Effects of hydrogen-rich products from methanol steam reforming on the performance enhancement of a medium-speed marine engine

Abstract

In order to improve the heat utilization of exhaust gas from the small and medium-sized ships without exhaust boilers, a methanol steam reforming (MSR) is proposed in the study. The combustion model of marine engine blended hydrogen-rich reforming gas was developed, and verified in terms of cylinder pressure, BSFC, and NO emissions. The compositions of reforming gas were obtained by the MSR model and employed to investigate the effect of reforming gas at different blending ratios on the combustion and emission characteristics of the marine diesel engine in the AVL-Fire environment. The results obtained show that the performance, emission, and economic characteristics are improved due to the existence of reforming gas. Specifically, the indicated power is decreased by 0.5%–4.26% and the NO mass fraction is reduced by 2.95%–18.25% at different loads, but the CO mass fractions increased by 20.21%–54.73%. Similarly, the NOx weighted emission is reduced by 34.10%, which is close to the NOx emission limit of Tier II, but the CO weighted emission is increased by 30.89%. In addition, the equivalent fuel consumption rate is reduced by 0.45%–3.59% at the maximum blending ratio, and the converted fuel cost is reduced by 6%–10% at medium and high loads. Finally, based on the comprehensive performance analysis, the optimized blending ratio at each load is obtained as follows: Rg7.5 or Rg12.5 for 100% load, Rg10 for 75% load, Rg7.5 for 50% load, and Rg2.5 for 25% load. Thus, the MSR reaction is feasible to improve the energy efficiency and reduce NOx emission of the marine engine.