Browse Publications Technical Papers 2009-01-0869

Blow-by Gases Coalescing Separation: Performances on Passenger Car Engines 2009-01-0869

In reciprocating internal combustion engines, the gas that leaks at the piston, rings and liner system is usually called blow-by. The blow-by is a complex mixture of air, burned and unburned gases and oil mist. In order to avoid external pollution, the blow-by is recycled in the air intake system. This is called Closed Crankcase Ventilation (CCV). The CCV is the cause of major issues as air intake system fouling, oil consumption and contribution to the exhaust catalyst poisoning phenomena. During the recent decades a quite simple oil separation system based on baffles was acceptable. Emissions regulations are now tougher and a more efficient blow-by separation system is required.
  • Knowledge of the engine parameters and of the blow-by characteristics, including droplets size distribution, oil mass flow and chemical composition is mandatory.
  • Several separation principles are known, all have advantages and drawbacks. A suitable and efficient means to achieve a good separation is to use the coalescence principle through a specific media.
  • A wide range of media technologies has been evaluated on the test bench. Then selected solutions have been evaluated on the engine test stand. Coalescing separators giving acceptable pressure drop have been tested on the road to verify their behaviour versus real life conditions.
  • The coalescing separation principle is flexible. It allows integration to existing parts and association of functions as the pressure regulation valve.


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