Combuistion and fuel starting point.

110 burned coal originally, then was converted to oil. NHVRR now burns recycled waste lubricating oil from diesel powered backup generators in engine 17. This fuel is free for the fetching....so far. It's of highly variable quality, and we're using a standard Van Boden style burner which can deal with dirt and variability. It seems a similar burner was mounted under the throat of the firebox on 110, aimed back towards the firebrick lining under the door. No measurements yet of the firepan and draft openings.

So, we want to consider whether to keep using this fuel; what other fuels might be as economical; whether finding a way to clean and alter the fuel might allow for a more efficient burner; what a new burner for whatever fuel might be, where it is installed, and how it is drafted; any other firebox or firepan alterations to make for a cleaner and more efficient and complete combustion.

I wrote a fairly long post on this which seems to have disappeared.

About the only reason to use a solid fuel is if there is grant money to test something renewable -- for example, if the 3463 effort actually gets the locomotive-specific torrefied fuel program up to the point that fuel combinations are being tested.

My chief concern with waste oil is whether EPA cert will become necessary.

The general burner design ought to be OK -- it is certainly not one of the parts of the locomotive needing the most attention! I would prefer to use something more like a Racer or Pritchard burner. Thermal barrier coatings for potential impingement zones; ceramic or refractory material all over the place. Snyder-style preheaters for both primary and secondary air where possible.

I'd at least look into using a Nigel Day-style swirl firepan. Is he participating in this project?

A fundamental principle is long flame path where you can get it. The characteristics of the waste oil fuel make burner location at the throat practical. The travel needs to be enough to get the fuel injected, then carbureted, then combusted completely before any products of combustion impinge on surfaces below transition temperature. I wonder whether finer control over the jets in the burner would allow better response to 'transient variations in fuel quality' (e.g. slugs of antifreeze or water).

What is consensus on reignition system? We don't want furnace explosions or puffs, and explosion doors don't really work well even if we had room for them.

Progress Energy was just bought out by Duke Power and they have a nuclear plant that is a neighbor. IF Duke would donate an annual carload of coal....that might be a reason. Otherwise, sticking with what we already have and know seems logical. No reason not to start with a broader perspective, however. Our State Government has been less friendly to alternative energy (apart from fracking) since the last election cycle, so other solid fuel production programs may be unlikely that could be game changers. Pellets made of agricultural waste? Dunno.........

I respectfully disagree about not looking at burners as an integral part of the system - achieving a better atomization and more complete combustion might require a different design.......and Nigel, BTW, is available to help us with specific inquiries but doesn't want to be a full participant. I think his aimed airflow firepan idea is of great merit, as is his superheater of atomizing steam loop in the firebox idea. I'm not sure how he's applied the firepan thing to longer fireboxes.......but I know it could be beneficial to 17 having an almost square box. I've been tinkering on paper with centrally located burners for waste oil also. I'll post a couple sketches.

Dave

Did I actually say not to do burners as part of the system? yikes, I'm either slipping or senile before my time.

I do not like centrally located burners. They are the wrong answer to a question nobody asked. Oil does not burn like coal, and imitating a coal fire is not more than a kludge along the way to better combustion... ALTHOUGH the idea of the lava-rock grill on a grander scale proves very effective at solving one issue with liquid firing: how you avoid puffs or detonations with intermittent fuel-flow or atomization integrity.

Swirl needs to be relative to the plane of the nozzle, which (as in von Boden-Ingles) points in the direction of proper "laminar' flow to give the longest flamepath INSIDE the box without impinging on the walls. Logically this would be just as proposed, at the throat of the firebox, with the draft expanding as modified divergent nozzle outward from the nozzle, flowing back over the arch to give long combustion path. Too much swirl, or the wrong components od vertical swirl, just promote impingement.

Note that the angled tubes in the firepan need to reflect axial swirl pickup, not vertical radial.

Vertical firing is fine for little square boxes; better still in modified LaMont coils. Not for an engine like 110.

Effective air preheat, on the other hand, is a top priority for this application, as it is for coal or most other solid fuels.

Agreed, I was thinking of a central burner and swirl firepan for 17. Sulzer has made a success of cluster burners on their rack locomotives, though......

