Towards a wood fueled pulsejet

[vturbine]

Mark, do your piglets run well in summer, and what are your starting and ignition methods for them?

[Mark]

On a hot, humid day I wouldn't even attempt to run my piglets. It's like night and day compared to a brisk sunny day in winter. I once saw a large pulsejet for sale on eBay, a really nice, sleek valved pulsejet I think around 50 pounds of thrust. It was built to run on methanol. The seller was from Florida and his comment has stuck with me. He said it "will not run in summer in Florida". Of course a pulsejet will run in summer in Florida on methanol if designed properly. I have run my Tigerjet on methanol in summer and also a homemade valved engine 3 inches in diameter. But you can tell the difference in the sound they make and also starting my homemade pulsejet is much harder in summer. Starting pops are very sluggish.
The neat thing when conditions are right is that if I prime or coat the insides of my homemade valved pulsejet with methanol and then spark it with a simple piezo sparker, there is a fair chance that it will start on the first pop, if the outside temperature and humidity are favorable. I'm a big fan of the instant on effect and methanol can do that for you if you have cool, dry air to work with. Nothing is more exciting that not running a pulsejet for months on end and you go to start it and it bang starts, running full grease instantly.
I couldn't even get my pint snorkelers to really run in the air conditioning of my house yesterday. They just started and died, loud for a second and then rapidly falling off the chart, a failure to thrive. Whereas in winter they are off and running, eager to play - effortless and carefree.
You will see how fast a flame front can travel with methanol if you play in the cooler, dry days of spring, fall, or winter. Then, methanol will make you look good, like a sorcerer. ha

A useful tool for jam jar performance.
http://www.cigarextras.com/ProductImage ... ter-ce.JPG

Not the whole story but a start.
"Sorry Ted, but higher humidity means the air is *less* dense. Water vapor is invisible and is *lighter* than air. When the water vapor in the air condenses it becomes fog/clouds. Most think that since water is heavier than air, moist air must be more dense than dry air.but that is not correct.
Increased humidity increases the density altitude and that means longer TO distances and poorer engine performance... Took me awhile wrap my brain around that fact - almost ran out of runway on a hot, humid day and that convinced me."
http://74.125.95.132/search?q=cache:v8O ... clnk&gl=us

[vturbine]

mark is your sparker used at the snorkel, or do you spark a plug, and if so, where is the plug located?

[Mark]

For my snorkelers I just slosh the methanol around on the big ones or invert them and then right them to coat everything. I always light them from the tip of the snorkel with a long nose butane lighter made for lighting fires.
I put a tiny 1/4 32 spark plug on one pint snorkeler but I hardly use it. If you were to get the spark plug wet with methanol, it won't spark very well. So if I did use the spark plug I would try to be careful not to get the electrodes wet, but swirl the methanol enough so that there is enough vapor for starting.
One fun thing I did was use some platinum sponge and platinum wire which hung just below the lid of a canning jar. Then I added methanol through the hole in the lid and swirled the jar gently and set it down. A little bit later, perhaps 10 seconds the jar would instantly start up on it's own. The neat thing is you don't know when it's going to fire, but it's funny to be startled from the ignition out of the blue.
Platinum sponge will heat up in methanol vapor and transfer the heat to the platinum wire which then glows red hot and eventually ignites the methanol. Platinum catalysts will also light hydrogen.
I had a liter flask with methanol in it and sprinkled in the tiniest bit of talc-like platinum on alumina powder. The little particles would glow as they fell/floated through the methanol vapor. Then the vapor ignited suddenly and it startled me so much that I dropped the flask and it broke. Another thing I would do is put some of that powder in a petri dish and mist it with some methanol from my squirt bottle. Shortly a fire would break out. I suppose you could sprinkle some platinum dust down a snorkel if you wanted to be different. ha

[Rossco]

Steve, sorry i have not jumped in before to welcome you, and let you know that i am a big fan of your stuff.

Separately i have stumbled upon or read a lot of your work, i feel we're old mates!
And now you show up here, hearty welcome mate!

