Welcome! Log In Create A New Profile Recent Messages

Advanced

New rotary expander with only two moving parts.

Posted by Rolly 
New rotary expander with only two moving parts.
September 03, 2015 02:04PM
There are people still coming up with new ideas for steam power.

New rotary expander with only two moving parts.

[www.youtube.com]


Mechanology's TIVM Expander Explained

Rolly
Re: New rotary expander with only two moving parts.
September 03, 2015 11:22PM
A little surfing reveals the fact that Mechanology's intellectual property was offered for sale three months before the u-tube posting.

[www.bizjournals.com]

The following link is a description of the effort to use the machine for hydrogen fuel cell applications.

[www1.eere.energy.gov]

IMHO, the "hydrogen economy" thing was a scam start to finish. Still, an interesting machine though it seems to have had sealing and lubrication issues.


Kerry
Re: New rotary expander with only two moving parts.
September 04, 2015 03:35AM
Yes Kerry the company no longer exist.
They could not get enough business in the heat recovery market as fuel cost dropped off.

Steve Chomyszak is now a Professor of mechanical engineering at Wentworth Institute
He gave our Model Engineering club a talk on this unique expander. Great guy

Rolly
Re: New rotary expander with only two moving parts.
September 04, 2015 12:12PM
Rolly,
When you have a few hours to spend, go to "Museum of Retro Technology" then to "Power Generation" then to "Rotary Engines". Huge list that goes back to something like 1775 or so. Absolutely fascinating read. Thanks, but I'll stick with Felix and his successful engine, it works.

Quite true, the market for waste heat engines doesn't exist large enough to support even a backyard hobby company. Something a few we know have yet to discover.
Jim
Re: New rotary expander with only two moving parts.
September 05, 2015 08:39AM
The issue with nearly all non piston designs is sealing. A round piston in a round bore can be made to seal fairly well up to high temperatures and pressures with common materials and primitive machinery. Both were available over 200 years ago. As the extensive engineering on Wankel engines proves, it's tough to seal rotaries even with modern materials and machinery.

Lohring Miller
Re: New rotary expander with only two moving parts.
September 05, 2015 12:45PM
Hi Lohring,
Quite true, with basic sealing, cooling, warping of the rotors and the subsequent changes in running clearances with heat, rotor cooling and seal lubrication condemning these rotary engines to the scrap heap. NSU, Curtis-Wright, Mercedes, GM, and quite a few others and finally Mazda spending millions on overcoming these problems with the Wankel design, which eventually they successfully accomplished.

After owning an RX-3 coupe and giving it the full Racing Beat treatment, I must confess an admiration to what Mazda accomplished and fortunately they continue to work with the Wankel engine. Winning the 92 Le Mans race outright was a big shot in the arm for them. Blowing off 911 Porsches with mine was great fun. Of the many designs, the Wankel was the only successful rotary to reach the market and succeed.

What is fascinating is the number of otherwise intelligent people who constantly reinvent some ancient rotary engine design and actually find some initial funding. As if the basic fact that some rotary is going to be superior to the piston and crankshaft and actually will be better, it won't. The Wankel does offer some advantages that Ken and I detail in our White Paper. Whatever, it continues to fascinate.
Jim



Edited 1 time(s). Last edit at 09/08/2015 11:49AM by Jim Crank.
Re: New rotary expander with only two moving parts.
September 08, 2015 09:00PM
Hi,

My rotary only had two moving parts too. I have to admit I like the inventiveness of their mechanism. It is cool. Some sealing for it might be possible, but then it would need oil.

Best,

Bill G.
Re: New rotary expander with only two moving parts.
September 21, 2015 08:09AM
Thanks Rolly, this is an interesting device. High pressure usage would seem a challenge due to leakage I agree.

There is another thing I wonder about: Heat transfer in the expansion chamber walls.
We know that smaller chambers increase heat transfer area per volume, and it is hard to avoid a resultant increase in exergy destruction.
This thing has as many expansion chambers as there are vanes on the main rotor, so accordingly they are very small when there is lots of vanes, as there seem to be in the examples. But their power stroke is about (number of main rotor vanes)/2 times shorter in time than the one of a crankshaft mechanism.
So how can that balance out in terms of exergy destruction by heat transfer to the chamber walls, for a cylinder and crankshaft engine versus a mechanology engine?

