A reduced chemical kinetic mechanism of a diesel fuel surrogate (n-heptane/toluene) for HCCI combustion modelling

摘要

The combination of a CFD (Computational Fluid Dynamic) code and a detailed chemical kinetic mechanism is a very powerful tool for its use in the development of new Internal Combustion Engines (ICE). However, the large computation demands of this combination have encouraged researchers to develop efficient reduction techniques that produce relatively small kinetic mechanisms while keeping the relevant information (reaction paths and compounds) from the detailed reaction schemes. This challenge is especially significant when simulating new combustion concepts such as Low Temperature Combustion (LTC) modes, in which the fuel oxidation chemistry, together with the mixing phenomena and turbulence, play a very important role. In this work, a multi-technique reduction methodology has been used to obtain a reduced kinetic mechanism of a diesel fuel surrogate (consisting of a mixture of 64% n-heptane/36% toluene (% by wt)). Firstly, Directed Relation Graph with Error Propagation (DRGEP) was used since it has been proved in the literature to be a very efficient method to remove species from a large kinetic scheme. Further reduction can be achieved with the use of Reaction Analysis (RA), a methodology capable of detecting unimportant reactions from a reaction mechanism. Finally, a lumping methodology was applied in order to reduce the number of isomers in the kinetic scheme. The methodology has been proved to produce very accurate results when reducing large kinetic reaction schemes such as the diesel fuel surrogate mechanism. The detailed kinetic mechanism, that includes 772 species and 3216 reactions, has been reduced to a scheme consisting of 184 species and 463 reactions which reproduces accurately the behaviour of the diesel surrogate under different engine LTC conditions.