Stirling Cycle Engine- a primer

[aerohead]

There has been some mention of the Stirling engine and here is what I have so you all don't think it's some new savior technology:

The Stirling Cycle is,as is the Erricson Cycle,given a theoretical enthalpy efficiency,as the Carnot Cycle,80%.
In 1955,GM Research Labs were investigating the engine.
In 1973,with the Arab Oil Embargo and 'energy-crisis,' interest was renewed.
GM,Ford,Philips Research Laboratories,Holland,and NASA were all doing R&D with it.
When crude prices fell,so did interest for some.Ford quit it after umpteen millions of dollars spent on it.
GM had achieved BSFCs of 0.418-0.358 pounds/Bhp-hr ( 39% enthalpy efficiency ).
When Reagan/Bush cut 90% of alternate energy research funding in 1983,NASA dropped out.
NASA had developed a Mod 1 engine and was poised for Mod 2 when the money dried up.
Hydrogen embrittlement of metals operating at elevated temperatures required the use of exotic,extremely expensive,strategically critical materials to withstand the rigors of the extreme delta-Ts encountered within the engine.
SAE Transactions,Volume 687,1960,pp.665-684 is the only source I have as a reference to actual lab data.

As a comparison for efficiency,the 2010 Honda Insight, with CVT and Chevrolet Volt,with constant-speed serial hybrid engine,both should achieve enthalpy efficiencies on the order of 40% due to high-load/fixed-rpm operation.

These current-day technologies may dampen enthusiasm for expenditures for continued investigation of the more exotic Carnot-type engine technologies.

[dcb]

I don't know about transportation, but the sterling has seen some use in solar power
The Energy Blog: About Dish/Engine Concentrating Solar Power

Also, not sure the volt will be at 40% once you get the power to the axles, I haven't seen anything but speculation there, and don't know of any super efficient CVTs for that matter.

Edit: found a whole DIY Sterling engine deal, little nicer looking than the tin can approach perhaps:
http://www.solarheatengines.com/

http://www.youtube.com/watch?v=AUCRD...yer_embedded#!

[aerohead]

Originally Posted by dcb

I don't know about transportation, but the sterling has seen some use in solar power
The Energy Blog: About Dish/Engine Concentrating Solar Power

Also, not sure the volt will be at 40% once you get the power to the axles, I haven't seen anything but speculation there, and don't know of any super efficient CVTs for that matter.

I think that as a general talking point for heat engines,that folks are going to look at the efficiency available at the 'flywheel.'
At torgue-peak load and constant rpm,an IC gasoline can achieve 40% efficiency.
Honda will do this with the CVT 'throttling',leaving the engine alone,and GM will do,using the engine like an Onan generator exporting the power to a 98% efficient electric drive.A little worse if they have a single planetary gearset.
These throttling-losses are the reason I make such a big deal about traffic signals.With synchronized lights you blow through town with your engine running at a constant rpm,geared for it's BSFC sweet-spot.
I've seen very small-scale Stirling solar applications but I think the big boys are going with oil-filled concentrating-tracking-parabolic collectors to make steam for turbo-generators.Compound-turbines are very efficient.

[dcb]

Originally Posted by aerohead

...
Honda will do this with the CVT 'throttling',leaving the engine alone,and GM will do,using the engine like an Onan generator exporting the power to a 98% efficient electric drive.A little worse if they have a single planetary gearset.

Im with you 100% on the get rid of the throttle/pumping losses, but I have yet to see anything that approaches 98% efficiency in terms of cvt or "electric transmission" under a wide range of vehicle speeds.

Not to totally hijack here, just wondering if there is a source (link) that someone has actually solved the myriad number of issues with %98 efficient transformation/storage of power to keep the engine happy under a wide range of vehicle speeds and loads.

My beef is that the engine being at/near happy bsfc in this scenario seems to require a vaporware transmission and storage scheme (vs an honest to goodness real driver).

[aerohead]

Originally Posted by dcb

Im with you 100% on the get rid of the throttle/pumping losses, but I have yet to see anything that approaches 98% efficiency in terms of cvt or "electric transmission" under a wide range of vehicle speeds.

Not to totally hijack here, just wondering if there is a source (link) that someone has actually solved the myriad number of issues with %98 efficient transformation/storage of power to keep the engine happy under a wide range of vehicle speeds and loads.

My beef is that the engine being at/near happy bsfc in this scenario seems to require a vaporware transmission and storage scheme (vs an honest to goodness real driver).

