Energy and exergy conversion enhancement of a premixed hydrogen-fuelled wavy-combustor for micro-thermophotovolatic application

Abstract

• A wavy micro combustor is proposed to improve thermal performance. • Fuel flammability limit is greatly broadened by wavy combustor. • The effects of wavy number and depth in on the exergy and radiation energy are discussed. • Quantitively sensitivities of each objective parameter to the wavy design parameter are summarized. In this work, a wavy-shaped micro-combustor fuelled by hydrogen/air is numerically simulated with a detailed chemical-kinetic mechanism to evaluate its improved thermal performance. Effects of the equivalence ratio, wavy number and depth are examined and discussed in detail. It is found that the average temperature on outer wall in the ARC combustor is higher and the temperature distribution is more uniform compared to those in the REF combustor. This is mostly due to the enhanced heat transfer as a consequence of the enlarged contact surface between combustion products and inner walls in the presence of the wavy. Furthermore, the equivalence ratio of 1.0 tends to be associated with a high wall temperature, but the temperature uniformity is optimal at the equivalence ratio of 0.8, whatever the wavy is implemented or not. Increasing the wavy number is found to give a rise to the radiation energy and exergy. In contrast, the exergy varies non-monotonically with the wavy depth. A high wavy depth contributes to improving the radiation energy from the combustor. Finally, sensitivity analysis indicates that the average temperature and exergy have a stronger dependence on the equivalence ratio, while the mass flow rate plays the highest role in the temperature uniformity and radiation energy.