Efficient oil separation

Through the LongLife fiber demister

Higher pressures, smaller droplets: the requirements regarding oil separation in connection with crankcase ventilation are increasing. The new Lon­gLi­fe fiber demister from MANN+HUMMEL meets these requirements. It separates even the smallest droplets highly efficiently and in addition offers greater design flexibility.

Blowby is inevitably produced in the crankcase through gas leakage which primarily occurs at the piston rings. Along with other substances, the aerosol includes a large number of ultra-fine droplets. Depending on the engine design and operating conditions, the size of these droplets ranges from a few micrometers down to nanometers. Therefore, an important task of the crankcase ventilation system is to separate the small oil droplets from the blowby. In this process it is particularly important that the separation is performed efficiently. This is because the remaining blowby is directed back to the combustion process, whereas the separated oil should be returned to the oil circuit. If this is not made in a reliable manner the oil consumption will increase. The oil separation is also decisive for compliance with the exhaust gas regulations for modern engines. If deposits of oil residues accumulate on the turbocharger, the inlet valves or the intercooler, this will have a negative effect on the service life and function of these components.

Ultra-fine droplets are also separated

Up to now, mostly passive inertia separators have been used to prevent this fouling. Solutions such as the SD oil separator from MANN+HUMMEL reliably separate the oil droplets without an additional energy supply over the lifetime of the engine. The separation performance, however, is subject to limitations with regard to the maximum permissible differential pressure and the given particle size distribution in the blowby. 

The trend of downsizing leads to higher charge-air pressures. Furthermore, the use of low viscosity oils is increasing in order to reduce friction. This, in turn, makes the oil droplets ever smaller and partly considerably smaller than 1 micrometer. This is where passive inertia separators reach their limits. For a reliable separation, the inertia force of the particles therefore has to be increased through the input of additional energy.

Impressive performance, easy integration

The LongLife fiber demister from MANN+HUMMEL, which is now ready for series production, takes a different approach. The passive oil separation system is able to even separate ultra-fine droplets significantly smaller than 1 micrometer, is reliable and highly efficient at all operating points of the engine and manages to achieve this without the need for additional energy. A further advantage is that the fiber separator can be designed to be round, flat or even curved. This enables a high degree of design flexibility as the elements can be individually adapted to the available installation space and easily integrated in complex installation spaces without having to compromise on separation performance. Numerous tests on engine test benches have established that the service interval of the replaceable element is at least 100,000 kilometers. In combination with the elastomer-free and almost universally chemically-resistant RobustPlus pressure control valve from MANN+HUMMEL, the new LongLife fiber demister thereby ensures the reliability of the complete system and also meets the highest requirements.