Finally trying that Thunderchine...

[zohrke]

Hello everyone,
I haven't been to this Forum for a few months as I wrote my bachelor thesis. When I last posted I reported starting problems with the Thunderchine which I and a Frien had built here in March. As I have now finished my thesis, we are again trying to get this engine to run. We have modified the injector system to a preheat system, which we try to fuel on liquid propane. We did it pretty much the same way as Johansons (or "like the crazy swedes" as we put it ). I wanted to ask you if there are any tips for starting regarding injector position and area and also if it is a good idea to cover one intake for starting. The setup consist so far of an 5 kg propane tank, a heating coil wound araound the transistion cone, and to injectors which are tubes crimped to ~1mmx10mm.
Any tips are greatly appreciated.

Greetings

zohrke

P.S. I will try to put some photos of the setup here as soon as I can grab a Digicam.

[zohrke]

As promised here are a few photos of the engine:

and of the injectors:

The injectors are pseudo-Rossojector with approx. 2x 3mmx7mm
They are mounted approx. 53mm inward from the flare.

I did a test run today which already sounded quite promising, but i could not get the engine to self sustain. I will post the video as soon as its uploaded to my youtube channel.

Greetings zohrke

[GRIM]

Hi Zohrke, welcome back ,
I have not run my engine on Liquid propane yet so I cant really comment on the injector sizing , but ;
The coil looks good , that zone gets plenty hot ,

The injector placement at about 50 mm in from the flare sounds about right ,

Personally I would consider crimping the centre of the injector closed with some cutters thus producing two holes or a
figure 8 shape , this is just a personal opinion ,

I have tried closing one inlet for starting and found it to be of not much help, HOWEVER ,
try this , remove one of the injectors , and securely plug the Y piece , temporarily close the inlet , you may be able to clamp some sheet metal over the hole with a hose clamp and try to start the engine on one inlet with one injector only , (this is on my to do list, just havent got round to it yet ) this would be most interesting ,

I worry about your plastic tubing , that stuff gets brittle with cold and very flexible with heat , the reinforced rubber hose is much better,

You would do well to insulate the vertical piece of tube that comes off of the coil , as it will cause condensing of the vaporized gas , use aluminium foil squashed round it, It is the air between the layers you need, so dont wind it too tightly ,

One other tip , if at all possible pre heat the coil , maybe a blowlamp , or some kind of burner ,

Above all be careful , Good to see you back , please let us know how you get on

[Johansson]

Another Thunderchine, nice!

I have spent some time running it on (or trying to) on liquid propane, one thing I noticed was that I didn´t use enough preheat tubing since they were frozen all the way to the injectors. The engine became very hard to start and consumed lots of propane, with more preheat area it would probably have been easier to start.

Are you using a leaf blower? It needs lots of air and it is pretty difficult to find the right distance and angle for the starting air, try to start the engine on gasseous propane first before you go for liquid.

Good luck and keep posting updates!

[GRIM]

I Agree with what Anders says, re vapor coil length , you are probably short , do consider some external heating ,

wrt running on vapor , you are way short on cylinder size , if you cant get a larger cylinder or paralell up multiple smaller cylinders you wont get that engine to start on vapor

[zohrke]

Hello everyone,

I'm pleased to finally report to you the test run with video. (See link below, you probably can skip a good part of the beginning) The engine is run on vapour until 5:30 in the Video, after that with liquid propane. The only thing which seemed really promising was when I used a wet cloth to stuff one intake, and fuel with liquid propane. You can see that at approximately 6:30 the engine blows the cloth out of the intake. This seems to me as it is starting up but can't sustain without the intake blocked. Though this is my interpretation and I would really like to hear yours.
After fueling on liquid the flames became really large so I aborted the test because my "hideout" from where I control the engine doesnt seem to be safe enough for flames of this magnitude.(Are flames of this size normal or am I getting something wrong with the starting procedure?) I will rearrange that, so safe operation is possible.Also put on some non-inflammable clothes.
GRIM: I dont know what you mean by "plastic fittings"? All connections for gas use semi-transparent reinforced rubber hose. Maybe they just look like plastic on the pictures? They only other thing which is plastic is the extension for the blower.

