Study of Fuel Injection Strategy for a Methanol and Diesel Dual-Fuel Large-Bore and Medium-Speed Marine Engine

The popularization and application of methanol in internal combustion engines is of great significance to energy and the environment. With its high methanol substitution rate (MSR) and low fuel consumption, the methanol/diesel dual direct injection scheme is receiving increasing attention. In the current research, a three-dimensional simulation model with high fidelity was established to predict the combustion and emission characteristics of the large bore and medium speed methanol/diesel dual direct injection engine. From the view of the problems of long combustion duration and low combustion efficiency of large bore methanol engines applying a diesel pilot, a study on the injection strategy of diesel was proposed under the condition that the methanol injection strategy was fixed. The results show that shortening the injection interval between pilot diesel and methanol can effectively improve the engine power. Moreover, the appropriate extension of the duration of the pilot diesel injection can ensure the overall ignition and uniform combustion of methanol, resulting in higher power and lower emissions. Meanwhile, with the extension of the duration of the pilot diesel injection, the optimal injection interval also shows an increasing trend. This paper reveals how to utilize effectively the low proportion of pilot diesel energy by adjusting the diesel injection strategy to maximize the MSR and provide theoretical references for the engineering optimization of large bore methanol/diesel dual direct injection marine engines.