Exhaust Modifications for #17

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Exhaust Modifications for #17

Post by Low_Water_Odom on Wed Jun 19, 2013 9:04 am

Let's start with a drawing of #17's as-built exhaust arrangement (all dimensions are in inches):


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17 other interesting specs.

Post by DaveLathrop57 on Wed Jun 19, 2013 10:13 am

OK, I'm looking at the Form 4 among other things.....

basics: 14X22, 37" drivers, 195 PSI - we run about 190.

16.3 square feet grate area. 60 firebox. 19.3 flue sheets. 656.4 tubes. total 735.7.

Estimated steam generating capacity 10, 299 Lbs/hr.

15 MPH track speed on the railroad. I'd use 12 as a general average for free running between restricted sections at either end.

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Re: Exhaust Modifications for #17

Post by Michael Guy on Wed Jun 19, 2013 1:09 pm

Using that 10,300 mass flow I get a 12 inch mixing chamber and four nozzles at 1.9" diameter. Predicted vacuum is 12 inches of water. This assumes a diffuser of Cp .65 and in/out ratio of 1:2.5. Nothing cast in stone about this, just a first look.

Michael.

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Re: Exhaust Modifications for #17

Post by DaveLathrop57 on Wed Jun 19, 2013 1:24 pm

Thanks Michael. Now if we can just move all the 17 posts and divert the replies from the other thread to this one......It's going to get confusing otherwise.

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Re: Exhaust Modifications for #17

Post by JJG Koopmans on Wed Jun 19, 2013 7:33 pm

Michael,
The numbers should be slightly different. The steam for the oil burner cannot be used as exhaust steam and is part of the products to be expelled.
Kind regards
Jos

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Re: Exhaust Modifications for #17

Post by Michael Guy on Wed Jun 19, 2013 8:05 pm

This is true. Good point.

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Re: Exhaust Modifications for #17

Post by DaveLathrop57 on Wed Jun 19, 2013 8:32 pm

And, we run a dynamo and an air compressor......and we don't run wide open with 100% cutoff.

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Re: Exhaust Modifications for #17

Post by Michael Guy on Wed Jun 19, 2013 8:44 pm

Actually I used 85% bp and 60% cut off on that one. Just didn't mention it. Smile

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Re: Exhaust Modifications for #17

Post by Michael Guy on Wed Jun 19, 2013 8:54 pm

Ignore that last post it isn't true. Still at work trying to do too many things at once.

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Re: Exhaust Modifications for #17

Post by DaveLathrop57 on Wed Jun 19, 2013 11:29 pm

Let this ride......plenty of time to give it some uninterrupted thought later on.

If this works out well, it would be very useful to do electronic digital versions of indicator cards so we can really see what's going on.

Dave

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Re: Exhaust Modifications for #17

Post by Michael Guy on Wed Jun 19, 2013 11:42 pm

The potential for some real testing and proper data logging is really interesting. I attempted a series of nozzle tests last year with a steam tractor but the results were inconclusive. The thing was perfectly happy with little or no forced draft at all.

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Re: Exhaust Modifications for #17

Post by Michael Guy on Thu Jun 20, 2013 12:49 am

I just noticed that #17 seems very similar to Flagg Coal #75. The builders cards are almost identical. Do you guys know what the front end looks like on the 75?

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Re: Exhaust Modifications for #17

Post by JJG Koopmans on Thu Jun 20, 2013 9:00 am

What is the dimension of the orifice of #17. The 3 1/4 in. from the drawing gives weird results in my spreadsheet.
Kind regards
Jos

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Re: Exhaust Modifications for #17

Post by DaveLathrop57 on Thu Jun 20, 2013 10:02 am

It has been opened up to somewhere in the 4" range....or a bit larger. I can't exactly recall off the top of my head. I had it when I worked out the Lima style arrangement for it, will see if I can track down the notes.

Dave

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Re: Exhaust Modifications for #17

Post by JJG Koopmans on Thu Jun 20, 2013 10:20 am

Dave, thanks!
A 4 in. orifice is far more likely!
Kind regards
Jos

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Re: Exhaust Modifications for #17

Post by DaveLathrop57 on Thu Jun 20, 2013 10:43 am

Looking back, I'm thinking it is now 4.25 - 4.5. There have ben some experiments with a bridge across it, etc which didn't result in much change in performance. I think 4 was the design spec for oil conversion by Vulcan.

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Re: Exhaust Modifications for #17

Post by DaveLathrop57 on Thu Jun 20, 2013 1:36 pm

Best I can determine after sorting through my piles of scraps of paper....a handwritten notation on the drawing that a 4" nozzle was to be supplied, and the likelihood that the subsequent enlargement was to 4.25 since 4.5 is the diameter of the hole in the stand into which it fits.

Dave

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Re: Exhaust Modifications for #17

Post by rconner on Mon Jun 24, 2013 12:13 pm

There is a notation on the front end drawings of 17 showing a change from the 3.25" nozzle opening to 4.00". There is a further noting that it was done after the initial trials at NY Shipbuilding. We believe this was done to help drafting at slow speeds like what would be experienced in the ship yard, and the fact that it was a one man operation. 

