1 Steam Cars : Phorum
General Steam Car topics
Scroll compressor / expander
Posted by: Rolly (IP Logged)
Date: August 06, 2003 03:26PM
<HTML>Hear is a nice site to help show how a scroll compressor works. In reverse it would make a good steam expander (engine) No valves. Like the Mazda Wankel engine side sealing probably is a problem.
Use the tools on the bottom of the page to run the scroll and slow it down.
[www.mat.dtu.dk]
Rolly</HTML>
Use the tools on the bottom of the page to run the scroll and slow it down.
[www.mat.dtu.dk]
Rolly</HTML>
Re: Scroll compressor / expander
Posted by: Tom Ward (IP Logged)
Date: August 07, 2003 12:22PM
<HTML>After watching the demo animation I see inherent limitations to using the scroll. First is the clearance between the rotor and the stator will be a source of considerable leakage at low speeds. Second is the expansion ratio is limited to only 3:1 which is equivalent to 33% cutoff. The combination makes for a poor steam rate.</HTML>
Re: Scroll compressor / expander
Posted by: Rolly (IP Logged)
Date: August 07, 2003 01:32PM
<HTML>Tom
There using these as compressors at over 1000 PSI.
I think the cut off can be changed by playing with the point of rotation. Use the tools to the right of the screen. Click on the line and start dragging it to different places.
Rolly</HTML>
There using these as compressors at over 1000 PSI.
I think the cut off can be changed by playing with the point of rotation. Use the tools to the right of the screen. Click on the line and start dragging it to different places.
Rolly</HTML>
Re: Scroll compressor / expander
Posted by: Jim Crank (IP Logged)
Date: August 07, 2003 03:13PM
<HTML>Rolly,
As you may already know, I spent the better part of a year working with the Lysholm screw compressor, in hopes that it would make a dandy steam car engine. The initial look showed not only unaflow expansion; but the unit can also take water in the steam with no problems. It looked at first to be a wonderful and compact solution to getting a good car engine.
I purchased a sample of the Lysholm supercharger from the Whipple Supercharger Co. as a study item, the best and most efficient version of the screw compressor known and now in world wide use with high efficiency and magnificent reliability. Watching the action of the two rotors, male and female, as they turned was like watching two worms mating, absolutely fascinating to see.
Jerry Peoples and George Nutz were also deeply involved with this investigation and their contributions to the research were massive. I am certainly greatful for all their input in this possible application of the Lysholm to be used as a steam car engine.
We did discover that while the Lysholm has been used with steam, it appeared that we were amongst the first to really look at the expander as a high pressure high temperature steam expander. Existing firms that are said to have looked at this application were notable in their lack of response. There are some good papers on the Lysholm design.
The Lysholm, and any other screw expander that has internal compression, can go above the 3-1 ratio; but not by a great amount, you need to stage it for a high expansion ratio.
One also must use the version with syncronizing gears between the rotors to eliminate massive friction losses and presumed high wear rates.
What we found is this:
1) The Lysholm has massive end thrust with high pressure steam, unless you make the pitch of the rotors opposite in the center of the rotors, and admit steam in the center, think of a herringbone gear, the same idea. This at least balances out the end thrust forces. One could, of course, couple two separarate Lysholms running opposed, on the same shaft, at least for the first stage. Also possibly with #2 and #3 also arranged the same way to balance out their end thrust, if desired.
2) The admission of superheated steam in the center of the rotor means that while you are certainly going to get unaflow expansion to both outside exhaust ports, the effect of high temperature in the middle and cool steam at both ends is certainly going to cause problems. Probably meaning that one would have to barrel grind the housings, so that hopefully when at temperature, the bores would be straight. Or taper grind the housings if two separate engines were used in opposition. Really not a problem to do today.
3) The clearances of course need to be as small as possible in order to get minimum leakage both radially and axially along the rotors. This proved to be a serious machining problem, and no doubt first attempts would have produced rubbing and ruined rotors and housings.