In contrast to a crankshaft machine, each expansion chamber is cycled as many times as there are secondary rotors.

It doesn't seem to lend itself well to being a variable volume ratio machine, like the scroll also doesn't?
Re: New rotary expander with only two moving parts.
September 22, 2015 08:34AM
I personally prefer the scroll expander with only one moving part.
If I had the money I would have one built with the same volume of the 30 hp of Stanley engine machined from Invar-36 with edge seals just to see what it could do.

The rotary expander with the two intersecting vanes was built for low pressure wet steam for heat recover. The intersecting vane is a 600 degree plastic. The finished cut is done with the vane it intersecting with. They have run it for over 10,000 hours with no problems.

Rolly
Re: New rotary expander with only two moving parts.
September 24, 2015 09:51AM
Rolly, I think the scrolls have some very interesting properties, just to think that for each part of its expansion, the steam is kept in a chamber where only steam of similar temperature has been before (like in a turbine). On the other hand, I should be curious to know whether the heat transfer of superheated steam in a smallish cylinder really creates any significant loss once one gets above say 1000 rpm.
What I hear from piston compressor people is that water jackets don't make a difference, the compression is almost indistinguishable from isentropic (adiabatic) either way.

A scroll might lend itself somewhat to regeneration, by running feedwater inward through the stator spiral and sidewall. Maybe through the rotor as well. But how could a machine with such channels be fabricated?

Edit: How can you make a scroll with only one moving part? It needs an alignment mechanism, and it has a crank. I count at least three?



Edited 1 time(s). Last edit at 09/24/2015 10:18AM by sidrug.
Re: New rotary expander with only two moving parts.
September 25, 2015 03:05PM
This puts me in mind of Stanley's claim that there were only 15 moving parts in their engine and 37 moving parts in the whole car. Apparently, the balls in bearings, piston rings, packing, rod and valve packing and seals don't count. Rings, packing and seals don't move much, but they do move and this movement contributes to wear, maintenance and repair.

I grew up with oil sealed and lubricated rotary piston vacuum pumps. They are durable, easy to manufacture low maintenance machines. They have fallen out of favor in modern applications because they contaminate the vacuum space with oil that back streams out of the pump. They have often been replaced with scroll pumps in applications that demand freedom from oil contamination. Scroll pumps became practical due to CNC manufacturing. Unfortunately, the scroll pumps are not durable or low maintenance or unlubricated.

The tip seal is of some Teflon like substance that wears away with every rotation. There has to be some mechanism to force the tip seal against the opposing scroll- foam rubber in the case of vacuum pumps. The tip seals do not contribute oil contamination, but they do generate a lot of dust in their rather short life time. You don't get much notice of impending tip seal failure. If tip seal replacement was delayed a little too long, you now need to replace the scrolls- $$$. The dust generated by the tip seals is manageable in vacuum pump service as the dust is discharged to atmosphere and is relatively easy to catch with filters. I could see the dust being a real problem in steam expander service where it would gum up and the working fluid might be recycled to the boiler.

The theory is that it is easy to replace the tip seals and not necessary to replace the bearings very often. I have not found this to be the case. Invariably, when the tip seals need replacement, the bearings are on the way out due to contamination by the worked fluid. If you wait a little too long to replace bearings and shaft seals you now have to replace the crank and bearing housings which are integral with the machine housing and scrolls-$$$. Due to close tolerances required it is necessary to have an oven to heat components before pressing apart and back together.

The simplest scroll pump has two main bearings, two eccentric bearings and four orbital bearings in what Sidrug aptly calls the alignment mechanism. Due to close tolerances required, these are roller or ball bearings. In early scroll vacuum pumps (and many current ones) these bearings were exposed to the pumped fluid. Due to purity requirements these bearings are "sealed" and packed with some exotic lubricant that is non contaminating, but generally a poor lubricant. Moisture from pumped air or corrosives from pumped process fluids quickly finds its way past the seals and destroys the bearings. If you have good shaft seals (and are willing to live with more seals than would otherwise be necessary) it is possible to move the main bearings out of the working fluid but I don't see how this would be possible with the eccentric and orbital bearings.

