Optical investigation of the influence of passive pre-chamber turbulent jet ignition on the combustion characteristics of carbon-free ammonia-hydrogen engines
Linghai Han, Yanfeng Gong, Dingchao Qian, Mingli Liu, Hsi‐Yen Ma, Fangxi Xie
Abstract
Ammonia, as a carbon-free fuel, offers significant potential for sustainable energy applications but faces challenges such as ignition difficulty and slow combustion rates. This study aims to enhance the ignition and combustion characteristics of ammonia-hydrogen mixtures by employing passive pre-chamber turbulent jet ignition (TJI) under engine-relevant conditions, utilizing an optical constant volume combustion chamber (CVCC) for experimentation. The research focuses on three key parameters: pre-chamber nozzle diameter (D P ), hydrogen volume ratio in the main chamber (α H ), and equivalence ratio (Φ). The results show that increasing α H significantly reduces ignition delay and enhances flame propagation, with optimal performance observed at α H = 0.15. A D P of 3.5 mm provides the best balance between ignition stability and combustion duration, while excessively small (D P = 2.0 mm) or large (D P = 4.0 mm) nozzles hinder flame development. Leaner mixtures (Φ < 1.0) further delay ignition and slow flame propagation due to reduced reactivity. The optimal configuration—D P = 3.5 mm, α H = 0.15, and Φ = 1.0—substantially reduces ignition delay and combustion duration, providing valuable insights for optimizing zero-carbon ammonia-hydrogen engines.