HOWEVER, perhaps now this new carbon deposition process that Dick Vennerbeck found, could be of great use. It seems to be very good for high stress lubrication problem areas like wrist pins in race cars. NASCAR engines now go 1500 rpm higher by using this coating process, like 9800 rpm. Fantastic for a V-8 pushrod race engine that can go for a 500 mile race and survive, considering the massive forces involved with them.
This coating process just could make the Lysholm usable; but an intense research project would be the only way to make the determination. It could be a means of eliminating rubbing destruction if it worked out and if it was good for a long life. This certainly makes it worth another look at the Lysholm as the prime expander for a new steam car.
4) Jerry determined that the engine size I wanted meant that we would have to use three units in tandem, triple expansion. BUT; the first stage would, from clearance considerations, have to run at some 30,000 rpm, and the other two at less speed. This meant a serious gearbox would be necessary. While this is really not such a problem, I don't like the implications of noise and durability that goes along with such gearboxes. Although, when considering the other horrible problems of getting an efficient and compact car engine, the gearbox may not be all that serious.
It is certainly worth another look, with the idea of using this new coating. The efficiency potential is there with a three stage engine concept as is a high power output.
5) Cutoff can be achieved with a shifting piston valve that sequentially opens up inlet ports that have longer and longer admission arcs.
While the whole concept looked so promising at first, I just had to abandon the idea. Just too many long term and expensive research items that would first have to be investigated and then solved with many prototypes.
The Lysholm can certainly make a nice and super compact low pressure engine for, say, a boat, and make a very good exhaust steam engine for a car for running draft boosters or fan turbines, it is just not attractive for the prime mover, unless this new coating process worked out. I went back the the three rotor Wankel, it still looks very good to me; but now I want to really investigate the potential of this coating process as applied to the Lysholm.
It does have good packaging potential and it can be made efficient.
The Whipple Company offered to make the rotor blanks and have them machined at really acceptable cost to my specifications. Also the iron rotor housings, although those can be done by any competent CNC machine shop.
An interesting engine with potential possibilities if some problems are worked out first, yet it can fail if that coating process would not work and give long life, and be compatable with water.
Jerry and George, your comments?
Jim</HTML>
As you may already know, I spent the better part of a year working with the Lysholm screw compressor, in hopes that it would make a dandy steam car engine. The initial look showed not only unaflow expansion; but the unit can also take water in the steam with no problems. It looked at first to be a wonderful and compact solution to getting a good car engine.
I purchased a sample of the Lysholm supercharger from the Whipple Supercharger Co. as a study item, the best and most efficient version of the screw compressor known and now in world wide use with high efficiency and magnificent reliability. Watching the action of the two rotors, male and female, as they turned was like watching two worms mating, absolutely fascinating to see.
Jerry Peoples and George Nutz were also deeply involved with this investigation and their contributions to the research were massive. I am certainly greatful for all their input in this possible application of the Lysholm to be used as a steam car engine.
We did discover that while the Lysholm has been used with steam, it appeared that we were amongst the first to really look at the expander as a high pressure high temperature steam expander. Existing firms that are said to have looked at this application were notable in their lack of response. There are some good papers on the Lysholm design.
The Lysholm, and any other screw expander that has internal compression, can go above the 3-1 ratio; but not by a great amount, you need to stage it for a high expansion ratio.
One also must use the version with syncronizing gears between the rotors to eliminate massive friction losses and presumed high wear rates.
What we found is this:
1) The Lysholm has massive end thrust with high pressure steam, unless you make the pitch of the rotors opposite in the center of the rotors, and admit steam in the center, think of a herringbone gear, the same idea. This at least balances out the end thrust forces. One could, of course, couple two separarate Lysholms running opposed, on the same shaft, at least for the first stage. Also possibly with #2 and #3 also arranged the same way to balance out their end thrust, if desired.
2) The admission of superheated steam in the center of the rotor means that while you are certainly going to get unaflow expansion to both outside exhaust ports, the effect of high temperature in the middle and cool steam at both ends is certainly going to cause problems. Probably meaning that one would have to barrel grind the housings, so that hopefully when at temperature, the bores would be straight. Or taper grind the housings if two separate engines were used in opposition. Really not a problem to do today.
