System and method for determining engine out NOx based on in-cylinder contents

A system, comprising:

• an exhaust aftertreatment system in fluid communication with an engine;
• and
• a controller communicably and operatively coupled to the exhaust aftertreatment system, the controller structured to:
• interpret engine in-cylinder data regarding an operating condition within a cylinder of the engine, wherein the engine in-cylinder data includes an engine torque and an engine speed;
• interpret at least one additional in-cylinder data point regarding the operating condition within the cylinder of the engine, the at least one additional in-cylinder data point including an in-cylinder trapped air mass amount, the in-cylinder trapped air mass amount determined based on a residual mass and a charge air mass;
• and
• determine an engine out NOx amount responsive to the engine in-cylinder data and the at least one additional in-cylinder data point, wherein determining the engine out NOx amount includes determining an increasing engine out NOx amount as the in-cylinder trapped air mass amount increases and/or as a fluid pressure increases in a rail fluidly coupled to a fuel injector for the engine.

A method, comprising:

• identifying, by a controller, an in-cylinder data point indicative of one or more conditions within a cylinder of an engine;
• selecting, by the controller, one or more of the in-cylinder data points, the one or more in-cylinder data points including an in-cylinder trapped air mass amount, the in-cylinder trapped air mass amount determined based on a residual mass and a charge air mass;
• responsive to selecting the one or more in-cylinder data points, formulating, by the controller, a steady state approximation indicative of operating conditions of the engine in a steady state condition;
• and
• determining, by the controller, an engine out NOx amount at a transient engine cycle based on the steady state approximation.

A non-transitory computer-readable medium having instructions stored therein that, when executed by a controller comprising one or more processors, cause the controller to perform functions comprising:

• interpreting engine in-cylinder data regarding an operating condition within a cylinder of an engine, the engine in-cylinder data including an engine torque and an engine speed;
• interpreting at least one additional in-cylinder data point regarding the operating condition within the cylinder of the engine, the at least one additional in-cylinder data point including an in-cylinder trapped air mass amount, the in-cylinder trapped air mass amount determined based on a residual mass and a charge air mass;
• and
• determining an engine out NOx amount responsive to the engine in-cylinder data and the at least one additional in-cylinder data point, wherein determining the engine out NOx amount includes determining an increasing engine out NOx amount as the in-cylinder trapped air mass amount increases and/or as a fluid pressure increases in a rail fluidly coupled to a fuel injector for the engine.