Turbo compounding

Turbo-compounding recovers exhaust energy beyond what the turbocharger needs by passing part of the gas through a separate power turbine, whose output is geared back into the crankshaft or used to drive a generator. On a large two-stroke it can return roughly 3 to 5 percent of engine power as useful work, lowering specific fuel consumption. It sits within the wider waste-heat-recovery picture alongside exhaust-gas economizers and steam turbines.