Oil Aerosol Emission Optimization Using Deflectors in Turbo Charger Oil Drain Circuit

Closed crankcase ventilation prevent harmful gases from entering atmosphere thereby reducing hydrocarbon emissions. Ventilation system usually carries blowby gases along with oil mist generated from Engine to Air intake system. Major sources of blowby occurs from leak in combustion chamber through piston rings, leakage from turbocharger shafts & leakage from valve guides. Oil mist carried by these blowby gases gets separated using separation media before passing to Air Intake. Fleece separation media has high separation efficiency with lower pressure loss for oil aerosol particles having size above 10 microns. However, efficiency of fleece media drops drastically if size of aerosol particles are below 10 microns. Aerosol mist of lower particle size (>10 microns) generally forms due to flash boiling on piston under crown area and from shafts of turbo charger due to high speeds combined with elevated temperatures.

High power density diesel engine is taken for our study. It produces aerosol mist of low particle size (below 10 microns) & has fleece media for separation. Aerosol emission of test Engine is reaching till 3.0 gm/hr when operated at rated speed. Particle size measurement using light refraction technique reveals high count of aerosol particles having size below 10 microns. To understand formation of lighter size aerosol mist, turbo charger lubrication is disconnected from engine during measurement. 20 % improvement in aerosol emission observed without turbo charger lubrication. Deflectors are designed in turbo charger oil drain circuit which help the small size oil droplets to coalesce & covert to bigger droplets (above 10 microns) which can be separated more efficiently in the fleece separator. Oil aerosol emission improvement of 20 % observed with introduction of deflectors in turbo charger oil drain circuit. Improvement can be seen across all Engine speed load conditions. Oil aerosol emission optimized without making any change in standard oil separator system.