Stanley and White Burner Howl

Rolly, thats a good setup that you have there. I wonder if they drilled the Stanley plates at a lower drill speed back then and that would account for the number of breakages that they had. That or their drilling a rough casting. . . did they smooth off the grate face before drilling like you do? Did your Cobalt bits break or just get dull?

One trick with small bits is to break or cut off the bit to only about 1/4" to 3/8" fluted length and then redress the bit. Then chuck it up close enough so that it just goes through the metal that you are drilling. That will make the bit much more stiff and able to take the force or the drill press without bending too much.

Peter, so would the V sloted plates have more slot surface area then the flat plates? Seems like it should, maybe more fire for a given surface area. Gang cutters are a good thing, makes for a lot less time spent on the machine. I wonder if one could find reciporcating blades narrow enough for the slots, gang them together and if long enough do the whole burner width at once. . . maybe too much stress on the blades though.

Your flow experiments will be one huge leap forward for the vaporizing burner designs/designers!

Caleb Ramsby

Caleb
The bits brake, get dull, I’ve ground some short and made a D bit to get through some hard places on cast iron grates. I cast all mine in ductile now.
I’m sure a lot; most of them were drilled at very low speeds. Stuart Herman uses a ganged head on his Bridgeport See photo. He does a lot of burners both drilled and slotted.
Four or five members of SACA-NE have built burners. Another photo of a White done by hand SACA-NE. And my arbor for my universal mill with some 0.0250 slitting saws.

Rolly

Hi Caleb,

A ridged burner grate can be cut to give more slot opening area for a given grate diameter, than a flat slotted grate. That may be one of the things which the Stanley brothers had in mind. Years ago I thought that the effective slot area would only be equal to the horizontal length of the slot. Recently I realized that the effective slot length is measured on both sides, up to the peak, along the angled surface of the "ridge" (on bottom of grate). Fuel/air mix can enter the slots not only from below, but from the sides, flowing horizontally, parallel to the ridge. Interestingly, the "outlet area" of the slots is larger than the "inlet area", due to the thickness of the grate.

Same principle as pleated air and oil filter elements; more opening area in a given volume.

Cool slotting and drilling pictures, Rolly! My guess is that the gang slotter with .025 blades is for the pilot light?

Peter

This would be much the same reason SES used the conical shaped flame holder, to maximize the surface area. Biggest problem I ran into with a cone is that the flame intensity drops off right out near the end. If they'd ridged to get the same area, I'm sure that wouldn't be an issue.

Ken

Hi Ken,

Interesting idea -- a high-output once-through or recirculating boiler, with evap tubes right down in the "valleys" of a pleated flameholder... with proper fuel/air mix pressure upstream, the flameholder could fire sideways like the SES, or any direction desired...

Peter

A quotation from the "Questions Answered" column of "Railway and Locomotive Engineering" September 1908 page 394:

"What causes the drumming sound sometimes heard in oil burning engines which are not steaming well, other than the use of too much or too little atomizer?

The drumming of oil burning locomotives is caused by faulty construction of brick work in the firebox, careless handling of the oil valve by the fireman when the engine is working slowly or too great a volume of air passing through the dampers."

Oil burning locomotives used steam atomizing burners and heavy fuel oil, not bunsen type mixing tubes and fire grates as in steam cars. None the less, this issue has been with us for a long time.

If I interpret the remarks (and indeed if they apply to Stanley burners) the culprits seem to be poor acoustic damping of the firebox, improper mixture and excessive air velocity.

Kerry

Hi Peter,

The nice thing about using SES type tech is that I know from experience you can buy stainless steel perforated sheet in appropriate hole diameters and spacing; and the stainless holds up decently under heat. The cone they used had the advantage of sheer simplicity, but to me the burner ended up wasting a small bit of volume and kind of forced winding frustrum-conico tubes. As you say, pleating would work well. Other, more elaborate means, would be to do some metal spinning to make circular ridges or turn a die and stamp it out.

Ken

Hi Ken,

Or, how about spiral ridges, and a pancake coil to fit down in 'em? Mind-boggling array of possibilities for really pushing the envelope.

