A supercharger is an air compressor that increases the pressure or density of air supplied to an internal combustion engine. In every IC engine combustion and power depend on the amount of fuel and air supplied, since proper combustion requires a stoichiometric air fuel ratio of 14 : 1.There for the amount of fuel burned depends on air supplied. If we increase the mass of air i.e. its density and pressure, we can use more fuel for burning. More fuel means more power i.e., we can make more power without changing the size of an engine.
In 2-stroke marine engines, in order to achieve correct combustion, good scavenging and effective cooling, thrice the amount of ideal combustion air quantity is supplied. This is called Excess Air for proper combustion
Advantages of supercharging the engines :
> To reduce mass of the engine per brake power
> To reduce the cost.
> To reduce space occupied by the engine
> To reduce.consumption of lubricating oil
> To increase the power output of an engine when greater power is required
> Waste energy utilization in the case of turbochargers.
Supercharging methods
> Mechanical supercharging
If the compressor is directly powered by the engine or independently driven by motors, is classified as mechanical supercharging.
> Turbocharging
Turbochargers use waste heat of the exhaust gas to drive a turbine which in turn, drives a compressor on the same shaft to supply pressurized air.