- Sep 17, 2008
Turbo-compounding is not the same as turbocharging. Not at all. Turbo-compounding uses an exhaust-driven turbine that is directly geared to the crankshaft and helps drive it. It doesn't compress air for the intake. And it was complex and heavy and pretty much obsolete when it showed up."Turbo-compounding was used on on several airplane engines after World War II, the Napier Nomad and the Wright R-3350 being examples. Turbo-compound versions of the Napier Deltic, Rolls-Royce Crecy, and Allison V-1710 were constructed but none was developed beyond the prototype stage. It was realized that in many cases the power produced by the simple turbine was approaching that of the enormously complex and maintenance-intensive piston engine to which it was attached. As a result, turbo-compound aero engines were soon supplanted by turboprop and turbojet engines." from wiki
There are few piston engines of any sort that have flown above 40,000 feet. The reason jets can do it is that their true airspeed increases enormously with the reduced drag, and the ram recovery in the engine intake contributes a whole lot to the engine's compression. Piston engines aren't helped by that at all.