Numerical investigations on charge motion and combustion of natural gas-enhanced ammonia in marine pre-chamber lean-burn engine with dual-fuel combustion system

Abstract

Ammonia, an efficient hydrogen carrier with the advantages of lower storage cost and higher stability comparing to hydrogen, is becoming a potential solution for carbon dioxide emission reduction from marine engine. In this paper, the CH4/NH3 mechanism applied to simulate the combustion process of elevated-pressure engine was experimentally verified. Then, simulations were conducted on a marine pre-chamber lean-burn engine to investigate the feasibility of dual-fuel combustion with natural gas and ammonia. The results show that the combustion of the rich mixture ignited by spark in the pre-chamber produces high-speed turbulent jet flames into the main chamber, which promotes the combustion of the lean gas mixture. Additionally, an anomalous pre-ignition pressure rise is observed at 50% natural gas addition. Finally, the performance evaluation of engine indicates that for the design of marine dual-fuel engine, the ammonia fraction range of 50%∼80% should be employed to achieve good engine thermal efficiency.