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Force circulation steam generator design

Posted by SteveW 
Re: Force circulation steam generator design
February 07, 2022 12:02PM
Thanks Rolly,
I appreciate the information and your help. Even with studying a lot and looking at other folks boilers I still have a lot to learn it seems.

Re: Force circulation steam generator design
February 07, 2022 02:14PM
I’ve poster this before with drawings.
Raytheon years ago did a study on heat transfer when they needed to cool radar tubes.

Heat radiates in all directions at the same speed as light. Hot gases flow two ways, in laminar flow and turbulent flow. Turbulent flow of gases tend to wrap the gases around a object, tube layout determines how the gases flow. laminar flow tends to flow to the least resistance. Like in a fire tube boiler right up the center of the tube. Turbulent flow can do four times the work (heat transfer) then laminar flow. There is a lot more to it but it’s a study in itself.

When tubes are offset by half their diameter the gases have to change direction and tend to wrap the gases around the tube instead of passing between the tubes.

My old computer is down right now but I have posted drawing before on this subject, laying out the tube pattern can almost half the required pipe for total heat transfer. Keeping the boundary layer wet does more work then half full of steam. Forced circulation.

Combustion chamber need to be sized for the fuel to be used. (Dobel’s book by Walton gives all the math) 310 stainless combustion chamber will make the fuel have complete combustion and pass the heat right through it (no loss)

Re: Force circulation steam generator design
February 07, 2022 09:35PM
Rolly, I think my drawings need to be better as it sounds like what we are trying for is a turbulent flow.
I understand what you are saying and I agree that that is what we need. Since we are wanting to use natural gas we will need to size the chamber for that fuel.
Unless there is something better to use than ss310 then that is what we will use.
I've asked an acquaintance who is a metallurgist if there is anything new that is worth looking into.
What is your opinion on finned tubing for the recirculating coils?
Re: Force circulation steam generator design
February 08, 2022 07:11AM
What is your opinion on finned tubing for the recirculating coils?
Thanks Steve W

I have never used fined tubing in boiler construction. It has its place in heat exchangers taking steam to heat hot water. One power plant I built for a prison we used exhaust steam from the generators to feed the kitchen for cooking as well as making the hot water for heating the prison. Steam to hot water heat exchangers with finned tubing can cut the size of the exchanger, but it is not pressure vessel material. When finned tubing gets dirty say from pure combustion gasses in a boiler configuration it all most imposable to clean.

In a boiler with heat in the combustion chamber between 2300 to 2600F the type of metal really is immaterial to the equation. 90% of the work is done in the combustion chamber, that is the area of largest differential of temperature between the waterside and the burner. Heat radiates in all directions, after the combustion chamber it’s either laminar flow of the gases or turbulent. Gases flowing at 90 degrees to a surface as in a water tube boiler do four times the work as laminar flow gases up a fire tube boiler. The other major factor in the equation, is the circulation of the water, the boundary layer on the water side of the tube. Big factor. Forced circulation is the way to go. Keeping the boundary layer wet all the time as much as possible.

The preferred material for most boilers tube (tube size) is low carbon steel ASTM
SA-178 grade A C= 0.18
Pipe size material is A-106 is also excepted grade A C= 0.25 Max

Steel plate common for ASTM for boiler construction is SA-285, SA-515 & SA-516

Re: Force circulation steam generator design
February 08, 2022 09:37AM
You don't put fins on the tubing until the heat flux on the outer tube wall drops to the point where the inner tube wall is capable of carrying away more heat than the tube is receiving. The forced recirculation coil, being adjacent to the flame, receives enough radiant heat that it probably can't even absorb any significant degree of convective heat. Assuming a counterflow heat exchanger setup, other coils closer to the burner are also probably somewhere near the limit as to the amount of heat that they can absorb. On the other hand, in the economizer sections, the water and gasses are both cool. You can stick on a lot of fins and still not overtax the tubing.
Re: Force circulation steam generator design
February 08, 2022 03:30PM
Ken, so far you and rolly are both correcting anything we may have wrong and confirming other information.
The. Drawing was just meant to show a general layout to get input on the basic design. Your input is a definite help. For the initial radiant coils what formula would you use to figure the radiant output of the flam and the absorption of the coils
My brother is already doing calculations but it's good to make sure we are doing it correctly
Re: Force circulation steam generator design
February 09, 2022 05:24AM
Hi Steve,

