SUPERCHARGER AND TURBOCHARGERS

MECHANICAL TIPS AND STUDY MATERIAL


SUPERCHARGERS

The purpose of supercharger is to increase the manifold pressure above the atmospheric pressure so as to provide high power output. A manifold is the place or area where the air-fuel mixture rests before entering the engine cylinder. 


Before moving ahead you should must know what is Manifold Absolute Pressure ( MAP). It is the absolute pressure (sum of atmospheric and added pressure) in induction manifold and it is measured in inches of mercury (Hg).


Supercharger increases the pressure of the manifold and volumetric efficiency and hence the break horse power gets increased. A supercharger is placed next to carburetor and as the air-fuel mixture passes the carburetor it compresses it. It is directly driven by engine and it may consume up to 18% of engine power.


How is air- fuel mixture compressed by supercharger?

There is impeller/ diffuser assembly which is used for compression. When the mixture enters the high speed impeller and gets accelerated by centrifugal force to periphery where it enters the diffuser. Such action of impeller is very helpful in fallowing ways.

It provides proper mixing of air-fuel mixture.
Due to compression by impeller, the temperature of mixture increases which helps in complete vaporization of mixture.

Diffuser is a still/stationary divergent casing around the impeller which helps in converting velocity into pressure. The divergent passage of diffuser is of great importance as it smoothly retards the speed of air-fuel mixture leaving the impeller and hence pressure increases.

The temperature of the mixture at this stage is very high as such a heat exchanger is used to lower the temperature. 

TURBOCHARGERS


a turbocharger is device implemented before carburetor. It means that the inlet air first meet the turbocharger and then it passes through carburetor.


Very similar to supercharger, the compression is provided by impeller, diffuser and casing arrangement. The impeller blades picks the air and adds high velocity to it. At the same time it raises the temperature of air. Then the air reaches the diffuser where it is expanded. The air in turbo-equipped induction system is cooled by inter cooler, so called because it cools the air after compression, thus making it denser without decreasing the pressure. Due to compression the temperature of mixture is quite high, causing pre ignition or detonation (knocking sound).


The turbocharger is powered by energy of exhaust gases
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