Just heading out on work for a couple of days, and limited time now, although i would very much like to discuss some concepts when i get back.
On most of your projects actually, and at least solid fuel combustion!
For the time being, a note or two here.
I have run a PJ on solid fuel, plastic... kind of intentionally, although not for very long. It can be done.
I've played with Reynst cumbustors on wildly varying fuels, and cringe at the frustration of these things still.
And last, but not least, I know of an intermittent combustion chip furnace. My grandfather and Father used to run one.
I will get some more details soon, as i have been always interested in building/testing the concept.

I'm camping out at this job site, and along with my gasifier stove, now i will be taking some extra cans and pipe! You have me thinking a lot on reducing pyrolysis rate and wasteful (to updraft reliant systems) secondary air induction.

Rossco

PS Skype aussierossco

[Mark]

mark is your sparker used at the snorkel, or do you spark a plug, and if so, where is the plug located?

As I mentioned I put a spark plug on one of my little pint snorkelers. My piglet snorkelers I can screw a CM-6 10mm into a thread already on the side of the piglet. And on top of the piglet snorkeler I can screw in an Autolite 3095 which is a spark plug with 1/2 inch pipe threads. Then there is a 3/4 inch plug/igniter which I can with a reducer screw it in one of the 1 inch ports, it's a 3/4 inch pipe thread with a really long electrode. Those 2.5 gallon piglets have 7 female pipe thread ports, 2 of the 1/8 inch, two of the 1/2 inch. two 1 inch, and the big center one a 2 inch pipe threading. I bought them on eBay as a hydraulic tanks. Pipe thread heaven. ha
Anyway here's the little pint snorkeler, just to give you an idea.
And a picture of a 3/4 inch pipe thread spark plug igniter next to a tiny 1/4 32 spark plug, like the one on my pint snorkeler. The igniter looks nice but I haven't found a use for it yet. My old eBay days. ha

[vturbine]

Steve, sorry i have not jumped in before to welcome you, and let you know that i am a big fan of your stuff.

Separately i have stumbled upon or read a lot of your work, i feel we're old mates!
And now you show up here, hearty welcome mate!

Just heading out on work for a couple of days, and limited time now, although i would very much like to discuss some concepts when i get back.
On most of your projects actually, and at least solid fuel combustion!
For the time being, a note or two here.
I have run a PJ on solid fuel, plastic... kind of intentionally, although not for very long. It can be done.
I've played with Reynst cumbustors on wildly varying fuels, and cringe at the frustration of these things still.
And last, but not least, I know of an intermittent combustion chip furnace. My grandfather and Father used to run one.
I will get some more details soon, as i have been always interested in building/testing the concept.

I'm camping out at this job site, and along with my gasifier stove, now i will be taking some extra cans and pipe! You have me thinking a lot on reducing pyrolysis rate and wasteful (to updraft reliant systems) secondary air induction.

Rossco

PS Skype aussierossco

Hi Rossco! Well, to return the compliment, I've truly enjoyed what you've written here in this great forum. Although I don't think I've scratched the surface of your 573 posts!

But I really enjoy the Rossco flare -- I mean style! Surfin' on the big gun that was funny! Really great stuff you've done and a gas to read, too You've really advanced things, from what I can see.

Well heck, man turn that fertile brain of yours to this problem. I sure don't want to be the only one trying to make a pulsejet run on gidgee (whatever that is) or locust ( THAT I have) or even hemlock, which nobody likes to burn here.

The future of stationary combustion is unprocessed solid re-growable fuel, as far as I'm concerned. Why jump through hoops and take a perfectly burnable substance and remanufacture it using lots of energy in the process generating waste products and then, lets see, uhhhhhh burn it? I can understand processing and conversion for transportaion which favors fluid fuels. But for heat, stationary power, or generating? It's kinda like distilling tea to get the water out so you can make tea. The only thing that drives that is an inability to imagine that tea is already tea, and the profits to be made in distilling and selling distillation gear.

