I'm thinking of building a campfire-powered "flame licker" atmospheric engine to produce around 75 watts. Anyone ever build one and have some advice about size, rpm, seals, valves, governing (you know, hold my hand during the whole process)?
Your web search results will probably yield more if you try hot-air engine or stirling engine, which I believe are the same thing tou are referring to. There are a good number of sites which would be helpful, you'll just have to sift a bit to get rid of the firms pushing overpriced vaporware, and the occasional overpriced thing you can actually buy.
Ecnerwal wrote in news: email@example.com:
I've looked at a lot of sites, but in general they are showing off tiny model engines. Any sites which have larger engines are either bragging about their engines or are some company trying to sell alternative energy.
I was hoping I could get a few pointers from someone who has built a "larger" engine.
By the way, the campfire power would be a flue coming from just over the fire to the intake valve of the engine.
If you can pressurize the working fluid, you can get much more power out of a smaller engine. If you use Helium or Hydrogen as the working fluid, the power goes up dramatically over air. At 800 PSI, and a 600 C delta-T, you can get 2 Hp out of a 50 CC displacement Stirling engine with a regenerator (steel wool can be used for that). I'm still researching seals that can be run dry at modest temperatures to avoid coking of the lube oil. Then, I'd use a split crank fitted with sealed ball bearings for both mains and rod-end bearings. I'm thinking that seals made from Teflon should work in such an engine.
Just last weekend I was at Barnsley Gardens in Adairsville, GA, and in the really old house they have, the fireplace/furnace they had there had some sort of fan in the flue that turned axles that different things could be attached to. The plaque they had next to it said that Henry Ford tried to buy the furnace from the family. I don't know what they used it for, or if this helps you any, but I thought it was pretty interesting. This obviously wasn't a high rpm machine, but I guess it shows its possibly to do something with a wood flame.
Standard Christmas decoration on my Grandparents' table for Christmas dinner was a chiming set of angels that rotated by the heat off of a set of small candles rising up through a propeller. Not a lot of recoverable energy, but enough.
The original poster might do well to have a look at the likes of the Rider Ericson Stirling cycle engines. These were able to provide reliable, if limited output in a package that would not blow up in the face of the unskilled operator, as was the danger of boiler steam. They have a real advantage, for the survival or boondocks operator, that they do not rely on any high prescision seals or pressurised crankcases, such as the current lot of high output Stirlings require. Pretty straightforward design, anyway.
If the output is to provide electricity, what about a thermocouple set?
Soon after Dean Kamen introduced the Segway vehicle he was on 60 Minutes ore 20/20 showing a new design of Stirling engine powered generator. You might check his website for more info. The market for this was rural areas that burn wood for fuel to cook and stay warm. He may may have some updates.
As I inderstand, an Atmospheric engine is one which the steam is blown into the cylinder and then followed by the admission of water. The cool water causes the steam to condense and the vacuum created, relative to the atmosphere, is what drives the piston of these engines. Are we all thinking about the same thing? --Doozer in Buffalo
The definition of atmospheric engine encompasses far more than the steam engine you describe.
An atmospheric engine is one that uses atmospheric pressure to push the piston. Therefore, there must be some way of lowering the pressure in the cylinder to less than atmospheric. It can be done by condensing steam, as you describe, or it can be done by cooling off combusion gases.
The earliest internal combustion engines were atmospheric engines.
It seems odd, now, but it took a radical change in thinking to use steam pressure and/or internal combustion pressure, instead of the atmosphere, to move an engine's power piston.
Lyle Cummins' book "Internal Fire" covers this in depth.