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?
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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?
Thermodynamically speaking this system is possible. It does not violate the first or second law of thermodynamics as long as you are providing the gasoline/diesel into the first engine.
The thermal efficiency (gains) of the combined system would be far less.
The gains you would make will not be economically feasible. (The cost you incur making such a system - fixed as well as running costs).
The exhaust heat has less potential to get converted into power(work). The more and more chemical conversions any substance goes through, the lesser its capacity to convert it into work becomes.(also called 'availability' or 'exergy')
Considering all of this, you can still make possible this system. But making it economically feasible would be challenging but not impossible.
The I.C. engine has been the result of decades of improvements and research, somebody might have thought about it and there must be scientific material available.
Do try to find the papers on Google Scholar
Let everyone else here know if you find something.