Abstract
AbstractParticulate emissions from diesel engines are a matter of public concern and continued industrial development. For an internal combustion engine, particles may originate either from the after treatment box or from the crankcase ventilation system. This paper quantifies and discusses particle sources within the crankcase ventilation system of a medium-duty 4-cylinder and a heavy-duty 6-cylinder engine and their dependence on the engine oil parameters viscosity (expressed as Noack number) and HTHS volatility. Crankcase aerosol spectra were measured by an optical particle counter in the size range of 0.3–5 µm. For a few cases data of filter samples downstream the separator unit are discussed for the total blow-by aerosol. Engines were found to behave very similarly with regard to changes in either oil parameter, with volatility generally being the far stronger factor of influence. Total particle mass concentration increased by a factor of up to 5 for a rise in Noack volatility of about 13–25%. The mass concentration downstream of the separator also increases with oil volatility. A variation of HTHS viscosity from 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.
Highlights
Emission reduction in the automotive sector has often been driven by legislation, notably Euro VI, which in 2012 imposed particulate emission limits based on total number concentration
The impact of key parameters such as high-temperature high-shear (HTHS) viscosity and Noack volatility on aerosol production has never been investigated exhaustively. This paper investigates their effects on aerosol formation in the crankcase environment
The study was conducted on two diesel engines, a mediumduty 4-cylinder engine produced in series by Daimler Truck AG and a heavyduty 6-cylinder prototype engine
Summary
Emission reduction in the automotive sector has often been driven by legislation, notably Euro VI, which in 2012 imposed particulate emission limits based on total number concentration. After passing through a particle separator, the remaining, rather fine “blow-by” aerosol is either recirculated to the air intake or directly vented to the environment. Both closed and open crankcase ventilation systems are in current use and have their respective advantages and disadvantages [4]. The additional burden of oily crankcase aerosol represents a problem: In a closed system the particles can cause critical engine components to deteriorate, while in an open system they contribute to the overall emission level included in the emission certification on the test bench or the PEMS measurement procedure on a vehicle
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