CHARGE AIR COOLER

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Charge Air Cooling:

In pressure charged engines, the increased power output is the result of an increased weight of air trapped in the cylinder, enabling a greater weight of fuel to be burned.  The increase in air density is fractionally offset by the increase of air temperature consequent upon adiabatic compression in the turbo-blower, the amount of which is dependent on compressor efficiency. This reduction of air density due to increased temperature implies a loss of potential power for a stated amount of pressure charging.    For example, at a charge air pressure of, say 0.35 bar, the temperature rise is of the order of 33*C - equivalent to a 10% reduction in charge density. As the amount of pressure charging is increased, the effect of turbo-blower temperature rise becomes more pronounced.   For example, for a charge air pressure of 0.7 bar, the temperature rise is approximately 60*C, which is equivalent to a reduction of 17% in the charge-air density.   To recover this potential loss, charge-air coolers are interposed between turbo-blower and scavenge manifold.    In four stroke engine, with a moderate amount of pressure charging, the charge-air cooling is not worth while, but in two stroke engines it is advantageous to fit charge air coolers.

Charge air cooler has double effect on engine performance:

1. By increasing charge-air density, it increases the weight of air flowing into cylinders, resulting in higher output by burning more fuels.
2. By lowering the charge-air temperature, it reduces the exhaust temperature and engine thermal loading.

The moist air when cooled by air cooler separates water.  This water will affect the engine performance by entering the cylinder.  Hence adequate drain facility must be provided.  It may be necessary to employ water separator after air cooler.  The arrangement of water separator and the construction of an air cooler are shown on the following pages.

 Key: 1: Charge Air pipe. 2: Outlet connection case. 3: Measuring socket. 4: Seal.

         5: Fix tube. 6: Meter cooler. 7: Cover. 8: Venting screw. 9: Inlet connection case.

         10: Ring. 11: Seal. 12: Connection to turbocharger. 13: Bottom cover.

         14: Cooling water discharge. 15. Cooling water inlet. 16: Ring half.

         17: Seal. 18: Connecting pipe