NO emission and enhanced thermal performances studies on counter-flow double-channel hydrogen/ammonia-fuelled microcombustors with oval-shaped internal threads

Micro-combustion systems play a critical role in powering microreactors, micropropulsion and other micro-energy conversion systems. In this work, we have numerically investigated a double-channel counter-flow micro-combustor fuelled by premixed ammonia/hydrogen/oxygen parametric to investigate both NO emissions and thermal performance. The model is used to examine the effects of 1) the inlet velocity, vin, and 2) the inlet equivalence ratio, ϕ. The enhanced thermal performance is quantified by the increased mean wall temperature and the increased wall temperature uniformity. We find that thermal performance increases with increasing vin. The maximum level of NO is present atvin = 2 m/s. Meanwhile, the mean wall temperature benefits from ϕ = 1, and further increases in equivalence ratio can lessen the uniformity of the wall temperature. Furthermore, more fuel-rich ammonia combustion can lead to a lower NO emission and improve the thermal performance. To enhance ammonia combustion, further investigations are conducted by blending with different molar fractions of H2 (XH2). It is found that mixing ammonia with more H2 can stabilize micro-combustion, and increase the temperature in the combustion field. Additionally, it makes the emission worse. The maximum mean wall temperature occurs atXH2 = 0.25, While the NO emission peaks atXH2 = 0.3. Moreover, the OH mole fraction can affect the formation of NO, positively.