Thermal performances and NOx emission studies on an ammonia-hydrogen fueled double-channel outlet micro-combustor for thermophotovoltaic applications

Abstract

In this work, we propose and examine an ammonia-hydrogen fueled micro-combustor with a single-channel inlet and double-channel outlet (SIDO). The combustion characteristics and nitrogen oxide emission of ammonia/hydrogen-oxygen premixed combustion are explored. Comparison is then made between the conventional and the proposed SIDO combustors. It is found that our proposed new design could lead to an increase of the outer wall temperature and reduced nitrogen oxide emission. The performances of different hydrogen blended ratios (Φb), inlet velocities (Vin), and equivalence ratios (Φ) are evaluated. It is found that increasing Φb reduces the maximum flame temperature and the pressure loss, enabling the flame to move upstream. When Φb is set to 25 %, the convective heat transfer performance reaches its optimal level. The wall temperature and its uniformity can be improved by increasing Vin. However, it is accompanied by increased NO emissions at the outlet. Increasing Φ can significantly reduce nitrogen oxide emission, and such a reduction effect is much more remarkable at a lower Φb. Examining the exergy efficiency is shown to be greatly improved by increasing Φb. Increasing Φ could reduce the combustion efficiency of hydrogen in the mixed fuel and have almost no effect on ammonia. This study demonstrates the feasibility of improving thermal performance and reducing emissions by varying its structure for thermophotovoltaic applications.