Regarding coil length: As you can see at the end of the video all metall gas connections are completly iced which shows that the coil has bad thermal contact/is too short. I am thinking of moving the coil in front of the exhaust instead. (Generally cooler spot but direct contact with the hot exhaust gas.) Do you think this may give any problems regarding resonance?

To sum it up: The things which could be tried to get the Engine running:
-Permanently blocking one intake. Overcomes the cloth gets-blown-out problem.
-Isolating the whole coil with aluminium foil wrapping to get it hotter. Thermal contact is really poor on the lower side. (Approx. 4 centimeter distance between coil and engine.)
- Moving the coil in front of/into the exhaust pipe. Might give problems with resonace(?)
-Get a larger gas cylinder.(Which I would like to avoid since you have to buy the whole cylinder here in Germany which cost an arm and a leg.)

Would be glad to hear your opinions about these options, and the posed questions too.

Greetings

zohrke

VIDEO:

http://www.youtube.com/watch?v=rl43w72KU2g

[Johansson]

Thanks for the video, it was very close to running at one point there. Did you try to move the injectors in and out to find the best spot? When I ran my engine on liquid propane it growled and popped when I was close to running, then I had to move the leaf blower around a bit to find the perfect angle and distance before it started. You can hear this in the clip below.

http://www.youtube.com/watch?v=fL6NtpeB0iA

I tried closing off one intake but I never managed to start it that way, I got louder bangs but it always blew the rag out of the intake after a couple of seconds.

Try crimping down the injectors to 1x7mm instead, 3x7mm is much larger than you would need on liquid propane and a smaller injector area would give higher speed through the nozzle and better injection of air with the propane flow. I ran mine with aprox. 1x7mm on liquid propane and got plenty of thrust out of it.

[GRIM]

Hi Z,
Thanks for posting the vid ,
I agree the engine almost reached resonant running at the point where it blew the rag out of the intake ,
There is no question about it, the engine will sustain with both inlets open IF;
a, the engine is "in spec"
b, there is enough fuel
c, you keep the starting air in position long enough for the engine to get up to temperature ,

Yes flames of this magnitude are normal for this size of engine ,
re, "plastic fittings" I refer to your hoses , they "look" like semi transparent pvc hoses, not rubber , if you are comfortable with them disregard my comments,

wrt the vaporizing coil , , the icing does indeed indicate insufficient coil length , thermal contact etc , a much better location is on the CC, see pic , in either case the coil wont work correctly until the engine is running and generating its own heat , thus my suggestion to use an external heat source to help with the vaporization ,

I have found that it is better to hold the nozzle of the blower much closer to the intake flare , however this is very dependent on the volume of the blower and use what works for you

Semi permanent blocking of one inlet is a good idea , bearing in mind your limited gas supply (read cylinder too small ),
consider tack welding a plate on the flare ,
insulating the coil is a tricky one , it could help "keep the cold in"
moving the coil /increasing the number of turns and relocating to the cc is a better option than the tailpipe,
Beg , borrow , or steal, a larger gas cylinder, think relatives (for the borrow) not relatives (for the steal) (joking )

If borrowing a cylinder is not an option you might be able to hire one from a camping supply store, the deposit will be hefty but most of them will hire cylinders for a short period ,

Good luck , and let us know how you go

[zohrke]

Hello everyone,

thank you for your tips. I will try to work them into the setup over the next few days and maybe have another test run on monday or so. I have found out in the meantime that the biggest cylinders I can get at the local store are 35€+filling for 11kg propane.
This seems to be expensive but affordable, but I would first like to know if it is probable that the engine will run on this size of cylinder.
Especially since I think that Johansson has also used an 11kg cylinder (?) I'd like to know if that will work on liquid and/or vapour or not, before I waste 35€.

