A Review of Combustion Modeling Techniques for IC Engines: CFD Simulations and Experimental Correlations

Abstract

For a long time, internal combustion (IC) engines have been the mainstay of power generating and transportation systems. However, a move toward cleaner and more efficient engine technologies has been spurred by stricter pollution restrictions and growing environmental concerns. In this context, combustion modeling has emerged as a critical tool for understanding in-cylinder processes and improving engine performance. This review focuses on the evolution and application of various combustion modeling techniques for IC engines, with an emphasis on Computational Fluid Dynamics (CFD) simulations and their correlation with experimental data. Combustion modeling spans a wide spectrum – from zero-dimensional thermodynamic models to advanced three-dimensional CFD-based simulations. While zero- and one-dimensional models offer fast computation and are suitable for preliminary assessments, they fall short in capturing spatial variations and transient phenomena. Conversely, CFD techniques provide detailed insight into fluid flow, fuel-air mixing, flame propagation, ignition processes, and pollutant formation within the combustion chamber. The effectiveness of CFD models hinges on the integration of turbulence, chemical kinetics, spray dynamics, and heat transfer modules. Commonly used combustion models include the Eddy Dissipation Concept (EDC), Flamelet models, and Probability Density Function (PDF) approaches, each with its own strengths and limitations. Experimental validation remains a cornerstone for ensuring the accuracy and reliability of these simulations. Techniques, such as high-speed imaging, in-cylinder pressure measurements, and optical diagnostics, like Laser-Induced Fluorescence (LIF), play a vital role in refining and validating combustion models. Furthermore, empirical correlations for ignition delay, heat release rates, and emission predictions provide additional support for numerical modeling frameworks. This review aims to present a holistic overview of current combustion modeling practices, highlighting the challenges and future trends in the domain. The synergistic use of CFD and experimental data is crucial for advancing the predictive capabilities of combustion simulations and supporting the development of next-generation IC engines.

Keywords: Combustion modeling, internal combustion engines, computational fluid dynamics (CFD), experimental validation, ignition delay correlations, emission prediction.