Characterization of RME, RME Aged and Mineral Diesel Fuel Injected by a Common Rail Apparatus for EURO5 Diesel Engines 2011-01-1938

Alternative diesel fuels from renewable sources (biodiesels) have increased significantly interest due to their potential CO₂ emission benefits, capability to reduce unburned hydrocarbons and particulate matter emissions, biodegradability and non-toxicity.

Biodiesels undergo ageing effects due to autoxidation processes of their molecular chains. Ageing leads to a variety of decomposition products like peroxides, alcohols, aldehydes and carboxylic acids. They are detectable as alterations of chemical properties, odor and taste (rancidity).

The characteristics of Rapeseed Methylester (RME), RME aged and diesel sprays have been analyzed for different injection strategies in engines. The tests have been performed on a Bosch second generation common rail solenoid-driven fuel injection system capable of 160 MPa maximum injection pressure, fitted on EURO5 diesel engine for passenger car applications. Three different flux number injectors have been adopted at the injection pressures of 40, 80 and 160 MPa with 1.0, 0.6 and 0.3 ms solenoid energizing time. The characterization of the injection process for the defined fuels has been carried out in terms both of fuel injection rate as well as of spatial and temporal fuel distribution in a quiescent chamber in non-evaporative conditions.

Largest discharging nozzle area produced highest fuel injection rate while smallest area created longest injection duration at parity of solenoid exciting time. Digital processing of the spray images, captured at different instant from the start of injection, has enabled the characterization of the fuel dispersion in terms of tip penetration and cone angle. Differentiate behavior of the injected fuel has been noted for the diverse nozzles at early time from the start of injection.

Finally, a detailed reconstruction of the jet images, at very early time from the start of injection, has highlighted repetitive anomalies in the jet-to-jet propagations. Their absolute values and stabilizing time depend on the nozzle type and injection pressure. At late time, the sprays uniform themselves with a homogeneous pattern in the vessel.