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Drumless Boilers

Posted by frustrated 
Drumless Boilers
September 16, 2022 09:10AM
One of the problems that have always plagued steam automobiles is the overall system volume. The engine might be relatively compact but the overall system gets bulky when you start to add in a feed water tank, boiler and extra pumps. We can reduce feed water tank volume through more effective condensing, but that isn't a trivial issue -- it is a lot easier said than done. Pumps are also easier said than done -- you gotta get that water from Point A to B -- and add pressure in the bargain.

The boiler seems to be an area where improvements could happen. In the case of water tube designs, there is invariably a large volume dedicated to steam storage -- typically in the form of a drum although Baker also employed coils for the job.

This raises a question: "Can we eliminate the drum?" Drumless boilers aren't new, so that seems to be answered in the affirmative. Of course, there is the matter of implementation.

If we look at a forced recirculation boiler, we find that the water entering the "Lamont coil" starts out at lower velocity and accelerates dramatically as perhaps ten or twenty percent of the water is vaporized. That percentage is by weight -- the dramatic increase in volume as water turns into steam is what drives the large speed increase. As that steam/water mix is directed into the drum, the velocity is largely negated by friction and turbulence. If we eliminated the drum, a large fraction of that velocity could be preserved. This would seem to give a few advantages:

1. We need much less power for our recirculation pump
2. The flow could pass through a centrifugal separator to remove the steam
3. Curved pathways could partially separate steam and water prior to a separator.
4. The high-speed flow into the recirculation pump eliminates the possibility of vapor lock.

The idea then follows that we can readily separate steam from water in a centrifuge -- but that adds complexity, weight, volume, and cost.
The aforementioned vapor lock, however, tends to occur because the centrifugal pump is acting like a centrifuge -- the vapor collecting at the impeller eye jams things up.

So, I am forced to wonder, "Can we design a centrifugal pump that would separate the steam from the water?" If so, we would have an endless loop with a smaller inlet for feed water and a second for steam tapped off the loop. I can see the feed water being introduced right at the centrifgual pump discharge so as to replenish the volume in the recirculation coil lost as steam is withdrawn.

Any ideas?

Ken
Re: Drumless Boilers
September 19, 2022 10:53AM
Yes, I think theoretically, a centrifugal pump in combination with some type of water/steam separator device incorporated into the output stream of the pump could work. Perhaps it would be a unified device as pump/separator.

In the TS Diagram, you'd be working within the bell curve where the generating tubes are working with steam and water. Then after the steam is separated, run it through a super heat coil before delivering to the engine/expander. Note that the centrifugal separator could be smaller than a separator drum and integral with the pump. Again, theoretically, this can be done. Also, there then arises another question as to whether the pump can overcome the circulation resistance. Centrifugal pumps can cavitate. Piston pumps don't cavitate, they just blow up when locked up.

Using Chuk's mono-tube as an example: it requires 1100 - 1200 psi input to get 700 - 800 psi out in steam. Water has a strong tendency to adhere to its self and to the tube walls. It is a polar molecule. It can be influenced by magnetic fields. Yes, using circulation, one can reduce the length of generating tube. One can use fill within the generating tube to reduce length also. My quandary would be whether or not it is worth while.

I do favor a separator drum for it significantly lowers the level of feed pressure. My example is the British LSR that uses manifolds or drums.
The other important thing with a drum is that it provides a level of stored potential energy. Using Billy Barnes motorcycle land speed run as an example: he is able to run the mile with the charge of water within the Stanley 10HP firetube boiler. This is what makes his drive system simple (direct drive) .

My opinion, better to perhaps take an Ofeldt and put a Tesla check valve in the drum to make feed water go through the generating tubes during throttling. The boiler will just naturally circulate when at a stall with the burner on. Again, storing the energy. The control is a simple, proven water level control system. This provides for a good mesh from classic Ofeldt and mono tube design along with a good weight reduction over the heavier fire tube systems. The system would be called a multi tube boiler in this case.

Last thing to consider is adding a mono-tube in the vicinity of the super heat coil to improve the recovery or maintaining potential energy in the water. With this adaptation, I would include the feed water loop goes through the economizer back to hot well when the feed valve is open. When feed valve closed, water would go from economizer -> mono-tube -> bottom of separator drum. I have some evidence from a fellow steam guy who did just that...Gerry Hackett. He called it the Grzyb Coil.

