SUPERCHARGING

SUPERCHARGING

• IT IS THE PROCESS OF CHARGING THE CYLINDER WITH FRESH AIR GREATER THEN ATMOSPHERIC PRESSURE
• THUS IT INCREASES THE WEIGHT OF CHARGED AIR BY INCREASING DENSITY OF CHARGED AIR.
• POWER OF DIESEL ENGINE IS DEPENDENT ON AMOUNT OF FUEL BURNT. THIS IS LIMITED BY THE AMOUNT OF AIR AVAILABLE. IF MORE AIR CAN BE INTRODUCED INTO THE CYLINDER MORE FUEL CAN BE USED AND ENGINE POWER WILL INCREASE.
• FUEL CONSUMPTION REDUCES.
• MECHANICAL EFFICIENCY INCREASES.
• COOLING IS IMPROVED SINCE GREATHER MASS OF FRESH AIR IS SUPPLIED. HENCE REDUCTION IN NOX EMISSION.
• BETTER UTILIZATION OF WASTE EXHAUST GAS ENERGY WHICH CAN BE USED TO DRIVE TURBOCHARGERS.
• REDUCTION OF COST PER UNIT POWER DEVLOPED.

TYPES OF SUPERCHARGING

     (A)   MECHANICAL SUPERCHARGING

·         A ROTARY AIR BLOWER DRIVEN BY D.E CRANKSHAFT.

·         SCAVENGE PUMPS WHICH ARE OF ENGINE DRIVEN RECIPROCATING TYPE.

·         AUXILIARY BLOWERS WHICH ARE OF INDEPENDENTLY DRIVEN TYPE.

     (B)    TURBINE SUPERCHARGING

o   TURBOCHARGER IS USED

o   IT MAKE USE OF WASTE ENERGY OF EXHAUST GAS TO DRIVE A TURBINE WHICH IN TURN DRIVES A COMPRESSOR ON THE SAME SHAFT TO SUPPLY PRESSURIZED AIR.

TURBOCHARGING

·       IT IS A TYPE OF SUPERCHARGING BY USING EXHAUST GAS TURBOCHARGER.

·       EXHAUST ENERGY IS USED TO DRIVE TURBINE WHICH IN TURN ROTATES THE    CENTRIFUGAL COMPRESSOR CONNECTED ON THE SAME SHAFT.

       

     

. TURBOCHARGING PROCESS

(A) CONSTANT PRESSURE TURBOCHARGING

·         EXHAUST GAS FROM ALL CYLINDER IS LEAD TO A COMMON LARGE MANIFOLD.

·         THIS MANIFOLD SUPPIES EXHAUST GAS TO THE TURBOCHARGER.

·         PRESSURE PULSES DAMP OUT IN THE MANIFOLD.

·         THE GAS FLOW IS STEADY AND AT CONSTANT PRESSURE AT THE TURBINE INLET.

·         IT IS MORE EFFICIENT.

·         THE TURBINE OPERATION IS BETTER WHEN CONSTANT PRESSURE IS AVAILABLE AT TURBINE INLET.

·         EXHAUST GROUPING IS NOT REQUIRED.

·         GOOD PERFORMANCE AT HIGH LOAD

·         HIGH TURBINE EFFICIENCY DUE TO STEADY FLOW.

·         REDUCTION IN SFOC 5% - 7%.

·         THE WORK TRANSFER AT TURBINE WHEEL IS SMOOTH.

·         MORE SUITABLE FOR HIGH OUTPUT ENGINES.

·         AT LOW LOAD IT REQUIRES SCAVENGE ASSISTANT (AUXILIARY ELECTRIC BLOWER). BECAUSE AT LOW LOAD IT WON’T SUPPLY ADEQUATE AIR SUPPLY FOR SCAVENGING AND COMBUSTION.

·         POOR RESPONSE IN CHANGING LOAD.

(B)   PULSE TURBOCHARGING

·         MAKE USE OF PRESSURE PULSE WAVES TO EXPAND THE GAS FURTHER AT TURBINE NOZZLES AND BLADES

·         EXHAUST GAS FROM EACH CYLINDER IS DIRECTLY LEAD TO THE TURBINE INLET.