Gallery, Projects and General > The Design Shop

Maybe, the problem with vacuum, flame eater, atmospheric engines?

<< < (2/2)

John Hill:
Plasma, seems that would be even more susceptible to being mostly condensed before the port closes so the challenge remains, how to avoid this?

BillTodd:

--- Quote ---how to avoid this?
--- End quote ---

I had a couple of thoughts:

Plasma conducts electricity so when moving it will be affected by a magnetic or electric field. Therefore it may be possible to create an appropriate field to guide the plasma into the cylinder with out it touching anything (also requires a better understanding of em fields than I process!) -  When this is used in nuclear fusion research it is called magnetic bottling (see tokamak)

The other idea was to use two valves on top and bottom of a horizontal cylinder so that the flame can pass through both valves when they are open. When they snap shut (perhaps top before the bottom) they would trap the plasma in the cylinder

Bill

vtsteam:

--- Quote from: John Hill on June 23, 2012, 09:06:17 PM ---Maybe, the problem with vacuum, flame eater, atmospheric engines?

Atmospheric engines under various names and configuration are popular home shop projects and many seem to be a real challenge to get to run.

One of the popular types is the 'flame licker' where a port opens and hot gases are drawn into a cylinder then the port closes, the gases cool and while contracting atmospheric pressure pushes the piston down.

So lets look at this for a moment, the port opens at or near bottom dead centre and hot gases are drawn in as the piston goes 'up', the port closes near the top of stroke and the gases cool to produce the 'power' stroke.

But hangonaminute! As soon as those gases start to get drawn in they contact the cool cylinder walls they start to contract, ditto for the gases that contact the piston head.  Therefore by the time the piston gets to top of stroke we have cold, contracted, gases all around the cylinder and near the piston, around the cylinder head too if it is cooled.  Obviously a large proportion of the gases in the cylinder are already cool and take no part in the power stroke.  If the engine was turning slow enough presumably all the gas would be cool at top of stroke and there would be no power to be had at all.

So how to fix this?  Maybe a partial fix would be an insulating sleeve or liner to the cylinder geared to move and cover or uncover the cylinder walls according to crank position.

Bottom of stroke, sleeve right down, gases are starting to be drawn in.
Near top of stroke, most of the gas is still hot, sleeve moves up to expose cool cylinder walls, gases contact cool cylinder walls and contract for the power stroke.
Near bottom of stroke, sleeve moves down.

Now it might appear that this scheme would have a few drawbacks, and I can see a few.

For example the piston crown and cylinder head are not shielded, maybe it would be better if they had insulated surfaces and take no part in the cooling at all?

Friction, there would be an unavoidable increase in friction.

Something to think about?

--- End quote ---


I'm a bit confused here, but interested!

I thought that the flame was drawn in at TDC and the drawn in by the movement of the piston away from the overhead valve. The valve closed at BDC and then the contraction of the gas in the cylinder provided the motive force to bring the piston back up to TDC when the valve opens again.

As for the effect of insulation, I will need to think about that for a bit.

fcheslop:
Friction is the main killer of these engines.Keep the flame path as short as possible and valve duration of 110 to 120 degrees also an exhaust valve is beneficial but I like my engines to quack so don't use them and fuel has a great effect I use Shellac thinners
Good luck

Navigation

[0] Message Index

[*] Previous page