flash boiler

[clyde]

can anyone help i have a steam launch with a flash burner inside i have lost my burner over the years could anyone help me to get some plans to make one myself
regards Adam Todd

[kiwimodeller]

Adam, I have long had an interest in Flash Steam but most of the information I could find is very old. There was an article about a radio controlled flash steamboat in an old magazine. I have a copy and will look in the shed tomorrow and post details tomorrow night. In the meantime if you go to the Model Boat Mayhem forum
( http://www.modelboatmayhem.co.uk/forum/index.php )
and type "Flash Steam" in the search area at the top of the page you will find a lot of discussion about flash steam boilers and burners. Some of the ideas about electronic controls etc are way too complicated for my simple brain but there are some easier to understand postings. If you post this question there hopefully Steamboat Phil who has lots of experience with this will answer and give you some direction. It would be good to see a photo of your setup of boiler etc if you could post one. Cheers, Ian.

[clyde]

thank you very much
 

[FlashTwo]

Hi,

I 've just come in from the garden where I have just raised steam with my flash boiler for the first time in a test vessel that I have been constructing over the last few months.

Previously my flash steam boiler has operated a Stuart D10 connected to an electrical generator for development purposes, but has got to the stage where it needs to be tested in a boat.

If its just a burner you need, I made one out of a piece of 15mm copper pipe inserted into a 32mm copper pipe with turned brass inserts to support the 15mm in the end of the 32mm tube, just the same as a Seifert burner. The larger tube is just a mixing chamber/ flame retention cup  where the incoming gas/air stream becomes turbulent.

If you go to the  Bullfinch  website http://www.bullfinch-gas.co.uk/index.php?option=com_frontpage&Itemid=1 you will find information on gas burners.

If you go to the Amal website http://www.amalcarb.co.uk/documentDownloadList.aspx  and download the "AMAL Gas Injectors" document you will find a diagram of a basic burner with dimensions, which is what I based my design on.

Have you any idea how much gas you need to burn in grams/min, because that determines the nozzle size.

Steamboat Phil kindly invited me to share his stand at the Ally Pally Model Engineering Exhibition last January, where a lot of interest was shown in my computer controlled flash steam plant.

My system photographs are on the Model Boat Mayhem website.

Ian.

[kiwimodeller]

Adam, the article I mentioned was called "Ooyah" (after the sound you make when burning your hand on the burner!) and was in the August 2005 Model Boats magazine. I only have a poor photocopy but you might still be able to order the mag through the Model Boats website.
Ian, do I understand from your post that you have solved the problem of reduced flow of gas from cannisters or tanks due to temperature drop? I have looked at your photos etc on Mayhem but I am afraid the electronics are beyond me. I am still keen to do a flash boiler in a similar manner to the Ooyah article but George Thompson gave up on Propane/Butane mixes and went back to parrafin. If one is just looking at R C flash steam, not high speed stuff, does it really need to be as complicated as it seems to be? I had hoped to just be able to fit an electric water feed pump controlled manually through a speed controller to vary the water flow and thus the speed of the engine. I figured I might also need some sort of gas pressure regulator but had hoped to not have to go back to parrafin or petrol burners or to go to the sophistication of the electronics you are using. Is this dreaming? Comments welcome, thanks Ian V.

[clyde]

thanks guys that information has helped me a lot
adam

[FlashTwo]

Hello Ian V.,

Today I've operated the boat on the water (test tank!) for the first time with the engine ticking over at 250RPM under auto-control and then upto 500RPM as set on the transmitter. Good thrust from the 4.5inch prop!

When I started the project to make a fully controlled flash boiler I considered the various methods:-
a) Purely mechanical with linkages, gears etc.
b) Purely electronic, i.e. no software.
c) Software based control system.

Since there were so many conflicting ideas about flash boiler control and no established method, I wanted a very flexible development system that could be modified without vast amounts of re-machining, soldering etc.

So, I chose to make a software based system with which many ideas could be explored with the advantage of downloading the current or earlier version, whichever showed the most promise.

One of the most important understandings was to make the feed flow from the pump independant of the boiler pressure. This entailed measuring the pump speed and controlling the ESC connected to the pump motor.

The steam temperature also had to be controlled and this required a thermocouple and a servo controlled gas valve. If the cylinder pressure starts to drop, due to usage or temperature, the reduced gas flow will result in a lower steam temperature and the gas valve automatically opens to maintain the steam temperature (this all happens in a continous control loop, smoothly and not in steps).

There are limits, though, as when there is a continuous high gas demand or a cold winters day. I am thinking, as a contingency, of fitting aluminium fins that can be clamped to the cylinder to increase the surface area for ambient heat exchange. Perhaps a servo controlled parrafin valve could be considered?

Of course, the above ideas have many knock on effects - how to measure the pump speed, what speed does the pump need to run at, what temperature should the steam be considering the saturation temperature goes up with pressure. All these requirements could be "built" into the software without external mods, thats not saying the software writing was a walk-over!

My system has no steam throttle valve or regulator, so the engine speed purely depends on the amount of feed water and gas to the burner.

A typical control modification this week was what to do if the transmitter fails. All I had to do was write a little bit of extra software, unplug the controller from the boat, download the mod, re-install the controller and test - no extra components, machining, soldering etc.

Thanks for your interest, because it makes me question whether I'm going in the right direction or not. I would prefer a less sophisticated solution and I'd take my hat off to anyone that comes up with a simple mechanical system.

Over the next week I shall continue at the test tank, checking all the parameters, now that the engine is driving a prop as opposed to the generator, and the engine/prop shaft alignment etc.

If you require anymore details, I would welcome further discussion.

Ian G.



A STRANGE EFFECT!
During development, the controller had some very eratic behaviour, which I assumed was software related, but which only occured when steam was issuing from a test pipe. I combed through the software, wrote filtering programs for the incoming signals, all to no avail.

After some research, I found an artical about William Armstrong and his discovery of steam generated static electricity about which he corresponded with Michael Faraday. Well I earthed down the copper steam pipe and the problem went away! Well, for all the years I spent in industry, I had never heard of that effect.

[kiwimodeller]

Ian, I do not want to hijack Adams thread and will certainly not offer any advice on software etc but the one thing that I have been able to prove with my steam paddler (and it confirms what I knew from experience at work) is that when drawing off LPG/ Butane/ Propane the most important thing is surface area of the container you are drawing off. Increasing the area definitely counteracts most of the effect of temp drop due to the drawoff. My paddler goes much better for much longer with two cannisters in tandem than it did with a single cannister and no cannister heating is fitted. In early experimenting a wide flat tank was a definite improvement over a tall narrow one as was one of the cylindrical cans of gas once it was laid on its side to give a big surface. Hope this helps, Ian V.

[logoman]

Has anyone here tried the french style of gas tank where the gas outlet is at the bottom of the tank and flows out as liquid in to a copper tube, which then has some coils in through which the gas vapourizes, then onward to the burner? this way the tank doesn't cool.

[kiwimodeller]

Sounds plausible enough, where did you see this discussed or advertised Logoman? I have never heard of it but would be happy to try it if I had some idea of the size of the vapourizing coils. In theory you could just operate the standard gas cannister upside down I guess but the last thing you want is a pool of unburnt liquid in the bottom of the boat which might happen if the flame went out for any reason.

[logoman]

I have been discussing this with a friend who has seen it on French boats

[steamboatmodel]

I read that some of the Primus camping burners can be run with the fuel tank upside down, so that it is feeding liquid instead of gas. I don't have one so I can't verify this.
Regards,
Gerald