I answered your question as yes. However, I don't believe it to be practical in application. I'd be happy to talk more about this at the Meet...looking forward to it.
Re: Drumless Boilers
September 28, 2022 11:15AM
Hello Ken and Rick,

I woke up thinking about this. Such a system would seem to require a high volume/ low pressure pump. Hopefully this would avoid cavitation and survive through surging from a sudden drop in pressure from a suddenly open throttle.

The Ofeldt system does come to mind. With it's use of many steam circuits it is naturally a high volume/ low pressure recirculating system. Of course I would put pancake coils in it and pack em tight to get a higher density of coil stack. Two layers for each coil.

Now the recirculation pump would be high volume/ low pressure. Since we would be working with an already
handy tank, use a water turbine in it. This could be a stack of turbine blades and staters vertically inside the tank. I think maybe about 15 psi of pressure and about 500 rpm would do the job. The thing would not need to be high tolerance because of the low rpm's.

Best Regards,

Bill G.
Re: Drumless Boilers
September 29, 2022 07:36AM
Bill,
You peak my interest by saying one word, "Ofeldt". I attached a couple of pictures to show an Ofeldt design concept. If I'm understanding your verbiage correctly, I would put this vertical turbine and stater arrangement within the center separating drum. What do you think?

Also note that when ever you add moving parts to a boiler/generator arrangement, you're asking for trouble. Reliability is a big concern.

Again, in theory this would work. However, I would recommend a natural circulation system. By putting a Tesla type fluid diode in the drum to force circulation through the Ofeldt tubes when feed water is pumping into the boiler, will provide forced circulation. When not feeding the boiler and with burner on, the system will naturally circulate. I'm actually going to build an Ofeldt that will do this...hopefully next year. I'm still contemplating the check valve arrangement. Also pump/circulate feed water through the economizer to the hot well when by-pass valve is open.

The attached pics are really using a proven Ofeldt concept and the proven White boiler concept. Just thought it interesting to combine the best of both worlds (mono-tube & multi-tube).

I'm actually gearing up to make coils with the gearbox I already acquired. When returning from the Meet this year, I'm picking up the 3-phase motor to drive it.

Rick


Re: Drumless Boilers
September 29, 2022 10:13AM
I think one of the best drum less boiler / generators ever built was the Derr boiler.
The supper heater and feed water heater could be located where ever it was best for the application.

Rolly


Re: Drumless Boilers
September 30, 2022 08:51AM
I recently heard from Nick Mesmer that your Derr boiler is the best design. The staggering of the gradient tubes was an excellent concept. The hot gas as it flows through the tubes is interrupted, increases the turbulent flow to maximize on heat transfer.
Re: Drumless Boilers
September 30, 2022 10:49AM
Hi Bill,

You are right, your pump would be high volume, low pressure. In a Lamont style boiler, the recirculation coil is short, but of large diameter. This produces minimum pressure drop and the pumping energy is low.

One reason that I think you can make this work is that the Lamont coil already holds a lot of water, so a storage drum might not be as big an issue as on other boilers.

The pump power demand might also be smaller than expected. As the saturated water enters the coil, it transforms into steam. This produces a drastic increase in volume ... and velocity, since that volume has to go somewhere. Normally, that velocity is dissipated in the drum. If we can eliminate the drum however, we might be able to retain most of that velocity and reduce the pump power requirements. The volume coming out of the pump will be reduced since the steam has been separated, but we can make up the loss by bringing our feed water in at the pump discharge through an annular nozzle. Such a nozzle also gives you an ejector effect, which helps accelerate the flow.

There was a patent taken out in Egypt that covered cavitation effects in centrifugal pumps. They found that the biggest culprit was shear forces as the water entering the eye of the pump impacted the spinning rotor at a right angle. They added a recirculation line to recycle some of the water back to the suction at a perpendicular, so as to give the incoming flow a bit of spin. I would suggest that isn't necessary in this case because the water is already leaving the Lamont coil at velocity. If we put a can around the inlet and introduced the flow tangentially, there should be a huge reduction in shear. If the can has a decent diameter, conservation of momentum should have it spinning at a higher rpm as it approaches the impeller eye -- reducing shear even more.

Regards,

Ken
Re: Drumless Boilers
October 01, 2022 01:01AM
Hi Ken,

Well Egypt is covered with sand. I wouldn't expect too much water technology out of it.

Why would, other than to make a cheap rotor, someone design one where the impeller blade meets the incoming water at a right angle? If you ever tried to plane wood with the blade perpendicular to the wood you would soon see that your just grinding on it. A wood planer blade is at an angle. It cuts the wood.

