Search found 131 matches

by Bumpkin
Thu Feb 16, 2017 11:51 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Disappointing
Replies: 34
Views: 17960

Re: Disappointing

Back to the thread premise; I pretty much agree with this paper:
http://file.scirp.org/pdf/ENG_2015121717392471.pdf
Bumpkin
by Bumpkin
Mon Feb 06, 2017 10:26 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Pressurization
Replies: 20
Views: 11361

Re: Pressurization

I don't know how to interpret the text, but looking at the videos I can only imagine the extra pressure is in the interest of fun or science. As it is, the bores must leak enough that maintaining pressure probably takes more power than is produced. It probably wouldn't be very difficult to make a pr...
by Bumpkin
Mon Feb 06, 2017 12:03 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Pressurization
Replies: 20
Views: 11361

Re: Pressurization

Pressurized Siemens-type Alphas or double-acting Gammas don't need sealed cases, but rod seal leaks may require constant replacement pressure. Diaphragm/roll-sock designs solve that problem but have their own limitations. Just my opinion, but I'm not a fan of very high pressure. I don't see a Stirli...
by Bumpkin
Sat Jan 07, 2017 3:14 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Heater & Regenerator Design
Replies: 60
Views: 29235

Re: Heater & Regenerator Design

Hey Aviator. It sounds like Rich is venting the displacer to the crankcase, where it wouldn't affect the working volume dead space.
Bumpkin
by Bumpkin
Sun Jan 01, 2017 10:14 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Snifting valve
Replies: 30
Views: 12820

Re: Snifting valve

"A snifter valve on an atmospheric motor is just to maintain pressure and make up for losses from leaks from the displacer gland, and power piston." Ian, please know I'm not trying to argue, I'm just curious. I don't see how a snifter would help the pressure in an open crankshaft engine. I think tha...
by Bumpkin
Fri Dec 30, 2016 4:17 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Snifting valve
Replies: 30
Views: 12820

Re: Snifting valve

Ian , in review it seems like a snifter in an open crankshaft engine doesn't make sense. Could the valve in the picture you posted in this thread possibly be something else like perhaps a condensation drain?
Bumpkin
by Bumpkin
Wed Dec 28, 2016 12:17 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Snifting valve
Replies: 30
Views: 12820

Re: Snifting valve

cbstirling, other than the Manson, I'd never heard or thought of ports for a snifter before this, but if I were to try it in a Beta or Gamma it would open for minimal degrees at BDC (max volume) of the power cylinder. I'm not sure it would give as much pressure boost as a check valve but it might be...
by Bumpkin
Tue Dec 27, 2016 1:45 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Snifting valve
Replies: 30
Views: 12820

Re: Snifting valve

"Same thing as alpha. Snift in at minimum volume and snift out at maximum volume." Aviator, I respectfully disagree, but I'm always looking for new understanding. Why would you want to snift out? I believe the whole point of the snifter is to equalize at the highest volume to raise the average press...
by Bumpkin
Tue Dec 06, 2016 10:11 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Heater & Regenerator Design
Replies: 60
Views: 29235

Re: Heater & Regenerator Design

Found an image of what I mean. Of course it could be done myriad other ways.

Image

Bumpkin
by Bumpkin
Sat Dec 03, 2016 8:44 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Heater & Regenerator Design
Replies: 60
Views: 29235

Re: Heater & Regenerator Design

Hi Rich. I believe the tubular exchangers are typically employed where the displacer fits more like an ordinary piston and forces the air through the tubes back and forth in the chamber. The slotted cylinder does the same thing but note that where the slots are uncovered at either end of the stroke,...
by Bumpkin
Wed Oct 05, 2016 9:13 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Burnt pancake displacer (carbon foam)
Replies: 8
Views: 4176

Re: Burnt pancake displacer (carbon foam)

Hey Tom, thanks for posting this. Is the toast foam permeable/flow-through as in a Stirling regenerator matrix? Very interesting stuff.

Bumpkin
by Bumpkin
Thu Sep 01, 2016 7:41 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: dwell on displacer
Replies: 16
Views: 11082

Re: dwell on displacer

A counterpoint to the value of increasing dwell time occurs to me: The air transfer speed for a given cycle speed has to increase, thus internal aerodynamic resistance (which increases as a square of speed,) has to be greater, and/or regeneration has to be less. There are a lot of variables but in s...
by Bumpkin
Fri Jun 24, 2016 9:29 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Crazy Rotary Stirling Ideas
Replies: 9
Views: 7513

Re: Crazy Rotary Stirling Ideas

I see your point and agree it could have some regenerative affect. If the regenerator segments are thermally bridged but insulated from the heater and cooler segments it shouldn't be a direct short. Of course, there's always some thermal shorting in any displacer chamber. Since the title of the thre...
by Bumpkin
Thu Jun 23, 2016 7:43 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Crazy Rotary Stirling Ideas
Replies: 9
Views: 7513

Re: Crazy Rotary Stirling Ideas

I might not be visualizing your regenerator idea correctly but wouldn't it be a thermal short?

Bumpkin
by Bumpkin
Wed Jun 22, 2016 11:08 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Crazy Rotary Stirling Ideas
Replies: 9
Views: 7513

Re: Crazy Rotary Stirling Ideas

I agree about the problem of incorporating regeneration in rotary displacers. There's a similar related problem of the air moving from side to side without being forced through the heat exchangers. The disadvantages strike me as similar to thermal lag engines which have the same seductive simplicity...