For two employers each using dozens of machines I tried to train otherwise skilled mechanics and provide tooling to do this work in house. In both cases, I had to admit failure to my supervisor and revert to replacing the machines on an exchange basis with machines rebuilt by the manufacturers. I have found that even machines rebuilt by the manufacturer have short life spans compared to a new machine. In many cases, it is best to simply throw the machine away and buy a new one.

I often advise that I do not have much experience with steam. I do have experience with pumps and compressors of all types and expanders working fluids other than steam. Countless expanders are being used commercially. They must be reliable and cost effective. They are almost always turbines, occasionally piston engines in special applications. For a sanity check, go the venerable Douglas Self Site and spend some time studying rotary steam engines. You will find an unbroken string of failures going back centuries. In my humble opinion, Wankel, screw, and scroll expanders belong in the same category.

Kerry
Re: New rotary expander with only two moving parts.
September 25, 2015 06:25PM
Kerry
I have to disagree with you to some extent.
10 to 15 years ago you would be more correct then today.
With the advancement of CNC machining the scroll compressor has taken over most of the market share in all areas.
There are thousands of patterns on improvements to every area of the systems from seals to bearings and housings.
The earliest patterns I have found go back to 1863. Today there are thousands of them.
In the next 50 to 100 years we will need heat recovery systems on the low end of turbine steam generators. No one is building large-scale recovery systems now do to the market cost. This will change. I think the scroll expander will be in good shape for this market, as it will require a displacement expander, wet steam. It will have to be built in much larger sizes then now available. Time will tell.
Money will drive the advancement.

I was setting up missiles in the late fifties for down range shots when almost every other one didn’t make it off the pad. We had a Steam turbines in the Vanguard Missile no computer.

Rolly
Re: New rotary expander with only two moving parts.
September 25, 2015 09:56PM
Rolly,

I have a great deal of respect for your experiences and opinions, but I think rotary (non turbine) steam engines will never come to pass.

For more than 200 years, lots of people have spent tons of time and money on rotary steam engines and failed miserably. I think there are fundamental problems here that will not be resolved with new materials or machining techniques.

Scroll and screw compressors are as common as dirt. These days, it would have to be a VERY unusual application before you considered anything else.

Rotary expanders (other than turbines) that have proven themselves in service seem to be nonexistent. And given the scaling issues, the only feasible bottoming engine for a steam turbine is a steam turbine with another and larger set of blades.

I believe the problem with rotary expanders is lubrication and sealing. My employer uses lots of scroll and screw compressors. They are wet machines using oil to seal and lubricate. It is an easy thing to get seal/lubricating fluid out of the discharge gas. Three coalescers will do the trick even in the most demanding service.

The velocity of the gas leaving the surface of the coalescer is strictly limited. In the case of a compressor, the relatively high pressure of the discharge gas works for you by making the gas more dense, occupying a smaller volume. This makes the coalescer smaller and less expensive.

The reverse is true of an expander. The velocity issue makes coalescers scale up with reducing pressure. And separating oil from water or wet steam is a whole 'nother problem.

I suppose you might get around this if you had an expander that was lubricated and sealed with water, but no one seems to have accomplished this. It certainly doesn’t seem feasible with an engine made of the materials ordinary mortals can afford.

I have experience with dry lubricated expanders too- Teflon, carbon, molybdenum disulfide and more. They have all proven to be expensive, short lived, and suitable only with the purest fluids. And dry lube machines generate a lot of dust that you will have to deal with sooner or later.

Forty years ago I worked for a well-respected world class company who was experimenting with waste heat recovery. Even with the fuel price and availability scares of the time, it just wasn’t worthwhile. I am always willing to be wrong, and always eager to learn something new (especially from you) but I just don’t see rotary steam engines ever being practical.