I woinder if there's any practical means of removing the impedimants to vaporizing burners from waste oil before it even goes into the fuel bunker?

Dave

The problem with waste oil is that it's randomly contaminated with other oils and fluids. IIRC transmission and brake fluids are somewhat hygroscopic, and if there is antifreeze it will selectively 'dissolve' it in solution, but sti suspended in a greater volume of more typical 'oil'.

I don't know of a good, cost-effective way to take this stuff out. Of course there are the 'refining' processes used to make that 'second-chance' recycled oil you can buy cheap at Wal-Mart or the auto stores, but much of the price advantage over #2 diesel goes away when you do. It is possible that there's a water-based 'wash' that would selectively remove the less combustible stuff, but the economics of that process won't favor an organization that does not have its own fairly-large storage facilities to 'stage' the waste oil before using it...

My own prejudice is to design the fuel system so that, to the greatest extent possible, it would run either on waste oil or 'gasoil' diesel, without needing to change much more than the orifices and heater settings.

I put some notes on firing in the boiler section by mistake; I will not repeat them here unless requested.

Dave is considering a triple-pass system: rear-mounted burner aimed at throat, reverse pass under a refractory arch and reverse at upper backhead/crown, then forward under the crown to the tube sheet. I had a bunch of detail comments about the best burner, primary air, and secondary air requirements to make that work. I just added some comments in a post on steam_tech and repeat the relevant ones here:

"I'm also thinking you will need an extended shelf from the backhead to maintain the flow correctly and form the "z". I have no experience with how that shelf should be dimensioned, or of what material it would be made, but I would be highly pleased if some directed flow of heated secondary air could be introduced through it. You will almost certainly need secondary air to the plume during its travel up to the backhead reversal…

I see the gas path as horizontally laminar, 'just filling the box', and the passes up through the Z expanding as a divergent nozzle or folded horn. I would suspect a considerable amount of empirical tweaking will be needed to determine actual flow and combustion patterns in a box this size."

And I replied there.....pretty much that it's an option that is easy to learn more about and with decades of exprience we can find out what the problems are in its use. It might not be what we want....but until we know that, let's not throw it away. Nobody seems to be offering many alternatives here so far.....please do.

Dave

As the admittedly non-engineering type here, I guess it falls to me to ask this question. Why are we so set on keeping No. 110 an oil burner? Is it because the NHV folks are experienced with oil firing and have a source of waste oil? I keep thinking about problems with oil firing -- contaminants, spills, explosions, leaks, etc. Is converting the engine back to coal firing off the table? If so, why?

Nothing is off the table at this point in the process. If I knew of a way to build a kudzu burner I would, that stuff grows so rapidly in the Carolinas it would be an endless source of fuel........

What we lack is a source of coal at the minimal acquisition cost of the waste oil we get for picking it up. So, we're very able to deal with oil in terms of storage and use. Let's also not forget that coal ash, cinders and other byproducts require disposal and coal is physically more difficult to handle without incesting in a loader and ramp or other rigging capability.

That isn't to say that those difficulties couldn't be overcome but there's no plan to overcome them to try. Do you want to start a thread about it?

Dave

At this point, it makes some sense to consider the firebox as just what it is: a bounding volume with no pieces inside. We can fit one of the oil-burning systems in that space, or a coal-burning system, or a pelletized-wood system. To an extent, we could even make the installations modular so that firing could be switched.

In my opinion, the troubles involved with a coal-burning system, even if the fuel were free, outweigh any gain over a waste-oil setup, even with the problems of firing with that 'fuel'. That does not mean that coal firing options can't be considered, or even designed for.

Another thought I had on fuel- the CSR 130 guys (http://www.csrail.org/) are planning on burning "torrefied biomass" (basically synthetic coal made from wood chips) supplied by the University of Minnesota. I wonder if there's any chance the University of Minnesota would be willing to supply fuel to us so 110 could serve as a pilot project for burning the stuff in a locomotive?

Here's their page on the fuel: http://www.csrail.org/index.php/research-areas/solid-biofuels

As much logging industry as there is in NC, there seems like there might be some interest in producing this fuel there for that matter.

John Rhodes (known to some of you) is associated with the project and he indicated he might participate in this forum.

