Williams ws. Rankin

Hi Andy:

The short answer is that in my opinion it is just a chart. I respect the work of Professor Stumpf all to hell, but it isn't like this chart got handed down on a mount engraved in stone tablets or passed along by a burning bush. Fleischmann and Ponns appear to have had a pretty good reputation but some basic testing errors led them to assume cold fusion, and a number of reputable institutions and researchers initially confirmed their results. Not a slam on anyone but a good cautionary tale about the pitfalls of trusting authorities blindly and of obtaining sufficient independant verification. Probably also a good warning that when you want something desperately enough you may see patterns in the numbers that aren't there no matter how careful and responsible you are.

As a case in point of potential pitfalls in established wisdom, consider US patent # 4621592 issued to Vapor Corporation. Conventional wisdom says that a boiler with water and combustion gasses in counterflow will be most efficient, but this patent argues otherwise and seems to have some pretty fair evidence to back it up. The core of the patent is that the time delay between a thermodynamic event occuring and it manifesting itself can be significant enough to distort the expected output. As an aside, I'd recommend everyone read this patent as it would seem to be critical if true and seems to explain the nice performance of the SES boiler.

I also note the Stumpf chart doesn't actually correlate the work generated or absorbed at the crankshaft on a degree by degree basis with the changes in temperature and pressure. Even if the chart IS true, the point may well be moot if the power absorbed to achieve these conditions is unexpectedly high. I'm not saying this is true, but it would seem as easy to argue this position based on the evidence available. Perhaps the time delays noted in the above patent are also evident in recompression and skew the numbers ... I'm not claiming that either but tossing it out as another 'fer instance'.

Anyhow, in summary, my position is that the chart is interesting but without a lot more verification I'm not sure it really means anything. Perhaps when I get a bit more situated I can take the time to verify this to my own satisfaction, or perhaps someone else out there will seek to do the experiment.

Regards,

Ken



Edited 1 time(s). Last edit at 07/02/2007 09:58PM by frustrated.

Hi Blake:

Actually, the question you post is pretty much the reason to have uniflow. In a simple, traditional slide valve counterflow engine the cold exhaust steam passes through the port and cools it off, robbing the incoming steam of heat on the next stroke. In a uniflow the cool exhaust goes out the port at the end of stroke so it doesn't cool the port where steam is admitted. At the same time, with enough compression the portion of the cool exhaust steam remaining in the cylinder is reheated as it is compressed in the cylinder. This heating keeps the head reasonably hot, the exhaust reasonably cool and cylinder temperature varies along the piston travel in proportion...more or less, anyhow. While Andy and I may not agree on the precise amount of reheating I think it is fair to say we both agree that in simple terms this is what happens.

I'm not sure the Forum is exactly the place to get into involved discussions of this nature as there are plenty of books out there that can describe this in far greater detail with appropriate charts and images. I'm sure the folks in the forum would be glad to recommend suitable references which can usually be found in either used book stores or through E-bay (got the same books myself through both sources).

Regards,

Ken

Hi Ken

Not sure what your referance to the SES boiler has to do with that patent. If as you say the patent goes against counterflow principals. The S.E.E. boiler is basicly a counter flow boiler but with a protected superheater. Each section is counterflow. Now where is that patent search site?

That patent sounds interesting. There are various time dependent process. The IAPWS steam and water property formulations talk about the formula being good for super heated liquid state and sub cooled gas state. A sub cooled gas is created through expansion to below the point it should be a gas. It's heat content should make it a liquid. But it taks time for it to condense and form water droplets. A super heated liquid is one that contains enough heat to be a gas but has not yet vaporized. Thoes states are not stable and vary quickly change. The IAPWS papers refer to them as matastable states. The time those states exist are in mili or micro seconds though. Heat flow is certanly time dependent. There is always lag in messuring temperature.

Andy

I have a DOE report from 1981 with charts that actually says that a 2-stage counterflow is better. However, they also said that not much work was done since 1940's and that they were not experienced with either.

I told Tom I have an idea for a uniflow that reduces the wear on the rings by having a sliding door as part of the cylinder wall vs. holes or slots in the bottom. I need to know how much of an opening I need for the slot size. an anyone out there estimate the size for me? The piston is a VW 1600 CC (3.375 D) and the stroke is 2.00 inches. The door will slide open starting near the bottom of travel of the piston and start to close as the piston heads back up. I need to know how much opening and duration.

Any help is appreciated.

Hi,,,Is the surface of the ''door'' flush w/the cyl wall,, OR like a sleeve engine,,,AND will the rings hop over the gap,,,This will help me/us visualize the details,,,Cheers Ben

The door will be flush with the cylinder wall. I plan to have them bored together to minimize the gap as much as possible. When the rings move over the door it will be as closed as possible to prevent the kind of damage as with others that just have openings. There may be some slight gap, but very minimal.