3) The clearances of course need to be as small as possible in order to get minimum leakage both radially and axially along the rotors. This proved to be a serious machining problem, and no doubt first attempts would have produced rubbing and ruined rotors and housings.
HOWEVER, perhaps now this new carbon deposition process that Dick Vennerbeck found, could be of great use. It seems to be very good for high stress lubrication problem areas like wrist pins in race cars. NASCAR engines now go 1500 rpm higher by using this coating process, like 9800 rpm. Fantastic for a V-8 pushrod race engine that can go for a 500 mile race and survive, considering the massive forces involved with them.
This coating process just could make the Lysholm usable; but an intense research project would be the only way to make the determination. It could be a means of eliminating rubbing destruction if it worked out and if it was good for a long life. This certainly makes it worth another look at the Lysholm as the prime expander for a new steam car.
4) Jerry determined that the engine size I wanted meant that we would have to use three units in tandem, triple expansion. BUT; the first stage would, from clearance considerations, have to run at some 30,000 rpm, and the other two at less speed. This meant a serious gearbox would be necessary. While this is really not such a problem, I don't like the implications of noise and durability that goes along with such gearboxes. Although, when considering the other horrible problems of getting an efficient and compact car engine, the gearbox may not be all that serious.
It is certainly worth another look, with the idea of using this new coating. The efficiency potential is there with a three stage engine concept as is a high power output.
5) Cutoff can be achieved with a shifting piston valve that sequentially opens up inlet ports that have longer and longer admission arcs.
While the whole concept looked so promising at first, I just had to abandon the idea. Just too many long term and expensive research items that would first have to be investigated and then solved with many prototypes.
The Lysholm can certainly make a nice and super compact low pressure engine for, say, a boat, and make a very good exhaust steam engine for a car for running draft boosters or fan turbines, it is just not attractive for the prime mover, unless this new coating process worked out. I went back the the three rotor Wankel, it still looks very good to me; but now I want to really investigate the potential of this coating process as applied to the Lysholm.
It does have good packaging potential and it can be made efficient.
The Whipple Company offered to make the rotor blanks and have them machined at really acceptable cost to my specifications. Also the iron rotor housings, although those can be done by any competent CNC machine shop.
An interesting engine with potential possibilities if some problems are worked out first, yet it can fail if that coating process would not work and give long life, and be compatable with water.
Jerry and George, your comments?
Jim</HTML>
Re: Scroll compressor / expander
Posted by: Rolly (IP Logged)
Date: August 07, 2003 04:34PM
<HTML>Thanks for your input Jim
The Lysholm compressor is long and has a higher degree of expansion problems then the scroll compressor. I have know idea how they seal the scroll compressor on the side edges against the case but I can see how there would be very little problems with expansion between one scroll and the other. The internal pressure will keep one scroll tight against the other. Coating may help.
One company is making a small scroll steam expander, see attachment. Go down the page a bit till you see the Scroll expander
[www.scrolllabs.com]
Rolly</HTML>
The Lysholm compressor is long and has a higher degree of expansion problems then the scroll compressor. I have know idea how they seal the scroll compressor on the side edges against the case but I can see how there would be very little problems with expansion between one scroll and the other. The internal pressure will keep one scroll tight against the other. Coating may help.
One company is making a small scroll steam expander, see attachment. Go down the page a bit till you see the Scroll expander
[www.scrolllabs.com]
Rolly</HTML>
Re: Scroll compressor / expander
Posted by: Jim Crank (IP Logged)
Date: August 07, 2003 09:46PM
<HTML>Rolly,
Saw the scroll data. Very interesting.
What bothers me is the huge leak path over the edges of each scroll radially, unless you put in some sort of seal strip. Then there is a lot of friction.
I don't think they do specially seal the two scrolls; but have a tiny axial clearance and hope for the best.
