Engine laboratory tests were conducted to assess the impact of B20 biodiesel on the performance of cordierite diesel particulate filters (DPFs). Test fuels included 20% soy based methyl ester blended into ultra low sulfur diesel fuel, and two ULSD on-road market fuels. B20 has a higher cetane number, boiling point and oxygen content than typical on-road diesel fuels.
A comparative study was performed using a model year 2007 medium duty diesel truck engine. The aftertreatment system included a diesel oxidation catalyst (DOC) followed by a cordierite wall flow DPF.
A laboratory-grade supplemental fuel doser was used in the exhaust stream for precise regeneration of the DPF. Tests revealed that the fuel dosing rate was higher and DOC fuel conversion efficiency was poorer for the B20 fuel during low exhaust temperature regenerations. The slip of B20 fuel past the DOC was shown to produce significantly higher exotherms in the DPF during regeneration. Therefore, the condition of B20 fuel slip may potentially impact the integrity of the DPF during extreme regeneration conditions depending on the DOC size, application and control strategy used. B20 fuel conversion across the DOC markedly improved as exhaust temperature exceeded 320°C.
The particulate matter (PM) produced by the B20 fuel was found to be somewhat more reactive than PM from ULSD fuels. The DPF tested with B20 fuel had up to 8% higher regeneration efficiency. The pressure drop and filtration efficiency of the DPFs were not significantly different for B20 and ULSD fuels.