Experimental investigation on the turbulence flame autoignition characteristics of ammonia in a high-temperature co-flow

Ammonia has a promising future for transportation and industrial power as an innovative zero-carbon fuel because of the harsh emission laws in force and the pressing need of low carbon fuels. Thus, the aim of this work has been to investigate the autoignition characteristics of an ammonia turbulence flame under a high temperature co-flow, on the basis of an experimental platform. The morphology, lift height, and stability of an ammonia jet diffusion flame have been explored under different co-flow regimes (in terms of temperature and velocity) and fuel injection pressures. It was found that when the co-flow temperature augments, the ammonia jet can form a stable lifting flame. Moreover, the combustion stability of the ammonia flame increases significantly and the fluctuation of the lift height of the flame clearly decreases over time. Forming a stable ammonia jet lifting flame under high co-flow velocities and injection pressures requires a high co-flow temperature. The length, area, and perimeter of an ammonia jet diffusion combustion flame increase as the co-flow temperature increases. The distance from the point of autoignition to the central nozzle outlet and the ignition delay both decrease when the co-flow temperature augments. The lift height of an ammonia diffusion combustion flame gradually decreases as the co-flow temperature increases. Moreover, there is a critical temperature of 1173 K beyond which the decline slope of both the lift height and ignition delay decreases.