What alloys is that perf sheet available in? So far, the best I've found is 302/304. Beats mild steel, but... 309 perf sheet would be "da bomb" for this...

Current hypothesis [needs testing, as always] is that steel angle-iron (black iron, no galvo) with ITC coating on the fire side should give decent results. The ITC bounces back about 98% of IR radiation into the fire & evap tubes, while the fuel/air mix keeps the grate cool to avoid warping, cracks, and backfire on shutdown. Better than Stanley's bare gray iron surfaces facing the fire [great emissivity!] at least. ITC is widely used in kilns, forges, and furnaces, allowing use of fire-exposed carbon steel parts, with lower cost & easier fabrication than hi-temp alloys.

Old iron-grate Stanley burners often run for decades without major grate maintenance. So an ITC-coated steel grate might be gilding the lily by automotive standards. Well, it's a fun/hobby project at this point, so going over the top here and there is OK.

I've been brainstorming the slot/holes flow test rig; now looking crazy simple; close to build; when I get some data from that I will know more. While I'm at it, I can also do flow tests for thin perf sheet with various hole sizes, to make the data a bit more widely useful. I recently looked into those materials myself...

What thickness and hole size/density perforated sheet did you use in your famous "driveway-buster" burner? Did you measure pressure behind the flameholder?

With digital cameras, wider bandwidths, etc, online photo documentation seems to be "the thing". I have missed out on documenting various interesting test rigs which I have built for design purposes. Need to change my approach here, get with the times, take/post more digital pix. It ain't the 1990s anymore, let alone the 1920s... Your "driveway buster" burner would be really interesting to see in jpeg etc, if it is still around... or your next-gen burner...?

Peter

What's funny about the driveway buster was that I was using a stamped perforated aluminum sheet for the flameholder! As long as I kept enough flow going to it, evaporation of the fuel kept the flameholder reasonably cool and the heat didn't seem to affect it. Use too high a turndown ratio until you get a backflash and it was only a couple seconds until the center of the burner turned into molten droplets...and we're talking about this happening at high turndown.

I have a number of old flameholders at home, I'll check them out tonight. As I recall, the most agressive burners seemed to be using .060 holes. You'd probably NEVER get that kind of intensity out of a vaporizing burner as I was using a 3 stage centrifugal blower and while it wasn't a massive powerhouse, it's hard for me to imagine a vaporizer running the same pressure as a multistage unit. Using larger holes ran OK, but the flames weren't stiff like the smaller holes and the turndown ratio wasn't much. Smaller holes gave more turndown, but just couldn't get the same peak capacity. I came to the conclusion that to get really large turndowns you really need to have a 2 or 3 element burner, and proably different size elements. For low power only the smallest element would have air flow, for more power the next would also open up and so on. You could still turn each one up or down to give infinitely variable control.

Backflash was an issue because once the flame propagated through the holder, you couldn't get it back short of killing the fuel delivery and then restarting once the flame was out. I'd think some kind of photocell on the back side of the flameholder much like you see in gas clothes dryers wouldn't be the worst idea in the world. Heck, appliance stores undoubtedly sell them cheap and with a cutoff solenoid is probably not bad insurance. This is all most likely an issue if messing around with extreme turndowns, which I was. On relection, I wonder what the pressure would be if the burner were lit or unlit. When lit there will be rapid thermal expansion of the gasses and associated acceleration away from the flameholder, wonder if this has a secondary ejector action to draw the fuel/air mixture through?

I never measured the pressure behind the flameholder, I sort of wish I had but I knocked the whole rig together in short order and really didn't have the time to even find a gage locally.

I'll have to see what I have lying around and take a few photos, can see about posting those.

I do wonder how well a simple electroplate on the face of a flameholder would work. Some materials like nickle or chrome (maybe both for nichrome?) may be a lot better than plain steel; you'd need an electroplater that does industrial plating (like for injection dies) rather than ones that make stuff shiny for hotrods. I've seen the difference in results when you put stuff to the test.

