Two Contrasting Approaches to Auto-Ignition Modelling for HCCI Engines

Abstract

This body of work entailed the broad contrasting of two hydrocarbon fuel auto-ignition models

formulated for the emulation of combustion dynamics in Homogeneous Charge Compression

Ignition (HCCI) engines.

The first (empirical) auto-ignition model was adapted from its previously published form, for

HCCI engine model implementation. This model was then combined with an explicit, single

zone, thermodynamic engine model in order to investigate combustion phasing control

strategies over a wide range of engine design parameters, experimental conditions and

hydrocarbon fuels. This investigation yielded new techniques for HCCI combustion phasing

control using convergent control parameter values and operation along curves of constant

combustion phasing. These techniques were validated experimentally using two HCCI engines

of novel design.

The second (functional global) auto-ignition model was formulated in this study, drawing on an

analysis of chemical kinetic schematics, a detailed auto-ignition behavioural study and a critical

evaluation of existing global auto-ignition models. The performance of this new functional global

model was evaluated using detailed chemical kinetic simulation data for a variety of

hydrocarbon fuels, across a wide range of experimental conditions.

The two studies, although different in approach and scope, enabled a broad and detailed

comparison of the two auto-ignition models, thereby highlighting their respective values and

limitations. The two models were shown to each possess particular advantages in the context of

HCCI auto-ignition modelling, which were unmatched by existing models of similar

classification. The models were also shown to exhibit individual drawbacks which played to

each other’s strengths. Both models were shown to be configurable to real world, full boiling

range fuels and were designed to accurately emulate the dynamics of two-stage auto-ignition

with excellent computational efficiency.

These two hydrocarbon fuel auto-ignition models, together with the engine modelling techniques

developed in this study, represent a novel and valuable contribution to the field of HCCI engine

combustion control and effectively move this technology one incremental step closer to its

anticipated commercial realisation.