Calibration and implementation of a functional global auto-ignition model

Master Thesis


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University of Cape Town

This research is based on a functional global reaction-rate-based auto-ignition model (FGAM) developed at the Sasol Advanced Fuels Laboratory (SAFL). During the development of the model, its performance had been validated against a detailed kinetic auto-ignition mechanism in regions of lean to stoichiometric air-fuel ratio for n-heptane, iso-octane, 1-hexene, toluene, methanol and a quaternary gasoline surrogate blend of iso-octane, toluene, nheptane and n-hexane. Subsequent to the publication of the model, sets of reaction coefficients for PRF (Primary Reference Fuel) and TSF (Toluene Standardisation Fuel) blends had been developed and published. In its original form, however, the model could not be implemented in typical engine and chemical kinetic model simulation software. In this work, an investigation was made into the form and stiffness limitations of the FGAM which prevented implementation into standard engine and chemical kinetic codes. Changes made to the form of the model that allowed implementation into these codes without significantly altering the behavioural functions of the model were investigated. Subsequent to the investigation, a modification was introduced to the FGAM in the form of a second pseudo-QSSA (quasi-steady-state assumption) which eliminated the need for calculation of the transient concentration of one of the model species. The resulting reduction in numerical stiffness allowed for the revised model to be implemented as a descriptor for combustions kinetics in engine simulations in GT-Suite.

Includes bibliographical references.