Turbocharger Construction, Working, Material In Marine Diesel Engine

      The figure below shows an axial flow type of turbocharger with important parts.

> Turbine
    It consists of an inlet exhaust gas casing with a nozzle ring, an exhaust gas outlet casing, a turbine wheel forged integral with the shaft and blades that are fitted through side entry slots. 
     The inlet side of the turbine has a nozzle blade ring which is used to guide the incoming gas onto the turbine wheel and also to house the turbine bearings. The outlet side of the turbine casing consists of blower and air passages to supply air to labyrinths seals.

> Compressor
    The compressor side is usually made of aluminum alloys and it also consists of two parts. The inlet part or casing deals with drawing air from the surrounding areas. The main parts on the compressor side are inducer, impeller, diffuser and inlet and outlet casing. The impeller throws the air outwardly with a centrifugal force. The diffuser at the discharge end converts the kinetic energy i.e. its velocity into pressure energy, and leads the air to the volute casing. The volute shaped casing decreases the velocity further and increases its pressure

> Bearings
   Bearings are of ball and roller type combination or of journal sleeve type and it is mounted in resilient type housings.

> Seals 
   Labyrinth seals are used to prevent exhaust gas leaking into the air side and into the bearing housing. Sealing air from the air side is leaked off to cool and seal the shaft

> Turbine Wheel, Nozzle Ring, Rotor Shaft and Blades made of Nimonic 90 (Nickel-Chrome alloy). These have impact resistance, strength, thermal stability and creep resistance at high temperatures of continuous operation upto 650 deg. C.
> Turbine Casing made of, Cast Iron 
> Compressor Impeller, Volute Casing, Diffuser & Inducer made of  Aluminum alloy for light weight strength and smooth surface finish.

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