Carbon reduction in the building sector is crucial in achieving the carbon neutrality goal by 2050. Combined cooling, heating, and power (CCHP) system is a practical technology to achieve energy cascade utilization for building. However, methane usage in the present CCHP system results in carbon dioxide emission, which causes great global warming potential. Ammonia is a non-carbon fuel, implying a potentially powerful measure to achieve carbon neutral burning when serves as fuel for the CCHP system. In this article, we propose the CCHP system that uses ammonia as the fuel source. An ammonia-based distributed energy system (DES) model was developed using brown and green ammonia fuel and an objective function based on ammonia fraction and gas power capacity ratio was proposed. It is found that brown ammonia is more carbon-intensive than green ammonia, but it is cheaper than green ammonia in 2022. However, it is shown that the DES with green ammonia is more economically competitive than brown ammonia by 2050.

The distribution of hydroxyl (OH) radicals in the laminar diffusion flame of n-heptane was studied by planar laser-induced fluorescence (PLIF). The influences of nitrogen (N₂) and carbon dioxide (CO₂) dilution on the formation and distribution of OH radicals were analyzed. The corresponding dilution ratios (volume fractions) of both N₂ and CO₂ vary from 0 to 5%. The results show that for the n-heptane flame, the OH radical is mainly concentrated in the two wings of the flame, presenting a radially approximate symmetrical distribution. Both N₂ and CO₂ dilutions decrease the intensity of the maximum OH radical fluorescence and the total OH radical fluorescence. Moreover, the flame temperature decreases more significantly with the CO₂ dilution ratio due to the combination of the dilution effect and thermal effect.