I would get a copy of "Steam, its Generation and Use" by Babcock and Wilcox and study the chapters on boiler calculations. My own personal take is that I would start my calculations with the forced recirculation coil because it is filled with a steam/water mix that is largely at saturation temperature -- meaning the constant temperature should make the ability to absorb heat roughly uniform along the length of the whole coil. Just about everything else, you need to average the conditions along the length of the tube. Knowing the internal temperature, the conductance of the tube wall, and the burner temperatures should allow you to solve for surface area of the recirc tube. Then you need to start looking at tube diameters. One thing I've noticed in discussions in this group is that the inside tube diameter is often glossed over in favor of the outside area. It's amazing how much resistance can take place along the length of the tube -- when I did the calculations, I almost fell off my chair. Of course, you need a pump to help offset this pressure drop and we would always like to keep that as small as possible. One thing to consider is that evaporation in the recirc tube will cause a very large rise in circulation velocity. I would suspect that any scheme which minimizes the velocity drop of the recirculation water as it passes through the steam separator would be beneficial as it would represent energy that the pump need not supply.


Re: Force circulation steam generator design
February 09, 2022 11:27AM
Ken, I have a copy that I had forgotten about. Many of my books got stored during a fast move from my previous residence. I'll pull it out and go over it again. Internal resistance is something that we had not forgotten about and IF we can figure a way to reduce it I'll bounce it off the phorum members. I'll be working with my brother most of the day on this. Finally have a day off with free time.
Re: Force circulation steam generator design
February 14, 2022 12:03PM
Hi Steve,
Note that I re-attached your concept. I have some questions:

- How are you going to control feed water
- What size/diameter are the tubes? (important to Reynold's No. and Turbulent flow/heat transfer)
- How many MBTU for the burner
- If OK to release, what length of the tubes
- Do you have any size or shape restrictions
- I'm guessing you have a feed pump planned, where would that go
- I'm also guessing you will have a 700*F X 700 PSI expander (rotary machine). If not, what is planned

I'm OK with your layout with one exception. My opinion, I would reverse the Radiant Heat Coils (RHC) with the Superheat Coils (SC). Reason is to keep a consistent temperature gradient. It would appear that the temperature of the RHC will be hotter than SC. Also, there may be something planned that I'm not seeing.

Interesting to talk about, thank you for sharing.

Kind regards,

Re: Force circulation steam generator design
February 15, 2022 03:43PM
Currently the feed water will be measured in the side tank with an upper and lower limit.. as we are planning on a closed system we will have a small tank where a feed water will draw from depending on results from the limit switches.
For this test boiler the recirculating tubes will be around 1/2 inch and the superheat to be determined as I'm not sure what is needed. To start with I'm figuring on 500,000 btu to start. This is really a test/learning boiler.
The recirculating pump will beinternal and magneticly coupled so no pressure problems. High temp magnets are available well above what we need.
As for the expander we are planning in the end on testing our rotary design. We think it has a chance of working decently. I'll put up more info later as I'm on break at work now.
Re: Force circulation steam generator design
February 17, 2022 06:06AM
I sometimes wonder if French and Waterman didn't come up with the slickest method of forced recirculation. They reasoned that their feed pump put out pulsations and that by taking advantage of this, they could extract energy to circulate water through the boiler. Basically, what they built was a hydraulic pressure intensifier -- but backwards. Instead of using a large piston to drive a smaller one at higher pressure, they used a small piston to drive a larger one at lower pressure... lower being a relative thing. Since the water in the low pressure circuit was already at boiler pressure, it just meant that it had a modest but adequate pressure head to provide circulation. For example, a 1 inch piston driving a 3 inch piston would move 9 cubic inches of water for every cubic inch developed by the feed pump. The nice thing was that the return force was provided by springs inside the pump so that there was no need for seals or bearings -- it was basically a free piston device. Actually, they didn't go quite so extreme because the circulating water powered an eductor which further amplified circulation. Better yet, you didn't need an external driving mechanism, the feedwater did that for you.
Re: Force circulation steam generator design
February 17, 2022 03:42PM
Ingenious! What was the date of that?


