ABSTRACT

Ammonia (NH₃) is considered a promising alternative fuel, capable of producing energy with zero CO₂ emissions. Its combustion, however, poses a series of challenges due to the low reactivity of NH₃ and the formation of very high quantities of NO_x. This work numerically investigates the combustion and emission characteristics of ammonia in three modern stationary gas turbine concepts, namely (a) lean-burn dry-low emissions (DLE); (b) rich-burn, quick-quench and lean-burn (RQL); and (c) moderate or intense low oxygen dilution (MILD), under operating conditions typical of commercial gas turbines (inlet temperatures of 500 K and pressure of 20 bar). Numerical simulations employing detailed chemical kinetic mechanisms are carried out to study the propagation speed of ammonia, the combustor temperatures, and the emissions of NO_x and NH₃. The simulations are first validated against literature NO_x data and then the most accurate mechanism is selected. The performance of the different gas turbine engine concepts is subsequently compared based on the results from the selected mechanism. The results show that the lowest emissions are achieved with the RQL and MILD combustion concepts, while the DLE combustion concept only presents acceptable emission values under conditions deemed unstable, where the laminar flame speeds are below 3 cm/s.

摘要

氨 (NH ₃ ) 被认为是一种很有前途的替代燃料，能够产生零 CO ₂排放的能源。然而，由于 NH ₃的低反应性和非常大量的 NO _x的形成，其燃烧带来了一系列挑战. 这项工作数值研究了三种现代固定式燃气轮机概念中氨的燃烧和排放特性，即（a）稀燃干式低排放（DLE）；(b) 富燃、快速淬火和稀燃（RQL）；(c) 中等或强烈的低氧稀释 (MILD)，在商用燃气轮机的典型操作条件下（入口温度为 500 K，压力为 20 巴）。进行了采用详细化学动力学机制的数值模拟，以研究氨的传播速度、燃烧器温度以及 NO _x和 NH ₃的排放。模拟首先根据文献 NO _{x 进行}验证数据，然后选择最准确的机制。随后根据所选机构的结果比较不同燃气涡轮发动机概念的性能。结果表明，RQL 和 MILD 燃烧概念实现了最低排放，而 DLE 燃烧概念仅在被认为不稳定的条件下呈现可接受的排放值，其中层流火焰速度低于 3 cm/s。