Burning wood straight is primitive. And burning high moisture content wood is prehistoric. High tech must mean conversion to synthetic fuels right? Whenever someone shows me a syn fuel they made at home with stars in their eyes, I always ask what is the waste product? Wood tars, acetic acid, glycerine from biodiesel, coal tars, etc. Almost every fuel conversion process produces another substance of concern. Yet syn fuel processing is where the big development money all goes. The focus would better be redirected to reducing fuel processing complexity, fuel processing energy loss and waste product problems. There is nothing that prevents the modernization of combustion technology for "primitive" cultivated woody biomass fuels. These could re-vitalize agriculture for woody brush growth in marginal agricultural areas, coppicing, etc. It does not mean the razing of forests or increased air polution -- or a return to the Franklin stove (unless you like them). It does mean treating the subject of wood combustion seriously and moving away from old ways of thinking about it.

I sense that pulsejets have some strong as yet undefined relationship with advanced woody fuel combustion, and possible power generation as well. My purpose here is to see if that relationship can be defined or proven in a very small (possibly even trivial )way. If it can be, maybe notice will be taken of the possibilities by others, and we can start on an energy resource direction that to me makes more sense than convoluted efforts to reinforce through synthetic mimicry our present failing fuel technology. Or simply transition to coal, with its attendant massive bound carbon release effects.

If not, at least we'll have had fun trying.

[vturbine]

Mark you're an amazing resource and one crazy experimenter. Fantastic curiosity and encyclopedic knowledge.....no...... experience... that's a more accurate word. Platinum powder and hand held paper egg explosions, ceilings on fire. I always want to read more but I also feel like I should donate to your life insurance.

Thanks so much for answering nube questions of mine.

I found out NGK CM-6 plugs are also called 5812. And also there are equivalents: Denso UM20U, and Champion Y82, in case that's any help to anyone.

Thanks also for letting me know about methyl wetted plugs. Makes sense.

I also thought about adding a bit of extra length to a typical spark plug electrode with spot welds. They aren't going into an IC piston engine cylinder.

EDIT:

Maybe a solution to the plug wetting problem would be an easily removable plug holder. Pull the plug before shaking the jar. Use that hole for air-out, too.

Looks like a mount spot near the top of the jar might help, as well, assuming it doesn't hurt the combustion.

[vturbine]

I ran the stainless tank jam jar today a few times with various sizes of snorkel. 5-1/2" provides easier start and longer runs but runs slowly and weakly. 6-1/2" runs hard fast and loud but is harder to start. Nothing ran for more than 20 seconds. Trials with short lengths and smaller diameters gave mixed results, but mostly not as good as the longer 3/4" pipe snorkels.

I'm pretty sure that the pipe fittings including the welded in socket are messing up the ability to run well. I did grind the transitions out to some small improvements. But I think an all welded cc and tail would work better. I also note that a lot of the more successful larger sizes of jars don't have the 2 to 1 height to diameter ratio, but are a little squatter. I'm sure the true Reynst jar works better, and just as sure I'll probably build one in the future, but I'm still interested in the simple cylindrical jar for now. I'd like to understand what makes for more reliable running in these.

This tank also has radiused corners, and I don't know if this is a help or a hindrance. Another question is, would a cone at the bottom of the snorkel help or hurt.

I don't think my tank jar can be improved without surgery, and the SS tank is too nice to cut up. I think I'll build a new jar from scratch this time, all welded mild steel. Then I can play around with modifications without worrying about it, and the transitions can be clean.

I also did put together and try out one of Pyrojoes J-draft pipe engines using 1/2" and 1" pipe fittings. This one had a 6" section of 1" pipe while the forum thread describing it shows a 4" section, though in the picture it appears longer? I didn't turn the pipe cap as Joe did. I did use a 5/16" hole first. I mostly just got single pulses, though there were one or two 1 second bursts of "angry bees". I did tilt it and did shake and tap it, but couldn't get it to sustain. I tried a slightly wider hole, and that really didn't seem to want to run. I then spot welded a 1/4" washer over the opening, and it seemed to want to run better than it had before. I got a few quick buzzes, but nothing sustaining.

