steam engine

[greenkarson]

I've been working on a steam engine.  Built out of a air compressor.  It runs very well on compressed air but now trying it with steam im running into trouble. On my fly wheel there is a wooden wedge that with every revolution triggers a roller valve.  That blows the air into the cylinder head. the weighted flywheel keeps it turning till it trips the valve again. ath the bottom on the piston stroke i'v drilled 8 1\4 inch holes to allow the compressed air/steam to escape.  All this work exceptionaly well with compressed air.  But as soon as i tried it with steam it seems to flood its self with water after 1 revolution. So im wondering does steam need bigger vent ports?  Or is there something else at play here? this may sound stupid but is it possible to have to wet of steam?
here is a few more specs
-runs fine on air from 60 to 120 psi
-seems to run the best at 80 psi (air)
-80 psi (air)=185 rpms
-all 1/4" fittings
-tried steam from 50 to 110psi same results flooding

[RP]

One thing that should help a lot is to insulate the cylinder. 

Those fins that helped to get rid of the heat when it was an air compressor are working against you now.  You want the cylinder to stay hot so your steam doesn't recondense back into liquid water.

[DanB]

I'm no expert here but I do have/run a steam engine and these are my thoughts...

steam will condense pretty quickly when it comes into a cold engine.  insulating the cylinder is a good idea, yours is all wrong at this time having cooling fins, which will serve to keep the engine cold (it needs to be kept hot)

All the steam engines i've known have pet cocks in the bottom of the cylinder to let the water out.  Upon starting the engine, the petcock should be opened and it should be run that way until the engine is hot and water stops coming out.  You can really damage an engine if you forget the step of doing that.  I always start with the petcocks open and shut down with them open (because usually when Im shutting down the pressure is low and the temp is down) .

[JW]

I can second what the others have said. Get rid of the cooling fins. Running on compressed air, they will work in your favor, since they are a heat source to ambeint air temp.

Insulation on steam engines is called "lagging"

Also you may need some supeheating of the dry steam to combat heatloss, resulting in condensation in the working cylinder. I would enlarge the 1/4 in holes to at least 1/2 in. "if" this will not weaken the cylinder to much, im not sure about what your cyl diameter is or wall thickness.

Be wary of the exhaust steam, because it needs some form of containment, so you dont get burned or colapse a lung.

Steam commands respect, observe Barlow's formula,(google) on bursting pressures, and maintain a 4 to 1 safety factor, even if your using a flash coil monotube boiler use a safety valve, and duct the release pressure away from you.

Be carefull

JW

SAFE COMPONENT SELECTION----When selecting a component, the total system design must be considered to ensure safe, trouble free performance. Component function, materials compatibility, adequate ratings, proper installation, operation, and maintenance are the responsibility of the system designer and user.

[greenkarson]

yesterday i drilled more vent holes all around the cylinder except in the direction of the flywheel.  Two rows of 1/4 inch holes tried it again with air.  It worked fine. So I fired up the boiler. tried from 60 psi to 100 psi (the range that seems to work best with air) engine seemed to want to start at first the flywheel made about 1.5 revolutions then stopped.  the cylinder seemed to vent fine this time with no water.  But seems like valve is not letting enough steam into the cylinder.  is it possible to need the valve to stay open longer with steam than with air.  I was spinning the flywheel until the wedge on the flywheel was compressing the valve but instead of letting it go i would hold it there for a second and it would build up a enough pressure to spin around about  3 times. but if i just rolled it to the valve and let it go on its normal timing it would only have enough power to spin about a 1/4 turn.  So I'm wondering if i might be able to make my wedge longer so it keeps the valve open longer. right now the valve is only open for about a 1/4 inch of the 2 inch stroke.

anybody have any idea about the life span of 12v solenoid valve?  just thinking it might be easier to play with the timing if they had a reasonable life span.
 
i think i may try the longer wedge in the next couple of days to see if more steam is the solution
again any info would be appreciated
thanks Karson

[RP]

On a cold engine, your steam goes into the cylinder and immediately condenses back into a few drops of liquid water leaving a vacuum in the cylinder.  You'll need to preheat the cylinder and piston somehow.

Can you install a vent valve in the head so you could "blow" it out for a minute or so with steam to get it hot?

