Exhaust Modifications for #17

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.

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

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.

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

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

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.

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?

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

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

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.

OK, it was a spelling thing, not a different term, and what was meant was through. Basically, the area of all the tube openings combined. Wall thickness is .112 (memory here) before rolling in, but that won't change the tube are beind the expanded section. Not nearly enough to bring it down to the place where 40% would rise to 80.

I have somewhere specifications for what the draft openings should be relative to tube opening area total, and the proportion to be at the burner VS in the pan. Those were based on heavy fuel oil in the standard style of construction......now if I can just find them.

Dave

Found it!! Old email from the source themselves, Monticello homework for the 401!
...To try to resolve the nozzle area/steaming issue, we're looking at opening up the air intake in the firepan.  When we designed all that, we used Ralph Johnson's figure of 30% of the open tube area for a intake air area for oil burners.  In discussing this with others, it appears we really should have been between 80 and 100% of the open tube area.  So, we've made plans to modify our existing intakes to get us to 80%, and we'll see what that does....

You better talk to them, there's know-how around!
Kind regards
Jos

In fact, I got an email today from Kent McClure there who seems very willing to share their experience with us. I don't know if he will join our group and post here,or send me some information I can pass along....whatever it is I'm very interested in finding out what worked for them and how they figured it out.

I think my information was the Ralph Johnson method, come to think of it.

Dave

To me it looks pretty clear what is happening. The firebox is full of atomized oil that is in need of oxygen. Whenever it gets an opportunity it flashes! The incomplete combustion will produce a lot of CO, carbonmonoxide. Since the combustion products are cooled while passing the tubes and mixed with exhaust steam they are below combustion temperature/flash point once outside the stack. However anyone daring to hold a pilot flame at the stack exit might see some spectacular fireworks.
I would like to suggest to ask the crews whether some of them have experienced headaches after duty on the locomotive, sure CO sign.
Kind regards
Jos

Probably.....and given the small square firebox, getting good air mixing with the atomized waste oil for complete combustion is a challenge.

Nigel has had a lot of success with his swirl inducing firepan designs used with central burners in even smaller squarer fireboxes, and we know that vaproized fuel burns more completely than atomized. His superheating rhe atmoizing steam with a lop of pipe in the firebox probably also does a lot of good - having the steam cool the oil while it blows it out is counterproductive in a vaporizing setup.

So we have the situation where the secondary draft from the door damper bleeds fuel out to combust in the cab rather than adds air to complete combustion within the firebox. I think this does argue for a better front end. What we want is air sucked in to promote combustion where it will do some good, not to let fuel and heat out where we don't want it.

So.....now I'm wondering about how far we can push the combustion efficiency of waste oil towards that of a vaporizing burner by cleaning the fuel and better firepan / burner design.

Dave

Dave- I'd think that the other advantage of superheating the burner steam is that less steam will be required to do the job, just like superheating the steam to the cylinders.  This means there's less steam used (the boiler doesn't have to produce as much) and therefore fewer pounds of steam are blown into the firebox, so the exhaust system can draw more combustion gases to boil water.

Hugh

Agreed, of course. Steam not used doesn;t need to be replaced.

I forgot about headaches. Everybody has them when I'm there, but they recover soon after I leave. I don't think there's a correlation with the combustion problem.

Dave

Dave,
Imho the present order of attack of the problems is a) proper air quantity firebox
b) vacuum to draw that quantity through the boiler c) optimisation of the locomotive effort to arrive at that vacuum.
Oil quality/burners a.s.o. should be kept in "steady state". Unless we start using the Japanese theory on approach to experimentation we better stick to changing one item at the time. If not we will never really understand what is/was happening!
Kind regards
Jos

Thank you for keeping me on the steady course, Jos - I tend to diverge in ways that aren't entirely linear. Which I'm going to do now......

First, our friends from Monticello are very willling to assist us, and will be joining us as soon as hugh can get them set up. They are now where we hope to be 5 years along the line. I also hope we can assist them as they continue to work on tweaking their performance on Southern 401.

Second, I'm starting to write a grant for the purpose of working on optimizing the combustion of cleaned waste oil in steam locomotives. It's going to be a small amount I'm requesting, just enough to cover the cost of the centrifuge, pump, filtering system, miscellaneous piping, making a few burners and some steel and firebrick to build test chambers for whatever we make to compare. I'm hoping to involve engineering students at NC State and machining and fabrication students at Wake Tech.

I look forward to the Monticello guys comments on air supply and adequate vacuum levels.

Dave

The way I've always described firing 17 to people is like this. Imagine the fire we need to run 17 as being the size of a grapefruit, and imagine the firebox as being the size of a matchbox. We're trying to put one inside of the other, that's why the fire keeps shooting out of the box.

The increased draft has helped us a lot since we put the bar on. The stack is running noticeably lighter and isn't having the trouble keeping steam like it use to. I've been able to go to the pop climbing a hill, back off on the fire and inject water to seat it, then go back to the pop while still climbing. 

I should also mention that 17 has an oil heater in the tank and we use it before runs.

Of course decreasing the orifice is a remedy for the problem. However it is a solution that carries a price tag in the locomotive effort. The solution lies in increasing the size of the air holes. If I write down in a spreadsheet my line of reasoning about the calorific value of your fuel, the amount of air it needs to burn and the amount of steam that can be produced I can calculate the pressure needed to get the air through the air valves. It is a whopping 6 inches of water, please repeat the calculation yourself as I am extremely untidy in math! Added to that the resistance of the boiler tubes of which I have no inclination to calculate giving the uncertain temperatures and the composition of the mixture in the tubes you will need a very high smokebox vacuum, imho unnecessary.
Kind regards
Jos

I also wonder if it isn't just the reduction in total opening area, but also the division of a single into a multiple nozzle with an interesting bit of turbulence and broadening of the exhaust stream included.

Robert wrote about air preheaters a while back.....maybe this would be a good time to think about those in conjunction with increasing the intake opening area. I know I don't have a clear vision of them.

Dave

It would be interesting to see what kind of combustion air pre-heaters we could come up with. Something as simple as an automobile radiator fed with exhaust steam to the inlet and a steam trap on the outlet might do the trick.

Hugh

I quite agree with more sophistication, but please one item a the time! #17 should be made a good to perfect steamer in its present state.  Then and only then the next steps with equipment that isn't there right now.
kind regards
Jos