Kerry
Re: New rotary expander with only two moving parts.
September 26, 2015 04:02AM
Kerry
Right now just about every car has more or less doubled its range of fuel consumption. Air conditioning and refrigeration also has cut its energy consumption with the scroll compressor. But with seven billion people on earth now, fuel cost will double and triple in cost. The total expected oil supply on earth is estimated to last only 150 years at its current rate. This could be cut in half with the ever-expanding rate of growth.
Ninety percent of our electrical power comes from steam turbines. These machines need dry steam; there is a vast amount of waste on the output end and damage to the low-pressure turbine blades as the steam condenses. When we removed the turbines at the L-street plant in Boston you could put your hand in the cuts of the blades. The scroll as an expander will work well with wet steam and added lubricant. The lubricant will have to be removed.


I believe the problem with rotary expanders is lubrication and sealing. My employer uses lots of scroll and screw compressors. They are wet machines using oil to seal and lubricate. It is an easy thing to get seal/lubricating fluid out of the discharge gas. Three coalescers will do the trick even in the most demanding service.
Kerry


I agree with you 100%,the need for lubrication, in the condensing Stanley’s a lot of us have been using Mobile one synthetic 634 gear oil. Not only does it stand up to 700-degree temperature but also it has a very good separation. Other lubricants may need to be developed.

The need will arise for heat recovery on at the low end of steam generation in the future as fuel diminishes and cost go up. I think the scroll expander has a very good shot at this.

At my age I may not be around to see it, but time will tell.

Rolly
Re: New rotary expander with only two moving parts.
September 27, 2015 04:55AM
I'm looking forward to see piston rings made of force field.
Re: New rotary expander with only two moving parts.
September 27, 2015 01:53PM
Gentlemen,
In place of all the speculation, why doesn't one of you just get the scroll and backing plate from a high pressure scroll compressor and try it out? As Rolly said, they are as common as dirt today.
Edge sealing, lubrication and warping from temperature differences might just make it impossible to use.

George and I spent a lot of time on the Lysholm, both as a single ended expander and as a opposed pitch expander with central admission. In the end axial and circumferential leakage and maintaining a tight clearance with varying steam temperatures killed the idea. I still have the little Whipple supercharger I bought to work with and as a study item.

I also have a good 13-B Wankel on hand,when time permits making a set of iron housings. I have the CNC programs for both the rotors and the housings.
In the mean time, our contact in Japan is keeping his eye on the Mazda oil free seal development, one always hopes. Mazda has not abandoned the Wankel. Ken's and my White Paper tells why.
Jim
Re: New rotary expander with only two moving parts.
September 28, 2015 03:40PM
An excellent question, Jim.

Unfortunately, I sold my house, my workshop, my tools and my vast collection of misplaced merchandise (junk) last time I went to Asia never to return. I never did have access to a steam generator.

I understand that Rolly is relocating and presumably downsizing.

I am living in a small apartment. I am approaching retirement. Who can predict the future, but I have advised my employer and colleagues that my present project is my last rodeo. My retirement plans involve a robe and a bowl and a monastery in northeast Thailand.

I perceive a scroll or screw expander to be a significant project that I am unable (unwilling?) to give justice. Given my bias against the success of this project, failure would be self-fulfilling. I find what I look for because I look for it as opposed to something else, because I create it in the act of looking for it and because I bring it with me.

The engineer in me tells me there is much more to this than “just get(ting) the scroll and backing plate from a high pressure scroll compressor and try(ing) it out.

I am truly happy to be wrong. I get this satisfaction often.

I believe this is a project for a younger, more resourceful and less jaded man.

Kerry
Re: New rotary expander with only two moving parts.
September 28, 2015 06:16PM
Hi Kerry
Yes downsizing big time.
I had a good size machine shop, woodworking/pattern making shop and welding and sheet metal shop. And a lot of other stuff. I’ve been all year liquidating and getting rid of everything. Hart breaking as well as backbreaking.

Attached are two photos one showing just my two mills and my 16 inch X 10 foot lathe in the background. There was also a drill press surface grinder and another lathe and 12 inch metal cutting band saw and more stuff not shown.
The other photo as it looks now not yet completely clean. The room is 16 X 28.

My wood working shop consisted of a table saw, a 24 inch Delta scroll saw, a 12 inch band saw a 30 inch band saw, a Parks 12 X 12 thickness planer, also a 10 inch heavy duty radial arm saw. And all the other powered hand tools along with hundreds of clamps.