[greenkarson]

the "vaccum in the cylinder" comment got me thinking it makes sense. The steam gets shot into the cylinder giving me the initial trust for the first split sec pushing the piston down.  But then condenses back to water creating a vacuum. which tries to reverse the piston direction.  Explaining why i only get a half revolution.
 I'm thinking I might avoid this by insulating the line between the valve and the cylinder head as well as the cylinder. And before trying to start the engine roll the flywheel so the piston is all the way down.  Then i could manually push the valve open letting steam blow through the line and cylinder and out the exhaust vent until it was all up to temperature.
  Now that I'm writing this i realize it's what you guys have said all along

Another thing I've been wondering about adjusting before i fire everything up again. is the Lenght of time the steam is blow into the cylinder compaired to the piston stroke.  right now mine is less then a 1/8 of the stroke.   Any recommendations?
thanks again

[JW]

Another thing I've been wondering about adjusting before i fire everything up again. is the Lenght of time the steam is blow into the cylinder compaired to the piston stroke.  right now mine is less then a 1/8 of the stroke.   Any recommendations?

It (duration) should be 1/3rd the downward(power) stroke... {calculate degrees rotation,(of the crankshaft) from (actual) liner movement at the top of the piston, moving down from the engine block deck height}

This cutoff setting will give you good low and midrange torque. Im guessing you wont need top end power, and this accommodates bad valve harmonics, which would limit top end speed anyway, regardless of supply pressure.

dont forget the "safe component selection thing"

JW

-edit- grammer correction-

[greenkarson]

yesterday fired up the boiler again with great expectations.  i had insulated everything, adjusted valve opening time and blew steam through the cylinder to preheat everything only to realize my valve was the problem.   It is a pneumatic roller valve worked fine with air but when it would get hot from the steam it would not return totally the closed position allowing some steam to still blow by and stopping the piston from returning to the top of the cylinder. So i abandoned the roller valve and this morning made a good solid bash valve. after a little adjusting it seems to work very well climbing to almost 1500rpm with no load. tomorrow i will try again with steam but I'm confident this valve will work this time.

So this brings me to my next question.  How to determine what wattage would be appropriate for this engine.  what is a accurate way to load the engine and measure the available power?

[TomW]

So this brings me to my next question.  How to determine what wattage would be appropriate for this engine.  what is a accurate way to load the engine and measure the available power?

Green;

Try a search for "prony brake" include the quotes too. That is pretty simple to rig up and commonly used for finding the torque for a power source. Once you have torque and RPM you can determine power with some math.

Tom

[harley1782000]

I have a question.  How long will this last since it wasen't for steam use??

[greenkarson]

Tried steam again today with some limited success at about 75 psi.  I could turn the flywheel until the steam fired i would make about 6 revolutions then stop its self.  It seems to me like it builds up water in the cylinder until there is too much for the flywheel to compress then stopping the piston from coming all the way up.  I just can't figger how its getting so much water built up in the cylinder. The cylinder is vertical with two rows of .25" vent holes at the bottom of the piston stroke around 3/4 of the cylinder (holes in the picture above are now continued farther around the cylinder)
  Is it possible that this is still not enough exhaust holes to allow the steam to properly escape? another thing i noticed that may be an issue is that the piston goes almost .25" down past the lower vent holes.  I'm thinking this may allow the piston to scoop up some of the condensing steam.  I'm going to take the piston out and drill another roll of holes down lower to try to prevent this from happening.
I'm just going to add a list of facts here. To help every body understand whats happening.

[greenkarson]

here is the list
-simple bash valve. very solid stainless steel
-works very well on air up to 1500rpms with now load
-even with cylinder very hot still seems to collect enough moisture to stop its self after about 5 revolutions
-cylinder and valve is insulated
-will run very slowly at about 90psi steam for about maybe 50 revolutions before it stops its self
-2 rows of .25"exhast holes around 3/4 of the cylinder near bottom of piston stroke

here is a fact that may be important that just popped into my head as i was tryping this
there is just the thicknes of the gasket between the top of piston and the bottom of the cylinder head when the piston is all the way up.  May be 1/32" at most maybe this is a issue?

