To increase the engine’s efficiency, torque and power, the exhaust gases from the engine cylinder is used to drive the turbine. The turbine and compressor are mounted on the same shaft. When the exhaust gases are passed through turbine, the turbine rotates as the gases import heat energy, hence the turbine produces mechanical energy i.e rotation of shaft for driving compressor. Now the compressor also rotates to compress the inlet air to the cylinder. The inlet air is compressed before reaching engine cylinder. As a result pressurized air reaches the engine cylinder and again the air is compressed during the compression stroke. So high pressure air is produced by turbocharger. This process is known as turbocharging. Turbocharging is commonly used in Compression Ignition Engines.
As the air is compressed in multistage, its temperature could exceed the maximum safe temperature, if it exceeds the maximum temperature, the cylinder parts will be affected like wear due to excess temperature. To avoid this incident, inter-cooler is used between turbocharger and engine cylinder. In inter-cooler the compressed air is cooled to reduce the temperature due to compression while keeping the same pressure.
What is the purpose to produce the high pressure air in engine cylinder or what are the advantages of turbocharging?
We know that, in Compression Ignition Engines, the temperature of compressed air is used to burn the fuel. If we want to increase the efficiency, power, torque, we have to supply more fuel to the cylinder. If we supply more fuel, the temperature of compressed air should be more to burn all the fuel. By using conventional methods we cannot burn the entire fuel using temperature of air produced during compression stroke. Hence we need extra air to the combustion chamber to burn all extra fuel using its high pressure and temperature to increase power and efficiency. So for supplying extra quantity of air, pressure and temperature to burn extra fuel, the turbocharging is used for increasing power, torque, efficiency.