Parameter study of the appearance and allocation of small oil aerosol particles at the piston, piston ring and cylinder liner surfaces in the engine blow-by and the evaluation of countermeasures

In addition to particle emissions from the aftertreatment box, a further known source is crankcase ventilation. Using a modern separation system, the particle mass limit is adhered to, thus enabling open crankcase ventilation into the atmosphere in heavy duty combustion engines. Since closed crankcase ventilation influences the powertrain negatively due to compressor coking, contamination and high ash emission, the open crankcase configuration is very common. The Euro VI legislation introduced a total particle number limit. This brought the focus onto smaller particles stemming from the separation system, in addition to the bigger particles that are of concern when meeting the particle mass limit.Efforts to reduce the engine particle raw emissions prior to the separation system have been successful, as has the improvement of the separation system itself.This paper focuses on the drivetrain as the suspected main origin of micron and submicron oil aerosol particles. A single cylinder engine with real-time piston temperature measurement equipment enables further insights into parameters for particle formation on the one hand, and the analysis of different countermeasures on the other.This article points out the engine oil temperature, the engine load and the piston oil nozzle flow rate as main formation parameters.Additionally, the connection between specific oil aerosol diameter modes to the combustion process and the piston surface temperatures is shown.Drivetrain tribology and heat management are highlighted as major countermeasure categories, and several ideas for reducing emissions are discussed.Finally, the influence on emission reduction of a piston filled with a heat transfer medium is demonstrated.