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Back in the early 60s, Chrysler built a turbine car powered by a turbine engine it had under development.

An interesting feature of the engine was a regenerator system to recover heat from the gases leaving the power turbine, using this heat to preheat the air on its way from the compressor to the combustor. The benefits of this were to improve fuel efficiency and reduce the final exit temperature of the exhaust. The regenerators involved some sort of rotating disks which somehow transferred the heat as they rotated. There are diagrams/animations depicting the gas flow through the engine and (generally) heat path through the regenerators, but in some ways they don't seem to make much sense.

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My question is: how did the regenerator setup actually work? How was the compressor output air (60 psi?) put into contact with a rotating(?) hot surface without the pressure leaking air away to the exhaust? Why would a regenerator need moving parts at all? Could it not just be a system of tubes within tubes?

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  • $\begingroup$ Would you think there may have been problems with the tubes within tubes at 1200 Deg C? Perhaps this was a solution that enabled the materials to withstand the high temperatures as it was for a short time... $\endgroup$
    – Solar Mike
    Commented Apr 22, 2018 at 22:40

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The main advantage of a rotary regenerator is that you can pack a lot more surface area into a given volume than with a shell and tube type device important for gas-gas heat exchange where heat capacities and heat transfer coefficients tend to be low compared to liquid-liquid. This obviously has advantages for packaging a turbine in a car.

Essentially they have a fine matrix of eg wire mesh which gets heated as it passed through the hot stream and cooled as it passes through the colds stream so you are basically heating up one part and moving that hot part to the cold side. A good analogy is if you have a bucket of hit water and a bucket of cold water you stick a copper rod in the hot bucket untill it gets hot and then take it out and put in in the cold bucket and repeat. A rotary regenerator is the same principal but continuous.

You do get some cross contamination but in a turbine where you are just mixing intake with exhaust this doesn't matter much and isn't that significant in terms of pressure loss and there is no direct path from one side to the other just the inherent limitations of rotary seals

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