A pathway for implementing ammonia solutions as fuel blends for achieving low-emission combustion in diesel engines

Abstract

The intriguing exploration of ammonia fuel has captured the spotlight of researchers, heralded for its status as a zero-carbon fuel and acclaimed as a potent inhibitor of NOx emissions in internal combustion engines. Ammonia solution, one of the forms of ammonia fuel, demonstrates its ability to blend seamlessly with conventional fuel. However, the slower combustion reaction of ammonia is a significant challenge to overcome. One of the effective approaches to improve the combustibility of ammonia fuel in diesel engines is to blend ammonia solution with diesel emulsion fuel. So, the focus of this study was to comprehensively analyze the effects of blending ammonia solution at various concentrations with diesel emulsion fuel and to closely examine their effects on combustion sustainability and emission profiles in diesel engines. The ammonia solution used is an aqueous solution containing 28 wt% of ammonia. Herein, five different fuel samples were examined: diesel, water/diesel (W/D), and W/D containing 1, 3, and 5 wt% ammonia solution (A1%-W/D, A3%-W/D, and A5%-W/D, respectively). The tests were carried out with a conventional diesel engine running at a fixed engine speed of 2400 rpm, while the loads were adjusted to a variety of levels. Interestingly, we found that the diesel emulsion containing a 5 wt% ammonia solution is ineffective in diesel engines, leading to performance degradation and unstable combustion. Compared with diesel, the rate of heat release was increased by 17.6 %, 15.3 %, 10.9 % for W/D, A1%-W/D, and A3%-W/D, respectively. Furthermore, the presence of ammonia solution prolonged the ignition delay period and facilitated the reduction of NO emissions. Compared with diesel fuel, the W/D, A1%-W/D, and A3%-W/D fuels reduced NO emissions by 39.3 %, 29.5 %, and 25 %, respectively. The results of this study demonstrated that the introduction of ammonia solution at concentrations up to 3 % by weight blended with diesel emulsion fuel can be effectively combusted in a diesel engine, promoting sustained combustion stability while contributing to a significant reduction in exhaust emissions.