This problem is why they flood the unit with oil as a high vacuum pump.
The clearance between the two scrolls would have to be awfully tight to stop any leak where the two scrolls meet.
Also the effect hot steam would have with warping those scrolls.
Jim</HTML>
Saw the scroll data. Very interesting.
What bothers me is the huge leak path over the edges of each scroll radially, unless you put in some sort of seal strip. Then there is a lot of friction.
I don't think they do specially seal the two scrolls; but have a tiny axial clearance and hope for the best.
This problem is why they flood the unit with oil as a high vacuum pump.
The clearance between the two scrolls would have to be awfully tight to stop any leak where the two scrolls meet.
Also the effect hot steam would have with warping those scrolls.
Jim</HTML>
Re: Scroll compressor / expander
Posted by: Rolly (IP Logged)
Date: August 08, 2003 09:20AM
<HTML>Jim
There is a lot of information on the net about scroll compressors. The scrolls seem to be manufactured so that one side of a scroll is machined to a flat plate. Side sealing of the scroll is only on one side of each scroll. One scroll is stationary and machined into a housing. Copeland Scroll compressors are made up to 25 HP units and they offer a duel compressor to 50 HP
All pistons (rings) have some blow-by, in the scroll compressor leakage would be into the continuous compressing cycle.
[www.copeland-corp.com]
From Copeland Scroll compressors site.
o Since there are no pistons to
compress gas, there is no
volumetric efficiency loss through
re-expansion, which typically
occurs with each piston stroke in
reciprocating models.
o Similarly, losses at valves are
eliminated, because valves have
been eliminated.
o During operation, centrifugal
force maintains nearly
continuous compression and
constant, leak-free contact.
o Separation of suction and
discharge gases reduces heat
transfer loss.
Rolly
George, Peter, and some others are at or on route to the SACA-NE meet.</HTML>
There is a lot of information on the net about scroll compressors. The scrolls seem to be manufactured so that one side of a scroll is machined to a flat plate. Side sealing of the scroll is only on one side of each scroll. One scroll is stationary and machined into a housing. Copeland Scroll compressors are made up to 25 HP units and they offer a duel compressor to 50 HP
All pistons (rings) have some blow-by, in the scroll compressor leakage would be into the continuous compressing cycle.
[www.copeland-corp.com]
From Copeland Scroll compressors site.
o Since there are no pistons to
compress gas, there is no
volumetric efficiency loss through
re-expansion, which typically
occurs with each piston stroke in
reciprocating models.
o Similarly, losses at valves are
eliminated, because valves have
been eliminated.
o During operation, centrifugal
force maintains nearly
continuous compression and
constant, leak-free contact.
o Separation of suction and
discharge gases reduces heat
transfer loss.
Rolly
George, Peter, and some others are at or on route to the SACA-NE meet.</HTML>
Re: Scroll compressor / expander
Posted by: Jim Crank (IP Logged)
Date: August 08, 2003 12:45PM
<HTML>Rolly,
This type of compressor/expander is most interesting in it's basic simplicity and ease of construction. For sure they are widely used, and in many sizes, and they do work very well as a vacuum pump/air compressor.
You are right, if you had steam going into the center, as you must do, then any radial leakage would go into the next outside volume. As long as this can be controlled by using a very fine clearance, or even spring loading one scroll against the other and using some anti-friction coating, it could work.
I would be concerned about warping with hot steam and really sealing the scrolls against each other. Perhaps not as an engine that could stand 1000 psi; but more as a low pressure engine. Anyhow, I find it most interesting.
Perhaps one should be obtained and then try it out as an engine and just see what would happen. It's worth a try.
Jim</HTML>
This type of compressor/expander is most interesting in it's basic simplicity and ease of construction. For sure they are widely used, and in many sizes, and they do work very well as a vacuum pump/air compressor.
You are right, if you had steam going into the center, as you must do, then any radial leakage would go into the next outside volume. As long as this can be controlled by using a very fine clearance, or even spring loading one scroll against the other and using some anti-friction coating, it could work.
