Reduction strategy Clause Samples

Reduction strategy. The reduction process starts with merging of selected reaction subsets, point B1 in Figure 1, and then the second step, B2, is executed. The Ant-Colony Reduction (ACR) method is utilized, in combination with manual steps, B3. The combined methodology is motivated by the challenge to construct a compact dual-fuel mechanism for two fuels with such varying reactivity, and over wide range of conditions. ACR is a semi-stochastic build-up mechanism generating algorithm with a customizable target function that accommodates multiple reactor models, scalar and vector target quantities, and it generates mechanisms with a very low number of reactions. During reduction, performance in the whole target space acts as feedback to the mechanism-generating algorithm. This marks a difference to a more common approach where mechanisms are tested against a broader target space at the validation stage. Predictions of the detailed mechanism were used as targets, while the starting point for the reduction was the base merged model described above. Several reactions were marked as “important” and forced to be included into all generated mechanisms. A number of reactions from the NOx subset, which do not belong to major reaction chains, were included manually. The preferred approximate range of sizes of the generated mechanisms can be selected before reduction, this was done after preliminary runs by finding an optimal trade-off between mechanisms’ size and their accuracy. The final candidate mechanism was selected from the generated mechanism pool based on the overall averaged accuracy, the average accuracies of each target quantity, maximal deviations from target for each target quantity, and on the mechanism size. As ACR is a semi-stochastic build-up method, certain reactions important to a smaller subset of targets might be omitted by the algorithm. In addition to that, it is possible to manually remove species while keeping the corresponding reaction pathways by reaction lumping. These manual steps were performed by validating the test versions of the mechanism against the same target space as during the ACR reduction. After ACR reduction, optimization and manual steps were applied in several steps, to produce a final mechanism (A305) with 57 species and 158 reactions.