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screw expander?

Posted by HYDRAGON 
screw expander?
March 25, 2015 06:38PM
Has anyone used a screw compressor as an steam engine?
Re: screw expander?
March 26, 2015 12:48PM
Yes, scroll-screw expanders have had considerable examination over the years..
Spiral types, how on earth do you seal along the mating spiral and fixed side without copious lubrication?
The Lysholm screw type, George and I spent a lot of time on this one, so did Lear. I bought a scroll supercharger to examine, still have it. There are serious problems.
What do you mean by screw compressor, define your question.
Re: screw expander?
March 26, 2015 03:15PM
Re: screw expander?
March 26, 2015 04:45PM
Oh GOD, Minto, he was one of the idiots and deluded parasites who thought he could cash in on the steam car feeding frenzy then. His so called screw expander was a bad joke. Even the Lysholm has fatal problems, in spite of how it looked at first glance. I still have that Whipple supercharger in my junk box,
I fell for that one too until George and I uncovered all the down sides. Too bad, it sure looked good at first.

Remember, Minto was the one who put a Stanley engine in a VW bus and tried to run it on one of the Freons. Only problem was his Freon boiled at a low temperature, so the only place the bus could run was in a cooled warehouse. The same Looney-Tooney ideas like the phony working cycles and impossible thermodynamic wet dreams we still see today.
Why steam has always seemed to attract the nuts who pontificate ad naseum on their computers and have no hands on experience with any steam car is a constant puzzle. For heavens sake take Ken's latest post to heart, he speaks the truth.

Build the expander and two speed into the differential, there is room going sideways, flat four, while fore and aft is usually just not sufficient.
Re: screw expander?
March 30, 2015 04:40PM
The problem with these screw expanders or Rootes blowers or nutating discs or whatever is that they are all based on point contact. In other words there is no way to put a conventional piston ring anywhere in there. The points keep moving around. These things work as an air compressor because the air molecule is about twice as big as a steam molecule and also because the Roote's blower is running under 20 psi and most screw compressors are making air at probably 125 psi. Steam engines like higher pressures. The other reason they work as air compressors and not steam engines is because of the heat of steam causing differential expansion. Either steam leaks all over or the thing binds up. There is just way too much surface area for steam to leak past. SPS-Dutcher made a single cylinder test engine and put 5 rings on the piston (I think they did not have room to machine any more grooves on the piston) and they were still getting 10% blowby. Tom Kimmel
Re: screw expander?
March 31, 2015 01:49PM
With all due respect, neither the Roots or the screw expanders like the Lysholm have the rotors in contact with each other. Why all of them have precision timing gears at one end keeping the two rotors from touching.

Roots: No internal compression, works beautifully as a wet-dry vacuum pump.

Screw-Lysholm: Has internal compression. As a high pressure steam expander exhibits gross axial loading on the bearings, unless each rotor has opposite rotation pitch on it half way and steam is then admitted in the center and exhausting at both ends. Differential expansion was a serious problem.
Possibly might be useful at modest pressure with extremely tight hot running tolerance and labyrinth seals on the edges of each rotor; but suffers from bad axial and circumferential leaking. Differential expansion from end to end is a killer if a large expansion ratio is used. Not as attractive as the Wankel or regular piston expander.
Needs to be staged with each one running at a different speed. Lears tried three in series and failed. George and i really went into this and gave it up as just not practical.

Edited 2 time(s). Last edit at 03/31/2015 02:58PM by Jim Crank.
Re: screw expander?
March 31, 2015 04:28PM
David Nergaard is running one as an exhaust motor to drive his condenser fan. He did have lots of problems at first but sorted them out and it works just fine. I road with him one day for over 100 miles and he still had half a water tank full.
Re: screw expander?
April 01, 2015 01:36AM
You also see many places like David doing something on that order with process steam on the auxiliaries....The PiIlgrims
chicken plants did that on on their boilers before releasing it into the air.Many times on a cool day sitting in the parking lot.
You watched it leave the exhaust pipe and rain in the shopping center parking lot 50yards downwind..(to give a idea of saturation level ).
Re: screw expander?
April 01, 2015 03:14PM
The question was using screw type blowers as high pressure steam expanders. The answer is no.
My sample Whipple supercharger will turn by just blowing in it, They work fine on low pressure and low temperature steam like David is doing.
Re: screw expander?
April 06, 2015 02:10PM
I’ve been looking at the screw expander with interest after seeing some at the hotrod shows.
Attached are some papers I have found, apparently some have been built and used for steam power.
I’m not sure how they worked out, but it is my opinion if they were designed for the operating temperature and the correct material was used they would work just fine. Not just trying to use off the shelf stuff and convert them.
But the Scroll expander I believe would be a better choice, as I have said in the past, also built with the correct material for temperature expansion.
I think Invar-36 would make a fine material to start with, no expansion up to 600F. but very expansive.
What the hell if you going to experiment you have to pay the piper.