Pyrojoe's J-Draft pipe engine with the proper 4" cc and turned cap:


I think the pipe transitions are really crude when I look at mine -- threads in the open, and on the single street elbow, the male end really has the wrong kind of taper on the outside of the pipe, instead of the inside. I'm not surprised it didn't run because it seems so crude -- plus the differences between mine and Joe's already noted.

[PyroJoe]

Remeasured the CC pipe and it truly is a 4" section. I tested the 6 inch in the past and had about the same results.Tested a 2",3",5", 6",8",10"and 12" also, but 4" gave the best results. It is important that there are no burrs from drilling, but, do not sand the edges of the hole smooth, it needs a good edge on the inside. Remeasured the hole, it is still .3125" Tail has to be 36". Test in low humidity environment.(near A/C)

It can take a teaspoon or more of fuel, and can run for reasonable amounts of time, usually running out of fuel. A few squirts of fuel and a relight and its off and buzzing again.

There is no wait for refresh as in jars, the draft pipe insures the CC will be cleared in a couple of seconds. After several runs the tail pipe will become to hot to hold with bare hands.

The one I have runs well enough to tilt completely horizontal with no need for continued draft. The fuel will eventually stack up at the intake and stop the engine. Haven't found a solution for that problem yet.

Many may think a flue pipe in pulse combustion is an abomination. I say test equally and weigh the strength and weakness.


Joe

[vturbine]

Hi Joe, I'll get a 4" nipple tomorrow.

I did notice that there was no need to wait for the engine to clear, just shake and relight -- a great joy after constantly working to blow out and recharge just the right amount with the pots. An inlet and a vertical stack are far from an abomination in starting reliably and easily, clearing the CC instantly with no need of compressed air. It also didn't seem to suffer from warming up. I had to wait for total cool-down with the large tank pot.

Sorry, I don't have A/C up here in Vermont, but I'm sure I'll get this one running with a little more care.

Thanks for another cool design.

[Mark]

On a hot, humid day I wouldn't even attempt to run my piglets. It's like night and day compared to a brisk sunny day in winter. I once saw a large pulsejet for sale on eBay, a really nice, sleek valved pulsejet I think around 50 pounds of thrust. It was built to run on methanol. The seller was from Florida and his comment has stuck with me. He said it "will not run in summer in Florida". Of course a pulsejet will run in summer in Florida on methanol if designed properly. I have run my Tigerjet on methanol in summer and also a homemade valved engine 3 inches in diameter. But you can tell the difference in the sound they make and also starting my homemade pulsejet is much harder in summer. Starting pops are very sluggish.
The neat thing when conditions are right is that if I prime or coat the insides of my homemade valved pulsejet with methanol and then spark it with a simple piezo sparker, there is a fair chance that it will start on the first pop, if the outside temperature and humidity are favorable. I'm a big fan of the instant on effect and methanol can do that for you if you have cool, dry air to work with. Nothing is more exciting that not running a pulsejet for months on end and you go to start it and it bang starts, running full grease instantly.
I couldn't even get my pint snorkelers to really run in the air conditioning of my house yesterday. They just started and died, loud for a second and then rapidly falling off the chart, a failure to thrive. Whereas in winter they are off and running, eager to play - effortless and carefree.
You will see how fast a flame front can travel with methanol if you play in the cooler, dry days of spring, fall, or winter. Then, methanol will make you look good, like a sorcerer. ha

A useful tool for jam jar performance.
http://www.cigarextras.com/ProductImage ... ter-ce.JPG

Not the whole story but a start.
"Sorry Ted, but higher humidity means the air is *less* dense. Water vapor is invisible and is *lighter* than air. When the water vapor in the air condenses it becomes fog/clouds. Most think that since water is heavier than air, moist air must be more dense than dry air.but that is not correct.
Increased humidity increases the density altitude and that means longer TO distances and poorer engine performance... Took me awhile wrap my brain around that fact - almost ran out of runway on a hot, humid day and that convinced me."
http://74.125.95.132/search?q=cache:v8O ... clnk&gl=us

Tidbit more on the importance of good air. Just some fun facts here and there.
(For me this first link will only open if you open it in a new window.)
http://www.aopa.org/special/weather/0307jw.html
http://blogs.abcnews.com/scienceandsoci ... ssett.html
http://www.usatoday.com/weather/wdenalt.htm

[vturbine]

I got the 4" pipe nipple today and also a 1/2" pipe coupling so I could add to the length of the draft pipe -- I wanted to see if I could get the 6" CC to work with a longer tail -- just out of curiosity.

