A Swiss engineer, Alfred Buchi, patented the turbocharger in 1905, but it wasn’t used until 1923 when it was incorporated into large marine engines used in the construction of two passenger liners. This was commissioned by the German Ministry of Transport. Turbochargers were first used in production aircraft engines in the 1920s but were kept out of widespread use due to the need for high-temperature metals for the turbine. Using turbochargers can improve an engine's fuel efficiency, reduce emissions, and generate more power.
Turbochargers, or turbos, utilize waste power to increase an engine's efficiency. The three main parts of a turbocharger are the turbine, the compressor, and the central hub. The turbine converts the heat energy from the exhaust into a mechanical rotation. Since the compressor and turbine are connected to the same shaft, the compressor also rotates. Therefore, the turbine is powering the compressor. Turbines and compressors are turbomachinery; they transfer energy between a rotor and a fluid. However, a turbine transfers energy from a fluid to a rotor and a compressor transfers energy from a rotor to a fluid. Essentially, what happens is that a turbine converts energy from a fluid flow into useful work.
A turbochargers performance is related to its size. Smaller ones can spin quickly but don’t perform as well at high acceleration. Larger turbochargers require more heat and pressure to spin the turbine, which creates lag at lower speeds. To balance the benefits of both sizes, combinations of the two were made. They are twin-turbochargers, twin-scroll turbochargers, and variable-geometry turbochargers.
Twin-turbos have two separate turbochargers that operate in a sequence or in parallel. Both turbochargers are each fed half of the exhaust in a parallel configuration. In a sequential configuration, one turbocharger operates at low speeds and the second operates at predetermined engine speed or load. They reduce turbo lag but use an intricate set of pipes. This setup is used because the pressure from one turbocharger amplifies the other. A bypass valve is used to regulate the exhaust flow. Twin-scroll turbochargers have two exhaust gas inlets and nozzles. The smaller one is used for quick response and the larger one is used for peak performance. Variable-geometry turbochargers use moveable vanes that adjust the air-flow to the turbine. It improves fuel efficiency without producing higher levels of turbocharger lag.