Search found 100 matches

by MikeB
Thu Mar 14, 2024 6:32 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Model LTD max power effort
Replies: 99
Views: 36015

Re: Model LTD max power effort

I guess it's all theoretical to a degree, but if going with kinetic theory then each gas atom or molecule is moving independently with a lot of space in between hardly interacting with each other at all. If that is true than the idea that some of the hot gas can exert "pressure" to the co...
by MikeB
Fri Mar 01, 2024 4:49 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Accordion style heat input plates
Replies: 53
Views: 9336

Re: Accordion style heat input plates

Tom Booth wrote: Thu Feb 29, 2024 1:29 pm Apparently a great deal of solar radiation is absorbed by the upper atmosphere resulting in temperatures of thousands of degrees.
Thousands? My understanding is that temps in the upper atmosphere were rather low.
by MikeB
Fri Mar 01, 2024 4:33 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: New Heat Engine
Replies: 3
Views: 152

Re: New Heat Engine

The efficiency of this kind of engine is going to depend not just on the relative heat of hot versus cold reservoirs, but also on how much energy is required to pump your working fluid around. This is fundamentally the same as for a Hot-Air engine, except that water has much more mass than air does....
by MikeB
Thu Feb 29, 2024 10:17 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Choosing bearings for Flywheel
Replies: 7
Views: 243

Re: Choosing bearings for Flywheel

Not directly answering your question, but my advice would be to make the flywheel narrower and larger in diameter.
by MikeB
Fri Feb 09, 2024 1:57 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Regenerator Material Selection
Replies: 8
Views: 950

Re: Regenerator Material Selection

My own personal, but completely unproven theory is that a regenerator will improve the efficiency of some badly designed engines, but I just can't see how it could improve on a theoretically perfect engine, as it will rob pressure when it absorbs heat.
by MikeB
Thu Feb 08, 2024 3:01 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Stirling phone charger
Replies: 35
Views: 4462

Re: Stirling phone charger

I'm sure it's worth looking at one of those, but from what I've seen in the past, they are _too_ highly geared - intended for a crank speed at least one-tenth of what an engine would run at, but maybe that can be overcome with different gearing?
by MikeB
Thu Feb 08, 2024 2:56 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Regenerator Material Selection
Replies: 8
Views: 950

Re: Regenerator Material Selection

I'm trying to build a LTD gamma configuration Stirling engine. From my research I've seen the two most popular material selections have been aquarium filter foam and a metal foam. Do you guys have an suggestions of other materials to make this engine more efficient? Your title mentions "Regene...
by MikeB
Wed Feb 07, 2024 4:04 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Atmospheric pressure ?
Replies: 33
Views: 1486

Re: Atmospheric pressure ?

Tom, What I see a few posts up, is a quote about a process seen in Botany , where sap gets lifted up trees beyond what 'positive pressure' can explain. I can't pretend to provide a full explanation of how capillary action works, but I do know that it has at least something to do with "surface t...
by MikeB
Thu Jan 11, 2024 9:24 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: "Thermoacoustic" Stirling - theory of operation
Replies: 129
Views: 161805

Re: "Thermoacoustic" Stirling - theory of operation

Tom Booth wrote: Thu Dec 28, 2023 1:09 am Smoke is difficult to see clearly...
Have you thought about using a coloured gas, such as NO2 ? Bit toxic apparently, but not a problem in a sealed engine.
by MikeB
Wed Jan 10, 2024 1:38 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: High Efficiency Power Generation for Hot Air Engines
Replies: 9
Views: 1505

Re: High Efficiency Power Generation for Hot Air Engines

Sounds like you need to measure the actual power draw of the Dremel, since you seem to be getting over 24watts out from only 8watts in ...
by MikeB
Fri Jan 05, 2024 1:37 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Stirling phone charger
Replies: 35
Views: 4462

Re: Stirling phone charger

As ever, watch out for quality with car chargers - converting 12v to 5v leaves plenty of head-room for really crap circuitry that might rob all your power at lower voltages. If you are going down that route (sounds like you aren't) then I would be looking at the kind of "buck-boost convertor&qu...
by MikeB
Fri Nov 03, 2023 9:17 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: I'm planning to build a Stirling generator to work off heat from our kitchen stove.
Replies: 85
Views: 137511

Re: I'm planning to build a Stirling generator to work off heat from our kitchen stove.

I read that pressurizing the cylinders adds efficiency, but I don't know how feasible it is with a diaphragm. I don't think it makes much difference whether you use a diaphragm or a traditional piston - pressurisation is a problem for both, as it is primarily the external/atmospheric pressure that ...
by MikeB
Thu Oct 12, 2023 4:19 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Rarefication
Replies: 33
Views: 20670

Re: Rarefication

what type of engine are you talking about that is easy/simple compared with Stirling/hot air? What I meant was that with IC engines you can quite confidently state that during the combustion stage, the only relevant processes are expansion and heating. In a steam engine or a jet turbine the various...
by MikeB
Tue Oct 10, 2023 2:29 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Rarefication
Replies: 33
Views: 20670

Re: Rarefication

... there could be more than one factor in play Ah, but that's the thing, isn't it? Some other types of engine it might be easy/relevant to use a simple model, but for Stirling/Hot-air engines there is ALWAYS more factors at play, the difficulty is in working out which ones have a significant effec...
by MikeB
Mon Oct 09, 2023 4:59 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Rarefication
Replies: 33
Views: 20670

Re: Rarefication

Tom, I don't think you need to be a believer in Kinetic Theory, or any other specific theory, to see that ultimately, the component molecules of your working fluid push on the power piston individually, though it is always easier to think of them "as a whole". All things being equal (which...