A Polynomial Repro-Model Applied to Propane Cracking
نویسندگان
چکیده
The application of a repro-modelling approach for the representation of chemical kinetic changes is described. The repro-model is constructed from fitted orthonormal polynomial equations describing the change in concentration of selected key species over a chemical time-step within the model. The number of key species required is established by a linear perturbation method. Application to a propane cracking kinetic scheme demonstrates that lack of mass conservation within the repro-model can pose a threat to accuracy at long reaction times, due to the accumulation of small local errors leading to large global errors. Within many previous applications of repro-modelling, the control of global errors has relied upon the accuracy of the fitting/tabulation method used for the key variables, i.e. the local fitting error. In the current approach the reconstruction of all model species is achieved and enables the conservation of predicted mass across the chemical time-step. The accuracy of the resulting repro-model is shown to be better maintained throughout the simulation when this mass conservation method is used. However, only values of the key repro-model variables must be operated on by any model of the non-chemical kinetic changes, e.g. flow, making the method applicable for use in, for example, computational fluid dynamics codes.
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