Search found 19 matches

by blade
Sat Mar 08, 2014 3:17 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Metal 3D printing
Replies: 6
Views: 4894

Re: Metal 3D printing

I wonder if 3D printing could be used to make every Stirling Engine part out of Tungsten. That would allow for operation at extremely high temperatures and the 3D printing may provide extremely good tolerances.
by blade
Sat Mar 08, 2014 3:15 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: What percentage of the Ideal Stirling Cycle Can Be Harnessed
Replies: 2
Views: 2670

Re: What percentage of the Ideal Stirling Cycle Can Be Harne

Maybe my question doesn't even make sense. With a 100% efficient regenerator and a 100% efficient mechanism, deviations from the ideal stirling cycle may not reduce efficiency. However, I'm not sure about this.
by blade
Sat Mar 08, 2014 2:35 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: improved regenerator displacer
Replies: 2
Views: 2679

Re: improved regenerator displacer

I wonder if this proposed design reduces the regenerator's dead space or simply shifts the dead space to inside the displacer.
by blade
Sat Mar 08, 2014 2:20 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: NASA Stirling research
Replies: 9
Views: 5957

Re: NASA Stirling research

'In particular, Pu-238 fuel, which generates about half a kilowatt of heat per kilogram of isotope, has been used to power space missions' That's from the article vamoose linked. I never realized plutonium had so little energy. I guess its the only option without oxygen or solar, when too far from t...
by blade
Sat Mar 08, 2014 12:23 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: What percentage of the Ideal Stirling Cycle Can Be Harnessed
Replies: 2
Views: 2670

What percentage of the Ideal Stirling Cycle Can Be Harnessed

Does anyone know what percentage of the Ideal Stirling cycle can actually be harnessed? Have any real world devices managed to harness more than 90% of the ideal Stirling cycle? Clearly, a sinusoidal piston motion is problematic to harnessing more of the ideal stirling cycle. Can other mechanisms ha...
by blade
Sat Mar 08, 2014 12:15 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Sneft ringbom engine simulation
Replies: 11
Views: 5631

Re: Sneft ringbom engine simulation

Sumit, If you're interested in efficiency, you may want to check out the following paper. http://www.readanybook.com/ts-3-thermodynamic-analysis-of-a-stirling-engine-including-dead-volumes-of-hot-space-cold-space-and-regenerator-pdf-i284489 Dead space plays a huge role in engine efficiency, and Senf...
by blade
Sat Mar 08, 2014 12:02 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Stirling engine with rhombic drive 75 ccm
Replies: 28
Views: 16854

Re: Stirling engine with rhombic drive 75 ccm

One could try self lubricating carbon graphite rings with a chrome plated cylinder. Several companies sell these. Some of the very long lasting Free Piston Stirling Engines use gas bearings. These are essentially very small notches that allow for a very small layer of air to pass on either side of t...
by blade
Fri Mar 07, 2014 11:34 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Rippled Displacer to Decrease Hot Dead Space
Replies: 0
Views: 11842

Rippled Displacer to Decrease Hot Dead Space

All dead space reduces the thermodynamic efficiency of a stirling engine. However, hot dead space is required for the heater tubes in order to allow for a thermodynamically efficient transfer of heat into the working gas. Instead of using heater tubes, is it possible to use a displacer which looks l...
by blade
Tue Feb 25, 2014 12:16 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Most Efficient Stirling Engine
Replies: 1
Views: 3763

Most Efficient Stirling Engine

What is the most efficient Stirling Engine that has ever been built? Has anyone ever crossed the 40% mark when converting thermaal energy into mechanical energy?

The most efficient engines I've seen are from SunPower, which seem to hold the record at 36%.
by blade
Mon Feb 24, 2014 10:24 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Gamma vs Beta Stirling Engine
Replies: 1
Views: 2380

Gamma vs Beta Stirling Engine

From a theoretical perspective, beta stirling engines have better efficiencies because they reduce the dead space. According to this link from SunPower http://www.sunpowerinc.com/library/pdf/productlit/Engine%20Brochure.pdf their free piston beta stirling engines have an efficiency of 36% when the T...
by blade
Thu Feb 20, 2014 7:17 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: NASA Stirling research
Replies: 9
Views: 5957

Re: NASA Stirling research

A lot of the information that NASA has developed is available in research articles and books. For example, work on the advanaced regenerators is available in the book Stirling Convertor Regenerators.
by blade
Fri Sep 28, 2012 8:05 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Stirling Engines with Supercritical Fluids?
Replies: 9
Views: 8370

Re: Stirling Engines with Supercritical Fluids?

rustybarrel, yes. even water exists as a supercritical fluid at very high pressures and temperatures. The main reason I was interested in supercritical CO2 is that the supercritical fluid occurs at lower pressures, which makes it more practical to actually use. Furthermore, work on Brayton engines i...
by blade
Fri Sep 28, 2012 8:03 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Stirling Engines with Supercritical Fluids?
Replies: 9
Views: 8370

Re: Stirling Engines with Supercritical Fluids?

NerdyEE, I believe superfluid helium is different from a supercritical fluid(or supercritical helium). I believe superfluid helium only exists at very low temperatures, which makes it useless for Stirling engines. However, supercritical fluids exist at high temperatures, which allow them to be used ...
by blade
Sun Sep 16, 2012 10:44 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Stirling Engines with Supercritical Fluids?
Replies: 9
Views: 8370

Re: Stirling Engines with Supercritical Fluids?

According to Wikipedia, supercritical fluids have between 5 and 10 times the viscosity of gases.
by blade
Sat Sep 15, 2012 9:55 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Stirling Engines with Supercritical Fluids?
Replies: 9
Views: 8370

Stirling Engines with Supercritical Fluids?

Have Stirling Engines that utilize a supercritical fluid as the working gas been built? Supercritical fluids are dense compared to gases and less dense than liquids. Supercritical fluids share many characteristics of gases and typically have a very high thermal conductivity and heat capacity. Superc...