Fuel injector temperature mitigation

An apparatus for fuel system protection in an internal combustion engine comprising:

• a direct fuel injector for introducing a directly injected fuel into a combustion chamber of said internal combustion engine;
• a fumigation system for introducing a fumigated fuel upstream of an intake valve of said combustion chamber;
• and
• a controller programmed to:
• selectively introduce said directly injected fuel through said direct fuel injector and said fumigated fuel through said fumigation system;
• and
• while operating said internal combustion engine with only said fumigated fuel:
• determine a temperature of said direct fuel injector as a function of engine operating parameters;
• advance intake valve timing of an intake valve of the internal combustion engine from a normal valve timing to an advanced intake valve timing when said temperature rises above a first predetermined value such that a duration of an overlap when the intake valve is open and an exhaust valve of said combustion chamber is open increases;
• increase concentration of exhaust gas in the combustion chamber by trapping the exhaust gas in the combustion chamber;
• hold intake valve timing of the intake valve at said advanced intake valve timing until said temperature is below a second predetermined value;
• and
• return intake valve timing of the intake valve to said normal intake valve timing from said advanced intake valve timing after said temperature is below said second predetermined value.

A method of fuel system protection for an internal combustion engine comprising:

• during calibration of said internal combustion engine:
• introducing a directly injected fuel into a combustion chamber through a direct fuel injector;
• introducing a fumigated fuel upstream of an intake valve;
• and
• selectively operating said internal combustion engine with at least one of said directly injected fuel and said fumigated fuel;
• and
• while operating said internal combustion engine with only said fumigated fuel:
• determining a temperature as a function of engine operating parameters of said direct fuel injector that directly injects fuel into said combustion chamber;
• calibrating said engine to advance intake valve timing of said intake valve of the combustion engine from a normal intake valve timing to an advanced intake valve timing when said temperature rises above a first predetermined value such that a duration of an overlap between when the intake valve is open and an exhaust valve of said combustion chamber is open increases;
• increasing concentration of exhaust gas in the combustion chamber by trapping the exhaust gas in the combustion chamber;
• holding intake valve timing of the intake valve at said advanced intake valve timing until said temperature is below a second predetermined value;
• and
• returning intake valve timing of the intake valve to said normal intake valve timing from the advanced intake valve timing after said temperature is below said second predetermined value;
• during normal operation of said internal combustion engine:
• determining said temperature of said direct fuel injector as a function of engine operating parameters;
• and
• performing a temperature mitigation technique when said temperature rises above a third predetermined value such that said temperature is maintained below a fourth predetermined value.