A question about flash boilers....ish

[Jasonb]

The guy who wrote the article mentioned took out a patent if anyone is interested

https://worldwide.espacenet.com/pub...n_EP&FT=D&date=19630410&CC=GB&NR=923235A&KC=A
He says he made about 15 engines based on the principal and that they performed better than similar bore/stroke on srun on traditional flash steam but as we don't see masses of them there were obviously issues. But really depends if the OP wants to build an engine for efficiency or just to see if teh principal works.

he does not state the cylinder material but from the couple of sketches I doubt very much it or the head are cast iron, pistons are carbon.

 

[Richard Hed]

If you start with cold water injected into the pressure chamber, you might have probs, but another thing is as one mention above--the energy (heat) it takes to bring water up to steaming temperature. If you were to heat the water to near boiling temp, THEN inject it, you would get more power AND less internal stresses. I thimpfks it might work

 

[Steamchick]

It is a patent, and most patents fail to become reality in my experience. Notwithstanding, a flash boiler can utilise a relative huge area compared to the finned head of this engine, or a suitable water boiler and superheater. Then the steam used conventionally can have the intake and exhaust ported and engine materials optimised for engine use rather than heat exchanger and engine.
Other external combusting engines (exhaust gas or flame eaters, Stirling, etc.) were only an interim between steam and internal combustion...
Not impossible. But I guess the infernal combustion engine simply won on efficiency....
K2

 

[Jasonb]

There are quite a few model engines about, particularly the more obscure designs that are based on little more than a patent drawing so even if the full size did not catch on certainly no reason to stop someone wanting to have a go at making a model just to see if it works. I've made a couple like this from other peoples designs and also designed my own models doing the patterns and castings.

This IF Allman was taken from a patent that showed just two elevations



And this Otto "flame sucker" is one I drew up and did the patterns for and am working on at the moment, just a patent drawing, damaged patent model and knowing that one was actually built is all there is to go on.

So I would say to the OP to give it a go, we know that Mr Hall managed to make working engines using the principal and even if tehy don't work particularly well it's more fun that just building another model that everybody else has.

 

[Steamchick]

Jason, I am impressed!
I have built a flame eater (from a casting kit) but didn't manage to get it working. Another guy reckoned he spent longer trying to get his (same model) going than all the machining and assembly...!
I did like the idea that these atmospheric engines lasted more than 20 years in industry - I read somewhere that they were huge and used the exhaust from foundry furnaces and powered blowers to force the fires. The pre-cursor of the Turbo-charger for infernal combustion engines, in principle? The only draw-back was the corrosive flue gases contained erosive ash particles in the smoke, so valve, piston and bore wear was a big problem. - A bit of history that hides in the transition between steam and ICE engines...
Modern large diesel generators that use non-oil fuel (such a chaff from a flour mill, sawdust, etc, gases from decomposing sewage, etc.) suffer very bad exhaust valve corrosion from those acidic exhaust gases too.
Keep on with your high quality modelling.
K2

 

[Jasonb]

The Otto works a bit differently to your run of the mill flame licker. Rather than drawing in the an external flame it has a small pilot light and as the piston goes down it draws in gas and air and that is ignited by the pilot and burns in the cylinder. Then the cooling air creates the vacuum pulling the piston back up in the same way as a licker. One has been completed from those castings and there is also a full size one made by a chap in Europe.





This is a nice little licker that I did scaled down from Alyn Foundries "CHUK" design. which seems to run well, several have been built to my scaled down drawings - all barstock except flywheel casting.



I also did a set of crankcase and flywheel patterns for a V twin version that will use the full size 1.5" bore cylinders

 

[Steamchick]

Ah! Yes! It is an atmospheric gas engine... I prefer to use the phrase "depression" rather than vacuum...
Also I feel that the timing of intake for half a stroke, then as the piston opens the side port to the flame the resultant explosion is really making it a zero-compression 2-stroke.
A pre-cursor to the Otto Cycle perhaps?
Maybe I shall plot the pressure versus stroke to compare them?
K2

 

[Jasonb]

Not sure where you are seeing a side port, it all comes in through the head with teh gas/air mix being ignited as it enters. Atmospheric exhaust valve lets the rising piston push out any spent (cooled) gasses.

 

[Steamchick]

I see. It is different from my Atmospheric Gas Engine, that has a side port where the flame on the outside ignites the gas-air mixture inside the cylinder... (Or not!) when the piston exposes the port. But your engine is quite different - as you show.
The significant problem I have is that when the inlet valve opens to admit the gas-air mix, it sucks so well on the gas pipe that the external flame - teed-off from the gas feed pipe - is extinguished. It needs re-plumbing, with a gas reservoir,,,

K2