Edited 1 time(s). Last edit at 02/17/2022 03:43PM by Mike Clark.
Re: Force circulation steam generator design
February 17, 2022 08:46PM
This would be circa 1923-24
Re: Force circulation steam generator design
February 18, 2022 11:59AM
Hi Ken,
I think Steve mistake you for me above...it's OK.

I'm curious if you ever ran across a Tesla Flow Valve (check valve) sometimes referred to as a water diode used in a boiler to convert feedwater to circulation? This would be the lose concept. I included a pic for reference.

Can you attach an example of a French inductor (injector) forced circulation?


Re: Force circulation steam generator design
February 18, 2022 01:45PM
Hi Rick,

Attached is the image for the Endurance steam system. The actual pump is only shown in schematic in the system drawings. Those drawings were black and white, poorly drawn and suffering from poor reproduction -- so I had to redo them on CAD and add color. Then I had to resize it to fit the Forum upload limit. You can see the feed pump is laid out horizontally and does double duty as its step-piston also acts as a vacuum pump for the fuel system.

To the top of the feed pump discharge is the circulation pump. The circulation pump valves and spring are mounted on top of the larger cylinder. The mechanism on the bottom regulates feed water flow, it is a diaphragm device that acts as an unloader valve for the feed pump.

The feed pump discharge goes through the boiler economizer and early stage heating coils before heading to the eductor -- this preheating causes the water to expand and increases flow velocity -- improving eductor performance. This flow is combined with the circulation pump discharge which also powers the eductor. The eductor output is then directed to the evaporator coil, this being a forced recirculation boiler.

This is the most advanced steam car system of which I am aware. The burner is blower driven, but vaporizing instead of atomizing. The burner design is very simple, being the recipient of a number of generations of refinement and simplification over prior burners. There is an electrical vaporizer in the burner meant to provide a small amount of vaporized fuel just for starting from cold and for supplying the pilot. An auxiliary steam engine drives the blower, fuel and water pumps plus condenser cooling fan -- once lit off the steam system was isolated from the vagaries of the main steam engine and could therefore cruise easily on a flat road or two a heavy load up a mountain without badly affecting the steam temperature and pressure. Both the main and auxiliary engines are uniflow, the fuel delivery is carbureted to maintain a relatively constant mixture. Two prototype Endurance steam cars went from California to Washington DC, in different years, in the mid 20s. They managed the feat at about the same rate of speed as gasoline cars of the day... Considering that they were meeting investors along the way, this was impressive. .This would be an impressive feat for steam cars today, even though roads are far superior.

I'm familiar with the fluidic diode and have considered it as a means of improving boiler circulation -- the check valve acting somewhat like the check valve in a pulse jet engine to establish one way flow. The Tesla valve is sort of restrictive and there are superior designs floating around, some used in nuclear reactors. The problem is that fluidic diode performance is not like a real check valve. Under certain conditions they work fairly well, though they do not entirely prohibit backflow. At lower circulation rates their effectiveness starts to drop off, dramatically. This isn't an issue in a generating plant where load is pretty constant but might not be as suitable in automotive applications.



Re: Force circulation steam generator design
February 19, 2022 04:08AM
You've put a lot of effort into that post Ken - much appreciated!
Re: Force circulation steam generator design
February 19, 2022 03:50PM
Neat isn't it. My brother has been looking at the Tesla valve.
Re: Force circulation steam generator design
February 19, 2022 03:57PM
Thank you for all this information. I agree with Rick that you have put a lot of work into it. Right now I'm standing back while my brother does calculations for the steam generator. He is a bit better on the math and I just don't have enough free time to work full time on this.
Re: Force circulation steam generator design
February 21, 2022 12:09PM
Thanks Ken,
I second the motion, nice job with CAD. I also agree that it is one of the best Rankine Systems designed. It is hard to beat the circulation system using the inductor in synergy with other functions.