On the topic of burner noise, I usually got a fairly good roar, but when you figure I was running something like 6 gph through a burner about 4 inches across, that might not be considered unreasonable. Using a few different hole sizes, spacing, and an infinite range of firing rates obtained by the electric blower....I never got any kind of howl...so I'm guessing that just has to be a function of the jet and mixing tube. Having worked in shops for a number of years...and considering the variety of jokers also employed with me...I've observed how guys blowing an air nozzle into the end of a tube can obtain various howling notes just based on the angle of the air nozzle. Wonder if the shape of the jet leaving the nozzle is having an effect, and if the shape is changing at different pressures?
Ken



Edited 3 time(s). Last edit at 04/13/2011 07:47AM by frustrated.

Gentlemen-

When I was testing and designing the burner for the new Dragster boiler that I built a few years ago, I used perforated s/s with .026 holes arranged in the standard SES pattern. The turndown ratio was huge, and when you turned it down past the point where the flame was unsustainable-it simply went out-It would never jump back thru the mesh. It was relatively easy to cleanly burn 25 gph in a burner with a flat mesh area of 1 square foot.

Another interesting thing that became obvious during my testing/development process--when I ran it with a rich mixture, it would scream in a high pitched whine-but when it was running lean, there would be a very low-pitched "ummmm" sound. I found out very quickly that adjusting the mixture to be just right resulted in very little sound-other than a low volume dull roar. From my limited experience, it seems like the howling problem has to do with the mixture and the volume of the area contained between the blower and the burner plate/mesh...but of course, burning howling has been around long enough to prove that solving it is not a very simple process!!


Chuk

Hi Peter,

Didn't find everything I was looking for, hard to find some stuff in the basement after the move, assuming I didn't toss it out.

The first photo is one of the flameholders I was testing. This one has about .023 inch holes, it burned nicely and good turndown, but wasn't the monster the first one was.

Second photo is the last rig on which I was testing flameholders, by that point I had ditched the cone and was just running flat screens to check the flame property. The holes in this flameholder are enormous, and there is a bunch of steel shot behind it with another perforated screen behind that. The idea was to test whether the turbulence through the coarse shot would make it blowback-proof. Not exactly, though it did let it turn way down. Of course, the top end combustion rate is lower. That was pretty much the conclusion I came to, depending on the flameholder porosity you could achieve higher generation rates at the expense of higher idle rates...I'd guess the turndown ratio is similar depending on hole spacing.

I got a flashback on this unit and my buddy twisted the speed control the wrong way, the screen on the front glowed but there was no damage to the aluminum can holding the shot though the combustion was inside. No open flame, or smoke, that I could detect. I wrote it off as a failure and about 6 months later while walking down the street I had one of those "hey wait a minutes" and realized that it had been putting out heat and no freaking smoke. Turns out it wasn't a bad catalytic converter, my research indicates I was even in the sweet zone as far as the pore size went, and iron is an OK if not fantastic catalyst.

Not shown is the carburetor (ripped off a snowmobile engine) with a homemade fuel tank and a GM electric in tank fuel pump. I had to modify the carb because it was a diaphram pump type. The pipe between the carb and the fan housing would be covered in heavy condensation, showing how much evaporating cooling was going on. Last two photos are a 3 stage blower identical (except for masking tape) to the one on the driveway buster.

Continued



Edited 1 time(s). Last edit at 04/13/2011 08:32PM by frustrated.

I did build a different style burner, but it didn't work very well. In the first drawing you can see the alleged flameholder. It was made of 1/2" wide steel band corrugated on a rack and pinion fixture and a flat band to back up the corrugation. As it turned out, the corrugations were too high, they needed much less altitude to make the thing work properly. I was kinda impressed that I managed to make it in one afternoon in the summer, shows what scrounging and a massive dose of good luck can do, good in that I didn't waste massive amounts of time on it. The second photo is a side view, it has a much less powerful squirrel cage blower due to the vastly reduced resistance, and fuel was sprayed in through a nozzle in the center of the damper door.

Other than all that, I tossed in a photo of the plug for my 5 foot steam launch model. I got busy and didn't do much with it for over a year. When the weather gets a little warmer I'll take it out and layup the glass mold around it, then cast a few boat hulls. OK, not germane to the topic on hand, but it was next to the shelf with the burners and I had camera in hand.....

