"Steam eater"

[F.Wissink]

Well, maybe I should elaborate a bit more, after my "intervention"/bump in the other thread: http://www.homemodelenginemachinist.com/f26/steam-vacuum-engine-anyone-built-one-19538/#post217342

What I am planning to do, is to build a "steam-to-vacuum" engine, with a working cycle that is similar to that of the well known "flame eater".

One would ask: Why?

Because I think that a design like that, could have some serious advantages over both the conventional steam engine, and the conventional flame eater.

On top of that, I'm planning to "designbuild" (so there will be no real "plans") an engine that can be built from hardware store materials, and/or waste materials, in order to enable "people on a budget" and with few sophisticated tools, to share in the fun of engineering.

In theory (all is theory, since i haven't built anything yet), I see the following operational advantages over "conventional" flame- and steam engines.

1. The boiler is unpressurized, so there is no danger of explosions, or the need to meet up with safety regulations whatsoever.

2. The operating temperature of the cylinder, is below 100 celsius, so even plasstcs could be used for piston(s) and/or cylinder(s).
(like PVC and epoxy)

3. A vacuum caused by steam, is "deeper" than a vacuum caused by air, and therefore probably more able to produce a considerable powerstroke. Compared to the conventional flame licker, that is. You might actually be able to drive something with it.

A Disadvantage could be:

1. While I think the stronger vacuüm, caused by condensing steam, might make the "steam eater" stronger than a conventional flame eater: I don't think it could ever beat a conventional steam engine in terms of power and efficiency.

A few real "Don't know"s are:

1. Would steam condense fast enough, to make the cycle work?

2. Would the process of forcing condense out of the cylinder cause too much resistance to keep the engine running?

So I'm yet to discover at least about these two last points.
Any advice would be welcome.

So, over now to the working cycle.
I'm not much of a computer type of person, so a few badly drawn schematics must do the job for now.



The theory is:

In figure A, the intake valve is open.
The piston is in its downstroke, sucking in steam, and maybe a little preheated air into the cylinder.

In figure B, the intake valve just closed at BDC, and the steam "collapses" into condense, creating a powerfull vacuüm, which draws the piston "upwards'.

In figure C, the piston approaches TDC, and the "exhaust" opens due to overpressure in the cylinder. The remaining steam and/or water are driven out of the cylinder. (back to A)

I could not get the drawing to properly scan as a whole, so I just cut the drawing in two pieces, taping them together. Off to a flimsy start!

In the larger picture on the right, is a schematic of the whole contraption.
The 'venturi" of the "carburettor-boiler" allows for air to be sucked in, in case of lagging steam production, while it allows a free "blow-off" as well, in case the engine can't keep up with the steam production.

I hope I hereby was able to create a better understanding of my plans.

And everything is out in the open.
If anyone feels the need to start with this project before I do: Just go ahead. If you want to share the schematics: Go ahead.

I'm a strong believer in open-source-everything.

Imagine the wheel still beïng the intellectual property of someone else..

 

[RLWP]

Once upon a time there was an inventor called James Watt. He studied the steam engines of the time and made a major breakthrough - he separated the condenser from the working cylinder. This vastly improved the efficiency of the steam engine by reducing the range of temperatures in the working cylinder

It appears you want to reverse his discovery

Richard

 

[F.Wissink]

Once upon a time there was an inventor called James Watt. He studied the steam engines of the time and made a major breakthrough - he separated the condenser from the working cylinder. This vastly improved the efficiency of the steam engine by reducing the range of temperatures in the working cylinder

It appears you want to reverse his discovery

Richard

If you had read my post properly, you would have seen that efficiency wasn't my main goal.

It was only meant to be more powerful than a flame eater, and to be easier to build than both flame eaters and conventional steam engines.

Not to supersede conventional steam engines.

So there's no need to act in a condescending manner.

And by the way: Some conventional steam engines do not have a condensor in the first place.

