Retrofit, Experimental, and Numerical Evaluation of a High-Speed Diesel Engine for Diesel-Methanol Dual-Fuel Operation

Abstract This research outlines the process for the modification of a regular marine diesel engine to enable dual fuel diesel methanol operation. It also includes the results of both experimental and numerical testing. The conversion involved integrating a methanol injector upstream of each intake port within the cylinder head. The methanol is supplied to the system by a common rail and is regulated by a separate electronic control unit (ECU), which operates concurrently with the original engine ECU, which controls the diesel system. For the evaluation of the engine in terms of performance and emissions, an experimental testbed was established in conjunction with a numerical combustion model. The experimental findings confirmed the success of the retrofit process. More specifically, the engine operated successfully in dual fuel mode with a methanol energy substitution ratio (MESR) of up to 35%, without compromising its performance or greatly deteriorating its emissions. In particular, the in-cylinder measurements indicated an increase in ignition delay and shorter duration for dual fuel combustion, while the peak cylinder pressure was reduced. The engine's thermal and combustion efficiency remained at acceptable levels, comparable to diesel operations, for low and medium MESR values, with a slight decline at higher levels. By injecting methanol, the NOX and soot emissions decreased by up to 40% and 90%, respectively. However, other uncontrolled pollutants such as formaldehyde, carbon monoxide, and other volatile organic compounds increased significantly because methanol was not completely oxidized, as shown by both experimental and numerical research.