Material Design Issues of the Turbines
Now that a basic overview of turbochargers and superchargers has been gleaned, it is now possible to consider the specifics of the machines that effect their overall function and efficiency. Considering first the material design of the turbocharger, application of these machines demonstrates that typically the turbocharger built into the exhaust manifold of the engine. By placing the turbocharger in this position, it is possible for the exhaust from the cylinders to spin the turbine. The resultant effect is similar to that of a gas turbine engine. To pressurize the air entering the pistons of the combustion engine, the turbine is connected to the compressor, which is typically found between the air filter and the intake manifold. As the exhaust pressure from the cylinders increases, so too does the air flow from the exhaust system, which spins the turbine blades. When exhaust pressure increases, the blades of the turbine in the turbocharger spin faster.
While the turbine in the turbocharger is run through the extent of the exhaust air flow that is produced by the combustion engine, the turbine is also attached to a compressor that pumps air into the cylinders. “The compressor is a type of centrifugal pump—it draws air in at the center of its blades and flings it outward as it spins”. To support the turbine, a fluid bearing must be utilized. This type of bearing supports the shaft on a thin layer of oil that reduces both temperature and friction. The fluid bearing must be used in this case, due to the fact that most normal bearings would not be able to sustain the speeds produced in the turbine of the turbocharger.
Although the supercharger seeks to produce the same results as the turbocharger, the material design considerations for machine are somewhat different. In the supercharger system the turbine is mounted to the engine, rather than the exhaust manifold, and is inline with the crank belt.Assessing the pros and cons of the design of both systems is has been noted that the most significant advantage of the supercharger design is that it allows for increased performance on demand. Because the turbocharger system relies on the exhaust produced by the internal combustion engine, the extra power needed to fuel the turbine in the turbocharger must first be pooled. This produces a lag in the time that it takes for the turbocharger to begin working. The supercharger, on the other hand, because it is connected directly to the crank of the engine produces no lag before it begins to work.
In addition to the lag issues associated with the turbocharger, it has been noted that the heat produced by the design of the system may produce knocking. Knocking occurs when the heat in the engine increases to the point that the fuel in the cylinder ignites before the spark plug fires. When this occurs, the engine creates too much boost and the efficiency of the system is decreased overall.