Piston temperature model using a physics-based split multi-model approach

1 . An engine, comprising:

a plurality of pistons configured to be actuated by combustion reactions within the engine;

a plurality of cylinders, each cylinder being configured to house a corresponding piston of the plurality of pistons and form a containment boundary for a corresponding combustion reaction of the combustion reactions;

at least one fuel injector configured to inject fuel into the plurality of cylinders, where the fuel is mixed with air disposed in the plurality of cylinders to form an air-fuel mixture;

a plurality of spark plugs, each spark plug being configured to ignite the air-fuel mixture in a corresponding cylinder to initiate the combustion reactions;

a plurality of piston cooling jets configured to spray engine oil; and

an Electronic Control Unit (ECU) configured to:

receive an engine oil temperature;

receive a current coolant temperature;

receive a current spark value and a calibrated spark value for each spark plug of the plurality of spark plugs;

receive a current engine speed and a current engine torque during an associated combustion reaction of the combustion reactions;

determine a non-firing piston temperature for each piston from the engine oil temperature;

determine a coolant temperature modifier from the current coolant temperature;

determine a combustion phase modifier for each piston from the current spark value and the calibrated spark value;

determine a firing piston temperature for each piston from the current engine speed and the current engine torque

output a predicted piston temperature for each piston based on the non-firing piston temperature, the firing piston temperature, the coolant temperature modifier, and the combustion phase modifier;

coordinate operations of the spark plugs and the at least one fuel injector based on the predicted piston temperature.

2 . The engine of claim 1 , wherein the at least one fuel injector comprises a plurality of fuel injectors, each fuel injector of the plurality of fuel injectors being positioned to inject a portion of the fuel into a first end of a corresponding cylinder of the plurality of cylinders.

3 . The engine of claim 2 , wherein the plurality of piston cooling jets is positioned to spray the engine oil towards a bottom of a piston crown, where the bottom of the piston crown is positioned at an opposite end of the corresponding cylinder from the first end of the corresponding cylinder.

4 . The engine of claim 1 , wherein the ECU is configured to subtract the current spark value from the calibrated spark value to form a differential spark value, and is further configured to determine the combustion phase modifier by multiplying the differential spark value and a spark coefficient.

5 . The engine of claim 4 , wherein the ECU is configured to determine the non-firing piston temperature by utilizing a regression model based on a correlation between the non-firing piston temperature and the engine oil temperature.

6 . The engine of claim 5 , wherein the ECU is configured to determine a differential coolant temperature by subtracting the current coolant temperature from a coolant temperature threshold, and is further configured to determine the coolant temperature modifier by multiplying the differential coolant temperature and a coolant temperature coefficient.

7 . The engine of claim 6 , further comprising:

an engine oil temperature sensor configured to determine the engine oil temperature;

a coolant temperature sensor configured to determine the current coolant temperature; and

a crank shaft position sensor configured to determine an angle of rotation of a crank shaft of the engine.

8 . The engine of claim 7 , wherein the ECU is configured to:

receive the angle of rotation of the crank shaft from the crank shaft position sensor;

determine the current engine speed from the angle of rotation and the current engine torque; and

retrieve the coolant temperature coefficient from a lookup table comprising inputs of engine speed values and engine torque values.

9 . The engine of claim 7 , wherein the ECU is configured to:

receive the angle of rotation of the crank shaft from the crank shaft position sensor;

determine the current engine speed from the angle of rotation and the current engine torque; and

retrieve the spark coefficient from a lookup table comprising inputs of engine speed values and engine torque values.

10 . The engine of claim 7 , wherein the ECU is configured to:

retrieve the firing piston temperature from a lookup table comprising inputs of engine speed values and engine torque values.

11 . The engine of claim 10 , wherein each of the plurality of piston cooling jets comprises at least one oil squirter.

12 . A method, comprising:

housing a plurality of pistons in a plurality of cylinders, where each cylinder houses a corresponding piston of the plurality of pistons and forms a containment boundary for a corresponding combustion reaction;

supplying air to the plurality of cylinders, which is mixed with air disposed in the plurality of cylinders;

injecting fuel into the plurality of cylinders with at least one fuel injector to mix with the air disposed in the plurality of cylinders to form an air-fuel mixture;

combusting the air-fuel mixture with a plurality of spark plugs situated within the plurality of cylinders;

spraying engine oil with a plurality of piston cooling jets onto an exterior of the plurality of cylinders;

receiving an engine oil temperature, a current coolant temperature, a current spark value for each spark plug, a calibrated spark value for each spark plug, a current engine speed, and a current engine torque with an Electronic Control Unit (ECU);

determining a non-firing piston temperature from the engine oil temperature with the ECU;

determining a coolant temperature modifier from the current coolant temperature with the ECU;

determining a combustion phase modifier from the current spark value and the calibrated spark value with the ECU;

determining a firing piston temperature from the current engine speed and the current engine torque with the ECU;

outputting a predicted piston temperature based on the non-firing piston temperature, the firing piston temperature, the coolant temperature modifier, and the combustion phase modifier with the ECU, and

coordinating operations of the at least one fuel injectors and the spark plugs with the ECU based on the predicted piston temperature.

13 . The method of claim 12 , further comprising: subtracting the current spark value from the calibrated spark value to form a differential spark value, and multiplying the differential spark value by a spark coefficient to determine the combustion phase modifier.

14 . The method of claim 12 , further comprising: subtracting the current coolant temperature from a coolant temperature threshold to form a differential coolant temperature, and multiplying the differential coolant temperature by a coolant temperature coefficient to determine the coolant temperature modifier.

15 . The method of claim 12 , wherein outputting the predicted piston temperature further comprises adding the non-firing piston temperature to the firing piston temperature and subtracting the coolant temperature modifier and the combustion phase modifier therefrom.

16 . The method of claim 12 , wherein determining the firing piston temperature further comprises:

retrieving the firing piston temperature from a lookup table comprising inputs of engine speed values and engine torque values.

17 . The method of claim 12 , wherein determining the non-firing piston temperature further comprises utilizing a regression model based on a correlation between the non-firing piston temperature and the engine oil temperature.

18 . The method of claim 13 , wherein determining the spark coefficient comprises:

receiving a crank shaft position from a crank shaft position sensor;

determining the current engine speed and the current engine torque from the crank shaft position; and

retrieving the spark coefficient from a lookup table comprising inputs of engine speed values and engine torque values.

19 . The method of claim 14 , wherein determining the coolant temperature coefficient comprises:

receiving a crank shaft position from a crank shaft position sensor;

determining the current engine speed and the current engine torque from the crank shaft position; and

retrieving the coolant temperature coefficient from a lookup table comprising inputs of engine speed values and engine torque values.

20 . The method of claim 17 , wherein the regression model predicts the non-firing piston temperature during vehicle deceleration.