Correct Answer - Option 4 : 2, 3 and 4 only
Concept:
Basically supercharging means supplying high-pressure air to the engine. When the high-pressure air is supplied to the engine, the mass flow rate of fuel also increases, and consequently, it results in more power output. Hence the efficiency of the engine also increases.
The amount of air supplied to the engine may be increased by increasing the speed of the engine or by supplying high-pressure air. The process of supplying high-pressure air is known as Supercharging. And the equipment used for supplying high-pressure air is known as Supercharger.
- It increases the power output of the engine without increase its weight and size
- An increase in the supercharging pressure increases the gas load and that increases the fraction forces, but the increase in bmep is much more than the increase in friction forces. So, the mechanical efficiency of the supercharged engine is slightly better than the naturally aspirated engine.
- An increase in the intake pressure increases the gas load, hence a large bearing area and heavier components are needed. Thus, the friction losses are increased
- Supercharging results in better scavenging and reduced exhaust gas temperature in the engine. The reduced residual gas fraction helps in better combustion and reduced temperature improves volumetric efficiency.
- Limit of supercharging is imposed due to maximum permissible pressure and temperature and thermal stress in the cylinder. Which depends on the compression ratio, air-fuel mixture, and design of the engine.
From the above conclusions, statements 2,3 and 4 are correct