 

[Jasonb]

Look up "Newcomen Engine" which was a very early form of steam engine, it used a jet of water into the cylinder to cause the steam to condense.

http://en.wikipedia.org/wiki/Newcomen_steam_engine

J

 

[F.Wissink]

Look up "Newcomen Engine" which was a very early form of steam engine, it used a jet of water into the cylinder to cause the steam to condense.

J

Nooooo!!
Not again Newcomen!
Newcomens engine had no crankshaft and flywheel!
On top of that, it had an entirely, manually operated cycle.
Not an autonomous one!

 

[Jasonb]

If you bother to read the link I posted you will see that later versions had the valves automated it was only the early ones that were manual.

It would also be quite easy to take the vertical movement of the pump rod and convert that to rotary motion by simply adding a crank on a spindle with a flywheel at the other end just like any rotative beam engine.

 

[F.Wissink]

If you bother to read the link I posted you will see that later versions had the valves automated it was only the early ones that were manual.

Fair enough.
I didn't come that far until now..
My bad.

It would also be quite easy to take the vertical movement of the pump rod and convert that to rotary motion by simply adding a crank on a spindle with a flywheel at the other end just like any rotative beam engine.

Maybe..
I guess in a way, I'm doing that, be it more simplified.

About the water injection: You can scale down an engine, but you can't scale down physics.
In a small engine, the cylinder is probably narrow enough to provide sufficiënt "natural" cooling.

 

[F.Wissink]

Hmm, they were even close to doïng what I'm planning to do..
Oh well.
Still nice to give it another "modernized" try..

The main problem with the Newcomen design was that it was very expensive to operate. After the cylinder was cooled to create the vacuum, the cylinder walls were cold enough to condense some of the steam as it was admitted. This meant that a considerable amount of fuel was being used just to heat the cylinder back to the point where the steam would start to fill it again. As the heat losses were related to the surfaces, while useful work related to the volume, increases in the size of the engine increased efficiency. Newcomen engines became larger in time. However, efficiency did not matter very much within the context of a colliery, where coal was freely available.
Newcomen's engine was only replaced when James Watt improved it in 1769 to avoid this problem (Watt had been asked to repair a model of a Newcomen engine by Glasgow University. A model exaggerated the scale problem of the Newcomen engine). In the Watt steam engine, condensation took place in a separate container, attached to the steam cylinder via a pipe. When a valve on the pipe was opened, the vacuum in the condenser would, in turn, evacuate that part of the cylinder below the piston. This eliminated the cooling of the main cylinder, and dramatically reduced fuel use. It also enabled the development of a double-acting cylinder, with upwards and downwards power strokes more suited to transmitting power to a wheel.
Watt's design, introduced in 1769, did not eliminate Newcomen engines immediately. Watt's vigorous defence of his patents resulted in the desire to avoid royalty payments as far as possible.
The expiry of the patents led to a rush to install Watt engines in the 1790s, and Newcomen engines were eclipsed, even in collieries.

 

[RLWP]

If you had read my post properly, you would have seen that efficiency wasn't my main goal.

It was only meant to be more powerful than a flame eater, and to be easier to build than both flame eaters and conventional steam engines.

Not to supersede conventional steam engines.

So there's no need to act in a condescending manner.

And by the way: Some conventional steam engines do not have a condensor in the first place.

Yes, but...

You are specifically making a condensing engine, that where you are starting from. And if you want to make such an engine you need to be aware of what that means i.e. much, much less power

And if you want further confirmation, in a rash rush of blood to the head, I set to to make a simple Newcomen engine using a copper tube and a valve, and it didn't work. It was pretty hard to get a sensible vacuum from the steam.

Before you chip in about cranks, I started by experimenting with just a cylinder and piston, parts common to your plan.

So... By all means try this out, but do be aware that physical laws will be working strongly against you

Richard

My personal fantasy engine of the moment is a flash steam motor with the water injected directly into a red hot cylinder...

MORE: Yes, I see what you say about sounding condescending - I apologise

 

[F.Wissink]

Yes, but...