I would be concerned about warping with hot steam and really sealing the scrolls against each other. Perhaps not as an engine that could stand 1000 psi; but more as a low pressure engine. Anyhow, I find it most interesting.
Perhaps one should be obtained and then try it out as an engine and just see what would happen. It's worth a try.
Jim</HTML>
Re: Scroll compressor / expander
Posted by: Roland Evans (IP Logged)
Date: August 08, 2003 07:30PM
<HTML>I will see Peter this weekend at our SACA-NE two-day meet. Maybe he knows where I can get one used and cheep to take apart.
Rolly</HTML>
Rolly</HTML>
Re: Scroll compressor / expander
Posted by: Peter Heid (IP Logged)
Date: August 10, 2003 10:33PM
<HTML>I have never seen the inside of one of these units. Unfortunately these units have never come into my hands in the broken state where I can open one up and look inside. I have helped install a few that I think used this type of compressor for HVAC apps but they never seem to go bad.</HTML>
Re: Scroll compressor / expander
Posted by: Howard Randall (IP Logged)
Date: August 11, 2003 10:16AM
<HTML>I ran a pair of these compressors at 50 % duty cycle, 24 hrs/day, 5 day a week for 15 years. The only problems were with the oil separators that showed up in the latter years of there life!</HTML>
Re: Scroll compressor / expander
Posted by: Jim Crank (IP Logged)
Date: August 11, 2003 11:13AM
<HTML>Howard,
There are two types, the oil flooded where one rotor drives the other, and the dry type that has syncronizing gears, so the rotors don't touch. That version is what the Whipple supercharger is.
Peter,
Also use now in a lot of car superchargers, Mercedes-Benz, Mazda, etc. So much better than the Roots it isn't funny.
Jim</HTML>
There are two types, the oil flooded where one rotor drives the other, and the dry type that has syncronizing gears, so the rotors don't touch. That version is what the Whipple supercharger is.
Peter,
Also use now in a lot of car superchargers, Mercedes-Benz, Mazda, etc. So much better than the Roots it isn't funny.
Jim</HTML>
Re: Scroll compressor / expander
Posted by: Rolly (IP Logged)
Date: August 11, 2003 11:53AM
<HTML>Jim
Are you talking about a screw compressor?
Are you saying that there are two method of driving the screws? One being both are connected with gears and the other method only one screw is driven and it drives the second screw.
I have only seen the type where both were connected with gears.
See attachment.
[www.copeland-corp.com]
Rolly</HTML>
Are you talking about a screw compressor?
Are you saying that there are two method of driving the screws? One being both are connected with gears and the other method only one screw is driven and it drives the second screw.
I have only seen the type where both were connected with gears.
See attachment.
[www.copeland-corp.com]
Rolly</HTML>
Re: Scroll compressor / expander
Posted by: George Nutz (IP Logged)
Date: August 11, 2003 05:16PM
<HTML>Rolly,
The Copeland you refer to looks exactly like a Lysholm that Jim, Jerry and I spent a huge amount of time on---think we have already given up on that one. Very high leak rate at low rpm's, they are made for very high continual rotative speeds. Will have to look into the scroll as far as performance data over a wide range of speed.
GOOD TO SEE YOU THIS WEEKEND! George</HTML>
The Copeland you refer to looks exactly like a Lysholm that Jim, Jerry and I spent a huge amount of time on---think we have already given up on that one. Very high leak rate at low rpm's, they are made for very high continual rotative speeds. Will have to look into the scroll as far as performance data over a wide range of speed.
GOOD TO SEE YOU THIS WEEKEND! George</HTML>
Re: Scroll compressor / expander
Posted by: Jim Crank (IP Logged)
Date: August 15, 2003 01:02PM
<HTML>Rolly,
As far as the Lysholm type is concerned, yes, there are two types used as compressors and vacuum pumps on the world market. Oil flooded when one rotor drives the other, and dry, where the two rotors do not touch; but are kept separate and driven by syncronizing gears. In the automotive supercharger world, they are all the dry types, like the Whipple I bought to examine.
