Charge Air Cooling :

The air density determines the maximum weight of fuel that can be effectively burned per working stroke in the cylinder, it also determines the maximum power that can be developed by the engine.

The increase in air density is fractionally offset by increase in air temperature resulting from compression by turbochargers. Much of this potential loss can be recovered by charge air coolers. Charge air cooling has double effect on engine performance :
  • By increasing the charge air density it increases the weight of air flowing in cylinder and
  • by lowering the air temperature it reduces maximum cylinder pressure, exhaust temperature and thermal loading.
Air Cooler : The most common type of cooler is water cooled design with finned tubes in a casing carrying sea water over which the air passes. For efficient cooling velocity of air should be low and cooling area large. This is obtained by making air inlet connection divergent and outlet is convergent to restore air velocity.
Condensation of moisture in the compressed air will occur during cooling and a drain is fitted to the outlet side to allow the condensate to be removed. The drain should be kept open and its discharge noted, this will also indicate if a cooling water leak has occurred.
The cooler consist of a tube stack of aluminum brass tubes bonded into two brass plates. Cast iron boxes are attached to the tube plates and allow sea water circulation. The air seal is maintained by a rubber joint ring.
Thin copper fins are soldered to the outside of the cooler tubes. The air will pass between the plates which greatly increase the area of heat transfer. Temperature and pressures are recorded at each inlet and discharge.
Too high air outlet temperature will increase the exhaust temperatures and will cause loss in efficiency due to reduction in air density.  Air at very low temperature will cause thermal shock when in contact with liner and pistons and will increase chances of corrosion.

charge air cooler
Charge air cooler

Author marineGuru

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