Heating and Evaporation of Droplets of Multicomponent and Blended Fuels: A Review of Recent Modeling Approaches

Abstract

In this review, recent models for the heating/evaporation of multicomponent and blended fuel droplets and their implementation into numerical codes, used for the analysis of the processes in internal combustion engines, are reviewed. In these models, the diffusion of species, recirculation, and temperature gradient inside droplets are considered. The focus of the review is on the group of models based on the implementation of the analytical solutions to the heat transfer and species diffusion equations inside droplets into numerical codes. Four key aspects are summarized: (1) application of the Discrete Component (DC) model and the Multi-Dimensional Quasi-Discrete Model (MDQDM) to a broad range of fuels, including petrol, diesel, ethanol, and biodiesel fuels and their blends, (2) formulation of fuel surrogates, with a focus on the recently introduced Complex Fuel Surrogate Model (CFSM), (3) overview of the recently introduced transient algorithm, Transient Multi-Dimensional Quasi-Discrete Model (TMDQDM), for an autogeneration of quasi-components, and (4) implementation of the latter into a computational fluid dynamics (CFD) code for a realistic engineering application to full cycle simulation in internal combustion engines. The original and modified versions of the DC model and MDQDM are evaluated for the heating and evaporation of droplets of bio/fossil-fuel (e.g., ethanol/petrol/biodiesel/diesel) blends. These were implemented into commercial CFD software and validated. The feasibility of formulating complex fuel surrogates for fuel blends, their implementation into CFD codes, and their application in the full engine cycle simulation before and after the onset of combustion (autoignition) are described.