Most "scroll" type of pumps are often used dry or wet. Like vacuum pumps are almost always wet pumps with an oil separator, so as to achieve a high vacuum level. Then the clearance problem goes away as the oil film does that job. We used dozens of them at Lockheed and I had a great time taking new versions apart to see how they were made. It depends on the use whether they are dry or wet.
The best one is the Lysholm; but it does leak at slow speed with large throttle opening as an engine, high delta P, thus the need for three stages. But; just how long do you stay at that specific condition when using it as a steam car engine? Not long, so in real practice it may not be a critical show stopper.
As Jerry found out during our investigations, the first stage has to go at very high speed, then the other two or three stages down stream run at progressively lower speeds, to keep the first stage leak loss minimized.
Jim</HTML>
As far as the Lysholm type is concerned, yes, there are two types used as compressors and vacuum pumps on the world market. Oil flooded when one rotor drives the other, and dry, where the two rotors do not touch; but are kept separate and driven by syncronizing gears. In the automotive supercharger world, they are all the dry types, like the Whipple I bought to examine.
Most "scroll" type of pumps are often used dry or wet. Like vacuum pumps are almost always wet pumps with an oil separator, so as to achieve a high vacuum level. Then the clearance problem goes away as the oil film does that job. We used dozens of them at Lockheed and I had a great time taking new versions apart to see how they were made. It depends on the use whether they are dry or wet.
The best one is the Lysholm; but it does leak at slow speed with large throttle opening as an engine, high delta P, thus the need for three stages. But; just how long do you stay at that specific condition when using it as a steam car engine? Not long, so in real practice it may not be a critical show stopper.
As Jerry found out during our investigations, the first stage has to go at very high speed, then the other two or three stages down stream run at progressively lower speeds, to keep the first stage leak loss minimized.
Jim</HTML>
Re: Scroll compressor / expander
Posted by: Tani Ricafrente (IP Logged)
Date: September 29, 2004 01:57AM
<HTML>Hi,
Can someone help me understand the detail on how scroll compressor work? I want to know by illustration how the oldham coupling ring perform its function.
thnks in advance.
Tani</HTML>
Can someone help me understand the detail on how scroll compressor work? I want to know by illustration how the oldham coupling ring perform its function.
thnks in advance.
Tani</HTML>
Re: Scroll compressor / expander
Posted by: JOSE TOVAR (IP Logged)
Date: October 04, 2004 03:49AM
<HTML>Hi Jim, I sure could use some help and after reading your posting I hope you can help me or point me in the rihjt direction. I have a GMC Yukon with a 5.7L gas engine with a Whipple super charger. The unit is sucking oil out of the gear case and into the engine. I called Whipple (559/442/1261) in Calif. and asked for a seal kit. They replied that my unit was an early model and that I need to buy a new unit ($1700). I'm wondreing if there is someone out there that can sell me a seal kit, or what ever it is I need to stop the flow of oil. You seem to know a lot about Whipple superchargers so here is Question #2. My whipple provides a 350 cu in (5.7L) at 6psi boost. Why can't it work with a 383 cu in engine? Backround, while rebuilding my 350 cu in engine I was going to install a stroker crankshaft in the engine to increase the displacement to 383 cu in. In my mind if the Whipple can supply a 350 cu in at 6 psi, then by increasing the diplacement by almost 10% would mean a decrease in boost from 6 psi to 5.4 psi, a boost I could live with, since I just smoked an engine at 6psi. Do you think Whipple was just gining me the run around? Thanks for any help in advance, and keep on posting.</HTML>
Re: Scroll compressor / expander
Posted by: moffett8 (IP Logged)
Date: February 15, 2009 04:31AM
why couldn't you run a closed loop system and run it on either freon or propane? Both of these are compatible with the oil used in ac systems in cars.
Another thought is they make Teflon sheets why couldn't the inside be lined with these to reduce friction?
Another thought is they make Teflon sheets why couldn't the inside be lined with these to reduce friction?
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