How about multiple expansion for internal combustion?

[MKimagin]

I wonder is the multiple expansion that is used in steam engine to improve efficiency can be apply to internal combustion engine.
I thought that the first cylinder will work exactly in the same way as it work in Otto or Diesel, the exhaust will go to second cylinder to do second expansion. The second stage could look very match as it do in steam engine with double piston stroke. I assume that the temperature in exhaust gases are low to be handle with that approach. The whole system could have (as in advance steam engine) 2,3 or 4 stages of expansion. As in steam engine the pressure after last expansion should be pretty low (probably no muffler will be needed).
I wonder what a theoretical limits of that approach? Could this work at all? Does single 4 stage expansion will work like 4 cylinder 4 struck IC engine in terms of vibration , power...?

Miroslav Karas
NYC
09/03/2007

 

[patprimmer]

It is done already.

It's called a turbocharger.

To be more in tune with your question, it is the exhaust turbine side of the turbocharger hooked to ancillary drives or the drive line rather than a compressor.

Regards

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[GregLocock]

Also called a turbo expander.

The problem with using a second piston to expand the exhaust from the first cylinder is that the remaining energy is quite small, yet the frictional losses in the second cylinder will be /higher/ than those in the hp piston.

You also lose energy in the transfer port.

To be honest few IC engines are really designed for maximum efficiency, as fuel is cheap, and there are more pressing concerns.





Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[SomptingGuy]

Highest efficiencies are always found where mass is not an issue. Like in marine diesels. And of course power plants.

 

[Andreb]

I believe the word you are looking for is turbocompounding.

http://www.google.com/search?client=opera&rls=en&q=turbocompounding&sourceid=opera&ie=utf-8&oe=utf-8

________
Andre' B.

 

[ivymike]

There was an article I stumbled upon somewhat recently describing a Rankine bottoming cycle that Cummins was playing with. One confusing aspect of the article was that it began by saying that the system was designed for introduction under a particular set of emissions regulations (2010, I think), and then it concluded by saying that there are no plans to productionize the system.

 

[ivymike]

so it's not multiple expansion, but it is for exhaust waste heat recovery (and EGR cooling, apparently)

different article:

http://www1.eere.energy.gov/vehiclesandfuels/pdfs/deer_2005/session3/2005_deer_nelson.pdf

 

[patprimmer]

Andreb, you are correct. I keep thinking turbo compounding is two turbo's in series.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[j2bprometheus]

Rather that expanding in a second or third cylinder or in a turbine, some folks have proposed over-expansion in the same cylinder.

Probably the first to do this was Mr. Atkinson in the late 1800's. He had an engine cycle where the expansion stroke was twice as long as the compression stroke. Efficiency was better than competative engines at the time.

Ralph Miller proposed the Miller cycle in 1947. It uses valve events to make the expansion stroke effectively longer than the compression stroke, plus turbocharging to keep BMEP high.

j2bprometheus

 

[GregLocock]

There's a nice graph or two showing the advantages and disadvantages of 'over expanded' engines in Heywood.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[SomptingGuy]

Speaking of over expanded engines, I was reading an ad from Gomecsys in this month's "Automotive Engineer". The link is interesting if you like "garage engineering":

http://www.gomecsys.com

I couldn't immediately work out why they needed to arrange the firing order in a way requiring a 1st order balancer shaft though.

Will be interested to see if this one takes off like all the other ones promise to...