Expanders

I forgot why I put this thread here, oops. Anyway here is another expander.



Edited 7 time(s). Last edit at 11/04/2009 08:29AM by sidrug.

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Hi Sidrug,

Here's mixed-bag for a link, Ive talked to this guy before, I forget his name, anyhow heres a link, Duane or something like that, seems pretty knowledgable, and Rolly's mention of the scroll-expander should come up in the link-

[www.redrok.com]


Jeremy

Hi Jeremy, thanks for the link. How about the seals in a scroll expander? That is the only thing keeping me on the fence with them, so far. Sliding surfaces should be slow and unloaded, ideally.

The Green steam engine is also mentioned in that page, and I like it because of the no fluid reaction force on the piston/cylinder, and it is very compact. Just not sure about the flex shaft integrity at high pressures and volumes. It's reciprocating so probably not the best for high revs. Also, a good bit of force has to be resolved via the shaft bearings, more so than some of the other geometries.



Edited 1 time(s). Last edit at 10/31/2009 08:48PM by sidrug.

Augggh!
My pet hate of all that is foul and horrible in steam development is the Green steam engine promoted by chezgreens on Youtube. Farcical claims "three factories in China" " More efficient than other engines" "500hp no problem" "The US army is testing it"
The plans are rubbish and even the developer has given up on the flexrod in the latest videos.
I'm finishing one off for a friend and I'm HATING it. O-rings for piston seals, lousy valve design, no lubrication for the cross heads (steel in alloy), the design of the seals at the bottom of the cylinders consists of soldering a brass olive in place and hand filling it ball shaped to be sealed by an oring forced over it. BLEECH!!


Sorry but this flogging tat to the general public and pretending it's the greatest really presses my buttons
You need to see odd ball steam engines? google to the Douglas Self website.
Cheers
Mark

Thanks! For both the insight on the Green Steam Engine and the Self site. There are a lot of similar geometries that use other things than the flex rod, such as a swash plate, I think. A person could also use a cam in place of the swash plate to get rid of some of the issue related to cyclic loading and to get more cycles/rev - in which case it might get similar characteristics to the CEM.



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Quasiturbine. This page explains a bit about detonation, why it is not good for crankshaft engines, what the advantages over deflagration are, and why a quasiturbine would be able to use it. Cam driven engines should also work, then.



Edited 2 time(s). Last edit at 11/03/2009 01:24AM by sidrug.

I looked at that site. It's just a lot of snake oil crap as far sa I can tell. The is nothing there on the thermodynamic cycle changes their ??turbine would do.

But they go into the disadvantage that piston speed at TDC imposes on slow detonation. Actually it is an advantage. It allows the pressure to build up and expand later on. It is during expansion where heat is converted to mechanical work. That tells me something is amiss.

Sorry. Using a lot of big words dosn't make them right.

Andy

Hi, I don't understand what is ment by "thermodynamic cycle changes that their turbine would do.



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Sidrug,

Perhaps you would edit your first post and let us know what information you are attempting to convey, or what question you are asking. If you are just showing all of the different expanders there are, it it ok, but SAY SO up top.

Best,
Scott Finegan

Hi Scott, I don't know, I forgot.

Hello Sidrug

Interesting list of expanders but rather than be negative about them let me ask what is wrong with the traditional crankshaft and piston?
Examine each of the designs you have posted and search within this forum for related discussions. I think most features have been discussed over the years. Some have obvious problems if used for steam.

Brian

crankshaft engines usually put load on the cylinder wall/piston sliding surface. Do you know what amount of friction this is in any example engine? Does it add much to the wear? They have a bit more complicated valve system than is possible to do with a rotary engine, I think. They are bigger and have less torque since there is less cycles per rev. They can go less fast than some rotary engines I think. You cannot choose so well how the volume should change over time as with a cam. I think it will be easier to make a rotary with less vibration.



Edited 4 time(s). Last edit at 11/04/2009 09:16AM by sidrug.

