Method of operating a diesel engine and diesel engine arrangement having plural operating modes

A method of operating a diesel engine having an exhaust aftertreatment system (EATS) including one or more apparatus for controlling exhaust NOX levels, comprising:

• operating the engine in a first mode with a first series of control setpoints for a plurality of base actuators of the engine;
• operating the engine in a second mode with a second series of control setpoints for the plurality of base actuators, at least one control setpoint of the first and second series of control setpoints being different;
• tracking exhaust mass or volume flow through the EATS, NOX levels exiting the EATS, and temperature in the EATS for the engine over a plurality of engine speeds and loads in the first mode and in the second mode;
• selecting one of the first mode and the second mode so that, for a given engine speed and load, exhaust exiting the EATS contains NOX at no more than a predetermined NOX level and a least amount of fuel is consumed per unit energy until fuel economy in the other one of the first mode and the second mode becomes superior to fuel economy in the selected one of the first and second mode and exhaust exiting the EATS contains NOX at no more than the predetermined NOX level;
• and
• selecting the other one of the first and second mode after fuel economy in the other one of the first mode and the second mode becomes superior to fuel economy in the selected one of the first and second mode and exhaust exiting the EATS contains NOX at no more than the predetermined NOX level.

A diesel engine arrangement, comprising:

• a diesel engine having an exhaust aftertreatment system (EATS);
• a NOX sensor arranged to sense NOX levels exiting the EATS;
• and
• a controller arranged to receive a signal from the NOX sensor, the controller comprising a map of fuel economy versus NOX levels exiting the EATS for a plurality of engine operating modes, each engine operating mode differing from any other engine operating mode with respect to at least one base actuator of the engine, the controller being programmed to select one of the plurality of operating modes and cause the engine to operate in the selected operating mode so that, for a given engine speed and load, exhaust exiting the EATS contains NOX at no more than a predetermined NOX level and a least amount of fuel is consumed per unit energy until fuel economy in another operating mode at which exhaust exiting the EATS contains NOX at no more than a redetermined NOX level becomes superior to fuel economy in the selected operating mode;
• and to select the another operating mode after fuel economy in the another operating mode at which exhaust exiting the EATS contains NOX at no more than a predetermined NOX level becomes superior to fuel economy in the selected operating mode,
• wherein, for each operating mode, the engine is adapted to interpolate between a high NOX mode and a low NOX mode by adjusting one or more engine operating parameters, the controller being programmed so that the engine is permitted to interpolate toward the high NOX mode in the selected operating mode to no higher than a point at which exhaust NOX levels are at or below the predetermined NOX level.