Fuel injector temperature mitigation

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

introducing a directly injected fuel into a combustion chamber through a direct fuel injector;

introducing a fumigated fuel upstream of an intake valve associated with the combustion chamber; 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;

advancing 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 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 said advanced intake valve timing after said temperature is below said second predetermined value.

2. The method of claim 1 , wherein said temperature is a transient temperature, said method further comprising:

determining a steady state temperature of said direct fuel injector as a function of engine operating parameters;

determining said transient temperature of said direct fuel injector as a function of said steady state temperature;

wherein said first predetermined value and said second predetermined value are related by one of:

said first predetermined value is greater than said second predetermined value;

said first predetermined value is less than said second predetermined value; and

said first predetermined value is equal to said second predetermined value.

3. The method of claim 1 , wherein a portion of exhaust gases enter an intake manifold from the combustion chamber when the intake valve opens with the advanced intake valve timing.

4. The method of claim 1 , wherein said first predetermined value is greater than said second predetermined value.

5. The method of claim 1 , wherein said engine operating parameters are determinative of directly injected fuel quantity and fumigated fuel quantity introduced into said combustion chamber and frequency with which said fuel quantities are introduced.

6. The method of claim 1 , further comprising retarding exhaust valve timing of the exhaust valve as a function of engine operating conditions such that said temperature is maintained below said second predetermined value.

7. The method of claim 6 , wherein said engine operating conditions comprise engine speed, engine load and intake valve timing.

8. The method of claim 1 , further comprising advancing ignition timing such that at least one of fuel consumption of said internal combustion engine and turbine inlet temperature are reduced.

9. The method of claim 1 , wherein said engine operating parameters comprise at least two of engine speed, air mass flow, engine coolant temperature, equivalence ratio, spark timing, combustion phasing, manifold air temperature, effective EGR rate, intake charge oxygen concentration, trapped oxygen mass, fumigated fuel mass fraction, and directly injected fuel mass fraction.

10. The method of claim 1 , wherein said directly injected fuel is selected from the group consisting of natural gas, gasoline, ethanol-gasoline blends and diesel, and said fumigated fuel is selected from the group consisting of gasoline, ethanol-gasoline blends, natural gas, ethane, methane, propane, biogas, landfill gas, dimethyl ether, hydrogen and known mixtures thereof.

11. The method of claim 1 , wherein the intake valve closes closer to bottom dead center in a compression stroke when opened with the advanced intake valve timing compared to being opened with the normal intake valve timing.

12. The method of claim 1 , wherein ignition timing remains the same between the normal intake valve timing and the advanced intake valve timing.

13. The method of claim 1 , wherein an effective compression ratio increases when the intake valve timing is advanced.

14. The method of claim 1 , wherein said directly injected fuel is different from said fumigated fuel.

15. The method of claim 1 , wherein said engine operating parameters in said function of engine operating parameters for determining said temperature include a directly injected fuel mass fraction and/or a fumigated fuel mass fraction.

16. The method of claim 1 , wherein the increasing concentration of exhaust gas in the combustion chamber by trapping the exhaust gas in the combustion chamber includes drawing the exhaust gas into an intake manifold of the combustion chamber and reintroducing the exhaust gas into the combustion chamber with the fumigated fuel and air.

17. 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.

18. The apparatus of claim 17 , wherein said first predetermined value is greater than said second predetermined value.

19. The apparatus of claim 17 , wherein said controller is further programmed to, in addition to or instead of advancing intake valve timing of the intake valve, retard exhaust valve timing of the exhaust valve as a function of engine operating conditions such that said temperature is maintained below said second predetermined value.

20. The apparatus of claim 17 , wherein said controller is further programmed to advance ignition timing such that at least one of fuel consumption of said internal combustion engine and turbine inlet temperature are reduced.

21. The apparatus of claim 17 , wherein the increase concentration of exhaust gas in the combustion chamber by trapping the exhaust gas in the combustion chamber includes drawing the exhaust gas into an intake manifold of the combustion chamber and reintroducing the exhaust gas into the combustion chamber with the fumigated fuel and air.

22. The apparatus claim 17 , wherein the intake valve closes closer to bottom dead center in a compression stroke when opened with the advanced intake valve timing compared to being opened with the normal intake valve timing.

23. The apparatus of claim 17 , wherein ignition timing remains the same between the normal intake valve timing and the advanced intake valve timing.

24. The apparatus of claim 17 , wherein an effective compression ratio increases when the intake valve timing is advanced.

25. The apparatus of claim 17 , wherein said directly injected fuel is different from said fumigated fuel.

26. The apparatus of claim 17 , wherein said engine operating parameters in said function of engine operating parameters for determining said temperature include a directly injected fuel mass fraction and/or a fumigated fuel mass fraction.

27. 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.

28. The apparatus of claim 27 , wherein said directly injected fuel is different from said fumigated fuel.

29. The apparatus of claim 27 , wherein said engine operating parameters in said function of engine operating parameters for determining said temperature include a directly injected fuel mass fraction and/or a fumigated fuel mass fraction.

30. The method of claim 27 , wherein the increasing concentration of exhaust gas in the combustion chamber by trapping the exhaust gas in the combustion chamber includes drawing the exhaust gas into an intake manifold of the combustion chamber and reintroducing the exhaust gas into the combustion chamber with the fumigated fuel and air.