Same with a well designed impeller blade. The eye part of the blade meets the incoming water at a sharp angle like a planer blade does. It doesn't knock it apart, it cuts it apart. Upon exit the impeller is curved backward to push the water away from the impeller.

At the inside, in the eye, the blades are thin and sharp and curved to point in the direction of rotation to "plane" off a slice of water, not to beat it to death. On the outside they are quite thicker and the leading edge is curved backwards to point in the opposite direction of rotation. This helps to push the water outward to increase pumping pressure.

The curve on the blades is not the same on both sides. The expansion of the water channel from the eye to the outer periphery is more gentle than is the case with the flat radial blades as found in a trash pump. In the trash pump situation the dramatic increase in volume can create much vacuum causing cavitation.

With a more gentle increase in volume through the channels much less vacuum and higher velocity. The water is accelerated by the inner curve of the channels leading edge which produces a pressure on the water to accelerate it outward. The blades are kind of an "S" shaped curve, or it's mirror image depending on which way it is turning.

Still one would get much less cavitation with a bigger diameter and slower rotating impeller than with a smaller, high speed one. Water on the verge of boiling is a "*****" to get into a pump. Any reduction in pressure and it boils. You have to be sneaky.

I was thinking that multiple, low rpm rotors might be sneaky enough.

Best Regards,

Bill G.
Re: Drumless Boilers
October 01, 2022 08:02AM
Bill
I had never designed a centripetal pump before I made one for a forced circulation boiler,
I went through many design changes. The problem is to move lots of water with minimal power. And the housing had to withstand fore times boiler pressure to meet ASME code.
My housing was cast in ductile iron and hydro tested for 4000 PSI. The bearing and seals was a whole other problem.

I played with all kinds of shapes and sizes. Took apart lots of old pumps, what I settled on is what worked in the size I needed. Creating reasonable pressure and volume
It pumped enough volume against a head pressure of sixteen feet and 65 feet of hose. Used in a forced circulation generator the suction side of the pump is at boiler pressure. The output pressure only has to be enough to move the volume of water.

The gap where the impeller meets the housing is very critical to pressure output. The cup shape also plays a role in the volume, and suction.

Photos show what worked best for me.

Rolly


Re: Drumless Boilers
October 02, 2022 09:25PM
Hi Bill,

I have no idea why the patentees being from Egypt would make a difference -- it isn't like they have no demand for pumping water or operating power plants.

They were not recommending that water be directed into the impeller at a right angle -- that's what centrifugal pumps have done since the beginning of time. Their argument was that the shear produced by introducing the water at a right angle causes cavitation. In a steam system, the high temperature water (if not outright saturated in the case of a Lamont) can flash to steam if the pressure drops. This is why we had main feed booster pumps delivering feed water to our main feed pumps onboard a carrier -- the booster pump maintained a suction head to prevent flashing.

It should be noted that they apparently did a lot of testing and found that their methodology reduced cavitation -- the patent was taken out by a major university and not a backyard inventor. The problem would appear to be a low-pressure zone maintained behind the rotating blade. We experience this everytime we pass, or are passed, by a large truck on the freeway. The low pressure zone immediately behind the truck is distinct. I can remember driving from northern Michigan to Newport, Rhode Island back in the mid 80s as part of the navy reserve. I hardly had any money to rub together an had to drive 1,000 miles. My car got about 32 mpg, which wasn't bad, but I managed to do quite a bit better drafting semis on the drive. It's dangerous, illegal, but effective.

So, their remedy is to put a spin on the water entering the pump, said spin being in the direction of the rotor motion in order to alleviate shear and allow the water to more evenly flow into the gap behind the blades.

Regards,

Ken



Edited 1 time(s). Last edit at 10/03/2022 07:09AM by frustrated.
Re: Drumless Boilers
October 03, 2022 03:56PM
Hello Ken,

I was just kidding about the Egyptians, I know they have more than sand there. They've got the Nile river and crockydials and everything modern civilization could want. Even we have an alligator swimming around in Orlando somewhere. That hurricane blew em right out of the swamp.

Anyway, Your big semi truck analogy is a good one. Now if instead of a truck it was a streamlined sports car there would be a lot less vacuum behind it. What I offered was a different approach in the eye of the impeller. The entrance to it is more streamlined and the blade cuts the water instead of beating on it as it enters the impeller. Thus less turbulence and cavitation. The initial acceleration of the water as it enters the impeller is from the blade curvature pushing it outward instead of sucking it out.

There is no good way that comes to mind to entirely eliminate a vacuum on the water which may cause it to boil and cavitate when trying to get it into a pump entrance. Something has to suck it in. So the boiling water has to have some pressure on it which increases its boiling point enough to counter that, or cool the water just enough to accomplish the same thing.

