Sterling engine made from scroll expander

[bptdude___2569]

wow...

Robert is ramblig a bit!?
Well, I have rambled before, but I think he does not understand the unique properties of a Stirling, he does not understand we are here to promote that particular engine design, and he has some fear of exploding oils that is beyond reason.

:)

I suppose a better question would be if a scroll expander type displacer/piston would help a Stirling design.

[davidha]

Looking at an old thermodynamics text with a schematic for a Stirling power cycle, it looks like a heated scroll expander piped to and from a cooled scroll compressor might work. Why not use air as the working gas? Of course the in-between pipes will need to make a heat exchanger for regeneration. By the way, each scroll unit will have a fixed scroll and an orbiting scroll, and more than one moving part to define the orbit. We also need a linkage to deliver power from the expander to the compressor. No, I have not made one, but I would like to.

[stan.hornbaker]

Two scroll expander/compressors interconnected do not constitute a Stirling engine out of date textbooks to the contrary. The fluid (gas, usually air) in a Stirling undergoes repeated cycles of heating-expansion, cooling-contraction producing an amount of mechanical output energy in the process.

A two scroll machine would be less efficient than a standard type Stirling.

A scroll expander running as a "Solar motor" would be problematical at best it it would run at all.

[davidha]

My old text makes no mention of scrolls, none in the entire text. It shows a heated expander and a cooled compressor connected by flows through the regenerator, and briefly explains the Stirling cycle (with p-v and T-s diagrams). It seems that regular pistons were assumed instead of scrolls.

As I understand scrolls, from diagrams, animations and texts from the internet, they are an ingenious way to compress and expand a gas. Their efficiency is a function of how perfectly they are built to match the mathematical curve. With a tight enough tolerance (and/or use of a sealing lubricant) very high efficiencies are possible. But looking at modest power production and plenty of space in a stationary application, and with a substantial heating load, low efficiency (even very low efficiency) works for me.

We have a high temp and a low temp, what is the simplest effective heat engine we can build? Maybe it involves two scrolls and a regenerator? Maybe it is not technically a Stirling?

[stan.hornbaker]

The simplest implementation of any device is usually the best. Avoid any complications to avoid the disappoint of failure.

Go to StarSpin.com and click on Stirling engines. Select Jim Dandy #6 to see a 2-1/2 HP Stirling engine run on wood.

Andy Ross of Ohio build several Stirling engines in various configurations. His book is no longer in print.

John Erricson built commercial versions of a modified Stirling engine to pump irrigation water in the west around the turn of the last century. Also build a huge side wheeler ship driven by a hot air engine of his design.

Stirling Energy Systems is touting a new iteration of an improved solar dish technology to drive a Stirling engine located at the focus of the dish. See: http://www.stirlingenergy.com/pdf/2009-06-23.pdf