Combustion Analysis of a Spark-Ignition Engine Fueled on Methane-Hydrogen Blend with Variable Equivalence Ratio Using a Computational Fluid Dynamics Code

Abstract

The main scope of the present work is to examine the combustion processes inside the cylinder of a spark-ignition (SI) engine fueled with a methane-hydrogen blend with variable equivalence ratio. This combustion analysis is conducted with a computational fluid dynamics code, which is an in-house code and has been initially developed for simulating hydrogen-fueled SI engines. Lately, its combustion model has been extended with the introduction of methane fuel and various routes are used for the calculation of the nitric oxide (NO) emissions. The first task is to conduct the validation of this code, focusing on this newly developed combustion model. This validation is based on both performance and emissions comparison with experimental data, in order to gain a complete view of the code capabilities. The available experimental data are from a two-cylinder SI engine with complete sets of measured values. For the current study, it was decided to focus on the effect of the equivalence ratio (from 0.7 up to 1), keeping the hydrogen content constant (30% by volume). This comparison revealed that a good match exists for both performance and emissions, showing that the code can be applied for detailed investigation of such combustion processes. A detailed combustion analysis is then conducted, by further processing the results of the numerical code, providing insight of the flame front propagation and NO emissions production inside the engine cylinder.