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A New Functional Global Auto-ignition Model for Hydrocarbon Fuels - Part 2 of 2: Model Formulation, Development and Performance Assessment
Abstract:
Homogeneous Charge Compression Ignition (HCCI) engine technology has been an area of rapidly increasing research interest for the past 15 years and appears poised for commercialisation through the efforts of international research institutions and manufacturers alike. In spite of significant worldwide research efforts on numerous aspects of this technology, the need still exists for accurate and computationally efficient fuel auto-ignition models capable of predicting the heat release dynamics of two-stage auto-ignition, especially for full boiling range fuels, sensitive to the effects of pressure, temperature, fuel equivalence ratio and inert dilution.
This study was the second of a two part investigation in which analysis of published alkane fuel oxidation kinetic schematics, detailed fuel auto-ignition behavioural studies and critical evaluation of existing global model formulations (Part 1) provided insight for the formulation of a new functional global auto-ignition model (Part 2).
The formulation of the new functional global auto-ignition model resulted in a computationally efficient model, able to accurately predict heat release dynamics of single and two-stage auto-ignition fuels across a wide range of temperature, pressure, fuel equivalence ratio and inert exhaust product dilution, thereby out-performing the predictive accuracy of currently available global models. The computational efficiency of the new global model out-performed skeletal and reduced chemical kinetic models which may possess similar predictive functionality with regard to 2-stage heat release dynamics.
Although the new functional global model was based on alkane fuel auto-ignition behaviour (iso-octane and n-heptane), it was also shown to fit 1-hexene and a quaternary gasoline surrogate blend without any changes to the model form. Removal of the low temperature chemistry section of the model allowed fitting to methanol and toluene as examples of single stage auto-ignition fuels. This flexibility indicates that the model could be fitted to any hydrocarbon fuel including full boiling range blends. This wide applicability of the new functional global model makes it particularly suitable for HCCI modelling applications.