Aqueous solution of ammonia as marine fuel

Abstract

The ignition of ammonia in aqueous solution was simulated in a two-stroke compression ignition engine model. Zero-dimensional chemical kinetic calculations were used to estimate the ignition timing of fuel air mixtures in homogeneous charge compression ignition and diesel combustion modes. The fuel consisted of a 25% m/m aqueous solution of ammonia and pure ammonia for comparison. Ignition was studied by varying the geometric compression ratio of the engine. To ignite ammonia in aqueous solution a minimum compression ratio of 25 was necessary under homogeneous charge compression ignition combustion conditions, whereas under diesel combustion conditions a minimum compression ratio of 27 was required. Ammonia containing ammonium nitrite or hydrogen were two potential ammonia derivatives that were shown to enhance aqueous ammonia ignition in the simulations, and allowed ignition to take place at a compression ratio of 24 for diesel combustion. When comparing the ignition of aqueous ammonia solution to pure ammonia, the minimum compression ratio necessary to ignite pure ammonia was approximately 24.8 and that for aqueous ammonia 26.7 in diesel combustion. This led to the conclusion that aqueous ammonia is not prohibitively more difficult to ignite than pure ammonia. Ammonia containing ammonium nitrite or hydrogen were found to be potential pilot fuels.