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An advanced gas dynamic/chemistry interaction code, SPRINT2D, has been developed to simulate end gas autoignition and knock. This confirms that an earlier hypothesis of three distinct modes of autoignition was not an artefact of the previous numerical code. A comprehensive chemical kinetic scheme has predicted autoignition onset and demonstrated a mechanism for creating the end gas temperature gradients assumed in, as well as generated heat release rates for use in, SPRINT2D. Using the combined modelling techniques, good matches between theoretical and experimental autoignition centre growth (at up to 750,000 frames/second), particle tracking and pressure development sequence at multiple transducer sites have been obtained for “thermal explosion” and “developing detonation” autoignition events.

A 2-D simulation of fluid dynamic and chemistry interaction following end gas autoignition has demonstrated three distinct modes of reaction, dependent upon the temperature gradient about an exothermic centre. All three modes (deflagration, developing detonation and thermal explosion) can contribute to knock; the developing detonation case, associated with intermediate temperature gradient, has been identified as the more damaging. The simulation code (LUMAD) has been used in a systematic parametric study designed to separate the complex interacting events which can lead to mixed modes in real engines. A most significant finding related to the sequential autoignition of multiple exothermic centres.