Regards,

Ken

Wild stuff, Ken! Thanks for the great pictures.

A fan burner can definitely make more fire in a smaller grate area and firebox volume, than a Stanley/White type burner. Also allows smaller tube stack -- less gas flowpath area/volume needed. I had forgotten about your -aluminum- flameholder! Good illustration of the cooling effect of fuel and air flow through the flameholder.

With an up-flow flameholder/grate, I suspect that there is a sort of thermsiphon/chimney effect through the holes or slots, heating/de-densifying/de-viscositizing and thus propelling the mix up through the openings at low firing rates and shutoff. Also, the mix flow and grate-cooling effect seem to be roughly proportional to the fire volume and grate heating -- which leads me to think that painting the grate with ITC may not be necessary -- just pack the "valleys" between slotted parts of ridges with ITC-painted refractory a la Stanley. Larger slot or hole depth-to-width ratio increases cooling/contact area to heated area ratio, for a given hole/slot spacing... and gives better "chimneying"?... thus less chance of backfires...?

================

That is an amazing firing rate for such a compact grate, Chuk!

Really small holes too -- how thick was the sheet? Large turndown ratio and no flashback, well done!

Some roar/rumble/hum [not to be confused with "howl" or whistle -- sorry about the highly technical terminology lol] seems to be one of the tradeoffs for a more compact burner... avoidable in larger, lower-pressure burners...?

Very interesting comments! I think that the fuel/air mix ratio is a major [but prob not the only] factor in burner noise, in many different types of burners. Too rich = howl... Ken's no-howl/whistle driveway-buster burner used a carburetor for perfect mix... Bunsen type vaporizing burners often get quieter with smaller jets -- which give leaner mix... and lower firing rates... and can also increase jet clogging as Pat notes... ah tradeoffs...

Peter

Peter-

The perforated S/S sheet was .020 thick--the real trick was the hole pattern. They were punched in a diagonal pattern with every 5th row not punched, so the bit of un-punched metal acted as a flameholder when the rate was turned up...quite ingenious. As Ken did-I experimented with various sizes and shapes...the bigger holes would allow much more mixture thru, but the flame would stand up 4 to 6 inches above the mesh-and the turndown was not good at all.

The SES-pattern mesh was the best that I experimented with-it had a good(approx 20 to 1) turndown ratio, and the flame always stayed attached to the mesh resulting in a short flame-which is what I required. As I said before-my mesh had an area of approx 1 square foot, and the firebox was only 3 inches high. Within that volume, I was able to cleanly burn 25 gph...no smoke, and no soot on the tubes!!

Cheers--Chuk

Hi Peter,Chuk.

I found a few old notes. My flameholder was right around 16 square inches of surface area. The 'driveway buster' had .060 inch holes, and the fuel consumption was about 5 gph (maybe a bit more), my derived rule of thumb was to allow 3.25 square inches of area per gallon per hour with that grate, which comes out to some ridiculous number like 45 gallons/square foot/hr. Using off-the-shelf perforated metal I was limited to regular hole patterns, some in a box formation and others staggered. Never really noticed a difference in how they worked except when it came down to what the percentage of open area was.

The flames were very compact, stood out from the flameholder less than an inch, triangle shaped like you'd see off an oxyacetylene torch, and almost utterly stiff--no real wavering. I'd suspect the reason the flame was so much different than what Chuk had for the larger holes was the difference in pressure. The 3 stage blower was small, but 110 volt, and running at about 18,000 rpm if the data I found was true. I think at those pressures and velocity the flame would either have to be very intense or blow out. The noise wasn't bad, a low, hard roar. It was the BLOWER that made the racket. "Vvwwvvvwweeeeeeeeeeeeeeeeeeeeeeee".

I wouldn't mind trying to make another corrugated flameholder some day. I'd need to look at building something that made corrugations with much less rise, perhaps more of a rectangular section rather than the more sine wave section I had. Really didn't take that much time or effort to make the flameholder....except for winding it and keeping the windings tight and preventing them from coming apart in assembly. With stainless steel elements 1/2 or more deep, that thing would be very hard to burn out.