I don't have,nor have I ever seen a mechanical powertrain efficiency rating above 95%,so I've just kinda stored that value away in the back of my mind as the 'best-case.'
For the modern hybrids,I think the notion of getting the engine into,and keeping it at the 'sweet-spot' is driving the interest in the CVT and serial -hybrid.
Honda's 1st-gen Insight had a 5-speed manual,geared for good BSFC if you 'kept yer foot out of it.'
The new Insight,with CVT will allow velocity to drift around a bit while maintaining a good BSFC.
Same for the VOLT.After 40-miles,when the batteries peter out,the constant-speed engine will fire up like a stationary generator providing enough juice for the elec traction motor and re-charging.It should be very efficient,but even,say at 40% at the engine,there'll be a couple % loss at the generator,and again at the motor.If the Volt has a planetary gearbox like EV1/2,then there should be another 5% loss before the power makes it to the wheels.
If VOLT has the Ultralite tires,that will be good for 2.6 mpg.That will help some.
Volt isn't as low-drag as EV1 so she'll lose back some efficiency there.Too Bad.But it looks like a Cadillac CTS so it shouldn't scare potential buyers away on account of 'styling.'
In 1992,there was a Infinitely Variable Transmission ( IVT ) under development with Epilogics Inc.,Los Gatos,California, invented by Paul Pires.
Epilogics was 'looking' for a 30 % fuel economy improvement with it.GM/Mercedes-Benz/Roger Penske's Detroit Diesel Corp. was looking at it.They would have been subtracting out their efficiency losses before arriving at the 30% mpg improvement.Pretty tasty!

[dcb]

http://ecomodder.com/forum/showthrea...ard-10874.html

Again, I "Get" the bsfc thing, but am pretty good at bsfcing with a 5 speed already, so trying to say it may be something that training/education is a better solution than technology. Best I've seen for a cvt is in the %75 efficient range, and that's pretty much a constant hit. I don't expect much better from an "electronic transmission", replacing lubricated metal teeth with electromagnets.

[aerohead]

Originally Posted by dcb

http://ecomodder.com/forum/showthrea...ard-10874.html

Again, I "Get" the bsfc thing, but am pretty good at bsfcing with a 5 speed already, so trying to say it may be something that training/education is a better solution than technology. Best I've seen for a cvt is in the %75 efficient range, and that's pretty much a constant hit. I don't expect much better from an "electronic transmission", replacing lubricated metal teeth with electromagnets.

dcb,now I've got to store 98% as the benchmark.Thanks!
75 % doesn't sound too good does it?
I don't have anything on 'electronic trannies',is that something being cooked up out on the fringe?

[ShadeTreeMech]

As has been said before, the reason technology is being pursued to improve efficiency rather than driver education is that the average driver doesn't care what is mpg is, nor does he really know how to improve it if he knew about it. Americans especially expect to get into a car and it does everything for you; why else would the AT be so prevalent here and no where else?

If they can get the CVT to work very efficiently and have the longevity or better than an auto or manual, I think it would be the best way to improve efficiencies of a vehicle with an ICE as we know them.

[dcb]

Originally Posted by ShadeTreeMech

Americans especially expect to get into a car and it does everything for you; why else would the AT be so prevalent here and no where else?

I'm not arguing w/you about the current state of affairs, but only education can change that.

Originally Posted by ShadeTreeMech

If they can get the CVT to work very efficiently.

It's possible, in the same sense that it is "possible" that George Burns could come back from the dead and become president, it just doesn't seem likely, to me anyway, having looked at a few implementations.

re: "Electronic transmissions", that is the current buzzphrase for the series hybrid crowd to describe everything between the engine and the wheels. I see a lot of losses there that are yet unaccounted for, especially if you have to charge a battery just to keep the engine in bsfc.


re: 98%, I think that might be a single speed, so take w/a grain of salt. Though it is not necessary to have all gears "meshed" all the time so something like 98% is certainly conceivable for a manual trans, imho, but the market isn't pushing for it with the manual trans being as efficient as it is for as long as it has.

[aerohead]

Originally Posted by ShadeTreeMech

As has been said before, the reason technology is being pursued to improve efficiency rather than driver education is that the average driver doesn't care what is mpg is, nor does he really know how to improve it if he knew about it. Americans especially expect to get into a car and it does everything for you; why else would the AT be so prevalent here and no where else?

If they can get the CVT to work very efficiently and have the longevity or better than an auto or manual, I think it would be the best way to improve efficiencies of a vehicle with an ICE as we know them.

We should probably do a separate thread dedicated to the CVT.Yes?