The formula Port area = Piston area times piston speed divided by 10,000
I would go three times this for exhaust.

Hi Andy:

For the patent search site I use www.google.com/patents and to the right of the search bar I toggle the 'Advanced Patent Search' hyperlink. You can either read the patent online or download as a .pdf file (my usual preference).

I don't consider the SES to be a pure counterflow because of the shielded superheater, the basic elements of the flow path are reminiscent of the Vapor Corp patent. Any way you look at it, a large portion of the SES heat exchange surface has something flowing though it that already passed through a hotter portion of the combustion gasses. Vapor Corp did run the inner coil flow and the superheater flow with the gas flow rather than counter, so the SES would be maybe half way between the pure counterflow boiler and the Vapor Corp patent boiler.

Anyhow, the patent is well worth a read, dry and dull as it is. I was already looking at a helical inflow forced recirculation boiler with a central combustor, so this is only a minimal change in design.

Regards,

Ken

Hi Ken

The S.E.S. boiler I know has a preheater section, super-heater, generator section.

The preheater is the longest section and it is counter flow farthest from the fire. The generator section is next to the fire. It has 2 or 3 coils and is counter flow. The super heater is just a copple of coils between the preheater and generator section. There are a lot of bolers that have super heater section out of the radiant heat areas. Each section of the SES is counter flow. The generator section has wide spacing between the tubes allowing radiant heat to pass through. The radiant energy could maintain the gas temperature. So the gas temperature may not of droped mesurably when reaching the super heater. The super heater is a small percentage of the total tube length in the boiler. So I can't agree that "a large portion of the SES heat exchange surface has something flowing though it that already passed through a hotter portion of the combustion gases". Maybe we are not talking about the same design?

Actually the secions of the S.E.S. are counter cross flow heat exchangers.

Rolly,

Thanks. I greatly appreciate it.

George

Rolly,

Is Piston Speed the RPM of the engine? Or is it the velocity of the piston rising and falling?

If the engine is 1800 RPM then do I calculate how fast it goes up and down?

George

Oh yeah...is the Piston area just the surface area, or the Bore x Stroke?

Piston area is surface area.
Piston speed is up and down velocity.

You really need to calculate totals volume of inlet steam after expansion and how fast you want it to leave as in a uniflow with no pressure behind it or if its dumping into a condenser and at what vacuum pressure. Then calculate the area of passage for that in the time you need to do it.

This is more then I can do with out a lot of books in front of me, and I don’t want to get into it.

Piston Area is surface area = pi * Bore^2 / 4

or, A = Pi * R^2 where R = Bore / 2

A = pi * R^2

R = Bore/2

R^2 = (Bore/2)^2 = Bore^2/2^2 = Bore^2/4

A = Pi * Bore^2/4

Hi GR,

Is your piston from one of the later water-cooled VWs? Bore on the old aircooled 1600 cylinders/pistons is 3.366" (85.5mm). There are larger pistons/cylinders for the aircooled 1600 blocks too, upping displacement to 1700, 1800, etc.. Actual displacement in these engines is a bit different from the rounded-off "nominal" displacement. I'm designing around the aircooled 1600 cylinders myself, fins removed & jugs insulated of course.

There is peak and average piston speed. Average is usually used for port sizing, etc, stroke in feet x 2 x rpm = piston speed in feet per minute.

Piston area is cross-section area of piston bore. 8.898 sq in for 3.366" bore, 8.946 sq in for 3.375" bore. Multiply this by steam psi, and there's your pounds of thrust on the piston, of course.

If you're using VW cylinders, you might consider TotalSeal gapless rings. That is my plan. They are available off the shelf (totalseal.com) in VW cylinder sizes, also for lots of other engines/bores. Excellent sealing, better than standard rings, but I don't know if anyone has tried them with steam yet, so their durability under steam is unknown. They need oil, though. Oilless steam cylinders might work, but are still considered experimental, and many attempts at oilless steam cylinders have failed. Conditions in superheated steam cylinders are severe. Personally I am planning on oil for now, until some oilless superheated steam engines achieve well-documented long service life under load, and until the specific parts/materials which last are easily available. Tests are one thing, extended practical service is another.

Peter

If I use 1800 RPM = 30 RPS and the stroke is 2 inches or 4 inches per second I get 0.003576??? If I use 30 RPS I get 0.02682??? If I use 1800 RPM I get 1.60 ???

Now I am more confused than I normally am

George
To be correct on the piston speed you need to know the connecting rod length, the piston travels at different speeds, Feet per second depending where it is in the stroke.

Another thing to consider is the exhaust port area can affect the recompression pressure as does the clearance volume.

Like Rolly said you need the conecting rod length and stroke to calculate peak piston speed.

If you can find a Mark's Engineering Handbook, it has all the formulas. An older edition may have how to calculate the port size.

The formula that relate torque to piston force basicly give you piston speed.