Hello Sidrug

In answer to your questions:

1) Yes crankshaft does apply load to piston and cylinder, but so does some of the cam engines you listed. Others use a cross-slide to displace the load, e.g. the scotch yoke is subjected to the forces of the crank and has to be supported to prevent this passing to the pistons.
2) Plenty engineering books will list equations for friction etc.
3) Friction = wear, so yes this load will equate to wear but the engine has to be designed for it. Long connecting rods reduce the load but increase the rotating mass. But if truck engines can last a million miles and my old LandRover is approaching 170,000 surely it can't be that big an issue.
4) Define rotary engine? My definition is vane and turbine types. I guess you may include those reciprocating piston and vane creations without a cranked shaft. If this is correct I would say the same amount of valving is required for comparible uniflow or cross-flow engines regardless of drive. I saw one engine on your list that had a rotary valve, again already tried on both IC and steam engines long ago.
5) Everything is limited by the maximum linear speed of the piston or vane blade. Therefore multiple piston cycles per revolution = slow output rpm with high torque, therefore transmission components have to be stronger to suit. Probable maximum speed for a STEAM engine is also set by the valve operation. For example where a four stroke engine can do 10k rpm a STEAM engine may only do 5k rpm.
6) Yes cam profile can create better volume control, but the amount of stroke is limited. Therefore to get enough displacement you require multiple pistons of short stroke. If you calculate the surface area of the components for a 7 piston engine, to a comparible displacement 4 cylinder, the heat loss should be greater for the 7 piston.

Beware some of your engines require expensive alloys and machining techniques to manufacture, one reason the crank engine still survives.


Now answer some of my questions.
1) What is your first name, I am little old fashioned that way.
2) What is your interest in steam?
3) Are you a student, engineer or enthusiast?
4) Where have all your links gone?

Cheers Brian

just use a search engine, the links are on the web.

I dont want to write more.

Sidrug

So I just wasted my time trying to answer your questions????

Brian,

You have to figure some things, first before you jump to that conclusion(wasted time).

Consider this-

A. this thread on Expanders is Sidrug's.

B. yesterday Scott F(site admin) snapped at sidrug, about leaving the very links that your asking about.

C. Although Jerry has been pretty cool with the new members Andy has not(atleast through there limited perception, ie: they have not been on the forum long enough to understand everyones personalitys).

D. this does not change the fact as older members, we tend to snap at each other without consequence (hopefully) in short these new members are not as thick skinned(sometime's you just gotta say "wtf"..)


I dont think its wrong for someone to post as much as they want to a thread they created, as long as there not all-over the board. Also, in that situation, posting many links to your own thread is a good way to archive data.

Anyhow thats just my 2 cents worth. Truly, its easier to have these type of discussions face to face, sometimes that is lost on the web...


Best


Jeremy

Hi, Brian, I realise it is not useful to discuss in too general terms (like "rotary engines" like I did. The reason was that the drawing I provided is not finished so some things must be assumed, such as valving, and a useful system for that can be extrapolated from some of the other other "rotary engines" I mentioned. The designs in my head are trying to adress perceived engine limitations, but the drawing or ability to describe them are not keeping up. I felt like we were going to talk past each other. I want: small, light, efficient, powerful, silent, simple, low friction, durable, multi fuel. I am not able to meet these as well with a crankshaft as with some other solutions, it seems to me. Look how tiny the big cyclone's cylinder block is. Maybe something can be made even smaller without sacrifice. Now, I want to reply to you.

Quote
Brian McMorran
Hello Sidrug

In answer to your questions:

1) Yes crankshaft does apply load to piston and cylinder, but so does some of the cam engines you listed. Others use a cross-slide to displace the load, e.g. the scotch yoke is subjected to the forces of the crank and has to be supported to prevent this passing to the pistons.

In my current ideas there is no scotch yokes, all forces are transferred from piston to cam via non reversing roller bearings. I also reduce the sliding friction between piston and cylinder as much as possible by providing a low friction guide. In the drawing this is one roller, the center one, which may or may not change angular direction, depending on direction of force on the piston. (I forgot to mirror the track for it).

3) Friction = wear, so yes this load will equate to wear but the engine has to be designed for it. Long connecting rods reduce the load but increase the rotating mass. But if truck engines can last a million miles and my old LandRover is approaching 170,000 surely it can't be that big an issue.

If this friction is responsible for adding mass to the engine, or for wearing it out, then it is an issue, to me.

4) Define rotary engine? My definition is vane and turbine types. I guess you may include those reciprocating piston and vane creations without a cranked shaft. If this is correct I would say the same amount of valving is required for comparible uniflow or cross-flow engines regardless of drive. I saw one engine on your list that had a rotary valve, again already tried on both IC and steam engines long ago.

