Quote:
Originally Posted by t vago
I know. Not all engineering types come across as dicks, either. However, as jerky as my posts come across, they're gentle love pats compared to how the real world would act. I'm not interested in gentle persuasion or cajoling, because the real world doesn't gently persuade or cajole people who engage in wishful thinking.
There are, to my knowledge, only three proven effective methods of reclaiming exhaust heat energy to do something useful. The first method involves shaping exhaust piping in such a way that the exhaust gases themselves generate a partial vacuum to help evacuate the cylinders so as to provide less dilution to charge air inside the engine. Devices that do this are popularly known as headers.
The second method involves passing hot exhaust gas under pressure through a nozzle to convert thermal energy into mechanical energy, and then recover the mechanical energy by use of a turbine wheel. Turbochargers are the best known device that uses this principle.
The third method is really only useful on engines that require a throttle valve to begin with. Exhaust heat energy is used in this case to heat up the intake air such that the throttle plate is forced more open than what would otherwise be needed, in order to lower pumping losses associated with that throttle valve.
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A variation on #2 that is also proven is turbo-compounding.
#3 is home-built used often on this site.
There are many other methods that have also been proven effective, however they have not been proven cost effective:
TEC Modules to recapture heat energy. IIRC one of the big 3 had created a cat covered with them that generated around 1KW average. Of course these things are ridiculously inefficient.
BMW used a steam turbine in the exhaust:
BMW Turbosteamer gets hot and goes
<insert heat recovery device here> Sterling engine, etc.