Calculating top speed on ice...

[Johansson]

My entire family has been involved in the search for the lost spray nozzle thread tap for a while now without success, so I plan to try vapour coil fueling first and order a new tap if it won´t work properly.

The idea is to fit a copper tube vapour coil around the combustor and have two tubes down the intakes as injectors, the coil will be preheated by propane and I will try to run it on diesel.

[Viv]

Hi Johansson

The amount of heat from that suggested coil arrangement for diesel at your kind of flow rates could be an issue, the available heat conduction rate of the CC wall to Copper may leave you short, the answer would be a lot more turns on the coil and improve the wall contact points to the CC as much as possible, use a metering nozzle (jet) at the coil inlet so the coil never floods with fuel.

Certainly a coil inside the CC would perform better but then you have the opposite problem of lots and lots of available heat Diesel will have dissolved oxygen and water in it so at those temperatures it will oxidize in the coil and form coke, you could boil it off first but then you will also lose the winter additives to stop it waxing and freezing, those additives could also be an unknown issue in a heat exchanger coil?

Viv

[ace_fedde]

it will oxidize in the coil and form coke

Viv,

It's the cracking, due to to high temperatures, that causes coke to form.
viewtopic.php?f=3&t=5346#p63285
Water (steam) is even added in cracking installations to prevent carbonisation.

Fedde

[Viv]

it will oxidize in the coil and form coke

Viv,

It's the cracking, due to to high temperatures, that causes coke to form.
viewtopic.php?f=3&t=5346#p63285
Water (steam) is even added in cracking installations to prevent carbonisation.

Fedde

And the dissolved oxygen in the fuel will do what? heat + fuel + oxygen =? its from a real world test and write up in a white paper on the subject by a few different researchers plus my own experience of liquid fueling pressure jet derived engines.

Edit looking at your post after I pressed the button what temperatures do you expect to see any chemistry taking place in the coil? as you say doubtful if will be high enough outside but as I said possibly high enough inside

Viv

[ace_fedde]

Viv,
Let's stay on topic and go to:
viewtopic.php?f=3&t=5346#p63285

Fedde

[Viv]

Done!

Viv

[ace_fedde]

I thougt it's better not to go to the above mentioned thread but to make a whole new thread in the Tools section:
viewtopic.php?f=7&t=5378
Fedde

[Johansson]

M, GRIM or anyone else who has experience with the Thunderchine, is it possible to get the engine to lock with a Rosscojector coupled to a small 5kg propane bottle?

The idea is to get the engine to heat up with the Rosscojector and when the vapour coil is heated enough I can start it on diesel, if it turns out that the bottle pressure is too low for this to work because of the cold weather I can still use the propane to manually heat the copper coil with a torch. Another good thing is that a much lower fuel pressure will be needed so the battery will last longer.

Edit: The copper coil is just a test, the problem is that liquid fuel can pool up in the bottom of the first turn if the coil is not hot enough and that might lead to overfueling once the coil starts to heat up. I figured that it is easy to try since no modifications has to be done to the engine itself, if it won´t work I will have to figure out something else.

[milisavljevic]

Hejsan Anders!

Is it possible to get the engine to lock with a Rosscojector coupled to a small 5kg propane bottle?

I will let Joe answer for himself, but I would think that the real problem here is the small size of the bottle.

Assuming the rosscojectors are properly sized and the engine is self-sustaining at a low thrust level (more
likely than not this will require continuous starting air), Thunderchine will easily require 10 kg per hour (at
least); the bottle will quickly chill and squelch the supply pressure. The external torch may be the best way.

Using a vapouriser coil is not a problem in and of itself, and Joe and I just started testing self-modulating
injectors suitable for the application (I can supply the specifications when ready), but I do have to wonder
whether or not diesel is the best fuel choice. Do you have access to other fuels (eg., kerosene, or jet fuel)?

Even lowly E85 may be the better choice over diesel for use with a coil. And that is saying something...

Cheers,
M.

PS: If you were thinking about home-brewing a batch of pure bio-diesel, then you may be on to something.

[milisavljevic]

.
Thunderchine reserves space between the intake couples and the combustor-transition join
specifically to accommodate vapouriser coils. Here are some photos of Joe's coil installation:

coil-setup_grim_1.png

coil-setup_grim_2.png

Keep in mind that it's ca. 450 mm around the transition in this area; a few turns are enough.

Cheers,
M.

[Johansson]

Looking good! From the pictures I can tell that he has done some experimenting with the engine, I am eager to find out how things works out for him.

My main thought with the diesel fuel was that it is less likely to transform into billowing clouds of fire should a flameout occur, but why exactly is diesel such a bad choice of fuel? I would prefer to use a gas station fuel instead of kerosine or jet fuel since they are not very common around here, so gasoline, diesel or E85 is what I have to choose between.

Home brewing is fun, but the last time I made something that could be used as jet fuel I ended up drinking it...

[ace_fedde]

Home brewing is fun, but the last time I made something that could be used as jet fuel I ended up drinking it...

And the morning after you had a green face like the smiley you were using?

[GRIM]

Hi Anders,

From the pictures I can tell that he has done some experimenting with the engine,

Yes currently experimenting , painfully slow progress due to real world commitments and the weather,

is it possible to get the engine to lock with a Rosscojector coupled to a small 5kg propane bottle?

I have my doubts, I have been using 45 kg cylinders , even on a hot day I have needed to run the cylinder valve full open to get sustained running on vapor , even then cylinder chill down is an issue , I have not however tried rosscojectors, but IMHO LIquid fuel is the way to go with this engine ,

I can tell you that the vaporizer coil works fine on gasoline , (93 octane ), I will keep you informed of progress , AND YES billowing flames are something you have to learn to live with ,

Peace
Joe

[Johansson]

And the morning after you had a green face like the smiley you were using?

Oh yes.

GRIM: So I guess that preheating with a torch is the way to go then. It looks like really neat with the short vapour coil, have you fitted some sort of nozzles to the injector tubes or are they just straight tubes?

Have you been able to reach rich extincion with this fuel system, and what thrust did you reach?

[milisavljevic]

Hejsan Anders,

Why exactly is diesel such a bad choice of fuel?

Diesel is a perfectly acceptable fuel; the concern here is the use of a vapourising coil with a fuel
specifically intended for use in high compression internal combustion engines. I think people will
whinge too loudly about diesel coking the coil (or worse), but this is not a concern in a speed run
limited to a very few minutes of burn time. I am more concerned with a "smooth" decomposition.

I would prefer to use a gas station fuel instead of kerosine or jet fuel.

Why not start your tests with E85? Yes, a total reversal from me, but that was for atomising fuel
injectors. I will supply you with specifications for a self-modulating injector that you may use for
the speed run, if these test out okay for Joe ("GRIM"). E85 should be the better choice for a coil.

Cheers,
M.