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Thread: High-temperature accordion/bellows engine

  1. #1 High-temperature accordion/bellows engine 
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    Could we make a «piston» from high temperature materials similar to carbon/carbon
    and phenolic resin which would work like an accordion/bellows?
    Corbon/carbon seems to be able withstand heat up to 1500°C. Is it flexible enough to bend for a many cycles?
    It would be able to reduce friction and allow to work without water cooling.


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  3. #2  
    Forum Ph.D.
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    NO, carbon/ carbon is extremely brittle and will not work as a bellows hence the impact failure on the shuttle. Furthermore it is subject to oxidation above 900F unless a protective coating is applied, SiC is used on the C/C shuttle panels.
    PS I worked in the lab where it was developed in the late 60s and we built the C/C shuttle leading edges.
    you will need an alternate material for your quest.


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  4. #3  
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    you will need an alternate material for your quest.
    Do you have any idea which material could it be?
    I read that they use in shattles some phenolic resin also,and different kinds of silicon resin are used as a heat resistant shields.
    What could be very heat resistant and easily bend in the same time?
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  5. #4  
    Forum Isotope Bunbury's Avatar
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    Probably nothing that currently exists or can be foreseen. You are looking at millions of cycles and a very thin, strong heat resistant material. At present this is science fiction. We make expansion bellows out of costly nickel alloys and they generally expand and contract by fractions of an inch. They have a cycle life of around 10,000 as long as you don't accidentally drop a hammer on them.
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  6. #5  
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    You are looking at millions of cycles and a very thin, strong heat resistant material.
    I`m not sure it has to be very thin.For example,typical accordion is not made of very thin material or resin either.But it bends easily and many cycles.Everithing is due construction.What is concerning Nickel alloys,what is efficiency of Nitinol engine?I know they make toys with it.Is it practical anyhow?
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  7. #6  
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    It has to be thin because it has to be flexible, and if it is thick the bending stresses will be large and the fatigue life short.
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  8. #7  
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    From what I read about new technologies I got new idea.
    There is mention that recently scientists developed piezoelectric which is 80% efficient.http://www.greenoptimistic.com/2010/...nt-conversion/
    Also, as I know, piezoelectrics such as PZT should be deformed not to much (0.1% of it`s size) to produce electricity.So, I think, we could make combustion camera out of high temperature material which is at least just a bit flexible.I think some high temperature fiber glass will bring succes.During fuel explosion it will contract 0.1% of it`s shape and external walls will make pressure on piezoelectric which will also contract and produce electricity.What do you think?
    One more question: how Carnot low applies to a usual piston engine?What is temperature of cold and hot sinks?Could you calculate efficiency?
    Antislavery
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