Hugh

I mentioned this already (back at the beginning of this topic)

You would not necessarily need the U of Minn to make this fuel; there are a number of torrefication operations operating today (the usual use for the product being co-firing with coal for emissions reduction). I believe the point of the University research is to find a better process for using some of the distillate hydrocarbons to make the torrefaction self-sustaining while preserving the more 'valuable' components of the destructive distillation, and modulating the process in ways that optimize the yield of salable material. As I noted on steam_tech, the form factor used in straight torrefied-fuel firing is likely to be very different from what would be commercially produced in quantity (and this applies to most of the fuel fabrication, including the early prep before torrefaction)

When 3463 gets to the point where its fuel system is being detail-designed, then there will likely be a fuel-production tie-in. I thoroughly agree that some early experimentation on small scale would be beneficial in designing that larger system -- but I am not sure (unless grants for the work were funded) that redesigning 110 to make the required controlled tests is the best idea.

I look forward to John's contributions.

I'd welcome a proposal from the CSR 130 team to partner with us as a smaller scale test bed for development of torrefied fuel providing they coud fund it with grants, not guaranteeing it would be favorably received by the NHVRR BOD of course but I'd be happy to present it. Also the 5 year plan might be too slow for their purposes. If we don;t try we'll never get anywhere interesting.

Dave

An interesting commentary on early oil firing is provided here:

http://books.google.com/books?id=rnwtAQAAMAAJ&pg=PA212&lpg=PA212&dq=oil+firing+front+end&source=bl&ots=unP0X4fVRm&sig=Y31_NEHQbeAI_mmAMow7IvOC-Rw&hl=en&sa=X&ei=oA6iUbjwGI_U8wSj34DABg&ved=0CEsQ6AEwBw#v=onepage&q=oil%20firing%20front%20end&f=false

(This is downloadable as a .pdf file -- click the red 'Get e-book' link and then select the small 'download PDF' link at the bottom of the box that opens.)

I found the language to be a refreshing look into how railroaders expressed themselves in 1907...

As a resource: see this link on burner tech, provided by Tom Kimmel:

http://www.scribd.com/doc/59931778/Burners

Having read through the Porta paper I'm starting to rethink some preconceptions I had about the 110........in particular the idea that the firebox geometry forces the choice of a horizontal single burner. Porta determined that the use of 4 burners essentially created 4 seperate little fireboxes inside one in the SLM conversion (althought he had real problems with theit SONVACO burners) each of which could work with increased turbulence and torroidal drafting for more complete air/fuel mixing and combustion.......

So I think we can open that idea for exploration. Our choices now seem to be a throat end positioned horizontal burner in usual practice, a door end positioned horizontal burner and brick arch in the Canadian practice, or an assembly of vertical burners over a firepan drafted with aimed tubes.

Leaving the exact burner design out of it for now, how can we compare these options from a combustion and efficiency perspective?

Dave

Dave,
From hearsay of the directly involved: a)the Lempor of the rack locomotives of SLM was too powerful and converted back to single orifice, heard in 2003 in the Brienz symposium. b) SLM supplied a DB 23 tanklocomotive to the Netherlands last year which had to have diesel oil as fuel as directed by the local government. Its consumption was horrendous.
Kind regards
Jos

Part of the thing involves fired fuel mass vs. 'carburetion' efficiency outward from the burner vs. full reaction time for the combustion. If very fine atomization and air preheat are available, a shorter and probably more stable flame path will result, and this might facilitate a 'four-corners' system (although I suspect the actual flow patterns will not be neatly from four corners!) I also suspect that toroidal burning is not actually what would be seen in a firebox the size of 110's ... but would be delighted to see that it is.

We need to keep the entire length of the reaction plume separate from the firebox surfaces -- this includes the length of the luminous plume, as any quench here would produce sooting. That was one of the presumptive reasons for the double-folded path from the rear-mounted burner.

Part of the traditional fun with pumped burners is that the rate of feed needs to be regulated by the draft, if forced draft is not provided (as it is with most home oil burners and steam cars) If we are going to forced draft, some sealing of the firebox volume will be needed (or we will have to bone up on our Stepin Fetchit routines!)

