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tim c cook Newbie Joined: 02/06/2010 Location: United StatesPosts: 11
Posted: 07:18am 08 Jun 2010
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Don B - I have been web searching the use of gerotor pumps as expanders, hoping to test the use of a small Mallory 12VDC electric gerotor automotive fuel pump as a mini-generator in a closed ORC system to produce a couple hundres watts electricity from a couple meters of solar collectors, (part of the discussion I linked to in my earlier post).
During the search I ran across the following discussion.
About 3/4 way down the page there are a couple Sept 2008 posts from Jeremy Holmes saying he is using 12 VDC water cooled electric solenoid valves with steam, states 4000 rpm, says the valves have an opening time of .004 sec and a closing time of .003 sec, unfortunatly he does not go in to detail on the make of the valve.Edited by tim c cook 2010-06-09
Don B Senior Member Joined: 27/09/2008 Location: AustraliaPosts: 190
Posted: 04:16am 10 Jun 2010
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Hi Tim,
I had a look at the Georotor site that you suggested and, although the poster (Jeremy) did not give any details about what sort of solenoids he is using, if he can manage 4,000 rpm from his 4 cycle engine as he claims, that is encouraging.
The only thing that is puzzling is that, at 4,000 rpm, his engine would be doing one rev per 15 milliseconds. If he is admitting steam for 1/3 of the downstroke, as he claims, this is an admission time of 15 X 60/360 = 2.5 ms. He claims that his solenoid has an opening time of 4 ms, and a closing time of 3ms, which is certainly feasible. The puzzle is that, to achieve a 2.5ms steam admission time, he must be starting to close the solenoid before it has opened??
Anyway, if he can somehow get to 4,000 rpm with his arrangement, then my hoped for 1,600 rpm should be easily achieved.
Good luck also with your Georotor pump experiments.
RegardsDon B
tim c cook Newbie Joined: 02/06/2010 Location: United StatesPosts: 11
Posted: 11:11pm 10 Jun 2010
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By clicking on the posters name I was able to see all his past postings, there are many, still reading through these for more info. He is still active on that discussion board so I suspect he could be contacted through it.
Yes, his description of the timing is pretty vague, he states he only starts admitting steam just after TDC but, as you say, the elapsed times don't add up. He does say he has used PWM in the past but not sure if it is being used to create these timings or not?
I wonder just what his definition of a "4 cycle" steam engine is, does not make sense to me? To get the "4 cycle" he may only be adding steam on every OTHER piston stroke?- no idea.
Solenoid valve speed - On our testing using the solenoid actuating hydraulic reversing valves - These valves come in many configurations, some use only one solenoid for opening and a spring for closing, others use a solenoid coil for both, we found that by using a valve that was both opened and closed using selinoid coils, plus by using the higher voltage through a resistor, the valves could be cycled much faster than when using only a spring for closing. These "DO" reversing valves also pass a lot of steam with only a slight movement of there internal spool valve due to having large opening. These valves are specked for continuous duty at very high hydraulic temps and pressures so no water cooling needed. Block off any in/outs you don't need to use
The following link goes to the "Northman" DO hydraulic valve page but all DO valves are the same standard no matter who manufacures them, There are PDF's for the various valves. Vickers makes them with aluminum bodies rather than cast iron. Study the many spool configurations before buying anything, the different spool configurations look the same but operate differently.
http://www.northmanfp.com/ - Click on "direction control valves".
I have bought about a dozen of these from Ebay, never paid more than $10.00 plus shipping for any of them.
Edited by tim c cook 2010-06-12
tim c cook Newbie Joined: 02/06/2010 Location: United StatesPosts: 11
Posted: 12:25am 11 Jun 2010
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Just looked at the DO3 valve open/close timing specks, say 20-60 MS to open and 20-40 ms to close, even with the high voltage actuation I suspect the opening time will be no more than maybe 6-7 ms so may not be fast enough (never did put a scope on it), they will pass a lot of steam though so that may make up for the timing.
tim c cook Newbie Joined: 02/06/2010 Location: United StatesPosts: 11
Posted: 07:25am 11 Jun 2010
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OK - in reading through the "re-compression" discussion that Jeromy Holmes had posted to 5 years ago I found reference to him having a website, found it and it explains what he refers to as the "four cycle steam engine". REAL different, it uses direct injected superheated water to power the first power stroke and then recirculates the exhaust steam from that stroke back in to the intake of the cylinder to power the second stroke (good animation at end of page 3).
