Virtual NO sensor for spark-ignition engines

Abstract

A control-oriented, physics-based model for the estimation of the NO emissions of spark-ignition engines has been developed. The model consists of three submodels for the estimation of the in-cylinder pressure, of the burned gas temperature, and of the formation of NO. All submodels are based on physics first principles and chemical reactions. However, they are simplified in order to allow for an efficient evaluation in a control-oriented environment. The submodel of the pressure estimation incorporates a combustion model whose parameters are continuously adapted using the feedback of crankshaft angular velocity measurements. Measurement data have been acquired from a V6 3.2 1 engine at a set of reference operating points, each of them serving as a support point of the model parameters. Measurement data were obtained from variations of the operating conditions and compared with the corresponding simulations. The simulation results for the in-cylinder pressure and the engine-out NO emissions agree well with measured values, while the evaluation time of the model was shorter than the duration of one engine cycle. The calibration effort was found to be small, while the model demonstrated its capability to extrapolate engine behaviour beyond the calibration data set.