You are specifically making a condensing engine, that where you are starting from. And if you want to make such an engine you need to be aware of what that means i.e. much, much less power

A flame eater doesn't have a lot of power, but it still runs.
If my contraption wil run, I'll be satisfied.
If it could drive something, that would be a bonus.

And if you want further confirmation, in a rash rush of blood to the head, I set to to make a simple Newcomen engine using a copper tube and a valve, and it didn't work. It was pretty hard to get a sensible vacuum from the steam.

What are you talking about?

[ame]http://www.youtube.com/watch?v=Uy-SN5j1ogk[/ame]

Someone else's did, and pretty powerful, I must say..

[ame]http://www.youtube.com/watch?v=5z4VkqP84D0[/ame]

So let there be no discussion about the possibility to scale down a Newcomen engine: It is.

Before you chip in about cranks, I started by experimenting with just a cylinder and piston, parts common to your plan.

That's a sensible idea, although you should make sure the line from the boiler to your engine is warm. Otherwise the steam wil condense before it even reaches the cylinder.
This means it will take at least some initial cranking in order to "steam-heat" the line between boiler and engine, before it will run..

So... By all means try this out, but do be aware that physical laws will be working strongly against you

If they do, they will probably point out a leak or something.
A serious risk, for someone with simple tools like me.

My personal fantasy engine of the moment is a flash steam motor with the water injected directly into a red hot cylinder...

Now there's some physics against you.
Water does not flash that fast, and oil doesn't respond well to red hot surfaces.
Nor do most pistons, by the way.

 

[RLWP]

Could we briefly go back to this bit please?:

{snip}

Any advice would be welcome.

{snip}

I have given you the benefit of my experience, together with some historical evidence to support my failure. I'm not trying to put you off trying something new, I'm letting you know that you may be in for a disappointing experience

Richard

 

[F.Wissink]

Could we briefly go back to this bit please?:



I have given you the benefit of my experience, together with some historical evidence to support my failure. I'm not trying to put you off trying something new, I'm letting you know that you may be in for a disappointing experience

Richard

Disappointment always is a possibility when you try something new and/or out of the ordinary.

And advice would still be welcome, just like the experiences you had.
But if there's empirical evidence that the problems you pointed out are possible to overcome, I might still give it a try.

Maybe I should talk a little less from here, and start doing some shopping.

Ps: It will by all means be an ugly machine, since aesthetics by my test engine will be less important than the working principle.

 

[RLWP]

Ugly is good. My Stirling engine made from scraps of wood, lead sheet and cat food tins was no looker, but was a lot of fun

If you think about it, the temperature difference between a flame gulper and a steam gulper are quite large. The steam gulper starts at 100C (steam at atmospheric pressure) and ends at the cylinder temperature, which will increase over time (perhaps 30, 40C?). The flame gulper starts an awful lot higher than that. So, comparing to an idealised engine using the Carnot cycle, you have much less energy to play with

Richard

 

[F.Wissink]

If you think about it, the temperature difference between a flame gulper and a steam gulper are quite large. The steam gulper starts at 100C (steam at atmospheric pressure) and ends at the cylinder temperature, which will increase over time (perhaps 30, 40C?). The flame gulper starts an awful lot higher than that. So, comparing to an idealised engine using the Carnot cycle, you have much less energy to play with

Richard

You might have a point there.
On the other hand: Steam collapses to about 1:1600th of its volume when condensing..
Does air do that, without changing from gas to fluid?
In other words: You might throw a lot of energy into the cylinder of a flame eater, but how much kinetic energy do you get in exchange?

If a flame eater is "done", the overpressure valve opens, and it blows of.. This can be long before the end of the powerstroke.
How much heat was left in that excess air, thrown out of the window?

I still have to experiment, but it seems like there are more factors to consider than temperature differences.
And the cylinder can be cooled as well.