[bj]

Green--been following with great interest.  Before I say anything, I have only built one, and about 30 years ago at that.
Your lack of condensate clearing issue might  be coming from the fact that you have used all the energy in the steam
long before bottom dead center.  If that is the case, then somewhere on the down/power stroke you could be creating
a vacuum in the cylinder, which would cause the condensate, or some of it, to be sucked back into the cylinder.  Liquids
don't compress worth a darn, so on the next upstroke, or two,  you start to hit a brick wall.  With the small head chamber                                                                                          that a compressor has, it wouldn't take a lot of liquid.
If your steam inlet valve timing is easily adjustable, maybe try lengthening out until you see noticeable steam waste out the
exhaust, and see how it runs.
If none of this applies,  feel free to ignore, but good luck.  It is a neat project.

bj Lamont AB Can.

[greenkarson]

anybody each think the same?  what would you recommend to remedy this?  drill another row of holes higher on the cylinder to let the steam escape earlier??

[harley1782000]

I think I would go with a longer burst of steam too.  I have been following this too and I would like to see it run.  If you drill more holes it would be harder to plug them than to just try a tad more steam for along period of time.

[bj]

   I went through the thread again, just to clarify, and RP had a suggestion to preheat, actually so did Dan.  Maybe put it at bottom dead center,
and manually hold open your bash valve until you get fairly dry steam out of the exhaust, and try again.
   You're close enough to know it can work, you've just got to find the sweet spot.

[bob g]

maybe i missed something,

are the ports at the bottom of the cylinder the only place for the steam to leave the cylinder?

do you not have an exhaust valve to allow venting of the cylinder once the piston returns up past the ports?

if you don't it looks to me like you are going to compress whatever is left in the cylinder after the ports are closed?

have you tried running your engine  on compressed air to make sure that it will run properly?

lots of questions i know  

bob g

sorry for the questions, i went and educated myself on bash valve engines
interesting concept, however they don't look to be very efficient?

carry on! 

[greenkarson]

Thanks again everybody for your ideas and suggestions.
   I've tried preheating the cylinder by letting steam blow through it until the whole out side of the engine was hot enough to boil water.  With the same results.  Now I've drilled a .25" hole straight down through the head beside my bash valve. And threaded it to accept a bolt for a plug hopping i can start the engine with the hole open a little to allow the compressed water somewhere to go.  I done some testing yesterday with air again i put a little squirt of water in the cylinder. just put the plug bolt down a little in the hole and fired it up with compressed air the water sprayed out around the bolt treads.
  IM hopping i can release some of the pressure off the piston up stroke this way until it gets up to speed then tighten the bolt.  anyother ideas how to release this pressure would be very appreciated.
   I should have some video of it running on air by the weekend hopefully steam as well
thanks

[blownoiler]

It sounds like you need an exhaust valve in operation.......

[harley1782000]

Woulden't you need some weight on one side of the fly wheel to help it out???  Most of the steam engines I have seen have a counter weight.  Just a thought or a ramble...

[JW]

Green K,

 If you view things from the theoretical periscope, you will realize, that when you run the engine from a compressed air source (non-condensable vapor), the air is in a superheated state.

 This highlights the perilous situation of "flash steam engine" design. Its interesting to me, that until superheated steam is entered into the equation, both live steam and flash steam engines fail to opereate.

You need to have the incomming steam far and away from the saturated range. even if its only by a coupla degres f.

JW

[greenkarson]

any ideas how to super heat the steam?

[greenkarson]

im using copper tubing now from the boiler to the engine because of its high burst strenght.  Do you think i can turn the tubing back into the burn chamber and form a coil and then back out to the steam engine ?

[Airstream]

Everything looks like a nail when you're a hammer! You seem like a kid living next door to a fireworks shop or something... Do be cautious!

[JW]

Hi,

 

any ideas how to super heat the steam? Do you think i can turn the tubing back into the burn chamber and form a coil and then back out to the steam engine ?

Yes that would work.

im using copper tubing now from the boiler to the engine because of its high burst strenght

I realize you mentioned you working with only about 75psi. But this is still a pretty scary comment. Copper is not the best choice. Use steel.

http://www.engineeringtoolbox.com/steel-tubes-working-pressures-d_98.html

The engine design your working with is called single acting. You need to spend sometime reading about boiler code before you proceed. Even if you dont have to get something certified, you owe it to yourself, to famiarize yourself with boiler code. Also you should consider a compound engine design. This can be single acting aswell. Do some more research...

