Chief Mechanic Turbocharger turbine
The size, shape and orientation of the blades of the turbine is essential for the correct operation of the turbocharger. The turbo speed reached is directly proportional to the surface of the turbine blades hits the exhaust gases and affect the shape and orientation of the thrust force. This will also affect the so-called ” late “motor or lag (see next item). The right design will optimize turbine engine speed at which enters the turbocharger operation, and thus minimize the lag. If the turbine is very large and heavy, will provide a large increase in engine power, but the engine will require a very high speed to begin working. A very light and small turbine come to operate at a relatively low engine speed, but the additional power that may provide the engine will be minimal.
Delay or “lag”
This term refers to the time it takes the turbine of the turbo to reach the speed required to start sending compressed air to the engine cylinders. Usually, there is a minimum engine speed at which enters the turbo function, at which time you feel a big “push”, the effect of the additional power provided by the turbocharger. The “lag” or delay is important because a turbo engine without delay respond faster than an equivalent delay. Also, too much lag takes away the feeling “sporty” to a vehicle, the engine will take longer to respond to the wishes of the driver. This is directly affected by the size of the turbine, as explained in the previous section.
Variations and Multiple Systems turbochargers
Although vehicle use is relatively recent, turbochargers and superchargers have been used extensively in aircraft engines and trains from before the Second World War. Its main use was to get to fly higher, where there is less air pressure, with the same power at lower elevations. Although it is preferred to use superchargers, as they required fewer modifications to the aircraft, turbochargers were also used in some cases. Today, most aircraft engine no compression whatsoever.
There are also so-called variable geometry turbochargers. In these, the blades of the turbine change dynamically, in order to optimize the highest compression possible, using the exhaust gases that are available at the time, which reduces the lag, and makes more efficient the engine. However, these suffer from several disadvantages, and it is now, very few car manufacturers use in their production models.
There are ways to further increase the power of an engine, installing multiple turbochargers, as detailed below:
- sequential turbochargers : Usually use two turbochargers of the same size, activating the second when the first is already running. This allows a further increase in power at high speeds, avoiding the disadvantages in the “lag” it has one large turbine.
- Twin-turbos or bi-turbo : As above, consists of two turbos of the same size, the difference will always remain active both. It is a simpler design, which provides most of the benefits above.
- Turbo compound: In this type, using two turbochargers, one small and one large, where large turbo compressed air enters the turbine of the turbocharger smaller. The pipe exhaust loss is configured so that first push small turbine and then the big one. This configuration allows large increases in compression, up to 200psi , and provides large increases in power. It is mainly used in large diesel engines.
Diesel engines and turbochargers
Diesel engines are suitable for use turbochargers, and usually bring them factory installed. In fact, today it is rare to see vehicles with diesel engines with no turbocharger. There are several reasons for this, as detailed below:
- A diesel engine produces less power than a gasoline engine of equal weight. This is because it requires heavier and stronger components, so the factor of power / weight ratio is much poorer than that of a gasoline engine. A turbo can significantly increase this factor, with greatly increased power, increased little weight.
- Diesel engines are designed to handle high pressures, since normal operation requires it. This makes very few changes needed to withstand the pressures you need a turbo.
- The speed range of a diesel engine is much smaller than that of a gasoline engine, which makes it feasible to add a turbo system, without the negative effects of wear at high speeds.
- Finally, only diesel engines inject air into the cylinders, as the diesel is inserted into the cylinder pressure by special injectors. This makes the turbo installation easier as not to pre-mix air with diesel. Furthermore, it is easy to regulate electronically the amount of diesel injected into the cylinder when using compression, providing all the benefits of a turbo, without the disadvantages of having to control the fuel mixture prior to entering the cylinder.
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