96 4 DLT ENGINE TURBOCHARGER Working Principle of Turbocharger The power output from an internal combustion engine depends on the mass of the air and fuel quantity that are available for combustion. To increase the engine horse power, more air for combustion and more fuel have to be delivered. In case of a naturally aspirated engine, the power increase is obtained by increasing the swept volume or by raising the speed. Increasing the swept volume, however, in general leads to larger and heavier engines that are expensive.While a speed increase involves considerable technical problems and obvious disadvantages, l ike low mechanical efficiency, increased wear and tear and increase in noise etc. Power increase with unchanged swept volume at the same engine speed can be obtained by what is known as supercharging of the engine. Super charger delivers precompressed air to the engine cylinders i.e. engine intake pressure is higher than atmospheric whereas in naturally aspirated engines it is slightly below atmospheric. The turbocharger is one of the common super charging devices used in an engine. It makes use of thermal energy of engine exhaust gases to run a turbine which in turn drives a compressor to pressurize the inlet air. AIR TO INDUCTIONMANIFOLD COMPRESSOR HOUSING COMPRESSOR WHEEL AIR FROM FILTER TURBINE HOUSING SHAFT & TURBINE WHEEL ASSEMBLY GASES TO EXHAUST PIPE BEARING BEARING HOUSING THRUST BEARING COMPRESSOR BACKPLATE GASES FROM EXHAUST MANIFOLD Fig. 185 OIL OUTLET OIL INLET
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