The solenoid valve he refers to is a custom designed version of what looks like a big gasoline engine fuel injector, it squirts the superheated water, so - no direct application for our simple use, sorry for the erroneous lead..
I actually had seen this website before, I found it when reading about corn burners used to heat steam boilers, we were burning corn for our various steam engine testing, I did not bother to read the steam engine info portion at the time.Edited by tim c cook 2010-06-12
MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329
Posted: 03:06pm 11 Jun 2010
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Ahem . . .
Let me jump in here for a minute. I started this thread and it's gone where it has and that's all good. I may be remiss in interjecting this, as I honestly have not read much of this since it got off onto building steam engines out of lawnmower engines.
I have built small steam engines for the last 40 + years as a hobby and the idea of using and re-using steam is nothing new. There is an engine called a "compound" engine and what they did a hundred years ago was this: The exhaust steam from the first fed the second, but the piston in the second was twice the size (bore) as the first (same stroke length of course) and the third was nearly twice the size of the second and so on.
Steam 'expands' and that's the key here. Until it has expanded to a point where it starts to condense, it's still got usable power and that's why it's used in that manner.
Several years ago, I stopped building engines that needed lubrication; it is just too big of a headache. I switched to ones that don't (ie peristaltic and such the like). The peristaltic ones, by the way, use compressed air instead of live steam to operate. The compressed air part is what got me into building windmills that pump air and now I've turned another corner and am building windmills that generate electricity. I think it may have something to do with that ying and yang thing the orientals tout so much.
Well, keep it up and have a good time. Steam engines are truly wonderful things; lots of hours of enjoyment for me at least. I'd steer clear of solenoid valves though. All the old timers used either "D" valves, spool valves or some other type of valve that can be timed with a cam and follower. Again, that needs lubrication and sooner or later you'll figure it out: oil and water just don't make good bed fellows!
. . . . . MacNothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
tim c cook Newbie Joined: 02/06/2010 Location: United StatesPosts: 11
Posted: 03:19am 12 Jun 2010
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Lubrication is one of the reasons I am using refrigeration fluid rather than water, Oils are intended to dissolve in the organic frig fluid and be carried through the system with no nead to be seperated, that, and the fact that it can be vaporized at temps far lower than water, this allows solar heat collection using more simple flat plate collectors. By reworking the top end of a 2 clinder automotive York frig compressor you have a 2 cylinder 10-12 cubic inch single ended engine that is designed for the frig fluid, these have sealed crankcases that contain liquid lube oil for the bottom end and are also sealed against the loss of any frig fluid to the outside world.
The electrically actuated "DO?" type hydraulic solenoid valves I am using ARE spool valves, just completely sealed ones, there opening and closing is far faster than if using a mechanical linkage (and no wear), the timing can be controlled electronically so is also far simpler than using mechanical cam actuation. Depending on just which ocnfiguration of valve you use you can control the steam inlet duration dynamically to compensate for power adjustment (torque control), and/or you can add dynamic valve opening timing depending on RPM.
Compounding - for electrical generation you don/t realy need a special engine with increasing cylinder sizes, simply pass the exhaust steam from one york engine over to the input of two york engines plumbed in parallel, then 4 engines in paralell etc., each engine turning it's own DC electrical generator (salvaged permanent magnet 12-24 VDC sidewalk scooter motors or 90 VDC treadmill motors used as generators), take whatever output each generator is capable of producing and use it as the input to a multi-input Universal Power Supply (UPS) that combines the input power from all the generators into one standardized and regulated electrical output, no mechanical connections or syncronizing needed between the individual units. A true multi-cylinder compounding engine would be more efficient but not something nearly as available as reworked junkyard auto parts.
MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329
Posted: 04:12am 12 Jun 2010
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tim c cook
That's a novel approach; good for you -- making use of salvaged compressors. I suppose two compressors with the same sized pistons would be the same as another piston twice as big as in a true compound application.
I think I'll stick with windmills for a while. They are just as much fun to build and watch spin as the little air engines as far as I can tell so far. I used to be of the opinion it was easier to compress and store 'wind' (air) and then run it through a modified steam engine to extract electricity. Now, I've changed my thinking and have fallen head-over-heels for the axial-flux alternator -- direct-coupled to a high-speed wind geny.
Keep up the good work. Looks like you're headed in the right direction.
. . . . . MacNothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
tim c cook Newbie Joined: 02/06/2010 Location: United StatesPosts: 11
Posted: 04:44am 12 Jun 2010
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Piston area - more vs larger - the piston area needed for the next set of engines will need to be deturmined by the temp (pressure) left in the vapor exiting from the prior stage of engine(s), depends on the losses through each stage, may need 3 or even 4 engines in paralell to get usable electricity, at some point the speed of the far bank of engines will have dropped so low there will no longer be any meaningfull amount of power produced, testing will tell.
Probably easier to just accept the extra efficiency losses caused by the need to do extra condensor cooling of the exaust vapor from only one engine. Building multiple stand-alone systems and feeding the power from each system to the UPS unit is probably better, this would also eliminate complete loss of power generation if something caused the shutdown of any one system.
(are you the same MacGyver that developed the upflow vegoil cleaning setup posted about on biodiesel infopop a couple years ago?)
Don B Senior Member Joined: 27/09/2008 Location: AustraliaPosts: 190
Posted: 09:30am 12 Jun 2010
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Hi Mack,
Yes you are probably right - solenoid valves for inlet valving may well be nothing but grief, but I need to have proved this to my satisfaction before I give up on them. As Tim says, at least they don't need lubricating (though they may need cooling).
I am using lawnmower engines because they are easy to modify (particularly the older ones with cast iron camshafts), and I acquired my collection from the local recycle shop for $4.00 each. The same is true for the induction motor that will be the generator, the air compressor that will become my vacuum pump and condensate storage tank, and the HP spray pump that will be used for the feedwater pump.
None of this stuff may be optimal, but at least it is affordable (or within my fabricating capabilities). If my rig is successful, then I can look to optimise or replace the parts that underperform. At the end of the day though, it is only experimental, and I don't expect it to be still running in 20 year's time.
The lawnmower engines have their crankshafts sticking out at each end, which made them easy to couple. The only criteria that I had when buying them was that they had to still have good compression. They are not the deluxe Briggs engines with cast iron liners, just the plain ole aluminium ones, but I am sure that they will hang in long enough for my purposes.
Yes, I will probably have some problems with water collecting in the sump oil, and oil in the steam, but I think that my arrangement will cope well enough with this. Time will tell.
Compounding, as you say, lets you extract the maximum amount of work from the steam before you either exhaust it or condense it and return it to the boiler. My engine has a single pass only, and I therefore have to rely on extracting the maximum amount of heat energy back out of the steam in the exhaust heat exchanger, and sending it back to the steam generator in the feedwater to go around again. Heat that comes out of the bottom end of the heat exchanger will be lost in the radiator that will do the final condensing, and that lowers the efficiency. Low efficiency means that I need a bigger solar collector area, which means more cost and more real estate occupied, both of which I want to avoid.
I think that Tim is on to something workable with his scheme of using refrigerant gas in a modified York type compressor (or several) which can work as a closed system at lower temperatures. It would be possible for me to put refrigerant gas through the exhaust steam heat exchanger rather than feed water, and this would let me run something like his rig at the bottom end. I need to do some sums though to see how much improvement in efficiency I would get for the trouble of adding a refrigerant gas bottom end.
I had not thought of a peristaltic type of engine but, as you say, there are a lot of potential advantages in never letting the working fluid out of the pipe. I would be interested to know what sort of tubing you were using in your engines, and what your experience was.
RegardsDon B
MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329
Posted: 01:28pm 12 Jun 2010
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[Quote=Don B]I had not thought of a peristaltic type of engine but, as you say, there are a lot of potential advantages in never letting the working fluid out of the pipe. I would be interested to know what sort of tubing you were using in your engines, and what your experience was.
