for developers to use. I'm letting OR do all the work for all of the parameters that the manual says it will do the calculations for.

Short answer: lots of synthesis of disparate sources.

#17 User is offline   R H Steele 

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Posted 11 October 2017 - 05:22 PM

Eric thank you very much for the link to Operators Manuals and the post above.

#18 User is offline   SP 0-6-0 

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Posted 11 October 2017 - 08:07 PM

Hmm, Lots of smoke from this SD9 struggling under load. Link

It could be caused by 645 injectors in a 567 engine.

Robert

#19 User is offline   espee 

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Posted 11 October 2017 - 08:44 PM

Somebody asked for smoke :D

My favourite time for trains was SP in the 70's and 80's, so I want exhaust and lots of it!

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  • Attached Image: alcos_smokin_it_up.jpg


#20 User is offline   railguy 

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Posted 12 October 2017 - 08:54 AM

Here is some more exhaust fodder for consideration, specific mostly to US locos:

Prior to the 1990's, exhaust smoke was pretty much ignored in engine design--the emphasis was on performance, serviceability, longevity, and cost. Fuel economy was, for decades, also a secondary consideration. The Alco shown above was an example. Alcos were notorious for turbo lag and overfueling coming off of idle. They would often smoke nearly pure black until the turbo spooled up. (The slow-spooling non-trubo Alcos would do a lot of the same thing.) Before the advent of electronic fuel injection, mechanical fuel injectors were less precise and also would contribute to smoking prime movers, regardless of manufacturer.

The early electronically fuel-injected prime movers had their own teething problems. The mid-1990's electronically fuel-injected GE FDL engines could smoke pure black when coming off of idle, with the added "feature" of flaming at the stack as the turbo spooled up and the exhaust temperature increased. Here is a photo that I took in 1996 of some GE AC swing helpers throttling up off idle to couple up with the head end of their train at Minturn, Colorado. Plenty of smoke. Not shown in the photo, as the locos passed me, they also flamed about 3 feet out of the stack until the partially unburned fuel in the stack finished "cooking off." Engineers in those days remarked that throttling up a GE AC or Dash 9 under a pedestrian overpass might possibly barbecue a pedestrian. Those fuel injection systems were later modified to eliminate at least some of the problem.
http://www.elvastowe...26627_thumb.jpg

As I noted earlier, however, quite often these GE's, so dirty coming off idle, would smoke less and less as they approached fuel throttle, with throttle-up in the higher notches eliciting far less throttle-up smoke. That pretty much remained true for GE's until the "smoke-free" Tier 4 GE's appeared.

Newer locomotives have had considerable more technology applied to fuel injection, turbo, combustion, exhaust systems, and the diesel fuel itself to minimize NOx and particulate emissions. The culmination of that is the Tier 4 locomotives that, under normal conditions, should emit no visible particulates at all, under any loading conditions.

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