Advancements in Combustion Modeling and Simulation for an Innovative Homogenous Reactivity-Controlled Compression Ignition (hRCCI) Concept

Abstract

<div class="section abstract"><div class="htmlview paragraph">The global imperative to develop clean energy solutions has redirected research efforts towards highly efficient combustion engines with ultra-low emissions. This has prompted investigations into alternative combustion concepts, including Low Temperature Combustion (LTC), utilizing environmentally friendly fuels. Within the scope of our research project, we are primarily focused on the development of an innovative combustion concept known as Homogeneous Reactivity-Controlled Compression Ignition (hRCCI), which employs renewable fuels such as ethanol and 1-octanol for a serial hybrid powertrain. The lack of predictive simulations for this concept presents a significant challenge in optimizing the engine's operation.</div><div class="htmlview paragraph">Most of the 1D system simulation models use a non-predictive combustion model for combustion simulations. Due to the dependence on auto-ignition chemistry, a chemistry based hRCCI combustion model for real time computation has been proposed with this work. Based on the thermal and chemistry data, a tabulated chemistry was generated using Ansys Chemkin. This table is further processed in Matlab- Simulink to predict the combustion in the proposed engine configuration. This helps in the simulation of combustion in real time and predicts the combustion profile before the start of combustion. This is one of the first steps in realizing multizone combustion modelling in 1D simulation to accurately predict the combustion.</div><div class="htmlview paragraph">Multidimensional computational fluid dynamics (CFD) simulation helps to refine the combustion process and provides a deeper understanding of the processes in the combustion chamber. Unsteady Reynolds averaged Navier-Stokes turbulence (URANS) simulations with detailed chemistry were previously conducted. For further insight into the hRCCI combustion process, a 2D CFD model of the combustion chamber with Large Eddy Simulation (LES), Partially averaged Navier-Stokes (PANS) and URANS turbulence model is developed using AVL FIRE M. The LES and PANS turbulence method consider the temperature variance due to the flow. This allows the precise depiction of the influence of turbulence on the combustion parameters like ignition delay, pressure rise, rate of heat release etc., and for the hRCCI concept it was found, that the flow field lead to a different temperature distribution compared to the URANS simulation and thus have an influence on the start of combustion.</div></div>