Unit V - SuperCharging and Turbocharging.ppt - UNIT V Supercharging and Turbocharging(AE 1008 AUTOMOTIVE ENGINE SYSTEMS Background The power output of

Unit V - SuperCharging and Turbocharging.ppt - UNIT V...

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UNIT V – Supercharging and Turbocharging (AE 1008 - AUTOMOTIVE ENGINE SYSTEMS)
Background The power output of an engine depends upon the amount of air inducted per unit time and the degree of utilization of this air, and thermal efficiency of the engine. Three possible methods utilized to increase air consumption of an engine are as follows:
Background Increasing the piston displacement: This increases the size and weight of the engine, and introduces additional cooling problems. Running the engine at higher speeds: This results in increased mechanical friction losses and imposes greater inertia stresses on engine parts. Increasing the density of the charge: This allows a greater mass of the charge to be inducted into the same volume.
SUPERCHARGING PRINCIPLES The amount of force an air- fuel charge produces when it is ignited is largely a function of the charge density. Density is the mass of a substance in a given amount of space. The more air and fuel that can be packed in a cylinder, the greater the density of the air–fuel charge.
SUPERCHARGING PRINCIPLES An engine that uses atmospheric pressure for intake is called a naturally (normally) aspirated engine. Another way to achieve an increase in mixture compression is called supercharging. This method uses a pump to pack a denser air–fuel charge into the cylinders. Since the density of the air–fuel charge is greater, so is its weight— and power is directly related to the weight of an air–fuel charge consumed within a given time period.
SUPERCHARGING PRINCIPLES In addition to the increased power resulting from combustion, there are several other advantages of supercharging an engine including: It increases the air–fuel charge density to provide high compression pressure when power is required, but allows the engine to run on lower pressures when additional power is not required. The pumped air pushes the remaining exhaust from the combustion chamber during intake and exhaust valve overlap. The forced airflow and removal of hot exhaust gases lowers the temperature of the cylinder head, pistons, and valves, and helps extend the life of the engine.
SUPERCHARGING EFFECTS Higher power output Greater induction of charge mass Better atomization of fuel Better torque characteristics over whole speed range More complete and smoother operation Inferior or poor quality fuel usage Smoother operation and reduction in diesel knock tendency Increased detonation tendency in SI engine Improve cold starting Reduced exhaust smoke Reduced specific fuel consumption, in turbocharging
SI Engines Supercharging in SI Engines is employed only in aircraft and racing engines. Apart from increasing the volumetric

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