Ken

Wow!

Corrugated flameholders/grates btw are far from an oddball or experimental thing. I just took a picture of a 1970s-era Coleman natural gas floor furnace burner. Note corrugated elements. The bigger ones will pass a 0.055" (#54) drill; the smaller "cross grate" which carries fire to the further-from-camera array, passes a #55 drill, 0.052".

A couple of fine-tooth metal (pref steel) gears with adjustable spacing between centers might be an easy way to make custom shallow-groove corrugated strips. Adjust spacing for deeper or shallower corrugations as needed.

They happened to be sitting nearby, so I put my P5 pilot prototype (slotted) and one of my P9 pilot prototypes (current design; not yet slotted) on top of the Coleman burner venturi. Ripe loquats on the tree in background. Yum.

Peter

Hi Ken,

Do you have a link handy to original accounts of how your "driveway buster" burner earned its name? Personally, that is one of my very favorite modern-steam true stories. Equal parts serious "experimenter beware" and "holy cow imagine the power output and possibilities".

It occurs to me that this might be of interest/use to newer steam guys...

I worry about the effects of even my lower-fire-density burner, and have developed some test-safety precautions based on your experience...

LOTS of radiant heat in a small area, during open-air burner tests, can have -very- unexpected effects...

Be careful when working with WEIRD, high-output equipment of the sort needed with steam cars...

Peter

Hey Peter,

I went into Karl's old LightSteam lists and found the original posts...just searched the archives for the word 'driveway', which hadn't been a topic of steam discussion before that. You need a password to get in to those archives, so I just cut and pasted the post below. It's easy to register for a password, and there is a lot of stuff in the List, so I'm not trying to discourage anyone from searchng Karl's list (recommend it even), but I just didn't want to leave a link that didn't work.

A few years back I did leave a post on this Forum about how to access Karl's list:
[steamautomobile.com]

The message left in things I forgot, such as that my nephew trashed out the 3 stage belt driven fan and I switched in a higher rpm 2 stage of calculated similar output. I also forgot I burned out the original aluminum flameholder with a backflash at very high turndown and replaced it with stainless which let me push it even harder until it glowed..and I still think that was purely due to radiant heat as all the flame was moving away at good speed. Fortunately I bought about 10 of those new fans because I trashed the replacement during the driveway busting test, but only took about 30 minutes to replace. The burner rig in the photos was a bulkier, later variant where I built a separate aluminum housing for the blower and the burner, with a connecting tube, this protected the fan nicely.

I was doing this on my dad's driveway and was a bit nervous when the pavement started tossing out small chunks, but he'd spent most of his life in product development and his only comment was something on the order of "That is AWESOME!"

Truthfully, I think the process is a bit energy intensive for breaking up concrete, a jack hammer looks much better...

I never really ran a burner that hot again, it was really neat but kind of nerve wracking and I had doubts about how well things would hold up. At those power levels the burner flame shifted from the triangular blue flames into a bluish tinged, clear, sort of incandescent cloud...a really hot, rumbling cloud.. I estimated this to be about 4 or 5 inches from the surface of the flameholder, but that is purely SWAG, could have been much less and just sheer atmospheric distortion for all I know. Really would have been better if it had been night and I could see the limits of the flame clearly.

Ummmm.....maybe I should also mention that it was a good thing that I wear glasses and back when I had hair it was sort of fair, because it was much harder to tell that I temporarily lost most of my eyebrows around this time....

Ken

Here's the original post:

#################################################

To anyone:

I have been testing a burner for use in a boiler similar to the old SES unit.
My burner uses a multistage centrifugal vaccuum fan which discharges to a
perforated stainless steel cone flameholder as on the SES burner. The fan
suction receives it's fuel/air mixture from an old Tillotson carb.

The first test rig generated clear, blue, needle-like flames and enormous
heat. There was a slight tendency to backflash at low power settings but all
in all it was a great first attempt.

Subsequent testing with larger perforations were harder to control and more
likely to backflash. My 2 year old nephew "helped" Uncle Kenny but putting
nuts in the air intake and when they contacted the fan at about 12,000 rpm it
was all over.