If you choose to work with a steam engine, safety and workability come with it. Unfortunitly theres not much out there in the way of kits.

I started to build my steam engine (flash steam) about 17 years ago, im just now becoming satified with the design. Im my work I wanted to get away from a boiler completely... Its hard to do i know. Also the design employs an "explosion proof"  engine block design. Also I made the engine design "open source" its not propretary here is a relevant link. http://www.flashsteam.com/steam_proj3.htm

Learn as much as you can from whatever sources you can find, this is a good resource for information on steam engines

http://www.steamautomobile.com/lcc/index.htm


SAFE COMPONENT SELECTION----When selecting a component, the total system design must be considered to ensure safe, trouble free performance. Component function, materials compatibility, adequate ratings, proper installation, operation, and maintenance are the responsibility of the system designer and user....

JW

[JW]

Green K,

 Ok, lets run down some things.

Your engine is single acting, as steam is only applied to only one side of the piston.

Your engine can be classified as a "Uniflow or Williams" type of engine. This is because you use side exhaust porting, in this case some of the remaining (working fluid) air or steam is recompressed.

You need to determine your clearance (sometimes reffered to as compression ratio).

Here is a proceedure-

Get a compresion tester at an auto parts store. screw the end of it directly to your cylinder head. Take some rope, wind it around the crankshaft and manually spin the engine over by pulling the rope briskly...

Note the reading on the gauge of the compression tester, that is your minimum pressure threshold, anything lower than this pressure and the engine will "stall" (not even run at idle). Anthing higher than this pressure will cause the engine to run, once its been spun over. Often single acting engine's are not self starting, unless multiple cylinders are involved.

Also to complicate things, steam is more dense than air when compressed. providing your not having condensation in the cylinder(which you are) superheating will only compensate for that, not the "min pres threshold".

Also, dont use some cheesy peice of copper tubing inbetween "you" and your "main steam supply". And if possible, locate the valve seat of your steam admission valve as close to the cylinder/head as possible.

best

JW

[JW]

Here's the stuff I use for my superheater coil<link>. The tubing is sch 80 @1.5in diameter, with external fins tig welded on. Inside the tubing (id) there is a turbulator. The coils (3) have an od of 8in in ther coil. Also ther is shielding/shell around the combustion chamber. The inconel is important because, sometimes the superheater is overheated (which causes loss to tensile strength), when there is not steam flow due to standby mode. While under operating conditions (with my engine system) the circuit handles 16psi or 1psia. However is not uncommon for inconel pipe to safely carry pressures to 1000psi, with good safety factor(4 to 1) that is temperature compensated. This is the main problem using copper tube: its tensil strength deteriates rapidly at temps over 212*f.

http://pacificalloys.com/Inconeltubing.html

Trust me the tubing is much cheaper than the hospital bill, if theres a loss of (dry/superheated steam)containment, while your making a bunch of steam... Are you using liquid or solid fuel?

Best

JW

[greenkarson]

Hey its Canada healthcare is free.  But more seriously I appreciate all the info you guys provide.  My boiler testing is on hold until i have sometime to do all the math and some research.   from the specs i found on line 3/8 copper tube is rated for more psi then steel http://www.copper.org/Applications/plumbing/techref/cth/cth_1stand_prop.html
is it steals ability to handle heat that makes it better then copper?  how many feet of tubing would the average coil need? is it possible to buy a premade coil for a woodfired boiler?
sorry for all the questions but there is such a wealth of information in this forum

[greend88]

Copper has no place in steam ever. When it gets hot it essentially softens lowering it's capability to handle pressure.  And I would only use Schedule 80 in Steam use if you expect to last at all.  I've seen schedule 40 pipe get ate away in months.

Union Pipefitter

[harley1782000]

So Mr. GreenKarson

Update us, does it work yet???  Very intrested in what you have found out lately.

Jim

[greenkarson]

Sorry still no video. Had some minor setbacks i broke my piston arm in a non steam related event.  But its fixed now as soon as i post this I'm going back out in the garage to tinker some more

[greenkarson]

A couple more questions.  Anybody ever have any experience with making a roller valve.  In my case it will have to be chain driven.  Here is a crude drawing done on windows paint to try to explain what I'm thinking.  My bash valve seams to be to unreliable to be of any long term use.  So looking for other routes.  Any ideas or thoughts on the subject.