Perhaps I'll get around to showing how I would use the fluid diode on an Ofeldt. Respectfully, I know you're not to keen on the Ofeldt. However, the idea is to turn the natural circulation into a multi-path tube boiler with the addition of albeit a check valve. Perhaps that might find some favor in your thinking.

I'm still busy getting my shop insulated and up to speed for building steam stuff.

Very best,

Re: Force circulation steam generator design
February 24, 2022 06:59AM
Hi Rick,

I think it's safest if we consider the Ofeldt, and any number of similar boilers, to be "percolators" rather than natural circulation. The big marine boilers with which I was familiar in the Navy had upper and lower drums connected by a multiplicity of tubes, with both the downcomers and circulation tubes being fully submerged at all times. The difference in the weight of water in both tubes caused the circulation. The thing to remember is that these suckers are big and the vertical height provides enough difference in pressure to force a vigorous flow. Cars, being the compact little wonders that they are, simply can't match the natural circulation. Percolators, on the other hand, have a completely submerged downcomer section but the circulation tubes exit into the steam space. As steam generates in the tubing, it spurts in the direction of least resistance, just like a percolator. This method gives you pretty vigorous circulation in a small unit, the only downside (if we can even call it that) being that the flow is intermittent rather than perfectly continuous.

Going back to the Endurance steamer, we see a few features that the Ofeldt (and similar boilers) lack -- and this can include units like the Stanley. The first of these is counterflow heat exchange. The hot fluid rises and the hot gasses are forced downwards by the blower, thus the hottest steam is closest to the flame and the coldest feedwater is near the flue -- which results in the highest heat transfer efficiency (see attachment). This is precisely why Abner Doble also put his burner on top. The problem is that hot fluids rise and both the water in the boiler and the combustion gasses from the burner want to travel in the same direction. This is why Rollin White put those funny loops over the top of his coil stack. He had a vaporizing burner at the bottom of his steam generator and wanted to force the flow from top to bottom. He was worried that steam in the generator would want to flow upwards, even as he was forcing the water downwards.Those loops at the top of his boiler were actually loop seals, which allowed him to force both steam and water downwards simultaneously. So, if we have both White and Doble both pushing the flow at the burner, we have to conclude it's the right thing to do.

The other thing we need to keep in mind with recirculation boilers, be they forced, natural circulation or percolators, is that only a fraction of the flow through the boiler at any given time will consist of steam. Since the steam and water are in constant contact, however, we have to conclude that the water is at saturation temperature up until the point that cooler feed water enters the boiler. This is all well and good, we like this because we can get more steam production per square foot of generating tube if the water is at saturation. The problem is that heat exchange is proportional to temperature difference and combustion gasses can transfer more heat to a cooler surface than they can to a hotter one -- which is precisely why those naval boilers, and the Endurance, have large economizer sections through which only feed water travels. We don't really get the same effect by injecting cool feed into the circulation loop because the feed is only a fraction of the mass, the temperature drop it induces is mild. If the proposed economizers are comprised of finned tube, we can keep the weight down and also greatly reduce the pressure drop through the section. Of course, we have to keep counterflow in mind when orienting the economizer with the inlet being right at the flue.

Now, if you could rework an Ofeldt (or other percolators and natural flow boilers) so that the burner was on top and there was an economizer at the bottom, we should see a bump in efficiency.

Beyond all that, water in the economizer expands as it heats, and this is much greater in the generating tubes as steam is produced. Both effects increase flow velocity. Anything that can be done to preserve this velocity during the recirculation would undoubtedly also improve the effectiveness of the boiler due to an increased Reynolds number and perhaps permit a reduction in size.

Now, keep in mind, I don't think any of this is naturally applicable to a boiler being used in a traditional sort of format. In those cases, you tend to want to emulate the feel of what was originally employed. On the other hand, if you are simply trying to build a modern unit, efficiency becomes important and the use of economizers and counterflow starts to look important.



Re: Force circulation steam generator design
February 24, 2022 12:03PM
Hi Ken,
Nice reply. You got me thinking about a downdraft Ofeldt configuration for a boiler design. Very interesting idea. Also, counter flow hot burner gasses to steam generation direction is a good idea.