I don't know how to define it so I'll refrain from using the term without qualification. You are right, crankshaft engines can also use rotary valves.

5) Everything is limited by the maximum linear speed of the piston or vane blade. Therefore multiple piston cycles per revolution = slow output rpm with high torque, therefore transmission components have to be stronger to suit.

All the transmission I have seen in cars are reduction. Having reduction in the cam shape saves parts. You will sooner or later meet the same torque requirement on the transmission line, even if you start at 20K rpm.

Probable maximum speed for a STEAM engine is also set by the valve operation. For example where a four stroke engine can do 10k rpm a STEAM engine may only do 5k rpm.

The rotary valves add no linearly accelerating parts. There still remains the issue of hole size. And the fact that large diameter rotary valve will open and close quicker (more square shaped admission) but may give less efficient sealing and more size.

6) Yes cam profile can create better volume control, but the amount of stroke is limited.

Some cam engine geometries will allow a longer stroke for the engine size than crankshaft engine, is my assessment.

Therefore to get enough displacement you require multiple pistons of short stroke. If you calculate the surface area of the components for a 7 piston engine, to a comparible displacement 4 cylinder, the heat loss should be greater for the 7 piston.

I want enough pistons to give smooth output, balanced mass and continuous torque. If possible, I will insulate the whole shebang, not the individual cylinders.

Beware some of your engines require expensive alloys and machining techniques to manufacture, one reason the crank engine still survives.

You'd have to be more specific, my cam engine ideas would benefit from strong, compact low friction roller bearings. Even good ceramic ones are not all that expensive.

Now answer some of my questions.
2) What is your interest in steam?
I want to make something, it needs a powerplant.
3) Are you a student, engineer or enthusiast?
sometimes the latter

Cheers Brian

My last idea may be even better than the previous, it decreases the speed of the seal surface (the seal around the piston rod, which would be necessary for a double acting cylinder), making the cylinders more gas-tight with less friction. This in order to reduce any eventual cross-contamination between cylinders containing different fluids, and easier lubrication requirements for the cam rollers and drive shaft bearings. It needs more thought before I can show it, if you want to see it.
.....

Jeremy, I don't wish to flood this forum with unwanted stuff. Nice to see that you thought the thread itself was not too intrusive.

Cheers. S

Sidrug,

I apologise for not being clear, nor did I intend to come across as snapping as Jeremy says I did. (My wife would say lecturing.)

I did not ask/expect you to remove any links. I found the links very interesting. General discussion is perfectly fine, it is your topic.

I was simply attempting to find out if there is a specific goal to this thread, because I was wondering if I have something to contribute (besides messing your topic up). I am sorry about that.


Scott

Jeremy,

Point taken, I was too quick to react to the first reply. If only I had waited for the full response above.

Sidrup

See better now where you are coming from. Compact and innovative good, but not sure of cam drive or rotary valves. Best thing is to build and prove the design as Harry did with the cyclone. On a personal level I liked the Saab wobble plate engine but the bevel gear reduction wasted some of the efficiency!

Good luck
Brian

ok Ihave something working but it is no steam plant yet. rather it is a biomass burner. If you look at luciastove on youtube, or worldstove.com, you will see the principle. The main ideas are: hot inert gases are pulled down through the fuel pyrolysing it. woodgas is then pulled out to the outer cylinder by venturi, mixed with air, then expelled through holes over the fuel, creating a lid of flames. These holes are made so that a swirl is created. fuel can be added at any time, and the woodgas is filtered through hot charcoal in the bottom. charcoal is left unburned due to lack of air but can be burned by adjusting the burner.

I can get very clean combustion it seems, with only very primitive tincan construction. turndown is great, it seems to sustain clean burn even on a very low setting. it seems possible to throttle the heat very fast by providing air to the hot charcoal. Gas can easily be extracted and burnt elsewhere or stored as a capacitor/power reservoir. Nataniele shows in one of his videos a 50kw pellet stove ca 5-8 liter outside volume I think, quite compact. Heat is recycled to the input air, which cools the metal parts, so there is only little benefit from insulation and no great requirement for advanced burner materials.

cheers to all steamers.

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File Name	File Size		Posted by	Date
cam dirve.jpg	13.5 KB	open | download	sidrug	11/02/2009	Read message