new generation cars

[student]

hi everybody
i am a post graduate student
doing my project on regenerator of stirling engine
stirling engines will be used in upcoming years in automobile industry
the interested persons can interact or help me in designing a regenerator, you can also mail me at prashant.cm@gmail.com.
thanking you
prashant

prashant

[citivolus]

Prashant,
A real quick explanation for those reading who may not be up to speed on regenerators. A regenerator is basically a thermal capacitor and is situated between the hot end and cold end of a stirling cycle machine. It's job is to store the thermal energy of the working gas as it passes from the hot end to the cold end and give that energy back as the gas flows in the other direction.

Regenerators are difficult to optimize because the desired characteristics are hard to blend well and often seem contradictory. Some of those traits are as follows:
Low volume - regenerators are dead space and lower your compression ratio.
High surface area - it needs to transfer thermal energy efficiently and quickly. Area isn't the only way to get a high transfer coefficient but it's easy.
Low flow restriction - the regenerator is the lung of a stirling and it needs to breathe freely.
Thermally long - what I mean is that because it sits between the hot and cold ends it should not conduct a lot of heat between the two.
Thermally narrow - there should be no thermal gradient in directions orthogonal to the flow direction. (Remember that long and narrow tubes have high flow restrictions so that, generally, doesn't work so well.)
A lot more - there are many more little peculiarities that I couldn't even begin to describe here but I think I've touched the biggest players.

I don't think there is a perfect material or design as each regenerator has to be matched to the particular engine. Depending on the engine design, it may be more forgiving to one parameter than another. A low delta T, low pressure, air breathing gamma engine will usually tolerate a large volume regenerator due to its low compression ratio. Other designs might handle a higher flow resistance than most.

You need to pick an operating point from which to base your design. What is the working gas? What is the temperature range and base pressure? What frequency and desired power output? Are there other constraints like size or weight?

Typically an easy place to start is a metal cloth, steel wool tends to rust if using air and doesn't take the high temperatures typically found in He filled units. You can try stainless steel, brass or copper but watch the thermal conduction especially on the copper. If you are running low temps, say < 380 - 400 K max, you might consider a plastic. If you have the budget and won't be using any oxygen, carbon fibers might provide good results. It may turn out that the best choice is a mixture of materials, for instance imagine building a regenerator made of several layers for different properties like a copper wool (thermally narrow) between alternating layers of glass ceramic fibers (thermally long) or a mix.

A few more points to remember are gas viscosity and how it is going to change as it passes across the regenerator and temperature and pressure changes.

Oh, one more thing. If you can find a copy of Organ's "The Regenerator and the Stirling Engine", get it, buy it, check it out of the library, borrow it, whatever... it'll prove invaluable. I know if I come across another copy I know I'm going to make it mine. Unfortunately, I can only check in about once a week but email me if you have questions and I'll try to get back to you in a timely manner.

Good luck,
Tim

--
swiftly flying

[X-man]

You made me lookup some information and I learned a lot at this site.
http://www.sesusa.org/index.html
.

Bob

[student]

hi tim.
thank you for your valuable information
i ll get back to you with further questions
give me your email id or else i ll post it here only..
bye



prashant

[pam]

Prashant, you can click on his forum name (which you will find underlined beside his post) and it will take you to his profile, which has another link to the ability to send him an email.
Pam

[citivolus]

Whoops, sorry about that, I had the email option turned off. It's all set now.

--
swiftly flying

[pam]

Thanks, Tim. And a note to the forum, now might be a good time (like changing your smoke alarm batteries 2x a year :) ) to go check your profile and be sure your email address is current. Of course, if you have it turned off by choice, that's ok, but if you're open to email, and have changed email addys, an update is a good thing. (I use it frequently if I have something to say that isn't for the whole list.)
Pam