Modelling and Analysis of the Heat Transfer Processes in a Diesel-CNG Dual-Fuel Compression Ignition Engine

Abstract

This study presents a comprehensive numerical investigation of heat transfer processes in a compression ignition (CI) engine operating under diesel-CNG dual‑fuel mode. Using a three‑dimensional finite volume computational fluid dynamics (CFD) framework, the work models transient in‑cylinder temperature fields, wall heat flux distribution, and combustion behaviour across varying substitution ratios, speeds, and loads. The model incorporates energy conservation equations, simplified combustion chemistry, temperature‑dependent thermo-physical properties, and validated turbulence formulations. Results reveal that moderate CNG substitution (25–50%) reduces peak cylinder temperature by 2–4%, decreases wall heat flux by up to 6%, and produces more uniform thermal gradients, thereby reducing component thermal stress. Combustion duration increases by 10–20% due to methane’s slower ignition characteristics. At high speeds and loads, wall temperatures rise significantly, demonstrating strong operational sensitivity. Model validation against benchmark data shows deviations below 9%, confirming predictive reliability. The findings demonstrate that controlled dual‑fuel operation can improve thermal management, enhance component longevity, and reduce cooling demands in marine CI engines. This study contributes a validated thermal modelling framework suitable for optimizing cleaner dual‑fuel marine propulsion systems.