Statement 1: Supercharging increases the power output and increases the volumetric efficiency.

Supercharging is a method used to increase the power output of an engine by compressing the intake air before it enters the combustion chamber. This increased air density allows for more fuel to be burned, resulting in increased power output. Additionally, supercharging helps to improve the volumetric efficiency of the engine.

When an engine operates at a higher altitude or under low atmospheric pressure conditions, the density of the intake air decreases. This leads to a decrease in the power output of the engine. However, by supercharging the engine, the intake air is compressed, resulting in an increased air density. This allows for more oxygen to be available for combustion, leading to increased power output.

Furthermore, supercharging also helps to improve the volumetric efficiency of the engine. Volumetric efficiency is a measure of how effectively the engine can intake and exhaust air. By compressing the intake air, supercharging helps to increase the amount of air that can be taken in by the engine, improving its volumetric efficiency.

Therefore, statement 1 is correct.

Statement 2: Supercharging is more suitable for S.I. engines than C.I. engines.

Supercharging can be applied to both spark ignition (S.I.) engines and compression ignition (C.I.) engines. However, it is generally more commonly used in S.I. engines.

In S.I. engines, the air-fuel mixture is ignited by a spark plug. By supercharging the engine, the intake air is compressed, resulting in a greater air-fuel mixture density. This allows for more fuel to be burned during the combustion process, resulting in increased power output.

On the other hand, in C.I. engines, the air-fuel mixture is ignited by the heat of compression. Supercharging a C.I. engine increases the air density, which can lead to higher cylinder pressures and temperatures. This can cause knocking and excessive thermal loading on the engine components, potentially leading to engine damage.

Therefore, statement 2 is incorrect.

Statement 3: The limit of supercharging for an S.I. engine is set by knock while that for a C.I. engine is set by thermal loading.

In an S.I. engine, knock refers to the undesirable knocking sound that occurs when the air-fuel mixture in the combustion chamber detonates instead of burning smoothly. Knocking can cause engine damage and should be avoided. Supercharging increases the air density, which can lead to higher cylinder pressures and temperatures, increasing the likelihood of knock. Therefore, the limit of supercharging for an S.I. engine is set by knock.

In a C.I. engine, the limit of supercharging is set by thermal loading. Supercharging increases the air density, which leads to higher cylinder pressures and temperatures. This can result in excessive heat generation and thermal loading on the engine components, potentially causing damage. Therefore, the limit of supercharging for a C.I. engine is set by thermal loading.

Therefore, statement 3 is correct.

In conclusion, the correct statements are 1 and 3. Supercharging increases the power output and volumetric efficiency of an engine. It is more suitable for S.I. engines than C.I. engines. The limit of supercharging for an S.I. engine is set by knock, while for a C.I. engine, it is set by thermal loading.