The flip side of this is whether to use mechanical atomization (cf. Ted Pritchard) which would require a reliable source of high-speed rotation (almost certainly electrical, not steam turbine) and also good high-pressure pumping at volume (screens, fuel conditioning, gear pump?) (probably also electric, for reasons at the other end of the spectrum). I love these things... but steam purists won't. I suspect you will also hear the noise they make. Those Golden Rock locomotives are examples of what you can 'get' with that general approach...

4 corners or two in a line down the center?

I'm thinking (danger) about a firepan with tubes above a firepan with dampers such that the draft can be regulated to all openings simultaneously......if there's room for such under the mud ring. If so, we can easily install preheating coils at the dampers.

Nigel's firepans with aimed tubes impart a swirl.....not sure how to create a torroidal turbulence, so perhaps swirl is what we can do.

I'll see about posting a few more things of interest early next week.

Dave

Two in line down the center would be pointless; one good one in the center would do better, I think. I am still wondering if, for waste oil, the old standby of linear burner, with brick arch for long plume AND some broken refractory for 'flameholding' in the pan, beats a vertical center gyro-burner.

The point of the four corners is that the spray can be directed conically out toward the opposite corner of the box, for the longest plume travel, and swirled if necessary, without impingement. You could also pulse-fire those burners in pairs or rotation for effective turndown, something that ain't gonna work right with a von Boden-Ingles or single pressure burner...

Not a 'firepan with dampers', a windbox. Cellular if necessary (this being better suited to GPCS than liquid firing, but what the hey...) The cells all have throttling dampers and are adjusted to suit the secondary air characteristics; I presume primary air would be drawn from this box via a duct for whatever architecture of burner we wind up using. Nigel's slanted tubes are the ports into the firepan area from the windbox...

Preheaters 'upstream' of the windbox, both Snyder tube bundles and something in a duct under the boiler; FGR from the smokebox if we want.

The thing about all these cyclonic-firebox things is how you are supposed to do flow straightening to get the gas into the tubes. The tacit assumption appears to be that you have some form of positive pressure in the firebox, and this transitions to smooth draft flow (and induced momentum transfer) ... somewhere between the, ah, toroidal flow and the rear tubeplate, with induced draft strongly in evidence by that point ...

I do have solutions for this (the vertical four-coil LaMont requires one, for example) BUT fitting a solution in 110's firebox would be ... interesting. Probably better to arrange two turbulent plumes (one per side of the box) that 'whirl' to a parallel front inside exit toward the center of the tubeplate...

I have gotten a return email from Nigel, who tells me his firepans don;t impart swirl, as swirl would cause irregular hot gas flow and as the air the tubes provide enter the combustion area, it stops being diirected and instead flows where the draft takes it.

So, I'm interested in the 4 corners idea......developing it to the point that we know how practical it could be and to the point that we can meaningfully compare it to single burner horizontal setups.

Dave

First question to consider: do we use steam, or brake air, or an external compressor of some kind, to run the corner burners? My understanding is that if we are to get good enough atomization, we will need some combination of primary blast and rotation, which then brings up the method used to rotate the atomization elements in all four locations,

Part of this discussion involves starting the locomotive from cold. To me it's fairly obvious that providing a small IC-engined compressor with pressure tank, on a transport cart, is the best method for lightoff and steam raising (and it has sooooooo many other uses around a shop site!) It's also fairly clear that air motors may be the most practical way to rotate the atomizers, although we then have to consider the deleterious effects of using the (cold) exhaust as either primary or secondary air anywhere in the system.

The alternative would be to run electric (which is likely to be quieter in operation if the right kind of air compressor is used), which would involve ... well, a version of the HEP generator that the 3463 people were saying was the primary point of the Project 130 effort. It could be argued that having a comparatively lavish amount of "head-end-available" power would be an advantage on an excursion consist; it certainly simplifies 'foreign' lightoff if the only thing you need to carry is the equivalent of a long extension cord...

I just wouldn't bother with combination steam/air devices for the burners. Those would work for the overfire-air jets, or primary forced-draft creation under the firepan or wherever, but not for stable operation of rotary burners, on the scale required. In my opinion.

