Effect of ammonia energy ratio and diesel pilot-injection strategy on the performance of ammonia-diesel dual fuel engine

Abstract

ABSTRACT The combustion strategy under a higher ammonia energy ratio (AER) is expected to improve the combustion performance of ammonia-diesel dual-fuel (ADDF) engines, leading to additional reductions in greenhouse gas (GHG) emissions. In order to meet the engine’s performance requirements while achieving the low carbon emissions, this study utilized CFD numerical simulations to analyze the combustion and emission characteristics for an ADDF engine at AER levels from 0% to 90%. It focused primarily on evaluating the effectiveness of diesel pilot-injection strategy in reducing GHG emissions at AER50%. The obtained results showed that the unburned NH3 and N2O emissions exhibited an upward trend with the increment of AER, leading to a degradation in the indicated thermal efficiency (ITE), while GHG emissions were more significant than in the original diesel-only combustion mode. Based on AER50%, the ITE exhibited a trend of initially rising and then falling with the increment of diesel pilot-injection ratio (DPR) from 0% to 60%, reaching a maximum value of 47.1% at DPR 40%. At this point, the unburned NH3 emission decreased by 42.4% compared to the DPR0%, and no longer declined after the DPR exceeded 40%. Based on AER 50% and DPR 40%, ITE peaked at 48.1% with the optimal timing for diesel pilot-injection, which represented a 1.6% rise in ITE relative to the original diesel-only combustion mode, while GHG emissions decreased by 35%, and NO emissions increased by 25%.