In-cylinder in-depth combustion investigation for a heavy-duty diesel engine

Abstract

This present study is part of the design improvement process of a specified high torque low-speed engine. This work aims at carrying out an in-depth analysis of in-cylinder combustion, mesh sensitivity, and engine performance at supercharge conditions to provide a foundation for the design improvement process of the given engine. The computational fluid dynamic (CFD) simulations are carried out on a 3D sector from $-130°$ to $130°$ crank angle (CA) by employing appropriate models to represent the different physical and chemical processes and using the finite volume method for solving the governing differential equations. An extensive investigation has been carried out for the choice of base mesh size and the number of local and temporal refinements to capture the phenomena happening in the combustion chamber at diverse temporal and local scales. The present results have been validated against available literature experimental and simulation results. Primary field variables and the well-known four phases of combustion have been studied for gaining in-depth insight into these phenomena. Cylinder average pressure, mean temperature, heat release rate (HRR), integrated heat release rate (IHRR), and emissions of ${\text{CO}}_2$, CO, ${\text{NO}}_x$, HC and soot are presented to assess the quality of combustion. Engine performance analysis has been done in terms of combustion efficiency, gross work, power, torque, and integrated mean effective pressure (IMEP). The base mesh of 1.4 mm may be an appropriate choice during the injection and combustion process spanning throughout around $40°$ CA from the start of injection while in the remaining simulation duration of around $220°$ CA base mesh of 2 mm gives a sufficient resolution. It has been found that maximum heat release takes place in Phase-III, the mixing-controlled phase, of the combustion process. More than 98% combustion efficiency has been achieved in all the simulations. Around 99% of the total heat release and emissions production takes place within $60°$ CA after top dead center (ATDC).