I also bought another 1" pipe cap and screwed it onto a short pipe nipple, chucked the nipple in the lathe and center drilled the cap at the pipe centerline. I opened that out to 5/16".

The day wasn't ideal -- probably 100% humidity threatening to rain, temps in the 70's. I did get some buzzing out of the 6" CC when I added 18" to the length of the 36" tail. I also tried a 6" addition. Nothing sustaining very long.

Then I switched to the proper 4" CC and tried it with the standard 36" draft pipe. I got some buzzes, nothing consistent or long lasting. Tried lots of different positions, and levels of agitation. I was using HEET methanol (yellow bottle).

I then tried Sunnyside denatured alcohol which I've had good luck with in the past, and it did indeed seem to give more frequent short buzzes, and a few times when the jet stayed lit even though quiet and could be jolted into life again for a couple seconds. Then I tried adding the 6" extra draft pipe, and got even more life out of the rig, though nothing I'd really call sustaining.

The 4" CC version with extra draft pipe extension

As a test of conditions I brought out my old faithful 2.25 D metal jar, and fired it up. It ran briefly, not its best, but certainly ran and sustained for maybe 20 seconds in air -- which isn't a record run, but okay for this particular situation.

So I'd say the J-draft pipe needs more work, or better conditions, or both.

Like I wrote earlier I don't like the look of the male end of the street elbow (the one under the cap). It's very crudely cast and tapered the wrong way on the outside. See the second photo with the cap off below. Wondering if it would be a good idea to cut that end off flush with the end of the threads and taper the inside for a better transition?

Close-up of the rough end of the street elbow

Anyway, more attempts at getting something simple and small running reliably. I'd hate to have to wait for cool dry weather every time I want to run something outside. In fact, I don't want to run anything inside, so I'm going to have to keep trying different things. I do like the separate intake and exhaust for easier clearing and starting -- and also the draft style for the same reasons. Again, thrust isn't the object -- ease of starting, reliable operation, and high pulse amplitude, with low heat loss would be ideal.

[PyroJoe]

20 second runs from a jar in near 100% humidity shows your doing good work. Its amazing a 1" diameter engine will run at all in those conditions. The crudeness of the cast elbow are not as much issue as the quality of the cap and the hole, my casted elbow looks about the same as yours.

Joe

[vturbine]

20 second runs from a jar in near 100% humidity shows your doing good work. Its amazing a 1" diameter engine will run at all in those conditions. The crudeness of the cast elbow are not as much issue as the quality of the cap and the hole, my casted elbow looks about the same as yours.
Joe

Oh, I'm not that good at it, Joe, the jar is 2.25 D meaning diameter, not 1". Height is I think 4". I do notice that if I agitate it I get sustained runs after it first slows down. But out of water that quickly converts to over-rich as the alcohol begins to boil inside. I can see the bubbles erupting while peering through the hole. In water, it tends to just lean out and die, I think.

Here's what I think the sequence is on my jar in air:
1.) lots of fresh air and fuel coating the sides of the CC causes initial burst of high energy high speed pulsing.
2.) fuel disappears from jar sides, pulsing gets slower because mixture is lean and there is less oxygen as well.
3.) Pulsing stabilizes as the bottom alcohol heats up, releasing more vapor briefly restoring mixture
4.) Bottom alcohol boils and chokes out the engine with over-rich mixture.

If I shake it at stage 2 it speeds up but then stops abruptly if I continue at about 3 because it's too rich.