A turbo-compound engine is a reciprocating engine that employs a turbine to recover energy from the exhaust gases. Instead of using that energy to drive a turbocharger as found in many high-power aircraft engines, the energy is instead sent to the output shaft to increase the total power delivered by the engine. The turbine is usually mechanically connected to the crankshaft, as on the Wright R-3350 Duplex-Cyclone, but electric and hydraulic power recovery systems have been investigated as well.
The Napier Nomad engine. The power-recovery turbine sits underneath a two-stroke diesel engine.
Wright R-3350 Duplex-Cyclone Turbo-Compound radial engine.
Wright R-3350 Duplex-Cyclone
The Wright R-3350 Duplex-Cyclone is an American twin-row, supercharged, air-cooled, radial aircraft engine with 18 cylinders displacing nearly 3,350 cubic inches (54.9 L). Power ranged from 2,200 to over 3,700 hp, depending on the model. Developed before World War II, the R-3350's design required a long time to mature before finally being used to power the Boeing B-29 Superfortress.
Wright R-3350 Duplex-Cyclone
Wright R-3350 Turbo-Compound radial engine. Two exhaust recovery turbines shown outside impeller casing area (top (silver) and lower (red blading)) that are geared to the crankshaft.
Wright R-3350 Turbo-Compound radial engine fitted at the number four position on the starboard wing of a Lockheed Super Constellation
R-3350 on display at the Air Zoo
