Performance Assessment of a Model-Based Combustion Control System to Decrease the Brake Specific Fuel Consumption

The challenge of industrial carbon footprint reduction is led by the engine manufacturers that are developing new technologies and fuels to lower CO2 emissions. Although the deployment of relevant investments for the development of battery electric vehicles, diesel, and gasoline cars are still widely used, especially for their longer operating range, faster refueling, and lower cost. For this reason, more efficient traditional internal combustion engines can guide the transition towards new propulsion systems. In this document, the innovative piston damage and exhaust gas temperature models previously developed by the authors are reversed and coupled to manage the combustion process, increasing the overall energy conversion efficiency. The instantaneous piston erosion and the exhaust gas temperature at the turbine inlet are evaluated according to the models' estimation which manages both the spark advance, and the target lambda. In the first part of the work, the exhaust gas temperature model is reversed and converted into a control function which is then implemented in a piston damage-based, spark advance controller. This controller targets the piston erosion speed (i.e., the cumulative erosion at the end of the engine life), using more aggressive calibrations. This strategy significantly increases the combustion efficiency and lowers the exhaust gas temperature under knock-limited operating conditions. Furthermore, this decrease in exhaust gas temperature is converted into lowering the fuel enrichment with respect to the production calibrations. In the last part of the work, the complete controller is validated for both the transient and steady-state conditions, reproducing a real vehicle maneuver at the engine test bench. The results demonstrate that the combination of an accurate estimation of the damage induced by knock and the value of the exhaust gas temperature allows to reduce the brake specific fuel consumption by up to 25%. Moreover, the stoichiometric area of the engine operating range is extended by 20%.