I used latex tubing like the stuff in a Wrist Rocket sling shot. It is cheap and readily available in many wall thicknesses. I always kept my working pressure under 40 psig and found that to be sufficient to run all my toys. Any higher pressure popped the tubing if things hung up. By the way, you haven't lived until you've popped surgical tubing! Talk about a loud "Bang!"
By way of a suggestion; I found the best valving for the lawnmower engine conversion was to construct a rotary valve. I pulled the valves out of the original engine, cut the stems down and reinserted the valves back into their lands. I also pulled the timing gear out of the crank case to relieve the friction of it rubbing the cam lobes on the main shaft.
Next, I used a solid aluminum head and line-bored a hole through it from one side to the other using a running fit of about .005" clearance between the valve and the head. The valve was just a piece of pipe (thick brass) and I fitted a sprocket to one end and a shoulder on the same side. There was another shoulder on the far side, with a 1/4-20 set-screw holding it there; again a rather loose fit.
I cut a hole in part of the pipe, which ran clean through the side and a partial annular groove in the pipe about an inch away. I should mention that the diameter of the hole down the center of the pipe was about the same size as the wall thickness. I made the pipe out of a solid 1" brass round bar.
As the chain from the main shaft turned the sprocket attached to the valve, it rotated the annular groove past the inlet port letting the pressurized steam (air) into the cylinder. Next it rotated the exhaust hole past the outlet port and let steam (air) out. The spent steam (air) exited through the open center of the rotary valve (pipe) slick as a whistle! Timing was just a matter of adjusting the position of the sprocket on the pipe.
The inlet port was rather small and the outlet port was HUGE in comparison. The reasoning here is: you want to get the low-pressure (used) steam (air) out fast. Getting it in under pressure is no feat, it's the getting-it-out-fast part that makes things work well. Remember, momentum and that piston are being used to shove the spent steam (air) out and you want to make it as easy as possible for the thing. Mine ran like a scalded dog!
That's about it; have fun with it.
.....Mac
Nothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
GreenD88 Senior Member Joined: 19/05/2009 Location: United StatesPosts: 104
Posted: 03:42pm 12 Jun 2010
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I would be really careful. Heated Liquid refrigerant can easily reach 1000+psi if not controlled precisely. And unless you use a high enough pressure you will have to cool the vapor well below ambient to liquefy it again. On a 100*F day you would have to have a pressure greater than 200 psig for R-22. Then after you heat it the pressure will skyrocket. And for R-134a for a 100*F you would only need around 125psig. Unless of course you water cooled down below 60*F. That would lower R-22 down to around 100psig and R-134a down to 60psig for the liquid side. And never allow liquid refrigerant to enter a pump it will destroy it faster than anything. The only type of compressor that can handle a LITTLE bit of liquid refrigerant is a scroll compressor. Piston ones will be destroyed from the tremendous hydraulic pressures when operating as a compressor.
Is this kinda what your were thinking about? Just a crude drawing I drew up.
Only thing would be figuring out how to keep the high pressures evaporator vapor from going back into Liquid reservoir while keeping a flow of liquid to the evaporator. You'd have to have feed pump. In my opinion a low pressure water steam system would be so much easier and safer.
On a side note if you guys used superheated steam you wouldn't have to worry about lubrication problems. Dry steam works great with oil.
Edited by GreenD88 2010-06-14Licensed Master Plumber / EPA 608 Universal License / 410a Safety Certified / Medical Gas Brazer/Installer
MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329
Posted: 05:26pm 12 Jun 2010
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Side Note:
Seems to me, if my memory serves me well, R-12 at least, turns into some kind of poison gas called "phosgene" or something like that, so if you're using a concentrating collector with refrigerant, be careful. Also, seems to me the figure of 1620*F was where it happened; maybe not, I dunno.
Of course, it's been 40+ years since I went to AC&R school in the military. AC&R stands for "air conditioning and refrigeration"; I remember that much for sure!