Over the winter we took another look at the front end arrangement to see if we can stop blow back into the cab on hard pulls. A new petticoat was built according to the prints the winter before last so we focused on the nozzle this year. At the first of the season I mounted a .50" piece of square tube over the center of the pipe to reduce the opening down to 3.25" per the prints.

Its been hard to make a conclusion on the adjustment, we've had bad runs since it was added, but most of the problem has been attributed to either bad oil or other problems that have cropped up. The good runs we did have, showed quite a bit of improvement. Aside from drafting better and running hotter, the engine is more responsive to the johnson bar. Up until this point, when coming up long grades we've only been able to run in the corner or one notch up, we weren't able to notch up for any length of time. One thing we've noticed on the last set of runs is we were able to nearly center the bar without killing the boiler and reduced the amount of blow back out of the box.

As of now it looks like we're heading in the right direction, just need to make a few more runs to make sure.

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Re: Exhaust Modifications for #17

Post by JJG Koopmans on Mon Jun 24, 2013 12:46 pm

Hi,
Do you know the free area of the air valves compared to that of the trough area of the fire tubes? Is the smokebox airtight?
I am really amazed by the 3.5 in orifice, since the more or less standard momentum calculation with that value goes haywire!
Kind regards
Jos

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Re: Exhaust Modifications for #17

Post by DaveLathrop57 on Mon Jun 24, 2013 1:13 pm

I expect the young man that has been working on the front end will share his experiences on this forum shortly - at least he indicated he would - so we'll have a better idea what was tried and how it worked out.

I don't have the damper sizes available right now - it drafts through the firepan and at the door, with a small margin surrounding the burner entrance. Trough area is a term I'm not familiar with, but the length and number of the 2' tubes are 134.24" and there are 112 of them. once I get the damper sizes, we can compare.

Nobody has to my knowledge  indicated any difficulty with keeping the smokebox door tight.

Dave

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Re: Exhaust Modifications for #17

Post by rconner on Mon Jun 24, 2013 1:34 pm

I was the one that did the front end work this spring, the status is posted above. The smokebox is airtight.

I don't know the approximate size of the dampers off hand, but I have a good idea. There are two dampers, the primary at the ash pan and the secondary on the door. The opening at the ash pan is approx 14x8 at the door. The actual opening in the bottom of the firebox is around 14x5. The length of the trough running under the box is around 2.5 ft long. The firebox door is hood shaped with a rectangular damper at the bottom, the damper is around 14x5.

I don't know the dimensions of the box, the grate area is correct, but the height is different from the prints because of the ashpan which I think is around 2 feet below the mud ring.

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Re: Exhaust Modifications for #17

Post by Low_Water_Odom on Mon Jun 24, 2013 1:47 pm

I rode the cab of #17 earlier this spring, I believe shortly after the exhaust modifications. On the ride out from Bonsal, the locomotive steamed well but the pressure dropped significantly on the grade near the turnaround point.  At the turnaround point, they found that the damper had been left shut so that most air was coming in through the firedoor.  For the return run, they opened the primary damper, but it honestly didn't seem to make a measurable difference in the locomotive's steaming ability, and the boiler pressure again fell when climbing the grade approaching Bonsal.  The blowback seemed to be a little worse to me after the damper was opened.

Now, this was my first and only ride so far in #17, and actually my first ride in an oil-fired locomotive, so my observations may not be typical at all.

Rconner- can you post a drawing or photo of exactly what was added to the nozzle to reduce the area?

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Re: Exhaust Modifications for #17

Post by DaveLathrop57 on Mon Jun 24, 2013 2:03 pm

I think the difficulties with the variable quality of the oil need to be addressed by a cleaning program - whether it be settling, filtration, cehtrifuging or probably all 3 and some that we haven't discussed yet. What I'd like to further explore is just how much more we can push complete and efficient combustion with cleaned oil rather than whatever shows up. Given the geometry of 17's firebox, I'm thinking right now about a central burner and a swirl-imparting firepan and a superheating loop in the firebox for atomizer steam.

I know we can come up with a better front end design also. The manometer and back pressure gages should be installed for the August operating day if not for July. I think we will gain a lot of useful data.

Dave

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Re: Exhaust Modifications for #17

Post by JJG Koopmans on Mon Jun 24, 2013 2:53 pm

Correct me if I am wrong, total area through the tubes is 112*pi()/4*2squared or 352 sq.in.  and it appears that the valve area is 5*14 or 70 below and the same at the firedoor, total 140.  I have read recently, and I do not know where anymore alas, that the air area should be 80 to 100% of the tube area in an oil fired locomotive.
It appears here to be around 40% or so, (the tube dimension is probably the outside diameter). This % might also be the cause of the orifice diameter reduction.
Kind regards
Jos

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Re: Exhaust Modifications for #17

Post by rconner on Mon Jun 24, 2013 2:56 pm

Water logged oil has been the biggest problem over the past few runs. We've got it pretty well under control now, but we're talking about a different way to separate the water out.

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Re: Exhaust Modifications for #17

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