Types of Supercharging:
(i) Centrifugal type:
The centrifugal type supercharger is commonly used in automotive engines.
A V-belt from the engine pulley runs the supercharger. First,the air-fuel mixture enters the impeller at the centre. It then passes through the impeller and the diffuser vanes. Finally, air or mixture enters the volute casing and then goes to the engine from the casing. The mixture will come out at higher pressure and this condition is called supercharged condition.
Because of higher pressure more air-fuel mixture is forced into the cylinder.About 30% more air-fuel mixture can be forced into the combustion chamber.
The impeller runs at very high speeds, about 80,000 revolutions per minute.Therefore the impeller should be able to withstand the high stresses produced at this speed.
Impellers are usually made of duralumin, or alloy steels, towithstand the high stresses.
(ii) Root’s type:
The Root’s super-charger has two rotors of epicycloids shape, with each rotor keyed to its shaft.One rotor is connected with the other one by means of gears. The gears are of equal size and therefore both the rotors rotate at the same speed. The Root’s supercharger operates like a gear pump. The mixture at the outlet of this supercharger will be at much higher pressure than the inlet.
(iii) Vane type:
A number of vanes are mounted on the drum which is inside the body of the supercharger.The vanes can slide in or out, against the force of the spring. Because of this arrangement, the vanes are always in contact with the inner surface of the body. The space between the inner surface of the body and the drum decreases from the inlet to the outer side. In this way, the quantity of the mixture which enters at the inlet, decreases in volume, because of which the pressure of the mixture will increase as it reaches the exit.
Comments