My welding shop had a 300 amp Mig, Tig, and AC-DC stick welding machine. As well as Gas welding setup. On the sheet metal side I had three-foot rollers and box brake along with bead rollers. And cutting and grinding tools. Also a nice heating setup with a lot of hand tinning tools for soft soldering sheet metal.
The welding shop was in a fire proof 12 X 12 room with ventilation and a ten-foot long snorkel vacuum portable hood, one side opened with a rollup garage door to the outside.
Nice setup I could weld any time day or night. Also had a sand blasting setup although most of the time I did that outside with a heaver gun.

All gone now.

The gas torches and small cutting tools I’m taking with me. I have a new R-8 universal mill and a new 12-inch lathe in a single car bay to play with small stuff. Mostly models.

There are a few companies making Scroll expanders in small sizes. The larges one I’ve found is only 6+ HP and not for steam. I still have hope.
[airsquared.com]


All the power plants I’ve worked on dump millions of BTU up the cooling condenser. Some of the older plants use a little of it for auxiliary equipment but not much.
L-street in Boston uses electric to heat the piping and pumps for the Bunker C oil supply.

Rolly

I have also scraped
8000 lb of steel
600 lb Aluminum
600 lb Stainless steel
550 lb copper
400 lb lead
400 lb brass



Edited 3 time(s). Last edit at 09/29/2015 03:29AM by Rolly.


Re: New rotary expander with only two moving parts.
September 29, 2015 03:52PM
Rolly I'm sorry you have to downsize but it come to us all although we put it off as long as we can which is exactly what I am doing!!

You have done so many amazing projects over the years - how about producing an album of your work - if not a book on paper how about a gallery of pictures with your description and comments - maybe we could persuade the SACA to host it on their site. It would be a great addition to the new web site and would record it all for posterity.

Best wishes Mike
Re: New rotary expander with only two moving parts.
September 30, 2015 03:38PM
Thanks for the comment Mike
But right now is not the time. I hope all the boys across the pond are doing well.
Rolly
Re: New rotary expander with only two moving parts.
October 06, 2015 12:04PM
Ok, so it is well established that rotary expanders leak like a sieve. But since leakage increases exponentially with pressure, what would happen if you compounded several rotary expanders? There isn't much stopping someone from buying 3-5 vane motors, linking them all to a chain or gear drive, and plumbing them all together. The biggest obstacle would be that your average <$20 harbor freight rotary air tool doesn't have a piped exhaust as far as I know.
Re: New rotary expander with only two moving parts.
October 06, 2015 01:38PM
Actually, I think the key word here is "expander", meaning that admission is cutoff at some point and allowed to drop as the volume increases while the hardware absorbs power from the pressure applied against the side wall of the expansible chamber (or equivalent).

Most air tools aren't expanders, the expansion occurs after the air leaves the tool.

Compounding high pressure expanders usually leads to greater leakage. Take two expanders using 1000 psi working fluid, one is single expansion and the other is triple. Both start with 1000 psi at cutoff and experience the same differential pressure across the seals, so leakage is similar. The single expansion device had to cut off much earlier so as to perform all its expansion in a single stage, the compound cuts off much later since it must spread the wealth. The single (simple) expander must experience a much faster drop in pressure than the compound would in its first stage and therefore the average pressure (MEP - Mean Effective Pressure) would be much higher in the compound first stage and it would leak past the seals more than the simple expander. At this point the simple is ahead and it is done with its test, the compound still has two more stages. Reasonably, they won't leak quite as badly since the MEP is now lower but it IS even more leakage.

I'm paraphrasing what happened in the Dutcher compound engine. The piston ring in the high pressure stage was uncontainable even with 5 piston rings but much lower in the following....the leakage followed a clear trend correlating to MEP.

