turbocompound

Turbocompounding is an energy-recovery technique used in internal combustion engines, particularly large diesel engines, in which a turbine driven by exhaust gases extracts a portion of the energy contained in the hot exhaust and converts it into useful mechanical work on the crankshaft. The turbocompound turbine is usually placed after the exhaust-gas path and is connected to a power-take-off that drives the crank via a hydraulic coupling, gearbox, or other torque-transfer device. By converting exhaust energy into shaft work, turbocompounding can improve the engine's brake thermal efficiency without increasing fuel flow.

Operation and configurations: The exhaust turbine (turbo-compounding turbine) spins as exhaust gases expand. Its shaft powers a hydraulic pump or turbine that drives the crankshaft. A clutch or torque converter arrangement may be used to engage or disengage the turbocompound stage depending on engine speed and load. The system is designed so that the recovered energy supplements the torque produced by the piston engine, while the main turbocharger provides the normal boost for intake air.

History and usage: Turbocompounding gained prominence in mid-20th-century diesel engines, including marine, locomotive, and stationary applications, where it offered measurable fuel savings at steady or heavy loads. With advances in turbocharging efficiency and control, its use declined in many applications, though it remains a feature in some modern, high-efficiency large-diesel systems and/or dedicated power plants. Advantages include improved brake thermal efficiency and reduced fuel consumption; disadvantages include added complexity, weight, cost, and maintenance requirements, as well as packaging constraints.