Question

Supercharging is the process of -

1. Supplying the intake of an engine with air at density higher than the density of surrounding
2. Providing forced cooling air
3. Injecting excess fuel for raising more load
4. Raising exhaust pressure

Answer 1

Correct Answer - Option 1 : Supplying the intake of an engine with air at density higher than the density of surrounding

Explanation:

Supercharging

• The purpose of supercharging an engine is to raise the density of the air charge, before it enters the cylinders.
• Thus, the increased mass of air will be inducted which will then be compressed in each cylinder. This makes more oxygen available for combustion. Consequently, more air and fuel per cylinder will be forced into the cylinder, and this can be effectively burnt during the combustion process to raise the engine power output to a higher value.

Purpose of supercharging:

• Provides better mixing of the air – fuel mixture
• Increase the volumetric efficiency
• Increase the power output of the engine
• It tends to increase the possibility of detonation in a S.I. engine and lessen the possibility of knocking in a C.I. engine

Supercharging in SI and CI engine:

• Supercharging increases the pressure and temperature of the charge at the end of compression. This reduces ignition delay in CI engine, thereby the combustion becomes smooth, and the tendency for knocking is avoided. In SI engine the short ignition delay promotes detonation.
• Hence supercharging is preferred in diesel engine than in petrol engine.

Supercharging Limits:

• The limit of supercharging for an SI engine is set by knock while that for a CI engine is set by thermal loading.