Impact of engine oil volatility and viscosity on blow?by aerosol formation

摘要

Particulate emissions from diesel engines are a matter of public concern and continued industrial development. For an internalcombustion engine, particles may originate either from the after treatment box or from the crankcase ventilation system. Thispaper quantifies and discusses particle sources within the crankcase ventilation system of a medium-duty 4-cylinder and aheavy-duty 6-cylinder engine and their dependence on the engine oil parameters viscosity (expressed as Noack number) andHTHS volatility. Crankcase aerosol spectra were measured by an optical particle counter in the size range of 0.3–5 μm. Fora few cases data of filter samples downstream the separator unit are discussed for the total blow-by aerosol. Engines werefound to behave very similarly with regard to changes in either oil parameter, with volatility generally being the far strongerfactor of influence. Total particle mass concentration increased by a factor of up to 5 for a rise in Noack volatility of about13–25. The mass concentration downstream of the separator also increases with oil volatility. A variation of HTHS viscosityfrom 3.5 to 2.6 mPas generated a marginal change in aerosol output by a factor of about 1.2. However, and unexpectedly,the most viscose oil generated the relatively highest particle mass concentrations for both engines.