However, no matter the configuration, the increase in hot gas flow through the system is paramount. I side track to Chuk's presentation he gave at the last SACA meet. His burner blower is one of the biggest I've ever seen. Pretty cool looking too. His efforts increase the Reynolds number significantly for the hot gas flow through his mono-tube generator design. For 1 m/s increase in gas velocity, one gets an exponential gain in heat transfer. This is provided your in the turbulent flow region. Chuk's configuration is horizontal.

Doble is a down draft configuration. The F had an additional turbo added to the exhaust to increase gas flow. This addition made the most difference as stated in Jim Crank's book.

One better, is that the British Inspiration used a multi-path tube generation configuration with manifolds between stages almost like separator drums/tubes. There burner was IR. IR also has an exponential affect on heat transfer.

Interesting thoughts my friend,

Kind regards,
Re: Force circulation steam generator design
February 25, 2022 11:32AM
I have posted most of this before on previous post or another but through it might be a good reminder now.
Some thoughts on boiler design.
Laminar verses turbulent flow in more relevant to the flow of gasses thorough the tubing bank after leaving the combustion chamber. Raytheon in there extensive study on cooling radar tubes found that turbulent flow of gases around pipe or tube did four times more work then Laminar flow of gases. Heat radiates in all direction at the same speed of light in the combustion chamber and generator bank. Hot gases on the other hand are controlled by the burner pressure and tube configuration. Wrapping the combustion chamber with the appropriate size pipe with forced circulation water has the highest differential in temperature, and does more work then any other location in the steam generator, being at a higher pressure then generator pressure by the forced pump there should be little on no steam bubbles generated in this tube till the water gets back to the main drum that is at a lower pressure. It is my opinion in a 200 HP generator this coil should be at min one inch ID.
From the combustion chamber the hot gases flow in either laminar flow or turbulent flow based on the tube layout and winding configuration. The winding pattern in a wound coil generator should be wound so the gases flow through the bank in a turbulent pattern to achieve the highest output of a coiled generator, reducing the overall size of the tube bank and size of the generator. Turbulent flow coil windings can be as close as one-quarter-tube diameter to each other. Of course this will increases combustion chamber pressure and require higher HP burner. I don’t think I have ever achieved the correct combustion chamber pressure as I have had many combustion chamber explosions.

The choice has to be made as to the burner firing method, straight in or tangential. I have used both but tangential with a combustion chamber liner seams to me to have a much cleaner burn and controlled fire. If tangential you should be aware or your running location for as clock wise or counter clock wise firing.

The preferred material and by the ASME code for most boilers and generator tube is low carbon steel ASTM SA-178 grade A C= 0.18 and A-106 is also excepted grade A C= 0.25 Max
Steel plate common for ASTM for boiler construction is SA-285, SA-515 & SA-516


Re: Force circulation steam generator design
February 25, 2022 12:08PM
Hi Steve,
Back to your steam gen design concept. What Rolly and I are suggesting is that you will get the most bang for the buck if you plan on forcing the hot gas burner flow through the set path at the fastest rate you can.

Next best bang for the buck is to force the water through the tube path the fastest rate you can. This has to be a consideration of tube diameter and length. The attached video uses 3/16 brake line as a monotube boiler, flash boiler. Think about how fast you would need to force water through that tube to supply 200 HP. Perhaps not practical but consider the trade off of Diameter-length to steam amount of lbs/hr steam. What you see in the video is in the neighborhood of 8 HP. A good starting point is the Doble boiler design.

Hydroplane boat steam speed record

I re-attached your concept so one doesn't have to scroll back and forth. Both suggestions are considering the highest Reynolds No. possible which correlates to the greatest heat transfer.

Hi Rolly,
You do pretty good for working out of the library computer my friend.

I like the tangential burner design. I know a gentleman whom I consult to who will be interested in this tangential burner design. He has just built an Ofeldt and putting it into his condensing Stanley. Some of you reading this might know who I'm talking about. He posts on Facebook often. I'm advising him on a burner configuration and suggested just this concept. However, your attached picture shows an excellent method.