Edited 1 time(s). Last edit at 04/06/2015 02:15PM by Rolly.
Re: screw expander?
April 06, 2015 05:25PM
Don't forget what Tom mentioned about steam vs air, can't over look that.
Re: screw expander?
April 07, 2015 09:22AM
Do your own study and work.
Re: screw expander?
April 07, 2015 03:51PM
I do Rolly, what is your point? Was I out of place giving a weighted reminder?

I also thought that was the purpose of the forums, to help participants achieve their objectives, or whatever else the community can offer. I was just going to put forth a new question/thread related, but I'm feeling a bit thrown off an am hesitant. maybe I should just do my own research.

Edited 1 time(s). Last edit at 04/07/2015 03:58PM by kdc2.
Re: screw expander?
April 07, 2015 06:05PM
My point from my past post was I did not agree with anything anyone else had posted and I took exception to all of it. You were trying to remind me of what I did not agree with.
Don’t be hesitant, it fun to agree or disagree when confronted. I have been encouraged or convinced that the Scroll compressors could be used as expanders for well over eight years now with no support from anyone on the Forum and now someone is making a power generator. I believe it would make a great steam compounded expander.
Keep posting Keith.

Re: screw expander?
April 07, 2015 07:40PM
Thanks for clarifing Rolly. Funny, I was just thinking a scroll might be easier than a screw earlier. -keith
Re: screw expander?
April 07, 2015 08:05PM

Don't get over sensitive and leave. We need all the help we can get.

I got all upset and left once, but nobody said anything, so I calmed down and was back a few days later. Nobody said anything about that either. Still somewhere, deep down, I think they care.

Rolly, I've been looking for a steam motor that would run on wet steam only and of a generally set temperature. I remember that "Star Rotor" engine which was a dual rotor engine with one rotor internal to the other like some oil pumps. It would need a maximum expansion ratio of 3:1 and some leakage wouldn't be a bother.


How do you think that might compare to a scroll expander?

Best Regards,

Bill G.
Re: screw expander?
April 08, 2015 09:17AM
Bill the problem with all these conversions to another use, is temperature and expansion and sealing. Unless you have the equipment and skill and material to build your own it’s a large problem.
The Scroll has only one moving part and less area to seal. There making them now for over 10,000 PSI
Almost all air compressors in cars and refrigerators are using them.
Re: screw expander?
April 08, 2015 01:42PM
Thanks Rolly,

It sounds like the scroll expander may be a good possibility to investigate. Especially since some leakage would be OK for where I contemplate using it.

Best Regards,

Bill G.
Re: screw expander?
April 08, 2015 04:46PM
Just what are you guys calling a "screw expander"? There is a big difference between them.
This thing Rolly posted is an oil pump and impossible to seal unless flooded with oil.
People may read the posts; but often the information doesn't sink in or personal bias clouds the answers.
George and i spent two years on this exact subject. Read my post of 3-31, if you want more detailed data, just ask, we have it.

The Roots is not normally called a screw expander; but the two gear driven rotors are often given a modest helix because the straight ones scream like mad, the old S Series Mercedes, you could hear them a block away.
The Whipple superchargers are a true screw expander because both geared rotors have a real twist to them and this one has internal compression, the Roots does not. Look on the Whipple Supercharger web site and tell me if this is what you are talking about. They are now the much preferred supercharger.
With high boost pressure, the Roots heats the charge and must have an intercooler. They had big use long time ago, because the only ones we could get were from the old GM Diesel engines.

For low temperature and pressure wet steam both will run a fan or something small as long as your main expander doesn't see too much backpressure.
Re: screw expander?
April 08, 2015 07:05PM

I read your post (3-31-15) and don't disagree at all. The "Star Rotor" is one of several similar oil pump configurations and several years ago was proffered as a new and latest and greatest steam engine. Later it seemed to only work with saturated steam and now is being developed (supposedly) as a Brayton cycle engine or some such.

Rolly has brought up the scroll expander which is a different item and I was thinking of it as perhaps usable but not as the main engine expander.

Anyway when I first revived my interest in steam over eleven years ago, I was thinking of my "wonderful version" of a Roots blower type expander. It was to be a three stages of expansion system and I thought it might still have promise at that time. Patent # 3,498,184 shows the first two stages and the third was to be counter rotating on the same shaft.

