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Purpose of Charge Air Cooler?

The exhaust gas from the engine is utilized in the turbocharger for compressing fresh air to charge the engine with a positive pressure greater than ambient conditions. This compression causes the temperature of the air to increase, which thus cannot be fed directly into the engine as it is out of operating limits. Thus a cooler that brings the air temperature back to near ambient conditions is fitted on the engine. When the air is hot its density is less and thus the mass of air charged into the engine is less when compared to the mass when the air is cold. Thus the charge air cooler improves the charge air density and its temperature.

The compressed charged air at the outlet of charged air cooler will have a reduced temperature of about 40 to 50 degrees celsius from a temperature of about 200 degrees celsius. This reduced temperature of the air will increase the density of the charge ait at low temperatures. Increased air density of the charge air will raise the scavenge efficiency and allow a greater mass of air to be compressed inside the engine cylinder so that more fuel can be burned inside the combustion chamber giving an increase in power. Also the engine is maintained at a safe working temperature. The lower compression temperature reduces stress on the piston, piston ring, cylinder liner, and cylinder head. The charge air cooler has another advantage in that it reduces the exhaust temperature. It has been proven that every one-degree Celsius drop in scavenging air temperature will reduce the exhaust temperature about 5 to 10 degrees celsius. This does not mean that the air can be charged at cryogenic temperatures. IF very cold air enters the cylinder liner it could cause thermal shock leading to cracking of liner.


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