A method and apparatus for operating a diesel engine under stoichiometric or slightly fuel-rich conditions, as is often necessary to maintain effective operation of certain post-combustion emission reduction devices, such as Lean NOx Traps, includes a readily vaporizable fuel injection nozzle disposed in the intake manifold system in communication with a combustion chamber of the diesel engine. The readily vaporizable fuel mixes with the intake air and produces a mixture of pre-mixed air and fuel when introduced into the combustion chamber. A diesel fuel, which is directly injected into the combustion chamber through a conventional diesel fuel injection nozzle. Combustion of the pre-mixed air and readily vaporizable fuel, with controlled injected of the diesel fuel, reduces the particulate matter (soot) emissions when operating the engine under the necessary stoichiometric or slightly fuel-rich conditions.
Rudolf H. Stanglmaier