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This paper investigates flow and combustion in a full-cycle simulation of a four-stroke, three-valve HCCI engine by visualizing the flow with pathlines. Pathlines trace massless particles in a transient flow field. In addition to visualization, pathlines are used here to trace the history, or evolution, of flow fields and species. In this study evolution is followed from the intake port through combustion. Pathline analysis follows packets of intake charge in time and space from induction through combustion. The local scalar fields traversed by the individual packets in terms of velocity magnitude, turbulence, species concentration and temperatures are extracted from the simulation results. The results show how the intake event establishes local chemical and thermal environments in-cylinder and how the species respond (chemically react) to the local field.

Diesel particulate samples were collected from a light duty engine operated at a single speed-load point with a range of biodiesel and conventional fuel blends. The oxidation reactivity of the samples was characterized in a laboratory reactor, and BET surface area measurements were made at several points during oxidation of the fixed carbon component of both types of particulate. The fixed carbon component of biodiesel particulate has a significantly higher surface area for the initial stages of oxidation, but the surface areas for the two particulates become similar as fixed carbon oxidation proceeds beyond 40%. When fixed carbon oxidation rates are normalized to total surface area, it is possible to describe the oxidation rates of the fixed carbon portion of both types of particulates with a single set of Arrhenius parameters. The measured surface area evolution during particle oxidation was found to be inconsistent with shrinking sphere oxidation.

The heat release type models have been classified as zero-dimensional because they have no spatial resolution and therefore don't contain any information on the fluid mechanics in them. They have been a significant contribution because they incorporate the rate processes occurring in the engine and are an aid in the analysis of the data. Because they are thermodynamic models it is necessary to define the control volumes on which the thermodynamic analysis is to be performed. The different control volume descriptions, called one, two and three zone models, and the analysis of the combustion event using these models is discussed. Finally a description of second law zero-dimensional models is given. These models have similar limitations as the First Law models; no spatial resolution and a control volume definition is required. These models are useful because they enable one to analyze the magnitude of the losses that occur in the different processes which comprise the engine cycle.