Transportation Engineering (Mar 2021)
Implementation of multi-component diesel fuel surrogates and chemical kinetic mechanisms for engine combustion simulations
Abstract
Recent developments have led to the formulation of multi-component surrogates that closely match physical and chemical properties of diesel fuels. These surrogates have been characterized and extensively tested in constant pressure vessels as well as engine experiments. The adoption of such surrogates in simulations is an important step towards predictive engine simulations. However, significant challenges remain in adoption of such surrogates. The complex chemical kinetics associated with a multi-component fuel leads to an extremely large and stiff chemistry mechanism with thousands of species. Such chemistry mechanisms are prohibitive to be directly used in engine simulations using traditional solvers due to the excessively-high computational cost. This work describes some of the experimental investigations of a 4-component diesel fuel surrogate in constant volume combustion chambers that provide useful validation datasets for numerical models. In addition, a chemical kinetic mechanism for the multi-component diesel surrogate with 1544 species is proposed. A previously validated unsteady flamelet model, accelerated by a sparse solver and analytical Jacobian, is used to implement large chemistry mechanisms for realistic diesel engine simulations. A flamelet solver is used to generate multi-dimensional unsteady flamelet libraries for the multi-component surrogate for a range of conditions. This approach is then used in a large eddy simulation (LES) framework to model combustion of the 4-component surrogate in a constant pressure spray vessel over a range of ambient oxygen conditions. The current chemistry mechanism and computational methodology can capture the two-step ignition delay as well as flame lift-off length trends observed in the experiments. Some of the low temperature combustion characteristics are analyzed in detail. The computational setup and the validation results demonstrate the feasibility of using these latest multi-component fuel surrogates for engine simulations by leveraging multi-dimensional chemistry tabulation methods.Highlights:1. Detailed experiments with the multicomponent V0A surrogate were carried out in the High Temperature Pressure Vessel facility.2. A detailed chemistry mechanism with 1544 species was developed for the V0A surrogate.3. The LSODES based flamelet tabulation method was used to implement and validate these high-fidelity surrogates and mechanisms in engine relevant LES calculations.
