Study on ammonia/hydrogen combustion for disruptive heat engine development

Zhang, Fangyu (2024). Study on ammonia/hydrogen combustion for disruptive heat engine development. University of Birmingham. Ph.D.

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Abstract

Ammonia and hydrogen portrays a favourable potential to act as alternative fuels due to no carbon-related emissions. This thesis aims to investigate the characteristics of ammonia and hydrogen combustion, providing guidance for the development of a disruptive heat engine using ammonia and hydrogen.

Nakamura’s mechanism is found to best predict the fundamentals of ammonia and hydrogen combustion and employed in the numerical study. The premixed laminar flame speed, ignition delay and flame structure of ammonia and hydrogen combustion are explored with various parameters. It shows an equivalence ratio of 1.1 is advantageous for both combustion stability and emission control. Hydrogen enrichment and oxygen enrichment effectively promote the laminar flame speed and reduce the ignition delay time. However, they comes at the cost of higher NO emission. Elevated pressure tends to reduce NO emission.

A lab-scaled swirl-enhanced combustor rig is established to analyse the characteristics of non-premixed ammonia and hydrogen flame. The results indicate increasing hydrogen blending ratios, initial gas temperature and decreasing the swirl numbers are effective ways to broaden the flame stability range. The optimal emission control occurs at stoichiometric condition. More hydrogen involvement leads to the increase of NO and NO2 emissions and the decrease in ammonia slip. However, the effect is weakened under fuel-rich conditions.

The numerical and experimental emission results are compared with those from various ammonia-based heat engines. Most results exceeds EURO 7 regulation standards. The two-zone rich-lean neat ammonia fuelled micro gas turbine shows the best control of emission with thermal efficiency of ∼ 22%.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):