A Physical Two-Zone NOx Model Intended for Embedded Implementation
Carl Wilhelmsson, Per Tunestål, Bengt Johansson, Anders Widd, Rolf Johansson
This paper offers a two-zone NOx model suitable for vehicle on-board, on-line implementation. Similar NOx modeling attempts have previously been undertaken. The hereby suggested method does however offer clear and important benefits over the previously methods, utilizing a significantly different method to handle temperature calculations within the (two) different zones avoiding iterative computation. The new method significantly improves calculation speed and, most important of all, reduces implementation complexity while still maintaining reasonable accuracy and the physical interpretation of earlier suggested methods. The equations commonly used to compute NOx emissions is also rewritten in order to suit a two-zone NOx model. An algorithm which can be used to compute NOx emissions is presented and the intended contribution of the paper is a NOx model, implementation feasible for an embedded system, e.g. embedded processor or embedded electronic hardware (FPGA). For that purpose parts of the algorithm can be pre-computed and stored in tables allowing significant acceleration of the computation.
In SAE Technical Papers 2009-01-1509, SAE World Congress & Exhibition, April 2009, Detroit, MI, USA, April 2009. (Also in Modeling of SI and Diesel Engines, Vol. SP-2244, 2009, ISBN 978-0-7680-2140-0, April 2009).