Kind regards,

Re: Force circulation steam generator design
February 25, 2022 05:23PM
What you, Rolly and Ken have suggested is the direction we have been taking. The design is a burner on top with the hottest flame with the hottest water or steam in the super heater area. I gave my brother a different design idea which we are looking at right now. Would you mind some time talking over phone with us about it sometime? If it sounds reasonable then we can take it to the phorum for further discussion. One thing that is slowing us down is the physics behind the math. My brother is doing most of the calculations as I work full time but he is retired ie has more time for this endeavor.
Re: Force circulation steam generator design
February 28, 2022 06:39AM
And, of course, you can always lay a boiler down sideways, if it helps with installation. The Newcomb boiler was a pretty amazing design circa 1901, or so. The fuel/air mixture came down a central tube so that the fuel was preheated and vaporized when passing through the flame holder. The conico-frustrum coils meant that you could get more surface area by winding fewer coils -- and it allowed you to stack identical coils like pancakes whereas each helical coil would have to be a different diameter. The flow through the boiler is counterflow.

SES was an extremely high output, extremely compact boiler from the 1970s. It also had the central tube, albeit larger because the fan could push a lot more air than the vaporized fuel jet could manage in Newcomb's day -- it still used the flameholder. The flow was almost counterflow -- the coil closest to the fire did not function as a superheater. They called it the "quench coil" and its job was to lower the flame temperature so as to reduce the amount of nitrous oxides produced.

The SES was mounted as shown, the Newcomb actually has the burner on the bottom but I rotated it 90 degrees because I was comparing and contrasting the two machines. Also note that SES has far fewer coils, despite far higher output. If you will look carefully, you will see that some of the coils are finned and the surface area goes up by something like a factor of 10. (Edit -- I should have mentioned that SES also has exhaust gas recirculation -- obviously reduced emissions were part of the design goals.)

The McInerney patent is interesting because he sort of refutes the counterflow argument. Actually, he doesn't do that at all. He is a firm believer in "hot to hot, cold to cold". What McInerney found was that the fluid running through a monotube would actually start to cool off in the area where steam generation was high. What appears to be happening is that there is some time delay in the formation of steam and therefore the water is briefly in a supersaturated state. When steam does form, it absorbs heat from the surrounding water and tube wall in order to supply latent heat of vaporization. Therefore, in order to obtain best heat transfer by maintaining counterflow, McInerney causes the tube to travel towards the flue as the contents were cooling off. This was an interesting patent in that I don't believe anyone had ever noticed this phenomenon previously -- I assume that boiler looked like a porcupine with all the thermocouples sticking out of it. Now, I had to read the patent something like three times to figure this all out. Vapor Corp. sort of hid this information inside a lot of other verbiage describing the boiler and didn't go to great lengths to spell it out. I'm assuming that they didn't want competitors to know so they sort of hid it in plain sight under a layer of gobbledegook...



Edited 2 time(s). Last edit at 02/28/2022 08:10AM by frustrated.

Re: Force circulation steam generator design
March 03, 2022 07:50AM
Attached find a drastically over-simplified drawing I did up for the Endurance steam car burner. The fuel/air mixture passes into the central vaporizer tunnel, which is essentially a rectangular box with a pair of doors situated at the far end from the induction tube. The fuel/air mix passes through these two doors and then reverses course as it flows through the two side wings. Each of these wings has a slitted bottom surface which acts as a flame holder, the fuel/air mixture passes through these slits before it is ignited by either spark plug or pilot. Obviously, this is a downwards blowing unit. The vaporizer tunnel, being exposed to both radiant and convective heat, gets quite hot. It is, however, cooled by the volume of air passing through. We can classify the fuel suspended in the fuel/air mixture into two categories, that in which the droplets stay in suspension and that in which the droplets fall out of suspension and rest on the floor of the vaporizer tunnel. That in suspension is vaporized by convection as heat rises off of the vaporizing tunnel floor. The droplets falling out of suspension rest directly on the vaporizer tunnel floor and are also vaporized.