After reading what you had to say about such types of expanders and the total difficulty of sealing them, I gave it up. Wendel Mason said something similar when I showed him the drawings but he was very kind. He published a small article about it in the Quarterly. I felt good, knowing that my success in steam engineering was assured at the ripe old age of twenty four. I even went looking at sail boats, just in case.

I am older now and much more mature and so I believe in pistons.

Best Regards,

Bill G.
Re: screw expander?
April 09, 2015 01:04PM

As a Brayton cycle engine? Can you just envision the cooling problems and the sealing using that cycle. Fear not, like so many we know about they will just fade back into the dream world they came from after loosing their shirts and attempt some stock pump and dump scheme.

I think all of us at one time or another saw the mechanical simplicity of the real screw expander possibility, I know I sure did with the Lysholm. Then when George and I really went into it, the nasty problems started showing up. Different clearance from the hot end to the cooler end and having to taper grind the bores and worst of all, the axial and circumferential leaking, needing to have opposing pitches with the steam admitted in the center to eliminate that big end thrust if single ended and using high pressure and on and on. Packaging three or four of them in series and all running at different speeds was one big mess.

I know the actual flat spiral compressor Rolly likes and have used a few. But; they were flooded with oil which had to then be removed from the compressed air. Sealing along the mating edge of the spiral and the differential temperature from the center to the outside edge would kill it as a steam expander.
The Roots will turn if it sees a different pressure from the inlet to the outlet. As such it does work as an inefficient condenser fan motor. This lack of internal compression makes a Roots a dandy wet/dry vacuum pump.
I hate to keep saying it; but one that does have great promise is the Wankel, because for one thing now one isn't held hostage by the then few firms who had the Gleason grinders. Ultra precise CNC can machine the housings now, I have that program. Ken and I went into this expander in depth in our paper. Something I personally still find more than attractive after living with a fully souped up Mazda RX-3 for several years. Converting the concept to steam is not hard, the fundamental needs are known and can be accomplished.
But, you are right, hard to beat a V-4 or flat 4 piston expander.
Re: screw expander?
April 09, 2015 09:49PM

That's all fine and dandy, but a true Wankel is 4 cycle, there is no such thing as a 2 cycle Wankel. This is determined by the crank eccentrics. The pattern must be a tri lobe rotor running in a figure 8. The only way to run such an engine on steam is with a direct injection valve (2) one for each rotor.

This leaves us with the argument of volumetric efficacy and high compression IC engines... I see the Z cycle engine as nothing more than a single acting piston engine with dual acting characteristics, thru the use of an electromagnetic DE- pressurization relief valve. If you want an engine to have zero compression why not use a railroad dual acting piston cylinder arrangement it will have more low speed torque.

Edited 1 time(s). Last edit at 04/09/2015 10:05PM by Jeremy Holmes.
Re: screw expander?
April 09, 2015 11:05PM
I visited with Harry a year or three ago, he ran a MK5 on compressed shop air. I was impressed that a coil of 1/8 tubing got hot as the motor run, here is a example of his

Referring to FIG. 7, at lower engine speeds the steam injection valves 53 are partially closed and a clearance volume compression release valve 46 is opened to release steam from the cylinders 52. The clearance volume valves 46 are controlled by the engine RPM's. The clearance volume valve 46 is an innovation that improves the efficiency of the engine at both low and high speeds. Minimizing the clearance volume in a cylinder 52 is advantageous for efficiency as it lessens the amount of super-heated steam required to fill the volume, reduces the vapor contact area which absorbs heat that would otherwise be used in the explosive expansion of the power stroke, and, by creating higher compression in the smaller chamber, further raises the temperature of the admitted steam. However, the higher compression resulting from the smaller volume has the adverse effect at low engine RPM of creating back pressure against the incoming charge of super-heated steam. The purpose of the clearance volume valve 46 is to reduce the cylinder compression at lower engine RPMs, while maintaining higher compression at faster piston speeds where the back pressure effect is minimal. The clearance volume valve 46 controls the inlet to a tube 47 that extends from the cylinder into the combustion chamber 22. It is hydraulically operated by a lower pressure pump system of engine-driven primary poly-phase water pump 90. At lower RPM, the clearance volume valve 46 opens the tube 47. By adding the incremental volume of this tube 47 to that of the cylinder 52, the total clearance volume is increased with a consequent lowering of the compression. The vapor charge flowing into the tube is additionally heated by the combustion chamber 22 which surrounds the sealed tube 47, vaporizing back into the cylinder 52 where it contributes to the total vapor expansion of the low speed power stroke. At higher RPM, the pump system of the engine-driven pump 90 that hydraulically actuates the clearance volume valve, develops the pressure to close the clearance volume valve 46 thereby, reducing the total clearance volume, and raising the cylinder compression for efficient higher speed operation of the engine. The clearance volume valves 46 contribute to the efficiency of the engine at both low and high speed operation.