If your interest in all this is merely hobby, I'd use steam and just let the oil-water emulsified mess drip on the garage floor. If on the other hand, you're on a first-name basis the folks over at the Guiness Book of World Records, well, that's a horse of a different color!
. . . . . MacNothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
GreenD88 Senior Member Joined: 19/05/2009 Location: United StatesPosts: 104
Posted: 06:51pm 12 Jun 2010
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Here's the thing alot of them when exposed to too much heat will decompose into acids, and toxic gases similar to mustard gas. That's why when a compressor burn out happens it's recommend to do a flush. And the acids will eat away the pipes. So you really need to regulate the temperature below 125*F.
Best would be to set up a water solar collector and pump it into a storage tank keep the temp below boiling and then mix with cold water to get the temperature you want. R-22 tanks warn against heating above 125*F because all the liquid could flash and cause a tank explosion.
"Off Topic"
Beside unless you have a license all you gonna be able to buy is R-134a or use propane, or butane maybe a couple others. Some say high refined propane is better than R-22 but manufactures won't use it because of the liability of gas leaking and causing a fire. It uses lower pressures and some claim higher energy savings compared to R-22. It's actually sold as a drop in replacement for R-22 too.Licensed Master Plumber / EPA 608 Universal License / 410a Safety Certified / Medical Gas Brazer/Installer
tim c cook Newbie Joined: 02/06/2010 Location: United StatesPosts: 11
Posted: 08:07am 13 Jun 2010
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I actually do have a universal frig tech liscence but the intent is to use propane, cheap, and I happen to have a 1000 gallon tank of it on hand. The propane tank pressure rarely causes the 425 pound pop-off safty valve to trip even when in full sun but even poor solar exposure will create over 200 pounds pressure. The propane will also condense back to liquid at around 100 pounds pressure if cooled below 100 deg f, I converted an old window air conditioner to use for sucking propane vapor from smaller tanks, condensing it back to liquuid, and pushing the liquid back into the big tank. on a hot 90 deg day I have to spray a bit of water on the condensors to keep the condensing pressure down below around 150 pounds so I need to use more condensor area than is available from the two smallish radiators found in the small 5000 BTU window air conditioner that I am using for this.
I have been running temp tests on a cheap-n-dirty swamp cooler to possibly use to create cooler air, so far the swamp cooler shows it can convert 102 deg f air temps into about 78 deg f air if the relative humidity is under 10%, it evaporates about 2 gallon/hr of water in the process (testing this in Arizona).
The idea is to collect and store the solar heat in used deepfry vegitable oil so it can supply heat to the system 24 hrs/day, I have lots of used veg on hand also as I run my diesel pickup with it as well as heat my shop with it. Collect heat as long as the collectors are hotter than the insulated storage tank, use a veriable speed DC pump to move the hot oil through a small boiler tank to vaporize the propane in several feet of coiled frig-rated copper tubing inside the small boiler tank. The amount of heat storage fluid pumped through the boiler will control the pressure/volume of the propane vapor being supplied to the expander engine based on engine rpm which is based on generator load. A DC automotive generator will be used to charge batteries for electrical storage. I have a couple salvaged 24 volt 1100 amp-hr forklift batteries to use for the battery bank and a few old 24 VDC 1 and 2KW inverters to create 110 VAC. The solenoid operated hydraulic reversing valve used as the steam valve for the york engine dictates that the engine receive pressurized vapor for the full down stroke of the piston due to the other half of the valve exhausting steam for the full up stroke of the other piston, this is not the most efficient approach but produces high torque at some lower rpm. The york compressors also have a water jacket space around the outside of there cylenders so passing more heated storage fluid through that might cause some extra vapor expansion inside the cylinders to help with efficiency, still have to try it?). I have several 18-24 inch pulleys to put on the engine to spin the 2.5 to 3.5 inch pully on the 100 amp chrysler auto alternator(s) and/or 1 to 1.5 KW 90 volt permanent magnet treadmill motor(s) (I also have an old 2KW 90 VDC-to-110 VAC resonant inverter)). The older 100 amp alternator (70's and 80's chrysler products vehicles) has a larger diameter than modern ones and can produce the full 100 amp output at around 2000 rpm so the engine only needs to run at 300-400 RPM, if the setup has more available power I have more alternators.