Or get a pressure head on the water by taking it from the bottom of a tank, letting gravity do the job. Or loading it into the back of a pickup truck and taking it back to the swamp and letting it go.

Best,

Bill G.
Re: Drumless Boilers
October 04, 2022 06:03AM
Hi Bill,

The sports car analogy was what we did using a booster pump. Tangential flow, instead, acts like a freeway onramp rather than crossing an intersection.

The more I think about this whole topic, the more tangled it gets. The thing with a Lamont boiler is that the circulation water temperature is meaningless. The water could possess just enough BTU to reach saturation, and not one BTU more ... or it could be just one BTU shy of transitioning into steam. That's one huge gap.

I had originally thought that feed water should not be admitted to the pump/separator suction because it would condense part of the steam, but now I am wondering if that is relevant. Yes, it will condense part of the steam, but it has no effect on the energy balance because we are still burning the same amount of fuel and admitting the same amount of feedwater at the same temperature. The only difference is where the boiling onset begins in the coil. If boiling begins a bit later, then the fluid in the coil will have a higher average density and perhaps absorb more heat -- shifting load from the economizer to the Lamont coils.

This whole matter of average BTU is a head scratcher, I have no idea how you would reasonably model this. Does the mean BTU remain more or less steady over a varying load, or does it vary? Heck, does it hold fast during a steady load or does it oscillate? Does the average BTU in the recirc coil actually make a significant difference?

I think we can assume that lower mean BTU entering the recirc pump is less likely to flash into steam.

As I think about this, I am starting to suspect that mean BTU in the Lamont coil is largely a self-regulating phenomenon ... but it would be nice to know for sure.

Regards,

Ken
Re: Drumless Boilers
October 04, 2022 07:01PM
Hi Ken,

OK, Like the freeway analogy then, if we add some pressure to the incoming water before it enters the pump inlet it would be like having the on ramp higher than the freeway thus accelerating the water into the pump inlet. That's why the recirculation pump inlet should be at the bottom of the Lamont tank. The small head of water above would add some extra pressure to limit boiling.

Remember that the recirc tank has to be cooler anyway. If feed water were to encircle the tank on the outside that might help.

Ken, I think you are correct that the temperature of the water entering the generator coils is not a big issue. If it is at the water temperature of the steam/water slurry coming out of the coils or is a mix of that and some feed water the same number of Btu's go to heat it. Perhaps a little more heat would be extracted from the generator coil with colder water but the thermal efficiency would be the same. The purpose to mixing would be to lower the flash point in order to help avoid cavitation.

I believe that a high volume of recirculation would keep the generator coils full enough that the coils would be wet inside pretty much and not an issue. To this a lot of coils and thus relatively short and using lower pressure. On my condenser experiment the boiler pressure was sometimes as high as a whopping 6lb gauge. I had to use a check valve after the pump and before the coil or it would surge and blow out both directions. That pressure was lost going through the superheater down to atmospheric but enough heat was added to make certain that the steam was dry.

Engines don't always run at full power, so there will be plenty of generator tubing for partial power usage.

If it's cavitating, you will hear it, it sounds like a freight train. At least a steam heating boiler did when it's condensate pump cavitated. I added a tank above it which maintained a good 40" of water above it and that stopped it.

Best Regards,

Bill G.
Re: Drumless Boilers
October 05, 2022 01:00PM
Hi Bill,

Heat transfer is an interesting question. Assuming an 8:1 circulation ratio, we would assume that the flow exiting the coil would be 87.5 percent water, by mass. As far as volume goes, however, it is about 79 percent steam. If we assume a circular coil, and that the flow accelerates as the volume rises with steam production, then it becomes interesting to speculate to what degree centrifugal force will push the smaller (but heavier) volume of water against the outer coil wall -- which is slightly problematic since it is the inside of the coil which is exposed to radiant heat. Given that Lamont coils don't seem to burn out, I guess it follows that the thermal conduction of the tubing plus turbulent mixing of the flow keeps things in check. It would, however, be nice if someone had done an extensive set of tests and quantified how this all varies as pressure and flow vary.

Regards,

Ken



Edited 1 time(s). Last edit at 10/07/2022 06:28AM by frustrated.
Re: Drumless Boilers
October 05, 2022 01:52PM
Ken there are some very extensive test results in Jim Cranks original manuscripts of his book. Not the one that was printed. Also on the Besler generators when Jim worked there.

Rolly
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