Of particular interest was "46" and how it controlled volumetric efficiency

Edited 1 time(s). Last edit at 04/09/2015 11:06PM by Jeremy Holmes.
Re: screw expander?
April 10, 2015 01:54AM
If you follow each working chamber around, they work just like a two cycle unaflow. Inlet say at one side and exhaust about 160° on the other side. In function a two cycle expander.
Take one apart and look. Our illustration is correct.
Just as a matter of staying on the subject, what does Cyclone's failed Mk-5 have to do with screw expanders or the Wankel?

Edited 2 time(s). Last edit at 04/10/2015 12:21PM by Jim Crank.
Re: screw expander?
April 10, 2015 08:17AM
Rolly,your first paper nailed what chicken plant was doing with the ammonium refrigeration and process steam auxiliaries.
And you may be on the right track with remarks as well...Pilgrims used engersol Rand screw expanders for over 50years in the 500,000 cubic ft. refrigerator.
Re: screw expander?
April 10, 2015 03:28PM
Hi Jim,

The Wankel has a compression stroke. Im not so sure the MK5 failed it also has compression like the uniflow, unless diverted to clearance volume valve. Which the Z cycle uses, I read about the Z cycle engine in last months bulletin.

Jim you used to be a big supporter of Harrys work, what has changed?
Re: screw expander?
April 11, 2015 12:07AM
The Wankel does not have an individual or separate "compression stroke." The compression event takes place three times during each rotation of the rotor, one for each working volume during part of the single revolution of that rotor. As a steam expander our White Paper illustration is correct, a unaflow expander.
Go to Wickipedia and Google and type in "Wankel engine working cycle." Carefully observe the nice colored moving illustrations and learn.

I have no intention of muddying our web site with any listing of what was wrong with the Cyclone engine and the people who promote it. Suffice it to say my attorney investigated Cyclone and their business and stock practices and demanded I sever all connections to this fraud, which I did. Our members with long proven expertise in Rankine cycle systems deeply researched their thermodynamics and mechanical designs and have also come to the same conclusions for the same reasons.
If you believe in it, then good luck.
Re: screw expander?
April 11, 2015 02:57PM

each "rotor" has the same individual compression event.

I have worked at 2 Mazda dealerships as a Re-Certified Master Technician and worked closely with the 13b engine, actually I was the guy who made the engines pass emission standard. Its a very dynamic engine cycle and you cant simpily figure out how it actually works, by just taking one apart

"The compression event takes place three times during each rotation of the rotor, one for each working volume during part of the single revolution of that rotor"

that's incorrect Jim. One rotation of the rotor, one compression event. The only exception would be with a 3 rotor engine.

I was the one who said "um"(Harry) he is biting off more than he can chew. But at the time everyone was exclaiming how right Harry was. I wish Harry well with his engine development.

Edited 7 time(s). Last edit at 04/11/2015 04:03PM by Jeremy Holmes.
Re: screw expander?
April 11, 2015 04:26PM
"that's incorrect Jim. One rotation of the rotor, one compression event. The only exception would be with a 3 rotor engine."

You picked the wrong illustration. Too many reporters and magazine writers have no idea what they are seeing or writing about. The IC version is not of interest, the steam expander use is of interest.
Well, this is getting boring and no place. Since I have built up about eight 13-B engines for racing and still have the parts to look at, the Wankel has three intake phases for each rotation of the rotor. Three working chambers remember on each rotor, one compression event per chamber per one rotation of the rotor.
In fact, drop it because I refuse to answer you any more. You don't know what you are talking about.
Re: screw expander?
April 11, 2015 04:36PM
No Jim, if you indexed one of the lobes of the rotor you would see what im talking about.

Quote from my animation link.

"The rotary motion is transferred to the drive shaft by an eccentric wheel (illustrated in blue) that rides in a matching bearing in the rotor. The drive shaft rotates once during every power stroke instead of twice as in the Otto cycle.

The Wankel promised higher power output with fewer moving parts than the Otto cycle engine; however, technical difficulties interfered with widespread adoption. In spite of valiant efforts by Mazda, the four stroke engine remains much more popular."

I do know what im talking about you are just an old coot. smiling smiley
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