Boiler feed pump - The idea here is to use a small 250 pound rated SS air cylinder with external check valves as the feed pump, connect the cylinder ram to a reworked crank arm on a 12 VDC windshield wiper motor, only stoke it often enough to keep liquid in the boiler. Wiper motors have HUGE torque available and if a small 3/8 inch diameter, or less, cylinder is used, the plunger pressure needed to push the condensed liquid propane back in to the boiler only needs to be something less than 175 pounds even with a boiler pressure of 400 pounds.Edited by tim c cook 2010-06-14
GreenD88 Senior Member Joined: 19/05/2009 Location: United StatesPosts: 104
Posted: 12:57pm 13 Jun 2010
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Well it's good to hear you have a license messing with frig systems. And it sounds like you have a handle on things so I'd be glad to see how it all turns out keep us updated. Hopefully you'll get more out then you have to put in to run it. I bet it's gonna be one heck of a balancing act getting it running and running good.Edited by GreenD88 2010-06-14Licensed Master Plumber / EPA 608 Universal License / 410a Safety Certified / Medical Gas Brazer/Installer
neil0mac Senior Member Joined: 26/12/2009 Location: AustraliaPosts: 210
Posted: 10:35pm 13 Jun 2010
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Off topic: I have oftern wondered why Air cons weren't available with a small(ish) tank of water instead of the outdoor condenser. Yes, adjustments (Lower pressure?) would be necessary to prevent the inside from icing up. But consuming less power?
GreenD88 Senior Member Joined: 19/05/2009 Location: United StatesPosts: 104
Posted: 01:56am 14 Jun 2010
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Because water cooling isn't effective everywhere. Most effective in low humidity/low dew point areas. They do make water cooled condensers though most residential's don't use them. And you can convert one to be water cooled just by adding a pipe around the top with nozzles spraying on the fins and adding a fan pressure cut out switch to keep the pressures in the right area. And if you want to be real fancy add a sprinkler valve with a temperature control on it to automate it to use water only when it's really hot outside. Condensers start losing a lot of efficiency above 95*F.Licensed Master Plumber / EPA 608 Universal License / 410a Safety Certified / Medical Gas Brazer/Installer
neil0mac Senior Member Joined: 26/12/2009 Location: AustraliaPosts: 210
Posted: 02:03am 14 Jun 2010
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Because water cooling isn't effective everywhere. Most effective in low humidity/low dew point areas. They do make water cooled condensers though most residential's don't use them. And you can convert one to be water cooled just by adding a pipe around the top with nozzles spraying on the fins
I have used a normal garden hose nozzle cut back to conserve (bore) water. Problem, of course, was the water left a lot of calcium behind it. (This was behind my comment about the inside exchanger icing up.)
GreenD88 Senior Member Joined: 19/05/2009 Location: United StatesPosts: 104
Posted: 04:17am 14 Jun 2010
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The calcium would cause the pressures to rise by not allowing enough air to cool the condenser. This would raise the temperatures and not cause icing. Now if you cool it down enough with the water you will lower the pressure enough causing the temperature to fall below freezing at the evaporator. Low pressures and dirty filters cause icing of evaporator and lines. Dirty condensers cause lack of cooling (evaporator temp rise) by not allowing all or none of the refrigerant to condense to liquid. Now with a simple pressure cut out switch you can regulate the pressures at optimum. They screw onto the Schrader service port with a tee to still allow servicing, and are wired in series with the fan and water valve. Basically you want the fan and water to shut off if the pressure drops too low and come back on when the pressure rises above what you want. The switches are only about $20 at a HVAC store. And are essential in a properly converted water cooled system. You could use two of them or use one to control two relays. Or just one and turn just the fan on and off. Although it would be more effective to control both the fan and water.
P.S. Condenser coils should be cleaned regularly anyways. In my opinion at least every 2-3 months with a good coil cleaner during the cooling season.Edited by GreenD88 2010-06-15Licensed Master Plumber / EPA 608 Universal License / 410a Safety Certified / Medical Gas Brazer/Installer
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