Because of the conservation of energy law we have piston work must equal shaft work. Mechanical energy, work must be the same for the piston and shaft. Disregarding frictional losses.

Piston work = piston_force * piston_movement

Shaft work = torque * rotational_distance.

torque = piston_force * piston_movement / rotational_distance

Evaluating the limit as piston_movement aproches 0 you wind up with the torque transfer function. The torque transfer function is the ratio of piston travle to crank rotation.

Andy

If I have an existing design using a counterflow and use the opening area from the exhaust port, can I simply use that area for the new uniflow port? Seems like I should be able to.

GR, Yes, if piston speed is the same. 2" stroke x 1800 rpm = 600 fpm average piston speed, a good figure for steam engines, right in the sweet spot for many designs. Feet per minute is the usual figure, not per second. Makes comparisons with previous designs easier when you get into the engineering books. The closer you copy the parameters from a successful workhorse engine (same steam pressure, temp, valve timing, port sizes, conrod/stroke length ratio, etc), the better the odds for success. Professional IC engineers do this all the time for new engine designs.

Kent's Mechanical Engineer's Handbook, 11th Edition, 1936, chapter 7 is a good reference on the basics.

Best of luck with your project!

Peter

HI Guys all the Williams files are in good shape and vat means every pees of paper vay made a mark on. Is in the files. The patens are all there and larks casting and parts. I havent bin posting much as all my on line time goes searching for hi temp stuff for the second generation Williams engine to run 1500 and 1500 we are wicking on on a wetand a dry engine

Howard,

We are duplicating each other. I have already done that research and come up with a viable ( and cheap) experiment to try for dry lubrication. It's a special rings, cylinder liner and goop to lubricate it with.

Not giving away much on a public forum. e-mail me.

Best Regards, ---------- Bill G.

I am using a Reliable Engine V-4 that can either be used as a simplex counterflow or add the compound piston and use it that way for up to 100 HP. I figure that way, when I am ready for the larger 10 Meter system I can add the upper pistons and get the power I need.

I checked the drawings I have and calculated 0.38 inch for the port opening to the cylinder. That is bidirectional for either inlet or exhaust.

Now I'll check to see if that matches your number.

Thanks.

George

Peter,

Another problem is how much and when to open the exhaust port? I have read that you want the bottom 5% of the piston travel. I come up with an opening area of .54 inches. If I use a 1 inch wide slide that means I have to open .53 inches out of 2 inch stroke. That seems like a lot to me. If I only open 0.05 inches from the bottom, that opening would exceed the area of the cylinder.

Any thoughts?

I discovered something interesting, but it may just be me as I am naive at this steam thing so far: the Reliable engine inlet port to the cylinder is smaller than the calculation shows. However, the inlet from the boiler to the slide valve is the right size. Was this common? It has a 13/16 inch hole for the inlet to the slide valve which equals 0.518 area. The inlet to the cylinder from the slide valve is 0.5 by .875 oval and only has 0.3835 area.

Bill,

What is wrong with sharing information? All I see in here is people talking about old steam engine designs.

It seems to me that if we are a club, we should all be working toward the same ends: the promotion of Steam.

I have seen very little discussion on NEW steam engines vs. just patching up old ones or little improvements of what is already out there.

Why doesn't the Club have a joint project to develop an new engine from all the improvements we have collected?

If you really want a modern high output steam engine you have to do the engineering.
If you figure your feet per min travel of the piston, you need to fill the volume in split seconds. You need mass and volume in the steam pipe behind the port. It is stopping and starting with every valve movement.

Ralph Rasmussen was a good engineer but his V four was not one of his best jobs. Short stroke, large bore, high speed engines have a lot of blow by. Almost impossible to stop.

Double acting engines on the other hand still have the blow by but its internal to the cylinder and the piston rod packing pretty much keeps the recovery clean and in the condensate.

A friend of mine ran a V four in a small SV pickup truck but scraped it in a year and went with a 20 HP Stanley engine. Nice running truck now.
See attachment

Rolly,

My need is not start and stop or driving a car. I am using it for a constant 1800 RPM to turn a generator. I respect your viewpoint and I am all ears as I don't know as much yet as the rest of you. However, my need is different.

Stopping won't be a problem as I want it to run as much as possible continuously. If I could siphon some of that reflected light from the Moon things would be great.

Efficiency is not a problem since I have unlimited sunlight as long as it is not overcast. When that occurs it won't matter much either.

My efficiency problem is getting as much HP as possible to drive as large of a generator as possible. The larger means more power to sell for less content and cost.

Theoretically I should get 7 kWh from a 10-foot dish. After inefficiencies I am shooting for a >20% Steam engine so I am hoping for at least 2 kWh of power. That would be enough for a demo unit.

All files from this thread

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ThrottlingTurnDown.pdf	58.1 KB	open | download	Andy	11/22/2005	Read message
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P1010001aa.JPG	113.5 KB	open | download	Rolly	03/09/2006	Read message
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