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Four stroke waste heat engine?

Could we build a four-stroke engine that runs on the exhaust heat of another engine? My idea is to have a four stroke engine **** in the exhaust from another running engine, instead of fresh air. Compress that hot exhaust on it’s compression stroke, then at TDC inject a burst of steam, through some kind of injector. The boiler water could be preheated by the cooling system of the first running engine. Does this sound at all feasible?

5 comments

Comments (5)

justincorhad

Aug 09, 2022

Thanks for the reply! I’m curious how the combined efficiency would be less? Wouldn’t the efficiency of the system go up as whole since more of the fuel energy is being extracted?

Thermodynamics Forum

Aug 09, 2022

Replying to

I mean to say if we consider the energy that had been put into making of the waste heat recovery system (like for example the energy that would be required in making steel components).

I mean to say the impact on environment as a whole because of the additional components. This is my guess though.

You would need to do a 'Life Cycle Assessment (LCA)' to quantify the impact.

Yes, you are right. At the local system level the thermal efficiency would increase slightly.

justincorhad

Aug 09, 2022

Replying to

Okay I see what you’re saying now, and I completely agree with that! Actually when I originally had this idea it was to take a v8 engine, have one bank run on gas or diesel, feed that exhaust to the other bank which would then compress and steam inject. I wonder if it might be a better option To do it that way?