The Role of Crankase Filtration in Controlling Diesel Emissions

Two major types of crankcase ventilation systems are currently used. In the open crankcase ventilation (OCV) system, the blow-by aerosol is vented from the crankcase to the atmosphere contributing to total engine emission. Particulate emission from Crankase Ventilation (CV) system without any filter can be as high as 120% of the total engine emission allowed by the US 2007 Regulations specified at a level of 0.01g/hp*hr of particulate matter.

In the Close Crankcase Ventilation system CCV), the blowby is usually released to the engine air intake system between the filter and turbocharger. Engine producers specify the minimum filter efficiency that guarantees long life of the turbocharger since the build up of coked material in the diffuser section causes a decrease in turbocharger efficiency. Only high efficiency filtration systems with efficiency more than 90-99% for 1 micron and larger particles can efficiently protect high boost pressure turbochargers.

The Figure shows the development of separation/filtration technology for CV. Historically, mesh, foam, labyrinth, depth-type cotton-cellulose media, fiberglass, synthetic, depth and pleated media, cyclones, impactors, centrifuges, and electrostatic precipitators have been tried in engine crankcase ventilation systems.

Photo courtesy of Cummins Filtration Inc.

The new generation of long life coalescers made of hundrets of layers of different size fibers shown in the Figure has 99% efficiency for 0.3 micron particles (Cummins Filtration data). It can be used separately or combined with an impactor for extreme crankcase engine environment.

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