Diesel Dual Fuel, DDF, is a concept which promises the
possibility to utilize CNG/biogas in a compression ignition engine
maintaining a high compression ratio, made possible by the high
knock resistance of methane, and the resulting benefits in thermal
efficiency associated with diesel combustion.
A series of tests has been carried out on a single-cylinder lab
engine, equipped with a modern common rail injection system
supplying the diesel fuel and two gas injectors, placed in the
intake runners. One feature of port-injected Dual Fuel is that full
diesel functionality is maintained, which is of great importance
when bringing the dual fuel technology to market. The objective of
the study was to characterize and investigate the potential for
dual fuel combustion utilizing all degrees of freedom available in
a modern diesel engine.
Increased diesel pilot proved efficient at reducing
NOx emissions at low λ. Advanced combustion phasing has
the potential to extend the lean limit for operation.
Stoichiometric operation using high levels of EGR is identified as
a promising field in conjunction with raised inlet temperature.