Regards,

Ken



Edited 1 time(s). Last edit at 10/06/2015 01:39PM by frustrated.
Re: New rotary expander with only two moving parts.
October 07, 2015 01:14PM
Actually, Lear Motors tried three commercial Lysholm screw compressors in series, short, medium, long.
Ingersoll-Rand i believe. No effort was done to change the clearances.
The problems were that they had to run at widely different speeds to keep the leak rates under some control, the axial and circumferential leak rate was bad, the radiated heat loss was severe and there were some flow losses in the interconnect plumbing. The expansion per stage was not satisfactory unless different rotors with different pitches were made. Also, the expanders were not reversible. The experiment was ended to go on to the next idea.
Jim
Re: New rotary expander with only two moving parts.
October 08, 2015 02:43PM
Frustrated, I believe zimirken's idea was that the leakage past the first stage would end up in the second stage. Delta P over the rings/seals would be less and the leaked steam would not be "completely lost" to the condenser, other than from the last stage.
Re: New rotary expander with only two moving parts.
October 10, 2015 01:36PM
Rolly I watched that video with much interest. Believe it or not I was contacted by the original grant recipient about using my injector valve. The design level was at a lower stage (where I imagine they could have used injectors) and the art was different as there were two rotors.

Im positive that the machine run in the video is not running on steam... It is powered by a RVC (rotary vane compressor). When the original funding guy split off and distanced himself from the inventor (patent holder) the design was centered on tapping into compressed air stored in mine shafts. The problem is that carbon sequester works the opposite way. Also a heat source was to be introduced to expand the air.

I maintained a RVC for over 10 years, this machines use whats called a OLEO system which bathes the rotors in oil the a separator is used to provide air (shop air) oil free. In short the RVC that I maintained would have operated indefinitely if properly maintained. a year after I maintained this unit it failed. Now they have a new one, we will see how many years they get out of the new one.

Jeremy
Re: New rotary expander with only two moving parts.
October 10, 2015 02:21PM
Jeremy
The inventor and builder gave our group a very nice presentation along with video it showed the boiler outside the plant. They ran the machine every day for months.
I have to believe as stated from the presentation it ran on steam. The company went out of business and he is now a professor at at my old school Wentworth institute.
There is no reason to use an injector on this design, only a load governor as with any turbine.
Rolly
Re: New rotary expander with only two moving parts.
October 10, 2015 02:53PM
Quote
Rolly
There is no reason to use an injector on this design,

That's exactly what I thought I didn't go into it much with who emailed me.

If the expander is running on steam why isn't it insulated, nor the feed line..

Im not saying it cannot be run on steam, Im just noting my observations of the video you have linked to your first post.

Jeremy



Edited 1 time(s). Last edit at 10/10/2015 03:15PM by Jeremy Holmes.
Re: New rotary expander with only two moving parts.
October 10, 2015 04:46PM
Jeremy
You can only see a short section of the incoming steam line in this video and I can’t tell if it’s insulated or not. On my large boat I used a stainless steel flexible line that was insulated under the S.S. outside braid with ceramic fiber. But you can see the water trap loop under the gauge. This would not be necessary if it were air.
At the lecture I attended he stated the boiler was only rated at 150 psi and they ran at 140 psi saturated. This machine was to be used on heat recovery.
Rolly
Re: New rotary expander with only two moving parts.
October 20, 2015 12:01AM
While I'm sure this question has been rehashed and discussed, I must ask it. I'm planning on using a die grinder for the first expander in my steam bike. Well, when opening it up to verify that all the internal components are in fact metal, I noticed an interesting difference between it and the rotary steam expanders I've seen.

Most of the rotary steam expanders I've seen have relatively "square bores" in that the vanes are about as long as they are wide. The little china store vane motor stands in stark contrast to this in that the vane "chambers" are very long axially but very short radially.

From what I read, the biggest problem with rotary steam expanders is that they leak at the ends, and have rpm limiting friction between the vanes and the bore. I would like anyone to correct me in my thinking that the vane to bore interface tends to have acceptable leakage. Therefore, a more ideal rotary steam expander should be quite long axially, in contrast to the ones I have seen before.

What does everyone think about this? It would be nice if the vane motor was moved from "leaks like a sieve, not viable" to "design compromise: trade high leakage for simplicity and ease of procurement", if only to give steam novices an easier start.



Edited 1 time(s). Last edit at 10/20/2015 12:11AM by zimirken.
Sorry, only registered users may post in this forum.

Click here to login

All files from this thread

File Name File Size   Posted by Date  
P9240028.JPG 853.3 KB open | download Rolly 09/28/2015 Read message
PA230001a.JPG 163 KB open | download Rolly 09/28/2015 Read message