I obtained a few small 120 volt ac vacuum fans and built a new test rig with
much finer perforations in the flame holder (with much closer spacing). The
fuel tank still used an electric fuel pump as needed to run the previous unit
properly. The new burner lit off easily but exhibited unsuspected
characteristics. The earlier flame holders were cooled by the incoming air
and the housings ran cool. This unit saw the flame holder promptly glow
incandescent, even though the flame was moving away from the holder. (must be
radiative energy) The burner was about 4 inches above the driveway and
within a minute the concrete exploded over an area the size of my hand and
about 3/8 inch deep. Presumably trapped moisture was converted to pressurized
steam. Even though I never got to open up the choke the unit consumed a lot
of gas, apparently the vaccum was now strong enough to dispense with the fuel
pump. I cannot report on the condition of the flame because it was nearly
invisible, although it did seem to extend at least 5-6 inches in front of the
burner. I turned the needle valves down and tried a second run after the unit
cooled down. The flame holder only glowed in a localized area. Before
testing could continue the fan siezed up.

The fan contains light aluminum in the internals and this apparently warped,
destroying the fan. There was evidence that fuel charred or broke down inside
the fan although no evidence of open flame. Obviously stonger fans are needed
and better shielding to reduce overheating.

I am stunned although pleased by the amount of energy this small machine can
release. The incandescent flameholder does bother me, however. This seems
unlikely to hold up well in service. Does anyone have experience with this
type of flame holder? Is this glowing typical? How can flameholder life be
assured?

I look forward to any replies eagerly,

Ken Helmick



Edited 1 time(s). Last edit at 04/15/2011 05:35AM by frustrated.

Hi Peter,

I wish I could say I had thought of the Coleman stoves when I started on the corrugated heater. Actually, I was looking at some cardboard and thought the shape would make a great flameholder. About 15 minutes into figuring out how to make it, I suddenly realized Coleman stoves use the same thing. Since I mostly use a kerosene or a white gas Optimus stove for camping (tiny but much hotter than a Coleman), it wasn't way up front in my mind.

If I was going to try it again, I'd build a roller to make the corrugations. The simplest idea I came up with was to buy some stock hex steel stock and cut some 120 degree Vees onto each face, and then time the two pieces to turn in unison with chain or gears. You'd likely want to stone the surfaces smooth and then flame harden the things to make them hold up. I made a quick sketch to validate the idea and tossed it in below. The dotted lines are there to show the outline of the original hex stock and to emphasize how little metal needs to be removed. In a pinch a decent vice and a file could do the job.

Ken

>The burner was about 4 inches above the driveway and
>within a minute the concrete exploded over an area the size of my hand and
>about 3/8 inch deep. Presumably trapped moisture was converted to pressurized
>steam.

Yep, that's the stuff!

BLAM! Exploding concrete! Flying chunks of driveway!

The birth of the Driveway-Buster Burner!

Love it! Sorry, might just be a personal pet thing here. Still, it shows a lot of energy in a small volume. Good thing in my book, whatever my personal current steam-car-burner energy-density goals.

No preaching -- I'm fed up with that -- but I figure that if you get some amazing results by following a certain path, then maybe there is a message there, that you should continue along that path? Just a thought..

Peter.



Edited 1 time(s). Last edit at 04/15/2011 06:36AM by Peter Brow.

Peter, I made a corrugater for my ring expanders doing just that. A central spur gear on a shaft with a hand crank, and and array of holes around it to vary the center distance in .007" increments. By varying the pitch of the gears the pitch of the corregations can be controlled (I needed 2 pitches). By wrapping adhesive backed polyurethane tape on one of the gears to fill the excess void you get an even corrugation (without it becomes a zig zag, \|\|\| vs /\/\/\).

Keith

Hi Peter,

If I were going to use that burner in a boiler, I'd probably want to shift to Hastelloy or Inconel for the flameholder. When the stainless started glowing despite that much air and vaporizing fuel passing through, I started to have my doubts about how long even that would hold up. Of course, could always go the chicken route and dial things down to a more survivable level, too.