My own personal experience indicates that the fuel vaporization absorbs an amazing amount of heat, and this probably protects the relatively thin sheet metal burner. I built an SES style burner, which uses the same principles, and ran into an interesting phenomenon. On a hot summer's day (over 90 degrees), I noticed condensate forming on the tube between the carburetor and the blower (I was drawing air through the carb into the three stage blower). The gasoline was vaporizing in the low pressure area, and absorbing so much heat in the process that it made the tube cool to the touch. As it was, I was still not getting anything like complete vaporization and had to route the drip-off fuel through a coil surrounding the burner and reintroduce it at the blower suction. It had never occurred to me that I was building a rudimentary air conditioning unit.

Anyhow, most fan style blowers are atomizing and do not tend to burn quite as cleanly. Both the Endurance and the SES are vaporizing, blue-flame burners. French built a number of fan-driven blue flame burners prior to this, such as in the International Harvester tractor and the Coats steam car. The big difference was that those were elaborate whereas the Endurance burner was quite simple -- it appears that he managed to refine the concept to its basics and eliminate all the excess mechanism.

The big difference in the blue flame from my burner and a Stanley was that the blower produced a far more intense fire -- rather than being a bed of flame, it produced dozens of points of flame, each of these much like you would find on a gas welder. I am sure part of this was due to the high air pressures developed by the 3 stage blower ... but it explained how SES managed to develop so much more heat than a Stanley in a much smaller package. I was firing it horizontally and chips started exploding off of the driveway as water trapped in the concrete flashed into steam.

In any case, I don't think I've found a more sophisticated or elegant steam car burner than this one.

Re: Force circulation steam generator design
March 09, 2022 11:50AM
As I recall from one of the SACA talks that the SES boiler used a centrifugal blower to force the hot gas through the flow path. Also, the running of the water through the front row coils after what I might call an economizer coil was to meet NOx emissions. This front coil cooled the burn to meet emissions standards of the 70's.

Any idea on the steam generation and water rate?

Re: Force circulation steam generator design
March 09, 2022 05:08PM
Hi Rick,

This is just off the top of my head, I don't have the reports handy. I think John Bowditch told me that they were getting about 12 lbs/hp-hr (about similar to a White or Doble). As I recall, the engine was 150 horsepower, so that would work out to about 1800 lbs/hr at 1000 psi.


Re: Force circulation steam generator design
March 09, 2022 05:24PM
There's an interesting discussion of the natural circulation and forced circulation steam generators that can be downloaded. It was written in 1952 by Lieutenant Commander Walter Leslie Marshall as a thesis for his Masters in Mechanical Engineering at the Naval Post Graduate School. The abstract reads:

For a number of years, especially since the end of World War II, the engineering literature has contained an increasing number of references to forced circulation boilers. Most of these articles extol the virtues of some one kind of boiler or tend to justify the conventional natural circulation principles. The range of boiler types covered by the term "forced circulation" is much broader than usually realized, and since some of these types are basically quite different the existing confusion on this subject is understandable. We comaonly think of the United States as a leader in technological progress and development, and in many fields that is true. There are other fields, however, where from time to time we t^nd to lag. This has been especially so with regards to the application of forced circulation in boilers even though some of the working principles were originally discovered in this country. It is gratifying to note the rapid and accelerating interest which is now being shown towards making up the lost time. In this paper an attempt is made to classify and describe the common types of forced circulation boilers. By comparison with natural circulation principles, advantages and disadvantages are brought out. The ccmparison is not intended to minimize the importance of natural circ\ilation, but rather to show that forced circulation represents a step forward in steam generation similar to that of the watertube over the firetube boiler.

It can be downloaded at: W.L. Marshall Thesis

I've only downloaded the pdf. I should warn you that whoever scanned it made a copy of both sides of each page, even though he typed the thesis on just one side. So, half the pages will be images of the inked that leaked through the paper. Not that big of a deal, although we could remove the dead pages, if desired.


Re: Force circulation steam generator design
March 10, 2022 05:22AM
If you wish some fairly dry reading, there is an analysis of the SES boiler, particularly the control scheme. It is held online by the National Service Center for Environmental Publications and was prepared by the Bendix Corporation out of Ann Arbor for SES.

Steam Car Control Analysis
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