turbochargers were originalyy known as turbosuperchargers when all forced induction devices were classfied as superchargers.Nowadays the term"supercharger" is usually applied to only mechnically
driven forced induction devices.The key difference between a turbocharger and a conventional supercharger is that the conventional is mechnically driven by the engin,often through a belt connected
to the crankshaft,whereas a turbocharger is powered by a turbine driven by the engine's exhaust gas.Compared to a mechnically driven supercharger,turbochargers tend to be more efficient,but less
responsive.Twincharger refers to an engine with both a supercharger and a turbocharger.
Turbochargers are commly used on truck,car,train,aircaft,and construction equipment engines.They are most often used with Otto cycle and Diesel cycle internal combustion engines.They have also been
found useful in automotive fuel cells.
Energy provided for the turbine work is converted from the enthalpy and kinetic energy of the gas. The turbine housings direct the gas flow through the turbine as it spins at up to 250,000 rpm. The
size and shape can dictate some performance characteristics of the overall turbocharger. Often the same basic turbocharger assembly is available from the manufacturer with multiple housing choices
for the turbine, and sometimes the compressor cover as well. This lets the balance between performance, response, and efficiency be tailored to the application.
The turbine and impeller wheel sizes also dictate the amount of air or exhaust that can be flowed through the system, and the relative efficiency at which they operate. In general, the larger the
turbine wheel and compressor wheel the larger the flow capacity. Measurements and shapes can vary, as well as curvature and number of blades on the wheels.
On the left, the brass oil drain connection. On the right are the braided oil supply line and water coolant line connections.
Compressor impeller side with the cover removed.
Turbine side housing removed.
A turbocharger's performance is closely tied to its size. Large turbochargers take more heat and pressure to spin the turbine, creating lag at low speed. Small turbochargers spin quickly, but may
not have the same performance at high acceleration. To efficiently combine the benefits of large and small wheels, advanced schemes are used such as twin-turbochargers, twin-scroll turbochargers,
or variable-geometry turbochargers.
Twin-turboTwin-turbo or bi-turbo designs have two separate turbochargers operating in either a sequence or in parallel. In a parallel configuration, both turbochargers are fed one-half of the engine's
exhaust. In a sequential setup one turbocharger runs at low speeds and the second turns on at a predetermined engine speed or load. Sequential turbochargers further reduce turbo lag, but require an
intricate set of pipes to properly feed both turbochargers.
Two-stage variable twin-turbos employ a small turbocharger at low speeds and a large one at higher speeds. They are connected in a series so that boost pressure from one turbocharger is multiplied
by another, hence the name "2-stage." The distribution of exhaust gas is continuously variable, so the transition from using the small turbocharger to the large one can be done incrementally. Twin
turbochargers are primarily used in Diesel engines. For example, in Opel bi-turbo Diesel, only the smaller turbocharger works at low speed, providing high torque at 1,500-1,700 rpm. Both
turbochargers operate together in mid range, with the larger one pre-compressing the air, which the smaller one further compresses. A bypass valve regulates the exhaust flow to each turbocharger.
At higher speed (2,500 to 3,000 RPM) only the larger turbocharger runs.
Smaller turbochargers have less turbo lag than larger ones, so often two small turbochargers are used instead of one large one. This configuration is popular in engines over 2,500 CCs and in V-
shape or boxer engines.