Now, one of the control modalities needing research with this system is the ability to do considerable effective turndown without compromising flameholding: as with gas burners, we can pulse each unit to lower power sequentially, with at least one running at full authority at any given time. This involves more complexity in the drive system and fuel valves -- but not all that much, and probably using OTS components for most of the pieces and controls. This becomes a time-domain modulation, in a pinch via two bang-bang speeds, without ever having to take any one burner completely down or into an unstable-combustion region. It also guards against an unstart or massive failure of any one burner, for example if it gets a slug of water. Recovery does not involve 'puffs' or the need for delay before relighting (as differential contraction rises expectantly, and looks on and smiles...)

I suspect the burner design would involve some form of commercial ring tile flameholder, and you would want thermal barrier coatings, possibly graded, applied to the box corner walls behind potential impingement or higher-irradiation zones.

Before we work out specific burners, maybe we need to work out the overall geometry of such a system within the firebox to see if it in fact is suitable? Anyhow, we have some tested and documented steam atomized burners from such firms as Laidlaw Drew to begin with for the basis of a rough look. I'll post some Laidlaw Drew documentation in the enxt couple days if all goes well.

Sulzer used a small pilot burner in the center to light up the other 4, and to hold a spotfire. Seemed to work for them although their burners weren't too successful, and needed very clean light oil.

Robert, would you sketch out the basic idea based on maybe a 30 degree spreading burner in each corner? I'm also unclear on the wind box....sounds like seperate compartments with each controllable with seperate dampers?

Dave

Remember that this is supposed to be a waste oil, not light oil, burner. Many aspects of the design will be different.

Pilot in the middle is better suited to a four-burner system arranged in the center, aimed outward and perhaps with 'gyroscopic' rotation of the heads. That would also facilitate steam blast up the center, if that were desirable. Perhaps multiple nozzles on the heads, to give better 'filling' of the available combustion volume, with adequate swirl to give long enough flame travel and enough dwell time to get the luminous flame going. The next issue to decide is whether, at given transition temperature and combustion time, etc., there will be full combustion of all the little carbon particles (that will otherwise quench or plate out as soot) by the time they reach the tubeplate and practical combustion ceases.

One of my basic design principles, rightly or wrongly, is that the fuel plume should be kept off 'cold' heat-transfer surfaces (which in a waterleg firebox is just about any of the metal in the box), and that any areas where there is impingement should be given an appropriate coating to keep their surface temperature above transition to preclude quench. I like the four-corners approach, in principle, because the plumes have a potentially very long free length (they are located low in the bottom corners of the box, perhaps 'biased' so that the two at one end deliver more fuel mass than others; configuration would differ in the presence of an arch or other brick structure to lengthen the plume and preheat it).

Spray angle and dispersion, and the specific shape of the ceramic nozzle, are such as to keep the evolving combustion plume slightly away from the walls, but fully carbureted with preheated air so the carbon will react more quickly and fully. 30 degrees would then typify the solid angle, but the jet need not be fully conical. A reason to extend luminous flame is that it provides more usable transition energy that will couple via radiation; transparent combustion gas (or to a different extent, soot) are radiating differently. In the case of gas, the emitted radiation is sharply peaked, and the absorbance of the heat-transfer surfaces may not take best advantage of what's left of radiant transfer; a point of the Besler tube is that the central passive re-radiator takes the excitation of gas peaks and converts it to near-blackbody spectrum -- and the emitted re-radiation is precisely normal to the inside tube wall. (They also enhance convection and disruption of blanketing at the wall by keeping the gas turbulent in the annular space).

I posted the original (1935) reference I had on the windbox development, so it is somewhere on steam_tech but I no longer have the original cites. You are correct in that you have individual cells -- in the original, these fed air to that portion of a grate that lay above them, and by a combination of damper and nozzle control you can provide selective levels of forced draft each box and thence to 'just the zones that need them'. It's also a logical place to implement air preheat and perhaps FGR. In this particular case, the windboxes would be oriented (1) to provide appropriate secondary-air support for the combustion plumes, and (2) provide heated air at pressure to ensure full combustion in the box and, if there is one, chamber. I think this would imply something like a duct at the circumference of the firepan, perhaps interrupted, and some smaller ducting inside if higher airflow were required.