Water injection for gasoline engines can be an effective means to meet the ever stricter emission regulations. In this context, the water filter has an important role to play to ensure a smooth and clean injection process.
Combustion engines are subject to enormous challenges. On the one hand the statutory regulations regarding pollutant emissions are becoming ever stricter with a demand for real driving emissions tests according to the new WLTP test cycle. On the other hand there is a demand for higher engine performance. Previously one way to achieve this was through full load enrichment. This also makes a significant contribution towards component protection, but leads to higher emissions under real driving conditions (RDE) and therefore is in conflict with the objective of meeting the new limit values.
A modern approach to find a solution to this dilemma is the injection of water. This technology can be used to reduce the temperature of the intake air through the evaporation of water down to a defined temperature level. The objectives of water injection are to increase performance or to reduce CO2 emissions through a reduction in fuel consumption. The condition is that before the injection process the water has a high degree of purity in order to protect the injection nozzles against wear. Otherwise contaminants in the water can lead to wear of the water injection system.
In the development of the filtration concepts for renowned OEMs, MANN+HUMMEL was able to draw on decades of experience in the area of liquid filtration, and in particular in urea filtration. The filter concept was developed to enable simple integration in existing vehicle installation space as a stand-alone solution. The experts at MANN+HUMMEL made use of standardized designs and components to realize easy adaptation to new vehicle applications. The result of the development process is an inline filter which is positioned on the pressure side between the water pump and the injection system. This ensures high mechanical and dynamic stability which is important due to high operating pressures and fluctuating temperatures in the vehicle. The weight of the housing is low thanks to the use of plastic and functions can be easily integrated. The inline filter only takes up a small amount of space and can therefore easily be fitted to the underbody or engine compartment.
In order to ensure that vehicles with water injection also reliably function in winter, the water in the system and the filter unit have to be protected against freezing to prevent damage to components and avoid a negative influence on the filtration function. MANN+HUMMEL offers a range of solutions to achieve this. One of these is a bypass solution integrated in the inline filter which supports the emptying procedure in purging mode. After the engine is switched off, the water injection system is almost completely emptied to remove the possibility of damage caused by water freezing. In addition, the bypass valve prevents dirt particles from the filter media from reaching sensitive components such as the pump. As a further protection compensation elements can be integrated in the system. The elasticity of these elements enables them to compensate volume changes and thus prevents damage should extreme coldness nevertheless lead to icing. Apart from that, as an option the filter can be equipped with an electric heater which can be integrated in the housing using a minimum of space and ensures an ideal defrosting process. The geometry and output of the heating concept can be adapted to take the respective installation space situation and customer requirements into account.
The multi-layer, fully-synthetic filter media was designed to include two support layers to withstand the high mechanical forces experienced during the freezing process. The MULTIGRADE eM-WI filter media especially developed for water filtration has a filter fineness of ten micrometers and achieves highly efficient particle separation. The filter element is designed for a low differential pressure and high volume flow rate and therefore ensures a sufficient supply of water for the injection system. A remarkable feature is the functionalization of the filter media. A special coating offers protection against microbial growth, which could lead to the formation of a biofilm and thus to clogging of the filter element. The filter for the water injection realized through the combination of proven concepts and innovative development convinces with excellent functional reliability and a high efficiency level.