To ensure reliable engine operation, the reduction of fuel contamination and the separation of water droplets from fuel are decisive. MANN+HUMMEL has developed two new fuel filter concepts to address these issues.

Diesel engines continue to be attractive because of their high efficiency and their ability to meet emission standards in relation to both, carbon dioxide (CO2) and fuel consumption. An increasingly important issue impacting on the efficient working of a diesel engine is fuel quality, which can be poor in many emerging markets.

One main aspect for fulfilling emission targets is the use of highly efficient injection systems operating at pressure levels of up to 2,500 bar or more. In order to ensure the safe and reliable functioning, the reduction of contamination in the diesel fuel system using a highly efficient filter system is important. On the one hand, particles in the fuel need to be filtered and on the other hand, water droplets have to be removed.

Space restrictions require new concepts

A further challenge are the space restrictions imposed in modern vehicles, either in the engine bay, underbody or near the fuel tank. The existing technology and design parameters for particle filtration and diesel water separation have to be transferred and adapted to both, modular and flexible design concepts.

MANN+HUMMEL has decades of experience in developing a wide range of diesel fuel filter systems. The company’s two latest technologies provide new possibilities to meet the present demand for more flexible installation options.

Flexible fuel filter concepts – Flex Cell

The newly developed MANN+HUMMEL Flex Cell fuel filtration concept consists of several small filtration cells where fuel is filtered in parallel through each cell. This concept allows individual configuration, providing vehicle manufacturers maximum flexibility in terms of packaging and positioning in the vehicle. The new Flex Cell fuel filter has been developed specifically to operate in confined and more complex installation spaces that are currently not used for filtration. The idea developed by MANN+HUMMEL engineers was to separate the filtration volume into small filtration cells that can be flexibly located. They can be staggered or angled in non-traditional areas such as the wheel arch. Equally, the design flexibility will allow installation in the underbody area of a vehicle. A key objective in the design was to keep the number of sub-components as low as possible and at the same time to ensure the manufacturing feasibility. Furthermore, the system must withstand the internal operating pressure peak levels of up to 10 bar and temperature peaks of up to 90 °C occurring in the low-pressure system.

Flex Cell: Possible flexible design variations

Variable quality of diesel fuel

Another issue to be dealt with involves the quality of diesel fuel which in some areas of the world can be variable, especially in Asia, North and South America. As injection pressures continue to raise, the sensitive components within the system are increasingly affected by particles and also by water. Water can reach the tank directly through the action of filling with fuel and also in the transport or storage and especially by means of tank ventilation.

Reliable diesel water separation

The highly efficient, multi-stage water separation from MANN+HUMMEL delivers separation rates of between 90 and 100 percent over the complete lifetime of the filter element. The company has successfully introduced this technology to various customers and applications.

To enable easy integration of the diesel water separation within the fuel supply circuit in addition to the existing particle filter, a stand-alone water separator was launched last year. The system can be seen in its first application on the Audi A4 model. This vertically oriented water separator must be installed on the downstream side of the particle filter and is intended for use within the engine compartment whilst the particle inline-filter is located in the underbody area.

Horizontal design for installation in the underbody

Considering again space restrictions under the engine hoods, especially the underbody areas can offer some additional free installation volume in particular for flat geometries. This requires horizontal designs for diesel water separators. As a result, MANN+HUMMEL has started to develop a horizontal working principle for diesel water separation which can also meet the requirements regarding the separation efficiency in all driving conditions. Due to its design, the separated water has the possibility to settle and to be collected at the bottom area under the hydrophobic barrier downstream.

The main advantage of this concept is the possibility to install the system as an option for markets where the quality of fuel is poor. The water separator is easy and convenient to combine with a particle filter, and the complete system provides highly efficient multi-stage diesel water separation. This ensures a reliable and robust protection of the injection system over the complete lifetime of the engine.