System and method for increasing tolerance to fuel variation

1. A control system for a multiple fuel internal combustion engine, comprising:

at least one cylinder pressure sensor associated with each cylinder of the engine;

a data collection module configured to receive real-time cylinder pressure measurements from each of the at least one cylinder pressure sensors and calculate one or more actual combustion parameter values from the real-time cylinder pressure measurements;

a comparison module configured to receive the calculated one or more actual combustion parameter values from the data collection module and compare the calculated one or more actual combustion parameter values for each cylinder to theoretical combustion parameter values to determine any difference therebetween, wherein the theoretical combustion parameter values are derived independently from any actual combustion parameter values based on real-time sensor measurements; and

a process control module configured to control fuel injection of at least two different types of fuel supplied to each cylinder in order to reduce any difference between the calculated actual combustion parameter values for each cylinder and the theoretical combustion parameter values.

2. The control system of claim 1 , wherein the comparison module is further configured to receive the theoretical combustion parameter values from a memory storage.

3. The control system of claim 2 , wherein the theoretical combustion parameter values from the memory storage are combustion parameter values based on a theoretical power output that the multiple fuel internal combustion engine can produce with the same types and quantities of fuel as are currently being combusted by the engine while staying within allowable stress limits for the engine.

4. The control system of claim 2 , wherein the theoretical combustion parameter values from the memory storage are combustion parameter values based on a theoretical amount of emissions that the multiple fuel internal combustion engine will produce with the same types and quantities of fuel as are currently being combusted by the engine.

5. The control system of claim 1 , wherein the calculated one or more actual combustion parameter values and the theoretical combustion parameter values include one or more of peak cylinder pressure, indicated mean effective pressure (IMEP), maximum heat released, crank angle of start of combustion, crank angle of center of combustion, and crank angle of opening or closing of an inlet or outlet valve for each of the cylinders of the multiple fuel internal combustion engine.

6. The control system of claim 5 , wherein the theoretical combustion parameter values are combustion parameter values based on a theoretical power output that the multiple fuel internal combustion engine can produce with the same types and quantities of fuel as are currently being combusted by the engine.

7. The control system of claim 1 , wherein the process control module is further configured to control the timing of one or more of fuel injection of at least two different types of fuel and ignition of the at least two different types of fuel.

8. The control system of claim 1 , further including the data collection module being configured to recalculate one or more actual combustion parameter values from new real-time cylinder pressure measurements taken after the process control module controls fuel injection of at least two different types of fuel in order to reduce any difference between the calculated actual combustion parameter values for each cylinder and the theoretical combustion parameter values, the recalculation by the data collection module continuing in a closed loop process until the difference between the calculated actual combustion parameter values and the theoretical combustion parameter values is less than a predetermined threshold.

9. The control system of claim 1 , wherein the comparison module is further configured to receive the theoretical combustion parameter values from a calculation module configured to calculate the theoretical combustion parameter values using known, physics-based calculations based on the physical parameters of the engine, chemical characteristics of the type of fuel, and known thermodynamics of the combustion process for each type of fuel being used by the multiple fuel internal combustion engine.

10. A multiple fuel internal combustion engine operable in a combined liquid and gaseous fuel mode; comprising:

a plurality of cylinders;

a real-time cylinder pressure sensor associated with each of the plurality of cylinders;

a liquid fuel injection system;

a gaseous fuel injection system; and

a control system comprising:

a data collection module configured to receive real-time cylinder pressure measurements from each of the cylinder pressure sensors and calculate one or more actual combustion parameter values from the real-time cylinder pressure measurements;

a comparison module configured to receive the calculated one or more actual combustion parameter values from the data collection module and compare the calculated one or more actual combustion parameter values for each cylinder to theoretical combustion parameter values to determine any difference therebetween, wherein the theoretical combustion parameter values are derived independently from any actual combustion parameter values based on real-time sensor measurements; and

a process control module configured to control one or more of fuel injection of at least a liquid fuel and a gaseous fuel, and ignition in order to reduce any difference between the calculated actual combustion parameter values for each cylinder and the theoretical combustion parameter values.

11. The multiple fuel internal combustion engine of claim 10 , wherein the comparison module is further configured to receive the theoretical combustion parameter values from a memory storage.

12. The multiple fuel internal combustion engine of claim 11 , wherein the theoretical combustion parameter values from the memory storage are combustion parameter values based on a theoretical power output that the multiple fuel internal combustion engine can produce with the same types and quantities of fuel as are currently being combusted by the engine while staying within allowable stress limits for the engine.

13. The multiple fuel internal combustion engine of claim 11 , wherein the theoretical combustion parameter values from the memory storage are combustion parameter values based on a theoretical amount of emissions that the multiple fuel internal combustion engine will produce with the same types and quantities of fuel as are currently being combusted by the engine.

14. The multiple fuel internal combustion engine of claim 10 , wherein the calculated one or more actual combustion parameter values and the theoretical combustion parameter values include one or more of peak cylinder pressure, indicated mean effective pressure (IMEP), maximum heat released, crank angle of start of combustion, crank angle of center of combustion, and crank angle of opening or closing of an inlet or outlet valve for each of the cylinders of the engine.

15. The multiple fuel internal combustion engine of claim 14 , wherein the theoretical combustion parameter values are combustion parameter values based on a theoretical power output that the multiple fuel internal combustion engine can produce with the same types and quantities of fuel as are currently being combusted by the engine while staying within allowable stress limits for the engine.

16. The multiple fuel internal combustion engine of claim 10 , wherein the process control module is further configured to control the timing of one or more of fuel injection of at least two different types of fuel and ignition of the at least two different types of fuel.

17. The multiple fuel internal combustion engine of claim 10 , further including the data collection module being configured to recalculate one or more actual combustion parameter values from new real-time cylinder pressure measurements taken after the process control module controls one or more of fuel injection and ignition in order to reduce any difference between the calculated actual combustion parameter values for each cylinder and the theoretical combustion parameter values, the recalculation by the data collection module continuing in a closed loop process until the difference between the calculated actual combustion parameter values and the theoretical combustion parameter values is less than a predetermined threshold.

18. The multiple fuel internal combustion engine of claim 10 , wherein the comparison module is further configured to receive the theoretical combustion parameter values from a calculation module configured to calculate the theoretical combustion parameter values using known, physics-based calculations based on physical parameters of the engine, chemical characteristics of each type of fuel, and known thermodynamics of a combustion process for each type of fuel being used by the multiple fuel internal combustion engine.

19. A method for controlling a multiple fuel internal combustion engine operable in at least a combination liquid and gaseous fuel mode, the method comprising:

receiving real-time cylinder pressure measurements from each of the cylinders of the multiple fuel internal combustion engine;

calculating one or more actual combustion parameter values based on the real-time cylinder pressure measurements;

comparing the calculated actual combustion parameter values for each cylinder to theoretical combustion parameter values to determine any difference therebetween, wherein the theoretical combustion parameter values are derived independently from any actual combustion parameter values based on real-time sensor measurements; and

controlling one or more of fuel injection of at least a liquid fuel and a gaseous fuel, and ignition in order to reduce any difference between the calculated actual combustion parameter values for each cylinder and the theoretical combustion parameter values.

20. The method of claim 19 , wherein the theoretical combustion parameter values are combustion parameter values based on a theoretical power output that the multiple fuel internal combustion engine can produce with the same types and quantities of fuel as are currently being combusted by the engine while staying within allowable stress limits for the engine.