What this all taught me was, if you don't mind putting some serious power and pressure into the combustion air, you can generate some spooky serious temperature. Just of matter of CRAMMING that air and fuel together. Of course, something like a carburetor to hold the right fuel/air ratio didn't hurt. The typical squirrel cage blower isn't going to cut it, I was using high pressure ratio, backwards inclined centrifugal blades in 2 or 3 stages with intermediate stators to build up pressure. Mind you, this wasn't totally intentional on my part. I got a real good buy, they were very compact and I liked that, and although I'd seen a drawing of the SES boiler and burner I had absolutely zero idea what kinds of air pressures were

I really don't think you'd want a burner that intense in a boiler. The problem as I see it is that I think it would be very difficult to keep from burning out any tubes that were placed close to the heat. You'd likely have to move them out a few more inches. If you have to do that, you can increase the flameholder size, reduce the flame intensity and be back to about the same point with less drama...which is exactly the process Chuk was describing on his burner.

Of course, we could always do something radical like add internal ribs to the tubing to increase the ability to transfer heat to the water....

Regards,

Ken

Ahhhh.....ya hadda say it, dincha? Been thinking about it and came up with a fairly simple modification to the perforated flame holder and carburetor rig that should give the same top end output but let you have a massive turndown ratio with the likelihood of backflash actually diminishing as the burn rate drops. Sigh, now I have to put it on a tube and see what the results look like....

Ken

Ken,
Am I correct in that you used a centrifugal blower to suck air thru the carbureter--that the blower wheel was on the fire side of the carbureter?? Sounds like an explosion waiting to happen. As you probably remember John Weitz made several Doble type carbs with the blower pushing thru the carb. A wonderful carb to use would be a Fish carbureter as the particle fuel size is about 1/10th the size of a usual carb, unfortunately I don't think Fish ever made a sidedraft model. I made one once and using water instead of gasoline(tested in the machine shop) and it was like a fog/mist coming out of the damn thing. Unfortunately ran it too long and realized the next day the lathe and miller 20 feet away were covered with water droplets!! The Fish carb was highly used and acclaimed until fuel injection came along. I wonder what the particle size of the fuel droplets were after going thru your suction blower wheel. Interesting.
Thanks, George

Hi George,

Yep, the blower pulled the air through the carb. I don't see much chance of an explosion, the blower tip speed is so high that the flame propagation speed is well below the velocity in the fan. Kinda like trying to paddle up Niagra. The later unit had no line of sight and no problems ever occured; even when I intentionally induced backflash it wasn't able to propagate into the fan. Anyhow, why would having the fan closer to the burner than the carburetor be any more explosive than the other way around? The carb is the element with fuel in it and I'd rather have it further from the heat.

The internal fan elements were all lightweight aluminum, so no sparks. I selected blowers with external cooling fans, so no fuel/air mixture ever got near the electrical components. The autopsy on the dead fan showed no traces of combustion in the blower, but there was indication of gasoline breaking down. In that unit the blower face was in direct line of sight with the flame holder and at firing rates so high as to make the flameholder glow, the radiation was transferred to the blower.

Funny you mention John Wetz, I demonstrated the burner to him once and he rather liked the idea of not having to modify the carb as he had to do with the Doble style unit. Of course, John stored his gasoline in open Mason jars next to the burner, so maybe he was hard to faze.

I suspect the fuel/air mixture was extremely well vaporized before hitting the flameholder. The later model had a 1.5 inch diameter, 1 foot long delivery tube between the fan and the carb. On a summers day in the mid 90s the tube exterior would be wet and cold to the touch. The pressure drop between the fan and the carb was vaporizing the fuel and that was pulling heat off the tube. Hmm...wonder if I could claim that acted as a heat pump to improve burner output in that website investor scam I was thinking of? If nothing else, when the fuel got the bejeezus whacked out of it at 18000 rpm while passing through the blower, I'd think there might have been some atomization.

Atomization may be massively over rated for an SES type burner. You have smaller perforations in the steel, so all that fuel and air is going to have to decelerate at the flameholder then accelerate again passing the orifice. That's about exactly the same design some steam system moisture separators used, so I'd figure there's a good chance some of the fuel is dropping out of suspension as the mixture hits the wall. With enough temperature, however, it can be revaporized... Really need a unit built out of Pyrex....