 

[RLWP]

This is the fundamental issue with this type of engine. If you work on a hot gas cycle, air wins. It starts at a far higher temperature when it is drawn into the cylinder. If you really want to make it hot you would burn it in the cylinder, and then you would have an internal combustion engine

In an atmospheric pressure engine, water only starts to win if you condense it, but that introduces a whole new set of problems. You want to start with steam as hot as possible, but you are unlikely to exceed 100C, probably less. And you want the cylinder to be cold enough to condense the steam rapidly, and you need to hold it at that temperature, but you don't want to condense any steam until you have shut the valve. This is difficult, and is why this kind of engine used spray condensers. On top of that, you don't want to trap water in the cylinder because it is incompressible and may stop the piston at the end of the stroke

Not an easy engine to build. Not impossible, just not easy

Of course, if it all went wrong, you could convert it into a flame gulper*

Richard

*My flame gulper doesn't run

 

[F.Wissink]

I think our posts crossed..

but you don't want to condense any steam until you have shut the valve.

That doesn't matter, since the engine can suck in steam freely.
If some of it condenses before the piston reaches BDC, so be it.

On top of that, you don't want to trap water in the cylinder because it is incompressible and may stop the piston at the end of the stroke

i already thought about that.

A checkvalve in the head, like all flame gulpers already have, should be sufficiënt to drive out excess water. (see my bad drawings..)
I only should make sure that this valve is larger than usual, and at the absolute lowest point of the cylinder.
(So a lying or inverted cylinder is probably the best way to reach that goal..)

Not an easy engine to build. Not impossible, just not easy

I'm getting really curious now, hahaha!

Of course, if it all went wrong, you could convert it into a flame gulper*

Richard

*My flame gulper doesn't run

If you know a type of plastic that is able to digest flames..
Btw: Does your flame gulper has a check valve in the head to blow off?

 

[solarenergyadventures]

Hi F.Wissink. I think sometimes it gets forgotten that this is a HOBBY engaged in for fun, self education, and a way to express our artistic creativity or whatever. If it doesn't work, so what! I personally have learned far more from my failed attempts than I ever did from my successes.
Anyway, there is nothing as far as I know from a physics/thermodynamics standpoint that would keep your engine from operating. But there are some things to keep in mind:
1. Since you are creating a phase change from steam to liquid, and the latent heat of vaporization of water is very high, ( about 976 btu/lb IIRC) your cylinder is going to need to remove far more heat than it would if it was just cooling down air like in a flame licker. In order to run, you will need to remove this heat very quickly. This could pose a problem with keeping the steam from condensing before the intake valve closes.
2. You will have the potential for hydraulic locking when the piston comes up to tdc with condensed water in the cylinder. As mentioned earlier, the burp valve being at the lowest part of the cylinder would probably suffice.
3. Maybe you could incorporate an external condensor like Watt did.

Heck, if I had an operational flame licker, I would try it with steam just to see what happens! Good Luck and let us know how it goes, and dont forget pics. We Love PICS!
Cheers Everyone!
Chris

 

[F.Wissink]

1. Since you are creating a phase change from steam to liquid, and the latent heat of vaporization of water is very high, ( about 976 btu/lb IIRC) your cylinder is going to need to remove far more heat than it would if it was just cooling down air like in a flame licker.

That's very useful. Thanks.

In order to run, you will need to remove this heat very quickly. This could pose a problem with keeping the steam from condensing before the intake valve closes.

Well, I don't consider condensing before the intake valve shuts to be a real problem.
It won't fill up the entire cylinder in the brief moment of the valve being open.. Maybe it will make the engine "burp" a little earlier.

3. Maybe you could incorporate an external condensor like Watt did.

I might just do that, if the engine does not work in the simple layout I have in mind. Thanks, I'll keep that one in my neurological databank.

Heck, if I had an operational flame licker, I would try it with steam just to see what happens!

I wish I had one.

Good Luck and let us know how it goes, and dont forget pics. We Love PICS!
Cheers Everyone!
Chris

Well, I'll try to make some.. But don't expect long lines of pictures.
And I'll probably only present them when I'm finished.