Application of reformed exhaust gas recirculation on marine LNG engines for NOx emission control

Abstract

In the present study, the reformed exhaust gas recirculation (REGR) technique was employed on the marine engine fueled with LNG (i.e., marine LNG engine) for the reduction of emissions. A specially designed exhaust gas reformer was integrated with the marine LNG engine and then the performance of the closed-loop system of the reformer and engine was investigated, aiming at exploring the emissions reduction potential of the REGR technique for the marine LNG engine. The results showed that the NOx emission of the marine LNG engine with REGR was lower than that of the prototype engine by 60–70% and meanwhile can meet the Tier III emissions regulations. For the marine LNG engine with REGR, high rate of natural gas supplied to the reformer (RRNG) increased the concentrations of H2 and CO in the reformate. This advanced the flame speed of in-cylinder mixtures and led to a high peak pressure and heat release rate, resulting a 20–26% increase in NOx emission and a 10–12% decrease in the unburned hydrocarbon emission. Because of the variation in thermal efficiency of the reformer and engine, the fuel consumption rate of the closed-loop system showed a different trend with the increase of RRNG at different loads.