Optimization of Oil Separation Unit for Two Stage Turbocharged Engine

In addition to performance target, recent stringent emission legislation and reduction in oil consumption are the major driving force for engine design and development. In this reference importance of crankcase ventilation has increased immensely and the manufacturers are bound to develop most efficient system with high oil trap efficiency. In crankcase ventilation system, the blow-by gases from the crankcase are routed to the intake manifold through Oil separator system. The oil separator task is to retain the oil part from the blow by gas and send it back to sump. Developing an oil separator for the engine studied here was very challenging considering double stage turbocharger which produces very fine mist of oil and is difficult to separate. The study shows that oil mist coming in blow by is of size 0.3 micron and lesser than it. The major contribution of these fine mists was from turbocharger. Keeping this in view, an oil separation unit which is an integral part of cam cover had been optimized for 1.5 litre, 3 cylinder engine with two stage turbo charging. The separation unit consists of two stage separation, pre & fine separation unit. Pre separation unit trap oil of higher size (Oil droplets) while fine unit separates oil mist from blow by. The optimization had done in stages and finally the oil carry over targets of 2 g/hr & 3 g/hr at 100% & 200% blow by had been achieved with optimized separation unit. 200% blow by was taken for worst condition which replicate the life of engine. The final oil carry values were 1.4 g/hr as against 2 g/hr at 100% blow by while it was 2.3 g/hr as against 3 g/hr at 200% blow by. During trial, it was also ensured that other parameter such as crankcase pressure & air intake depression remains within the target value.