DOUBLE STAGE PRE-FILTER DIESEL WATER SEPARATOR Fernando Jun Yoshino, Fábio Moreira, Felipe Ferrari and Tadeu Geraldo Domingues MAHLE Metal Level S/A E-mails: fernando.yoshino@br.mahle.com, fabio.mmoreira@br.mahle.br, felipe.ferrari@br.mahle.com and tadeu.domingues@br.mahle.com ABSTRACT Nowadays, water separation from diesel fuel is a critical requirement for modern diesel engines. The main reasons are: corrosion, wear on the fuel system, irregular combustion and acceleration of microbiological growth that clogs filters, pumps and pre-filters. Due to this, a pre-filter is placed at chassis side between fuel tank and pressure pumps in order to separate water from diesel. However, this function is getting even more difficult because of higher biodiesel content. Higher biodiesel levels mean higher water absorption due to its higher hygroscopic characteristic. Additionally, it is more difficult to separate water from diesel due to biodiesel higher bond to water molecules. In this way, new pre-filters concepts are under development considering higher water separation efficiencies. This paper presents a new product concept based on double-stage filtration technology. At this configuration, small water droplets are first coalesced and contaminants retained by a first stage. In a second stage, protected from contamination, final water separation happens. In order to illustrate technology potential, laboratory and field tests with prototypes are presented in order to confirm concept robustness at this new boundary condition. INTRODUCTION Diesel engines are improving in order to attend new government emission regulations and customers fuel consumption reduction requests. In this way, new diesel common-rail engines have been launched with higher injection pressures in order to attend these demands. At same time, these new technology engines require new boundary conditions to work in these straight limits. Main boundary condition is the fuel quality. Fuel quality is critical because new engines are more sensitive to contaminant presence, sulfur and water level contents. Depending on their presence level, fuel injection systems reduce their performance and durability. Water content is one of these important fuel quality characteristics. When present in high levels, it causes fuel injection system corrosion and premature wearing. Beside this, water presence also contributes for microorganism growth at gas stations and truck tanks. This process creates a biological sludge that clogs fuel filters, fuel lines and fuel injection systems [1]. Blucher Engineering Proceedings Setembro de 2015, Número 1, Volume 2