Greetings

zohrke

[ace_fedde]

Zohrke,
You are in Germany, aren't you? Then you might think about using LPG. If you are also close to Holland you might find there surprisingly cheap LPG cilinders for cars on the scrapyards, and many times still filled with LPG
LPG (propan+butan) is nomally about 40 to 80 cents a kg.
Here in Holland it is totally normal to use these cilinders for a forklift and fill them up (without the forklift) on fuelstations. So if somebody asks, say it's for your forklift
Fedde

[Johansson]

For anything other than initial testing I really suggest that you build a liquid fuel system to avoid wasting money on propane, but a 11kg propane bottle is enough for liquid propane feed and it also get you at aprox. 30% thrust on gasseous propane as long as you keep the bottle warm.

One thing you should try the next time you attempt to run it is to have the propane bottle in a tub filled with warm water, that way it won´t freeze as quickly and from my experience bottle pressure is extremely important when you are trying to run the Thunderchine on a relatively small bottle.

With my bottle at room temp the engine started pretty easy the last time I ran it, but as the bottle got colder the engine lost power and became harder and harder to start. Once ice had started to build on the tank I couldn´t get the engine running at all.

[zohrke]

Good news everyone!

We made it to self-sustain operation. I couldn't be happier.
Although the engine sustained for only about 20 secs this seems to be a problem with the fuel supply when the engine gets hot, so the engine itself is working. Hooray. The fueling was done with liquid propane from an 11kg bottle. (35€ well spend ) The injector position was 50mm from the intake opening, the injectors crimped to "8" shape and the engine was tried for about ten minutes until it reached self-sustain.At the end of this post you can find the video of the test run. I am sorry for the crappy quality, but you can notice the movement of the hedge in the background once the engine starts. Nice.I might be able to upload a better video as soon as i can get a firewire cable.
One question I was thinking about is this: Is the engine stopping because of too much or to few fuel? I would guess it stops because of to much fuel as the coil heats up and more gas is vaporized. But I am not sure and would like to hear your opinions.
A funny story that happenend to us today was that when we finished running the engine one of our neighbours called me and told that a police car stopped beneath him and asked him if he had heard any bangs, because someone called the police because of loud bangs. Our neighbour told the police that he had heard "something" but that it was probably a car malfunctioning and then phoned me to warn me. (As he knows I build jet engines.) That was close but God bless our tolerant and clever neighbours. Next time we'll move to inhabitated area. (Which isn't hard to find in East Frisia. )
The plans for this engine are now that its "known-working": add a diesel fueling system and later mount it on a little cart. (Although this to be done in the next holidays, for these holidays I have spent enough money and also now want to relax a little. )

Anyway I would really like to thank you all for your support, help and tips. This is my second engine built and running and I am really proud of it. This was all possible only because of you guys. Thanks alot!

Have a wonderful evening

zohrke



VIDEO

http://www.youtube.com/watch?v=dfmoViv2TDA

[GRIM]

CONGRATULATIONS , WELL DONE ,
That hedge sure took a bashing , good to see that ,

IMHO the engine quit due to a lack of fuel , one of the problems with liquid propane , is the refrigerant effect, the change from liquid state to vapor state causes a huge temperature drop , and you state that it took about 10 mins to get the engine to start , your cylinder was probably chilling down too ,
Please do attempt to upload a better quality video , the audio in this one sucks , , not being unkind but every bit of data helps ,

Yes cops n neighbors can be troublesome , an uninhabited area is favourite

GREAT STUFF , and thanks for posting

[Johansson]

Great work guys!

I agree with GRIM, to me it sounded like the engine shut down due to a lack of fuel. When my engine had ran for aprox. 15s it started to lose power and flamed out, it behaved exactly like it had emptied the propane bottle. When I removed the bottle I felt that there were a couple of liters left in it but it was so cold that hardly any vapour at all was produced.

With an 11kg bottle you could try to run it on gasseous propane, I could run mine in +15C for 20 seconds before the bottle lost pressure. If you submerge the bottle in a tank of water you can probably run for a minute, not at 100% thrust but fairly high.

[zohrke]

Greetings

I finally got to uploading the better quality version of the test run. You sadly can't see how the hedge moves in this version but the quality is much better.

http://www.youtube.com/user/terrortv#p/ ... InePwIxyO8

GRIM: If this version is not enough for your sound analysis or whatever you are up to with the audio, contact me. I can then send you a zip file or such with fresh juicy uncompressed DV audio.

So long

zohrke