Towards a wood fueled pulsejet

[PyroJoe]

Wow 3% is pitiful.

"but I assume that the net is negative at the inlet -- true?"
If the gas line/injector is placed perpendicular to the intake flow, there should be net negative pressure across the gas/fuel supply. In-line flame arrestor would be a good idea.

Joe

[vturbine]

Do you guys use a flame arrestor in a propane line? I thought that was mainly for acetylene because of its instability.

In the gassifier of the type shown, the place that can backfire is not usually the gas line, but the open space above the fuel. If you pressurized the gas gen air inlet to feed the hot spot, it could force gas and air upwards through the chips. That's why the gas line usually has negative pressure -- to keep an explosive mix out of the top of the generator.

re thermoelectric devices: I did figure out a place where 3% efficiency is no problem -- in the baseboard or radiator of a home heating system. 97% passes through as heat, which you need anyway, and 3% is picked off as electricity. Cogeneration basically at any heat exchanger really, and so 100% practical efficiency. The temp differential and high temp limit for hot water heating is just right for a peletier device, too.

But back to pulsejets. The simplest form of gas generator is actually just a simple sealed chamber with one pipe outlet. This whole chamber (technically a retort) is then heated on the outside (over say a wood fire) until it hits about 700 degrees F at which point gas is generated, and it's a self sustaining exothermic reaction that eventually yields charcoal after all the gas is generated. Some people who make charcoal, use the gas coming out to heat the retort on the outside for faster conversion. We'd probably not do that, since we want it in the pulsejet.

[vturbine]

I have even thought that the simplest wood pulsejet form of all might just be a retort with a snorkel, or even forget the snorkel and just make a jar.

The fly in the ointment there might be the danger that a wood chip might bounce around and block the only outlet.

Probably not good.

Unlike blocking the hole of a meth jar, which puts it out for lack of oxygen, it's possible the exothermic woodgas reaction would continue, with no outlet. They used totally sealed vessels with some specially built charcoal retorts, but I don't know what the pressures are.

I don't know, maybe It would just stop, but not knowing makes me cautious about it.

[PyroJoe]

Flashlight and tape measure in hand, will have a dimensioned sketch in the morning.
Joe

[vturbine]

Thanks Joe!

Thinking more about a woodjar -- maybe if there was a grate just above the chips to restrain them? like expanded metal mesh?

By the way, wood pellets could be used for this, not just chips. In fact, I think high moisture chips will need a different confiuration altogether -- like one of my burners -- they are inverted stratified combustors -- totally different than a normal gas generator.

[PyroJoe]

"inverted stratified combustors" Man, I bet that was a trick. would like to see a sketch of that one. ha

There are some problems with scaling up jars, above about 4 to 6 inches in diameter things become more difficult. Snorkles appear to help.

This engine is by no means optimum.

[vturbine]

Thanks Joe! Running out to the shed to see if I have anything like a tank 10 by 13 inches. The pipe is no problem. And I can roll the cone. I suppose I could roll a cylinder from 16 Ga. and weld the tank as well, but I'd hate to (and I bet the rounded ends help).

errr combustion chamber, I mean

[Viv]

Hi Guys

I have been away on vacation so only just reading this interesting thread, can I just drop Bio oil in to the conversation and step back to see what happens? I have a load of work to catch up with so I cant join in to much at the moment.

All the best

Viv

[PyroJoe]

A local AC/Heating shop will probably have a dozen of these empty tanks stacked out back.
May be a good idea to just tack that 4" long intake pipe with 3 welds. The engine will jam jar fine without the pipe, my guess is that, there will need to be some adjustment of the length of that pipe. No worries on the rounded corners, though some volume of the CC will need to be reduced to account for them.
Joe

[vturbine]

Well nothing exact. The closest thing is the propane cylinder but that's much wider than your refrigerant tank (12")

Here's some of my collected stuff.

The interesting thing I just discovered is the second photo -- a stainless kitchen canister (very heavy wall) fits exactly a stainless wide mouth canning funnel, and the small end (about 2.25") exactly fits inside a piece of swing-set tubing, or fits exactly on the outside of a piece of bent EMT.

Also third photo 3 heavy stainless tanks 2 @ 13"x4" and one 9"x5" I think.

Lots of tubing and pipe all types and sizes up to 4", not shown.

Any ideas?

[PyroJoe]

Hi Viv,
Good to see you back. What are your thoughts on the bio oil? Also, do you think it feasible that a Collins collar could be applied to this type of combustor?
Joe

[PyroJoe]

Propane canister has my vote. Just have to cut it down to size.
I know ,you know, but make sure to take all the precautions.
Survivability increases when the tank valve is removed and the tank is filled with water. ha
Joe

[vturbine]

Hi Guys

I have been away on vacation so only just reading this interesting thread, can I just drop Bio oil in to the conversation and step back to see what happens? I have a load of work to catch up with so I cant join in to much at the moment.

All the best

Viv

I would imagine you could just run that direct if you heated it to fuming in the combustion chamber itself. Basically fill a propane cylinder partially full of oil, add some compressed air at the top and have a siphon to the bottom leading to your stinger. Heat the combustion chamber first with propane and switch to oil.

Similar to this:
http://home.iprimus.com.au/cmckeown/the_valley.htm

[Viv]

Hi Viv,
Good to see you back. What are your thoughts on the bio oil? Also, do you think it feasible that a Collins collar could be applied to this type of combustor?
Joe

Hi Joe

Thanks, I have been following Bio oil production technology for a few years as it looks an interesting and maybe economic way to convert bio mass in to a useful feed stock for making fuel and plastics, it can be done in a batch or continuous process but my interest is for mobile continuous feed type machine.

And yes I thought about bio oil to run a PJ so it has a place on topic here I guess.

Back in the early days of the BCVP project the Collins collar came to me from looking at Reynst jam jars and his fueling technique with the very closely spaced lips and small trough, so yes its a related idea so probably would work nicely here too

Will add that jam jars are known to work with coal slurry and coal powder and also I have seen other powdered fuels mentioned, my thoughts on wood chips are yes they burn but slowly, the same as lumps of coal burn slowly the key is that powdered coal explodes! as do a number of combustible powders.

I have had a long time interest in bio mass combustion and have a design for a combustor on the back burner (pun) waiting for an economic opportunity, with oil going up I may dig it out of my design book some time, like vturbine I also focused on heat production and low pollution combustion rather than work output, I find his idea idea of coupling a linear alternator very refreshing, thats worth thinking about.

Let me throw in to the melting pot, http://www.handbook.ifrf.net/handbook/cf.html?id=295 and Rayleigh's criterion.

Viv

[Viv]

Hi Guys

I have been away on vacation so only just reading this interesting thread, can I just drop Bio oil in to the conversation and step back to see what happens? I have a load of work to catch up with so I cant join in to much at the moment.

All the best

Viv

I would imagine you could just run that direct if you heated it to fuming in the combustion chamber itself. Basically fill a propane cylinder partially full of oil, add some compressed air at the top and have a siphon to the bottom leading to your stinger. Heat the combustion chamber first with propane and switch to oil.

Similar to this:
http://home.iprimus.com.au/cmckeown/the_valley.htm

Yes thats certainly one way to make a bomb
Viv