Charge Cooling, the Inlet and Exhaust Systems

  • N. Watson
  • M. S. Janota


The principal reason for turbocharging is to increase the power output of an engine without increasing its size. This is achieved by raising the inlet manifold pressure, hence increasing the mass of fresh air drawn into the cylinders during the intake stroke and allowing more fuel to be burnt. However, it is impossible to compress air without raising its temperature unless the compressor is cooled. Since the objective is to raise the density of the air, this temperature rise partly offsets the benefit of increasing the pressure, since
The objective must therefore be to obtain a pressure rise with a minimum temperature rise. This implies isentropic compression (figure 9.1) in which case the temperature rise will be given by the equation
Unfortunately due to inefficiencies in practical compressors, the actual temperature rise will be greater than that given by equation 9.2. In terms of the isentropic efficiency of the compressor (ηc) it will be given by
The more efficient the compressor, the closer the temperature rise approaches the isentropic temperature rise (figure 9.1).


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Copyright information

© N. Watson and M. S. Janota 1982

Authors and Affiliations

  • N. Watson
    • 1
  • M. S. Janota
    • 2
  1. 1.Imperial CollegeLondonUK
  2. 2.Queen Mary CollegeLondonUK

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