Regards,

Ken



Edited 1 time(s). Last edit at 04/15/2011 03:16PM by frustrated.

That is an ingenious variable-depth corrugator, Keith!

Ken, maybe a pyrex or ceramic flameholder/grate can be made from bundled rods, or small spheres between screens? Or these materials can be drilled with carbide bits. Then you can say "see ya later, corrugator". But drilled burners are a "hole" lot of work. Even though the result is "grate"...

Peter



Edited 1 time(s). Last edit at 04/16/2011 08:23AM by Peter Brow.

Hey Guys,

Chucks dragster burner, from the data given, looks to have been producing a fire density of over 11,000,000 btu per cf!

All of the burners that I have studied that produce fire densitys of that magnitude have done so with a very high velocity mixing of the fuel and air, this seems to be a key aspect for producing such an intense fire.

The highest output blacksmith forges(which can easily melt steel) use propane and a blower. The lower output ones use just propane to induce the air flow. I should mention though that propane requires more cf of air then gasoline or diesel per cf and genenrally runs at a much lower nozzle pressure, so they can't be compared directly.

Chuck, did you actually operate the dragster boiler with a modulated fire or did you use an on/off setup?

Ken, the oil well fire fighters use, or at least did use galvinised corrugated sheet metal to reflect the heat away from them when spraying the fire with water or to keep the explosives cool while getting them closer to the burning well. Something to keep in mind if you continue the burner experiments. Cool photos, interesting design.

Caleb Ramsby

Ken,
Thanks for the information. Sounds like the small 1.5" carb throat would have a great velocity going thru it and the fuel particle size just keeps getting smaller as this increases. Plus who knows the wet fuel particles that hit the blower wheel segments could have been flung off in even smaller particle size. What was the length from the blower outlet to the tangential? firebox. The nice thing about the Fish carb is that it works the same on either side of the carb as(push or pull) the float chamber is sealed and the incoming velocity head of air determines the amount of fuel pushed thru the teeny holes in the hollow throttle shaft. 18,000RPM zikes! Must have been some tip speed to the blower wheel.
Thanks again, I do have a fondness for carbureter air/fuel ratio characteristics.
George

Pretty normal in ic engine practice to have the blower on the engine side of the carburettor so I don't see the risk of fire being that great. It is normal to have a large blow off valve in the induction pipe between the blower and the engine to protect the supercharger from backfires.

I wonder if an SU carb would be good - it has very good mixture characteristics at all rates of flow.

Mike

Somewhat interesting diversion. The term waste gate came up as in the late 70's the roots blower lower manifold had a spring loaded plate, that I thought was called a waste gate, was employed to defer the total destruction of an engine due to backfire. Now a search pretty much limits the term to turbos.

Anyway, more to the point of this discussion is the fact that roots blowers become thermally inefficient because they generate so much heat, that the internal cumbustion engine will definately suffer from (intercooler become necessary). But mostly here, external cumbustion, this might be a notible benefit, fwiw.

Keith

sheesh, +o-u combustion



Edited 1 time(s). Last edit at 04/16/2011 08:57PM by kdc2.

All files from this thread

File Name	File Size		Posted by	Date
Cracked casting.JPG	192.5 KB	open | download	Rolly	04/04/2011	Read message
Old Venturi tube.JPG	150.9 KB	open | download	Rolly	04/04/2011	Read message
Drill Pattern.jpg	32.8 KB	open | download	Rolly	04/04/2011	Read message
Burner & Pan.JPG	152.3 KB	open | download	Rolly	04/04/2011	Read message
Cracked casting-2JPG.JPG	165.7 KB	open | download	Rolly	04/10/2011	Read message
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Drill pattern (2).JPG	77.9 KB	open | download	Rolly	04/10/2011	Read message
three gang drilling head.JPG	861.6 KB	open | download	Rolly	04/11/2011	Read message
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100_1680.JPG	1.11 MB	open | download	Peter Brow	04/14/2011	Read message
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